WorldWideScience

Sample records for image noise levels

  1. Training Methods for Image Noise Level Estimation on Wavelet Components

    Directory of Open Access Journals (Sweden)

    A. De Stefano

    2004-12-01

    Full Text Available The estimation of the standard deviation of noise contaminating an image is a fundamental step in wavelet-based noise reduction techniques. The method widely used is based on the mean absolute deviation (MAD. This model-based method assumes specific characteristics of the noise-contaminated image component. Three novel and alternative methods for estimating the noise standard deviation are proposed in this work and compared with the MAD method. Two of these methods rely on a preliminary training stage in order to extract parameters which are then used in the application stage. The sets used for training and testing, 13 and 5 images, respectively, are fully disjoint. The third method assumes specific statistical distributions for image and noise components. Results showed the prevalence of the training-based methods for the images and the range of noise levels considered.

  2. Development of low read noise high conversion gain CMOS image sensor for photon counting level imaging

    Science.gov (United States)

    Seo, Min-Woong; Kawahito, Shoji; Kagawa, Keiichiro; Yasutomi, Keita

    2016-05-01

    A CMOS image sensor with deep sub-electron read noise and high pixel conversion gain has been developed. Its performance is recognized through image outputs from an area image sensor, confirming the capability of photoelectroncounting- level imaging. To achieve high conversion gain, the proposed pixel has special structures to reduce the parasitic capacitances around FD node. As a result, the pixel conversion gain is increased due to the optimized FD node capacitance, and the noise performance is also improved by removing two noise sources from power supply. For the first time, high contrast images from the reset-gate-less CMOS image sensor, with less than 0.3e- rms noise level, have been generated at an extremely low light level of a few electrons per pixel. In addition, the photon-counting capability of the developed CMOS imager is demonstrated by a measurement, photoelectron-counting histogram (PCH).

  3. Minimum requirement of artificial noise level for using noise-assisted correlation algorithm to suppress artifacts in ultrasonic Nakagami images.

    Science.gov (United States)

    Tsui, Po-Hsiang

    2012-04-01

    The Nakagami image is a complementary imaging mode for pulse-echo ultrasound B-scan to characterize tissues. White noise in anechoic areas induces artifacts in the Nakagami image. Recently, we proposed a noise-assisted correlation algorithm (NCA) for suppressing the Nakagami artifact. In the NCA, artificial white noise is intentionally added twice to backscattered signals to produce two noisy data, which are used to establish a correlation profile for rejecting noise. This study explored the effects of artificial noise level on the NCA to suppress the artifact of the Nakagami image. Simulations were conducted to produce B-mode images of anechoic regions under signal-to-noise ratios (SNRs) of 20, 10 and 5 dB. Various artificial noise levels ranging from 0.1- to 1-fold of the intrinsic noise amplitude were used in the NCA for constructing the Nakagami images. Phantom experiments were conducted to validate the performance of using the optimal artificial noise level suggested by the simulation results to suppress the Nakagami artifacts by the NCA. The simulation results indicated that the artifacts of the Nakagami image in the anechoic regions can be gradually suppressed by increasing the artificial noise level used in the NCA to improve the image contrast-to-noise ratio (CNR). The CNR of the Nakagami image reached 20 dB when the artificial noise level was 0.7-fold of the intrinsic noise amplitude. This criterion was demonstrated by the phantom results to provide the NCA with an excellent ability to obtain artifact-free Nakagami images.

  4. Additive white Gaussian noise level estimation in SVD domain for images.

    Science.gov (United States)

    Liu, Wei; Lin, Weisi

    2013-03-01

    Accurate estimation of Gaussian noise level is of fundamental interest in a wide variety of vision and image processing applications as it is critical to the processing techniques that follow. In this paper, a new effective noise level estimation method is proposed on the basis of the study of singular values of noise-corrupted images. Two novel aspects of this paper address the major challenges in noise estimation: 1) the use of the tail of singular values for noise estimation to alleviate the influence of the signal on the data basis for the noise estimation process and 2) the addition of known noise to estimate the content-dependent parameter, so that the proposed scheme is adaptive to visual signals, thereby enabling a wider application scope of the proposed scheme. The analysis and experiment results demonstrate that the proposed algorithm can reliably infer noise levels and show robust behavior over a wide range of visual content and noise conditions, and that is outperforms relevant existing methods.

  5. Object reconstruction from thermal and shot noises corrupted block-based compressive ultra-low-light-level imaging measurements

    Science.gov (United States)

    Niu, Sen; Ke, Jun

    2016-10-01

    In this paper, block-based compressive ultra low-light-level imaging (BCU-imaging) is studied. Objects are divided into blocks. Features, or linear combinations of block pixels, instead of pixels, are measured for each block to improve system measurement SNR and thus object reconstructions. Thermal noise and shot noise are discussed for object reconstruction. The former is modeled as Gaussian noise. The latter is modeled as Poisson noise. Linear Wiener operator and linearized iterative Bregman algorithm are used to reconstruct objects from measurements corrupted by thermal noise. SPIRAL algorithm is used to reconstruct object from measurements with shot noise. Linear Wiener operator is also studied for measurements with shot noise, because Poisson noise is similar to Gaussian noise at large signal level and feature values are large enough to make this assumption feasible. Root mean square error (RMSE) is used to quantify system reconstruction quality.

  6. Noise Gating Solar Images

    Science.gov (United States)

    DeForest, Craig; Seaton, Daniel B.; Darnell, John A.

    2017-08-01

    I present and demonstrate a new, general purpose post-processing technique, "3D noise gating", that can reduce image noise by an order of magnitude or more without effective loss of spatial or temporal resolution in typical solar applications.Nearly all scientific images are, ultimately, limited by noise. Noise can be direct Poisson "shot noise" from photon counting effects, or introduced by other means such as detector read noise. Noise is typically represented as a random variable (perhaps with location- or image-dependent characteristics) that is sampled once per pixel or once per resolution element of an image sequence. Noise limits many aspects of image analysis, including photometry, spatiotemporal resolution, feature identification, morphology extraction, and background modeling and separation.Identifying and separating noise from image signal is difficult. The common practice of blurring in space and/or time works because most image "signal" is concentrated in the low Fourier components of an image, while noise is evenly distributed. Blurring in space and/or time attenuates the high spatial and temporal frequencies, reducing noise at the expense of also attenuating image detail. Noise-gating exploits the same property -- "coherence" -- that we use to identify features in images, to separate image features from noise.Processing image sequences through 3-D noise gating results in spectacular (more than 10x) improvements in signal-to-noise ratio, while not blurring bright, resolved features in either space or time. This improves most types of image analysis, including feature identification, time sequence extraction, absolute and relative photometry (including differential emission measure analysis), feature tracking, computer vision, correlation tracking, background modeling, cross-scale analysis, visual display/presentation, and image compression.I will introduce noise gating, describe the method, and show examples from several instruments (including SDO

  7. Acceptable noise level

    DEFF Research Database (Denmark)

    Olsen, Steen Østergaard; Nielsen, Lars Holme; Lantz, Johannes;

    2012-01-01

    The acceptable noise level (ANL) is used to quantify the amount of background noise that subjects can accept while listening to speech, and is suggested for prediction of individual hearing-aid use. The aim of this study was to assess the repeatability of the ANL measured in normal-hearing subjec...... using running Danish and non-semantic speech materials as stimuli and modulated speech-spectrum and multi-talker babble noises as competing stimuli....

  8. Blind Analysis of CT Image Noise Using Residual Denoised Images

    CERN Document Server

    Roychowdhury, Sohini; Alessio, Adam

    2016-01-01

    CT protocol design and quality control would benefit from automated tools to estimate the quality of generated CT images. These tools could be used to identify erroneous CT acquisitions or refine protocols to achieve certain signal to noise characteristics. This paper investigates blind estimation methods to determine global signal strength and noise levels in chest CT images. Methods: We propose novel performance metrics corresponding to the accuracy of noise and signal estimation. We implement and evaluate the noise estimation performance of six spatial- and frequency- based methods, derived from conventional image filtering algorithms. Algorithms were tested on patient data sets from whole-body repeat CT acquisitions performed with a higher and lower dose technique over the same scan region. Results: The proposed performance metrics can evaluate the relative tradeoff of filter parameters and noise estimation performance. The proposed automated methods tend to underestimate CT image noise at low-flux levels...

  9. High level white noise generator

    Science.gov (United States)

    Borkowski, Casimer J.; Blalock, Theron V.

    1979-01-01

    A wide band, stable, random noise source with a high and well-defined output power spectral density is provided which may be used for accurate calibration of Johnson Noise Power Thermometers (JNPT) and other applications requiring a stable, wide band, well-defined noise power spectral density. The noise source is based on the fact that the open-circuit thermal noise voltage of a feedback resistor, connecting the output to the input of a special inverting amplifier, is available at the amplifier output from an equivalent low output impedance caused by the feedback mechanism. The noise power spectral density level at the noise source output is equivalent to the density of the open-circuit thermal noise or a 100 ohm resistor at a temperature of approximately 64,000 Kelvins. The noise source has an output power spectral density that is flat to within 0.1% (0.0043 db) in the frequency range of from 1 KHz to 100 KHz which brackets typical passbands of the signal-processing channels of JNPT's. Two embodiments, one of higher accuracy that is suitable for use as a standards instrument and another that is particularly adapted for ambient temperature operation, are illustrated in this application.

  10. Effect of ultra-low doses, ASIR and MBIR on density and noise levels of MDCT images of dental implant sites

    Energy Technology Data Exchange (ETDEWEB)

    Widmann, Gerlig; Schullian, Peter [Medical University of Innsbruck, Department of Radiology, Innsbruck (Austria); Al-Shawaf, Reema; Al-Sadhan, Ra' ed; Al-Ekrish, Asma' a A. [King Saud University, Department of Oral Medicine and Diagnostic Sciences, College of Dentistry, Riyadh (Saudi Arabia); Hoermann, Romed [Medical University of Innsbruck, Division of Clinical and Functional Anatomy, Innsbruck (Austria)

    2017-05-15

    Differences in noise and density values in MDCT images obtained using ultra-low doses with FBP, ASIR, and MBIR may possibly affect implant site density analysis. The aim of this study was to compare density and noise measurements recorded from dental implant sites using ultra-low doses combined with FBP, ASIR, and MBIR. Cadavers were scanned using a standard protocol and four low-dose protocols. Scans were reconstructed using FBP, ASIR-50, ASIR-100, and MBIR, and either a bone or standard reconstruction kernel. Density (mean Hounsfield units [HUs]) of alveolar bone and noise levels (mean standard deviation of HUs) was recorded from all datasets and measurements were compared by paired t tests and two-way ANOVA with repeated measures. Significant differences in density and noise were found between the reference dose/FBP protocol and almost all test combinations. Maximum mean differences in HU were 178.35 (bone kernel) and 273.74 (standard kernel), and in noise, were 243.73 (bone kernel) and 153.88 (standard kernel). Decreasing radiation dose increased density and noise regardless of reconstruction technique and kernel. The effect of reconstruction technique on density and noise depends on the reconstruction kernel used. (orig.)

  11. Noise sources and noise suppression in CMOS imagers

    Science.gov (United States)

    Pain, Bedabrata; Cunningham, Thomas J.; Hancock, Bruce R.

    2004-01-01

    Mechanisms for noise coupling in CMOS imagers are complex, since unlike a CCD, a CMOS imager has to be considered as a full digital-system-on-a-chip, with a highly sensitive front-end. In this paper, we analyze the noise sources in a photodiode CMOS imager, and model their propagation through the signal chain to determine the nature and magnitude of noise coupling. We present methods for reduction of noise, and present measured data to show their viability. For temporal read noise reduction, we present pixel signal chain design techniques to achieve near 2 electrons read noise. We model the front-end reset noise both for conventional photodiode and CTIA type of pixels. For the suppression of reset noise, we present a column feedback-reset method to reduce reset noise below 6 electrons. For spatial noise reduction, we present the design of column signal chain that suppresses both spatial noise and power supply coupling noise. We conclude by identifying problems in low-noise design caused by dark current spatial distribution.

  12. BACKGROUND NOISE LEVELS IN STUDIOS AND AUDITORIA

    OpenAIRE

    James, A.

    1990-01-01

    The specification of background noise levels for auditoria must strike a balance between the lowest possible noise level from services and the need for some "masking" of extraneous sources. Studios are often designed to provide a suitable level of masking, using either aerodynamic or electronically-generated white noise. Data on noise levels in a large number of auditoria have been examined to determine whether a similar process is applicable to these. A wide range of seemingly arbitrary desi...

  13. Image reconstruction under non-Gaussian noise

    DEFF Research Database (Denmark)

    Sciacchitano, Federica

    During acquisition and transmission, images are often blurred and corrupted by noise. One of the fundamental tasks of image processing is to reconstruct the clean image from a degraded version. The process of recovering the original image from the data is an example of inverse problem. Due......D thesis intends to solve some of the many open questions for image restoration under non-Gaussian noise. The two main kinds of noise studied in this PhD project are the impulse noise and the Cauchy noise. Impulse noise is due to for instance the malfunctioning pixel elements in the camera sensors, errors...... that the CM estimate outperforms the MAP estimate, when the error depends on Bregman distances. This PhD project can have many applications in the modern society, in fact the reconstruction of high quality images with less noise and more details enhances the image processing operations, such as edge detection...

  14. An investigation of the trade-off between the count level and image quality in myocardial perfusion SPECT using simulated images: the effects of statistical noise and object variability on defect detectability

    Energy Technology Data Exchange (ETDEWEB)

    He Xin; Links, Jonathan M; Frey, Eric C [Department of Radiology, Division of Medical Imaging Physics, Johns Hopkins School of Medicine, Baltimore MD 21287 (United States)

    2010-09-07

    Quantum noise as well as anatomic and uptake variability in patient populations limits observer performance on a defect detection task in myocardial perfusion SPECT (MPS). The goal of this study was to investigate the relative importance of these two effects by varying acquisition time, which determines the count level, and assessing the change in performance on a myocardial perfusion (MP) defect detection task using both mathematical and human observers. We generated ten sets of projections of a simulated patient population with count levels ranging from 1/128 to around 15 times a typical clinical count level to simulate different levels of quantum noise. For the simulated population we modeled variations in patient, heart and defect size, heart orientation and shape, defect location, organ uptake ratio, etc. The projection data were reconstructed using the OS-EM algorithm with no compensation or with attenuation, detector response and scatter compensation (ADS). The images were then post-filtered and reoriented to generate short-axis slices. A channelized Hotelling observer (CHO) was applied to the short-axis images, and the area under the receiver operating characteristics (ROC) curve (AUC) was computed. For each noise level and reconstruction method, we optimized the number of iterations and cutoff frequencies of the Butterworth filter to maximize the AUC. Using the images obtained with the optimal iteration and cutoff frequency and ADS compensation, we performed human observer studies for four count levels to validate the CHO results. Both CHO and human observer studies demonstrated that observer performance was dependent on the relative magnitude of the quantum noise and the patient variation. When the count level was high, the patient variation dominated, and the AUC increased very slowly with changes in the count level for the same level of anatomic variability. When the count level was low, however, quantum noise dominated, and changes in the count level

  15. An investigation of the trade-off between the count level and image quality in myocardial perfusion SPECT using simulated images: the effects of statistical noise and object variability on defect detectability

    Science.gov (United States)

    He, Xin; Links, Jonathan M.; Frey, Eric C.

    2010-09-01

    Quantum noise as well as anatomic and uptake variability in patient populations limits observer performance on a defect detection task in myocardial perfusion SPECT (MPS). The goal of this study was to investigate the relative importance of these two effects by varying acquisition time, which determines the count level, and assessing the change in performance on a myocardial perfusion (MP) defect detection task using both mathematical and human observers. We generated ten sets of projections of a simulated patient population with count levels ranging from 1/128 to around 15 times a typical clinical count level to simulate different levels of quantum noise. For the simulated population we modeled variations in patient, heart and defect size, heart orientation and shape, defect location, organ uptake ratio, etc. The projection data were reconstructed using the OS-EM algorithm with no compensation or with attenuation, detector response and scatter compensation (ADS). The images were then post-filtered and reoriented to generate short-axis slices. A channelized Hotelling observer (CHO) was applied to the short-axis images, and the area under the receiver operating characteristics (ROC) curve (AUC) was computed. For each noise level and reconstruction method, we optimized the number of iterations and cutoff frequencies of the Butterworth filter to maximize the AUC. Using the images obtained with the optimal iteration and cutoff frequency and ADS compensation, we performed human observer studies for four count levels to validate the CHO results. Both CHO and human observer studies demonstrated that observer performance was dependent on the relative magnitude of the quantum noise and the patient variation. When the count level was high, the patient variation dominated, and the AUC increased very slowly with changes in the count level for the same level of anatomic variability. When the count level was low, however, quantum noise dominated, and changes in the count level

  16. Electronic noise in CT detectors: Impact on image noise and artifacts.

    Science.gov (United States)

    Duan, Xinhui; Wang, Jia; Leng, Shuai; Schmidt, Bernhard; Allmendinger, Thomas; Grant, Katharine; Flohr, Thomas; McCollough, Cynthia H

    2013-10-01

    The objective of our study was to evaluate in phantoms the differences in CT image noise and artifact level between two types of commercial CT detectors: one with distributed electronics (conventional) and one with integrated electronics intended to decrease system electronic noise. Cylindric water phantoms of 20, 30, and 40 cm in diameter were scanned using two CT scanners, one equipped with integrated detector electronics and one with distributed detector electronics. All other scanning parameters were identical. Scans were acquired at four tube potentials and 10 tube currents. Semianthropomorphic phantoms were scanned to mimic the shoulder and abdominal regions. Images of two patients were also selected to show the clinical values of the integrated detector. Reduction of image noise with the integrated detector depended on phantom size, tube potential, and tube current. Scans that had low detected signal had the greatest reductions in noise, up to 40% for a 30-cm phantom scanned using 80 kV. This noise reduction translated into up to 50% in dose reduction to achieve equivalent image noise. Streak artifacts through regions of high attenuation were reduced by up to 45% on scans obtained using the integrated detector. Patient images also showed superior image quality for the integrated detector. For the same applied radiation level, the use of integrated electronics in a CT detector showed a substantially reduced level of electronic noise, resulting in reductions in image noise and artifacts, compared with detectors having distributed electronics.

  17. A design on low noise imaging circuit for SWIR sensor

    Science.gov (United States)

    Fan, Ben; Han, Zhixue; Ma, Fei; Dong, Shuli

    2016-11-01

    SWIR (Short Wave Infrared) imaging is an important imaging technology in space remote sensing. According to the characteristics of SWIR detector, the whole scheme of low noise imaging circuit is presented in this paper. For certain key circuit which noise is sensitive in the design, such as bias generation circuit, analysis of noise sources and calculation of theoretical noise value of actual circuit which is usually ignored in previous researches are proposed in order to estimate the level of circuit noise and optimize the circuit to reduce noise. The structure of analog filter amplifier circuit is also analyzed by introducing noise-factor analytic approach, based on the analysis result some design principles of the circuit are proposed. The noise suppression methods in the design are separately analyzed in both time suppression and space suppression; some specific methods for these two kinds of measures are listed in this paper. The final experiment results indicate that the low noise imaging circuit design based on above methods is reasonable and effective, the circuit has a higher SNR and can work normally at room temperature, and the whole design meets the original requirement of low noise. This low noise circuit for SWIR detector and its methods to analyze and calculate noise value are valuable examples for future similar designs.

  18. Expectations of two-level telegraph noise

    CERN Document Server

    Fern, J

    2006-01-01

    We find expectation values of functions of time integrated two-level telegraph noise. Expectation values of this noise are evaluated under simple control pulses. Both the Gaussian limit and $1/f$ noise are considered. We apply the results to a specific superconducting quantum computing example, which illustrates the use of this technique for calculating error probabilities.

  19. Image upconversion, a low noise infrared sensor?

    DEFF Research Database (Denmark)

    for detection of infrared images. Silicon cameras have much smaller intrinsic noise than their IR counter part- some models even offer near single photon detection capability. We demonstrate that an ordinary CCD camera combined with a low noise upconversion has superior noise characteristics when compared...

  20. Image upconversion - a low noise infrared sensor?

    DEFF Research Database (Denmark)

    Dam, Jeppe Seidelin; Tidemand-Lichtenberg, Peter; Pedersen, Christian

    for detection of infrared images. Silicon cameras have much smaller intrinsic noise than their IR counter part- some models even offer near single photon detection capability. We demonstrate that an ordinary CCD camera combined with a low noise upconversion has superior noise characteristics when compared...

  1. Impact of image noise levels, scout scan dose and lens shield on image quality and radiation exposure in z-axis dose-modulated neck MSCT on 16- and 64-slice Toshiba Aquilion scanners.

    Science.gov (United States)

    Bauknecht, Hans-Christian; Jach, Cornelia; Bohner, Georg; Meyer, Henning; Scheurig, Christian; Siebert, Eberhard; Klingebiel, Randolf

    2010-02-01

    Assessing the impact of image noise (IN) levels, scout scan dose and lens shield use on image quality and radiation exposure in neck multislice CT (MSCT) when using z-axis dose modulation (DM). Neck MSCT phantom studies with/without z-axis DM were performed by using different IN levels (S.D. 7.5-30HU) and scout scan tube currents (7.5-50mA) on Toshiba Aquilion scanners (16-/64-slice). Image quality indices were evaluated by two radiologists and radiation exposure parameters calculated. Cadaveric phantom measurements elucidated lens shield interactions with DM efficacy. The lowest dose scan protocol with diagnostic image quality was introduced into the clinical imaging routine and retrospectively evaluated in 20 age-matched patients undergoing neck MSCT with/without DM. The highest image noise level in DM neck studies with comparable image quality to standard neck CT amounted to 20HU, resulting in a mean tube current of 50mAs (CTDI(w) 6.3mGy). DM reduced effective dose by 35% and organ dose figures (lens, thyroid) by 33%. Scout scan dose lowering to 20mA resulted in an effective dose (ED) decrease of 0.06mSv (5%). Avoiding lens shield placement during scout scan effected an organ dose decrease of 20%. Overall contour sharpness and image contrast did not differ significantly (DM/without DM) whereas image noise was rated higher in DM neck CT studies (pz-Axis dose modulation, as assessed on 16- and 64-slice Toshiba Aquilion scanners, is effective and mandatory in neck MSCT. DM efficacy can be enhanced by optimising scout scan doses and lens shield use. Copyright (c) 2008 Elsevier Ireland Ltd. All rights reserved.

  2. Restoration for Noise Removal in Quantum Images

    Science.gov (United States)

    Liu, Kai; Zhang, Yi; Lu, Kai; Wang, Xiaoping

    2017-09-01

    Quantum computation has become increasingly attractive in the past few decades due to its extraordinary performance. As a result, some studies focusing on image representation and processing via quantum mechanics have been done. However, few of them have considered the quantum operations for images restoration. To address this problem, three noise removal algorithms are proposed in this paper based on the novel enhanced quantum representation model, oriented to two kinds of noise pollution (Salt-and-Pepper noise and Gaussian noise). For the first algorithm Q-Mean, it is designed to remove the Salt-and-Pepper noise. The noise points are extracted through comparisons with the adjacent pixel values, after which the restoration operation is finished by mean filtering. As for the second method Q-Gauss, a special mask is applied to weaken the Gaussian noise pollution. The third algorithm Q-Adapt is effective for the source image containing unknown noise. The type of noise can be judged through the quantum statistic operations for the color value of the whole image, and then different noise removal algorithms are used to conduct image restoration respectively. Performance analysis reveals that our methods can offer high restoration quality and achieve significant speedup through inherent parallelism of quantum computation.

  3. Practical ranges of loudness levels of various types of environmental noise, including traffic noise, aircraft noise, and industrial noise

    NARCIS (Netherlands)

    Salomons, E.M.; Janssen, S.A.

    2011-01-01

    In environmental noise control one commonly employs the A-weighted sound level as an approximate measure of the effect of noise on people. A measure that is more closely related to direct human perception of noise is the loudness level. At constant A-weighted sound level, the loudness level of a noi

  4. Impact of measurement precision and noise on superresolution image reconstruction.

    Science.gov (United States)

    Wood, Sally L; Lee, Shu-Ting; Yang, Gao; Christensen, Marc P; Rajan, Dinesh

    2008-04-01

    The performance of uniform and nonuniform detector arrays for application to the PANOPTES (processing arrays of Nyquist-limited observations to produce a thin electro-optic sensor) flat camera design is analyzed for measurement noise environments including quantization noise and Gaussian and Poisson processes. Image data acquired from a commercial camera with 8 bit and 14 bit output options are analyzed, and estimated noise levels are computed. Noise variances estimated from the measurement values are used in the optimal linear estimators for superresolution image reconstruction.

  5. Preparation of Ultracold Atom Clouds at the Shot Noise Level

    DEFF Research Database (Denmark)

    Gajdacz, M.; Hilliard, A. J.; Kristensen, Matias Ammitzbøll

    2016-01-01

    We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^6 is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔN... on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level....

  6. Preparation of Ultracold Atom Clouds at the Shot Noise Level.

    Science.gov (United States)

    Gajdacz, M; Hilliard, A J; Kristensen, M A; Pedersen, P L; Klempt, C; Arlt, J J; Sherson, J F

    2016-08-12

    We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^{6} is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔNatom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level.

  7. Preparation of Ultracold Atom Clouds at the Shot Noise Level

    DEFF Research Database (Denmark)

    Gajdacz, M.; Hilliard, A. J.; Kristensen, Matias Ammitzbøll

    2016-01-01

    We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^6 is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔN... on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level....

  8. Preparation of ultracold atom clouds at the shot noise level

    CERN Document Server

    Gajdacz, Miroslav; Kristensen, Mick A; Pedersen, Poul L; Klempt, Carsten; Arlt, Jan J; Sherson, Jacob F

    2016-01-01

    We prepare number stabilized ultracold clouds through the real-time analysis of non-destructive images and the application of feedback. In our experiments, the atom number ${N\\sim10^6}$ is determined by high precision Faraday imaging with uncertainty $\\Delta N$ below the shot noise level, i.e., $\\Delta N <\\sqrt{N}$. Based on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level.

  9. Underwater noise levels in UK waters

    Science.gov (United States)

    Merchant, Nathan D.; Brookes, Kate L.; Faulkner, Rebecca C.; Bicknell, Anthony W. J.; Godley, Brendan J.; Witt, Matthew J.

    2016-11-01

    Underwater noise from human activities appears to be rising, with ramifications for acoustically sensitive marine organisms and the functioning of marine ecosystems. Policymakers are beginning to address the risk of ecological impact, but are constrained by a lack of data on current and historic noise levels. Here, we present the first nationally coordinated effort to quantify underwater noise levels, in support of UK policy objectives under the EU Marine Strategy Framework Directive (MSFD). Field measurements were made during 2013-2014 at twelve sites around the UK. Median noise levels ranged from 81.5-95.5 dB re 1 μPa for one-third octave bands from 63-500 Hz. Noise exposure varied considerably, with little anthropogenic influence at the Celtic Sea site, to several North Sea sites with persistent vessel noise. Comparison of acoustic metrics found that the RMS level (conventionally used to represent the mean) was highly skewed by outliers, exceeding the 97th percentile at some frequencies. We conclude that environmental indicators of anthropogenic noise should instead use percentiles, to ensure statistical robustness. Power analysis indicated that at least three decades of continuous monitoring would be required to detect trends of similar magnitude to historic rises in noise levels observed in the Northeast Pacific.

  10. Preparation of ultracold atom clouds at the shot noise level

    DEFF Research Database (Denmark)

    Gajdacz, Miroslav; Hilliard, Andrew J.; Kristensen, Mick A.;

    2016-01-01

    We prepare number stabilized ultracold clouds through the real-time analysis of non-destructive images and the application of feedback. In our experiments, the atom number ${N\\sim10^6}$ is determined by high precision Faraday imaging with uncertainty $\\Delta N$ below the shot noise level, i...

  11. Noise characteristics of CT perfusion imaging: how does noise propagate from source images to final perfusion maps?

    Science.gov (United States)

    Li, Ke; Chen, Guang-Hong

    2016-03-01

    Cerebral CT perfusion (CTP) imaging is playing an important role in the diagnosis and treatment of acute ischemic strokes. Meanwhile, the reliability of CTP-based ischemic lesion detection has been challenged due to the noisy appearance and low signal-to-noise ratio of CTP maps. To reduce noise and improve image quality, a rigorous study on the noise transfer properties of CTP systems is highly desirable to provide the needed scientific guidance. This paper concerns how noise in the CTP source images propagates to the final CTP maps. Both theoretical deviations and subsequent validation experiments demonstrated that, the noise level of background frames plays a dominant role in the noise of the cerebral blood volume (CBV) maps. This is in direct contradiction with the general belief that noise of non-background image frames is of greater importance in CTP imaging. The study found that when radiation doses delivered to the background frames and to all non-background frames are equal, lowest noise variance is achieved in the final CBV maps. This novel equality condition provides a practical means to optimize radiation dose delivery in CTP data acquisition: radiation exposures should be modulated between background frames and non-background frames so that the above equality condition is satisïnAed. For several typical CTP acquisition protocols, numerical simulations and in vivo canine experiment demonstrated that noise of CBV can be effectively reduced using the proposed exposure modulation method.

  12. Noise problem in a primary level classroom

    Science.gov (United States)

    Beristain, Sergio

    2005-04-01

    Noise was assesed in a primary school in Mexico City (six to twelve year old kids), known as having significant noise inside classrooms. Several sources were identified, among them, traffic noise and noise from the sports and recreational areas, which were in the center of the school with the classrooms surrounding them. Reverberation was an issue, but not very significant. But in some cases the most annoying sound (noise), was the one made by the students within the classroom, inducing a number of reactions in the lecturers. These reactions ranged from shouting to give the lecture, through trying to control the students, to ignore them and let it go. Lecturer's voice levels were also measured, finding out a wide spread in normal speech voice level, and some of their experiences and comments were analyzed. Results are sumarized in this presentation.

  13. Noise levels of amusement ride operators.

    Science.gov (United States)

    Gilbertson, Lynn R; Thies, Liza E; Vosburgh, Donna J H

    2017-04-01

    One of the leading causes of noise-induced hearing loss is occupational noise exposure; however, little attention has been given to the exposure among amusement ride operators. According to the International Association of Amusement Parks and Attractions, 600,000 ride operators are employed in the U.S. The first objective of this descriptive study was to evaluate if ride operators were exposed to noise levels over 85 dB. The second objective was to classify the ride features that led to the highest noise levels. 136 rides were measured at 17 total amusement parks, county fairs, and festivals in southern Wisconsin and northern Illinois during summer 2015. A sound level meter recorded noise measurements as close in proximity to the ride operator as possible. Each ride was measured for two or three complete ride cycles, which included loading and operating the ride. The sound level meter was programmed to measure noise as recommended by the American Conference of Governmental Industrial Hygienists and with no threshold. 18% of rides measured had projected noise levels greater than American Conference of Governmental Industrial Hygienists recommendation of 85 dB. A repeated measures model was used to analyze the complete ride cycle decibel levels. The model found that traveling carnival rides had significantly higher levels compared to the stationary amusement park rides (p levels than those without midway music (p amusement ride operators would be at risk for noise induced hearing loss and would require a hearing conservation program if the 8-hr time weighted averages were to follow the same trends as the complete ride cycle levels.

  14. Noise simulation system for determining imaging conditions in digital radiography

    Science.gov (United States)

    Tanaka, R.; Ichikawa, K.; Matsubara, K.; Kawashima, H.

    2012-03-01

    Reduction of exposure dose and improvement in image quality can be expected to result from advances in the performance of imaging detectors. We propose a computerized method for determining optimized imaging conditions by use of simulated images. This study was performed to develop a prototype system for image noise and to ensure consistency between the resulting images and actual images. An RQA5 X-ray spectrum was used for determination of input-output characteristics of a flat-panel detector (FPD). The number of incident quantum to the detector per pixel (counts/pixel) was calculated according to the pixel size of the detector and the quantum number in RQA5 determined in IEC6220-1. The relationship among tube current-time product (mAs), exposure dose (C/kg) at the detector surface, the number of incident quanta (counts/pixel), and pixel values measured on the images was addressed, and a conversion function was then created. The images obtained by the FPD was converted into a map of incident quantum numbers and input into random-value generator to simulate image noise. In addition, graphic user interface was developed to observe images with changing image noise and exposure dose levels, which have trade-off relationship. Simulation images provided at different noise levels were compared with actual images obtained by the FPD system. The results indicated that image noise was simulated properly both in objective and subjective evaluation. The present system could allow us to determine necessary dose from image quality and also to estimate image quality from any exposure dose.

  15. Low-Noise CMOS Image Sensors for Radio-Molecular Imaging

    NARCIS (Netherlands)

    Chen, Y.

    2012-01-01

    This thesis presents the development of low-noise CMOS image sensors for radio-molecular imaging. The development is described in two directions: firstly, from the technology point of view to reduce the pixel noise level, and secondly from the design point of view to reduce the pixel readout circuit

  16. Sensitivity of Image Features to Noise in Conventional and Respiratory-Gated PET/CT Images of Lung Cancer: Uncorrelated Noise Effects.

    Science.gov (United States)

    Oliver, Jasmine A; Budzevich, Mikalai; Hunt, Dylan; Moros, Eduardo G; Latifi, Kujtim; Dilling, Thomas J; Feygelman, Vladimir; Zhang, Geoffrey

    2016-08-08

    The effect of noise on image features has yet to be studied in depth. Our objective was to explore how significantly image features are affected by the addition of uncorrelated noise to an image. The signal-to-noise ratio and noise power spectrum were calculated for a positron emission tomography/computed tomography scanner using a Ge-68 phantom. The conventional and respiratory-gated positron emission tomography/computed tomography images of 31 patients with lung cancer were retrospectively examined. Multiple sets of noise images were created for each original image by adding Gaussian noise of varying standard deviation equal to 2.5%, 4.0%, and 6.0% of the maximum intensity for positron emission tomography images and 10, 20, 50, 80, and 120 Hounsfield units for computed tomography images. Image features were extracted from all images, and percentage differences between the original image and the noise image feature values were calculated. These features were then categorized according to the noise sensitivity. The contour-dependent shape descriptors averaged below 4% difference in positron emission tomography and below 13% difference in computed tomography between noise and original images. Gray level size zone matrix features were the most sensitive to uncorrelated noise exhibiting average differences >200% for conventional and respiratory-gated images in computed tomography and 90% in positron emission tomography. Image feature differences increased as the noise level increased for shape, intensity, and gray-level co-occurrence matrix features in positron emission tomography and for gray-level co-occurrence matrix and gray-level size zone matrix features in conventional computed tomography. Investigators should be aware of the noise effects on image features.

  17. Dvadasham (Dodeca Edge Filter for Impulse Noise, Gaussian Noise, Quantum Noise Reduction in Images (A Generic Image Filter

    Directory of Open Access Journals (Sweden)

    Naveen R Chanukotimath

    2013-07-01

    Full Text Available All image processing techniques need to extract meaningful information from images. However, the noise generated during image acquisition and transmission degrades the human interpretation, or computer-aided analysis of these images. Therefore, denoising should be performed to improve the image quality for more accurate analysis and diagnosis, So we thought of designing a generic image filter that can be applicable to remove Impulse noise, Gaussian noise, Quantum noise. In this paper we propose a novel image denoising technique Dvadasham (Dodeca Edge Filter (DEF. We applied this filter on various images, obtained the results by measuring parameters like Standard Deviation, Homogeneity and compared it with the results of existing Fuzzy Filter. The results obtained with DEF are quite promising than Fuzzy Filter.

  18. An algorithm for noise correction of dual-energy computed tomography material density images.

    Science.gov (United States)

    Maia, Rafael Simon; Jacob, Christian; Hara, Amy K; Silva, Alvin C; Pavlicek, William; Ross, Mitchell J

    2015-01-01

    Dual-energy computed tomography (DECT) images can undergo a two-material decomposition process which results in two images containing material density information. Material density images obtained by that process result in images with increased pixel noise. Noise reduction in those images is desirable in order to improve image quality. A noise reduction algorithm for material density images was developed and tested. A three-level wavelet approach combined with the application of an anisotropic diffusion filter was used. During each level, the resulting noise maps are further processed, until the original resolution is reached and the final noise maps obtained. Our method works in image space and, therefore, can be applied to any type of material density images obtained from any DECT vendor. A quantitative evaluation of the noise-reduced images using the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and 2D noise power spectrum was done to quantify the improvements. The noise reduction algorithm was applied to a set of images resulting in images with higher SNR and CNR than the raw density images obtained by the decomposition process. The average improvement in terms of SNR gain was about 49 % while CNR gain was about 52 %. The difference between the raw and filtered regions of interest mean values was far from reaching statistical significance (minimum [Formula: see text], average [Formula: see text]). We have demonstrated through a series of quantitative analyses that our novel noise reduction algorithm improves the image quality of DECT material density images.

  19. Noise Reduction for CFA Image Sensors Exploiting HVS Behaviour

    Directory of Open Access Journals (Sweden)

    Angelo Bosco

    2009-03-01

    Full Text Available This paper presents a spatial noise reduction technique designed to work on CFA (Color Filtering Array data acquired by CCD/CMOS image sensors. The overall processing preserves image details using some heuristics related to the HVS (Human Visual System; estimates of local texture degree and noise levels are computed to regulate the filter smoothing capability. Experimental results confirm the effectiveness of the proposed technique. The method is also suitable for implementation in low power mobile devices with imaging capabilities such as camera phones and PDAs.

  20. PERFORMANCE OF IMPULSE NOISE DETECTION METHODS IN REMOTE SENSING IMAGES

    Directory of Open Access Journals (Sweden)

    Mrs.V.RADHIKA,

    2010-09-01

    Full Text Available Remote sensing (RS images are affected by different types of noises like Gaussian noise, speckle noise and impulse noise. These noises are introduced into the RS images during acquisition or transmission process. The main challenge in impulse noise removal is to suppress the noise as well as to preserve the details (edges. Removal ofthe impulse noise is done by two stages: detection of noisy pixel and replacement of that pixel. Detecting and Removing or reducing impulse noise is a very active research area in image processing. In this paper three different existing detection methods are discussed with the intension of developing a new one.

  1. Evaluation of color error and noise on simulated images

    Science.gov (United States)

    Mornet, Clémence; Vaillant, Jérôme; Decroux, Thomas; Hérault, Didier; Schanen, Isabelle

    2010-01-01

    The evaluation of CMOS sensors performance in terms of color accuracy and noise is a big challenge for camera phone manufacturers. On this paper, we present a tool developed with Matlab at STMicroelectronics which allows quality parameters to be evaluated on simulated images. These images are computed based on measured or predicted Quantum Efficiency (QE) curves and noise model. By setting the parameters of integration time and illumination, the tool optimizes the color correction matrix (CCM) and calculates the color error, color saturation and signal-to-noise ratio (SNR). After this color correction optimization step, a Graphics User Interface (GUI) has been designed to display a simulated image at a chosen illumination level, with all the characteristics of a real image taken by the sensor with the previous color correction. Simulated images can be a synthetic Macbeth ColorChecker, for which reflectance of each patch is known, or a multi-spectral image, described by the reflectance spectrum of each pixel or an image taken at high-light level. A validation of the results has been performed with ST under development sensors. Finally we present two applications one based on the trade-offs between color saturation and noise by optimizing the CCM and the other based on demosaicking SNR trade-offs.

  2. A Review Paper : Noise Models in Digital Image Processing

    Directory of Open Access Journals (Sweden)

    Ajay Kumar Boyat

    2015-04-01

    Full Text Available Noise is always presents in digital images during image acquisition, coding, transmission, and processing steps. Noise is very difficult to remove it from the digital images without the prior knowledge of noise model. That is why, review of noise models are essential in the study of image denoising techniques. In this paper, we express a brief overview of various noise models. These noise models can be selected by analysis of their origin. In this way, we present a complete and quantitative analysis of noise models available in digital images.

  3. Seismic noise level variation in South Korea

    Science.gov (United States)

    Sheen, D.; Shin, J.

    2008-12-01

    The variations of seismic background noise in South Korea have been investigated by means of power spectral analysis. The Korea Institute of Geoscience and Mineral Resources (KIGAM) and the Korea Meteorological Administation (KMA) have national wide seismic networks in South Korea, and, in the end of 2007, there are 30 broadband stations which have been operating for more than a year. In this study, we have estimated the power spectral density of seismic noise for 30 broadband stations from 2005 to 2007. Since we estimate PSDs from a large dataset of continuous waveform in this study, a robust PSD estimate of McNamara and Buland (2004) is used. In the frequency range 1-5 Hz, the diurnal variations of noise are observed at most of stations, which are especially larger at coastal stations and at insular than at inland. Some stations shows daily difference of diurnal variations, which represents that cultural activities contribute to the noise level of a station. The variation of number of triggered stations, however, shows that cultural noise has little influence on the detection capability of seismic network in South Korea. Seasonal variations are observed well in the range 0.1-0.5 Hz, while much less found in the frequency range 1-5 Hz. We observed that strong peaks in the range 0.1-0.5 Hz occur at the summer when Pacific typhoons are close to the Korean Peninsula.

  4. Noise Reduction Effect of Multiple-Sampling-Based Signal-Readout Circuits for Ultra-Low Noise CMOS Image Sensors.

    Science.gov (United States)

    Kawahito, Shoji; Seo, Min-Woong

    2016-11-06

    This paper discusses the noise reduction effect of multiple-sampling-based signal readout circuits for implementing ultra-low-noise image sensors. The correlated multiple sampling (CMS) technique has recently become an important technology for high-gain column readout circuits in low-noise CMOS image sensors (CISs). This paper reveals how the column CMS circuits, together with a pixel having a high-conversion-gain charge detector and low-noise transistor, realizes deep sub-electron read noise levels based on the analysis of noise components in the signal readout chain from a pixel to the column analog-to-digital converter (ADC). The noise measurement results of experimental CISs are compared with the noise analysis and the effect of noise reduction to the sampling number is discussed at the deep sub-electron level. Images taken with three CMS gains of two, 16, and 128 show distinct advantage of image contrast for the gain of 128 (noise(median): 0.29 e(-)rms) when compared with the CMS gain of two (2.4 e(-)rms), or 16 (1.1 e(-)rms).

  5. Noise Reduction Effect of Multiple-Sampling-Based Signal-Readout Circuits for Ultra-Low Noise CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Shoji Kawahito

    2016-11-01

    Full Text Available This paper discusses the noise reduction effect of multiple-sampling-based signal readout circuits for implementing ultra-low-noise image sensors. The correlated multiple sampling (CMS technique has recently become an important technology for high-gain column readout circuits in low-noise CMOS image sensors (CISs. This paper reveals how the column CMS circuits, together with a pixel having a high-conversion-gain charge detector and low-noise transistor, realizes deep sub-electron read noise levels based on the analysis of noise components in the signal readout chain from a pixel to the column analog-to-digital converter (ADC. The noise measurement results of experimental CISs are compared with the noise analysis and the effect of noise reduction to the sampling number is discussed at the deep sub-electron level. Images taken with three CMS gains of two, 16, and 128 show distinct advantage of image contrast for the gain of 128 (noise(median: 0.29 e−rms when compared with the CMS gain of two (2.4 e−rms, or 16 (1.1 e−rms.

  6. Reduction of noise in medullary renograms from dynamic MR images.

    Science.gov (United States)

    Giele, E L; de Priester, J A; Blom, J A; den Boer, J A; van Engelshoven, J M; Hasman, A

    2000-02-01

    Dynamic magnetic resonance images of the kidney can be used to acquire separate renograms of the cortex and medulla. A high-quality cortical renogram can be determined directly from a region of interest (ROI) placed in the cortex. Due to partial volume effects, part of the signal from a ROI placed in the medulla is caused by cortical tissue. By subtracting a fraction of the cortical signal from the cortico-medullary signal, a purer medullary renogram can be obtained. A side effect of this subtraction is an increase in noise level. The noise level increases with larger partial volume fractions. Using a matched image filter, it is possible to exclude those areas from the ROI that have a high partial volume content, thus reducing the amount of cortical signal that has to be separated from the medullary signal. Noise reductions of up to 50% have been achieved in the medullary renogram, with an average reduction of 23%.

  7. Noise Removal in SAR Images using Orthonormal Ridgelet Transform

    Directory of Open Access Journals (Sweden)

    A. Ravi,

    2015-05-01

    Full Text Available Development in the field of image processing for reducing speckle noise from digital images/satellite images is a challenging task for image processing applications. Previously many algorithms were proposed to de-speckle the noise in digital images. Here in this article we are presenting experimental results on de-speckling of Synthetic Aperture RADAR (SAR images. SAR images have wide applications in remote sensing and mapping the surfaces of all planets. SAR can also be implemented as "inverse SAR" by observing a moving target over a substantial time with a stationary antenna. Hence denoising of SAR images is an essential task for viewing the information. Here we introduce a transformation technique called ―Ridgelet‖, which is an extension level of wavelet. Ridgelet analysis can be done in the similar way how wavelet analysis was done in the Radon domain as it translates singularities along lines into point singularities under different frequencies. Simulation results were show cased for proving that proposed work is more reliable than compared to other despeckling processes, and the quality of de-speckled image is measured in terms of Peak Signal to Noise Ratio and Mean Square Error.

  8. Algorithm for image registration and clutter and jitter noise reduction

    Energy Technology Data Exchange (ETDEWEB)

    Brower, K.L.

    1997-02-01

    This paper presents an analytical, computational method whereby two-dimensional images of an optical source represented in terms of a set of detector array signals can be registered with respect to a reference set of detector array signals. The detector image is recovered from the detector array signals and represented over a local region by a fourth order, two-dimensional taylor series. This local detector image can then be registered by a general linear transformation with respect to a reference detector image. The detector signal in the reference frame is reconstructed by integrating this detector image over the respective reference pixel. For cases in which the general linear transformation is uncertain by up to plus-or-minus two pixels, the general linear transformation can be determined by least squares fitting the detector image to the reference detector image. This registration process reduces clutter and jitter noise to a level comparable to the electronic noise level of the detector system. Test results with and without electronic noise using an analytical test function are presented.

  9. Noise levels in an urban Asian school environment.

    Science.gov (United States)

    Chan, Karen M K; Li, Chi Mei; Ma, Estella P M; Yiu, Edwin M L; McPherson, Bradley

    2015-01-01

    Background noise is known to adversely affect speech perception and speech recognition. High levels of background noise in school classrooms may affect student learning, especially for those pupils who are learning in a second language. The current study aimed to determine the noise level and teacher speech-to-noise ratio (SNR) in Hong Kong classrooms. Noise level was measured in 146 occupied classrooms in 37 schools, including kindergartens, primary schools, secondary schools and special schools, in Hong Kong. The mean noise levels in occupied kindergarten, primary school, secondary school and special school classrooms all exceeded recommended maximum noise levels, and noise reduction measures were seldom used in classrooms. The measured SNRs were not optimal and could have adverse implications for student learning and teachers' vocal health. Schools in urban Asian environments are advised to consider noise reduction measures in classrooms to better comply with recommended maximum noise levels for classrooms.

  10. Noise levels in an urban Asian school environment

    OpenAIRE

    Chan, Karen M.K.; Chi Mei Li; Ma, Estella P.M.; Yiu, Edwin M.L.; Bradley McPherson

    2015-01-01

    Background noise is known to adversely affect speech perception and speech recognition. High levels of background noise in school classrooms may affect student learning, especially for those pupils who are learning in a second language. The current study aimed to determine the noise level and teacher speech-to-noise ratio (SNR) in Hong Kong classrooms. Noise level was measured in 146 occupied classrooms in 37 schools, including kindergartens, primary schools, secondary schools and special...

  11. Airframe noise measurements by acoustic imaging

    Science.gov (United States)

    Kendall, J. M.

    1977-01-01

    Studies of the noise produced by flow past wind tunnel models are presented. The central objective of these is to find the specific locations within a flow which are noisy, and to identify the fluid dynamic processes responsible, with the expectation that noise reduction principles will be discovered. The models tested are mostly simple shapes which result in types of flow that are similar to those occurring on, for example, aircraft landing gear and wheel cavities. A model landing gear and a flap were also tested. Turbulence has been intentionally induced as appropriate in order to simulate full-scale effects more closely. The principal technique involves use of a highly directional microphone system which is scanned about the flow field to be analyzed. The data so acquired are presented as a pictorial image of the noise source distribution. An important finding is that the noise production is highly variable within a flow field and that sources can be attributed to various fluid dynamic features of the flow. Flow separation was not noisy, but separation closure usually was.

  12. Noise spatial nonuniformity and the impact of statistical image reconstruction in CT myocardial perfusion imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lauzier, Pascal Theriault; Tang Jie; Speidel, Michael A.; Chen Guanghong [Department of Medical Physics, University of Wisconsin-Madison, Madison, Wisconsin 53705-2275 (United States); Department of Medical Physics and Department of Radiology, University of Wisconsin-Madison, Madison, Wisconsin 53705-2275 (United States)

    2012-07-15

    of noise. This spatial nonuniformity led to large fluctuations in the temporal direction. In the numerical phantom study, the level of noise was shown to vary by as much as 87% within a given image, and as much as 110% between different time frames for a ROI far from isocenter. The spatially nonuniform noise pattern was shown to correlate with the source trajectory and the object structure. In contrast, images reconstructed using SIR showed a highly uniform spatial distribution of noise, leading to smaller unexpected noise fluctuations in the temporal direction when a short scan angular range was used. In the numerical phantom study, the noise varied by less than 37% within a given image, and by less than 20% between different time frames. Also, the noise standard deviation in SIR images was on average half of that of FBP images. In the in vivo studies, the deviation observed between quantitative perfusion metrics measured from low-dose scans and high-dose scans was mitigated when SIR was used instead of FBP to reconstruct images. Conclusions: (1) Images reconstructed using FBP suffered from nonuniform spatial noise levels. This nonuniformity is another manifestation of the detrimental effects caused by short-scan reconstruction in CT MPI. (2) Images reconstructed using SIR had a much lower and more uniform noise level and thus can be used as a potential solution to address the FBP nonuniformity. (3) Given the improvement in the accuracy of the perfusion metrics when using SIR, it may be desirable to use a statistical reconstruction framework to perform low-dose dynamic CT MPI.

  13. Noise in sub-micron CMOS image sensors

    NARCIS (Netherlands)

    Wang, X.

    2008-01-01

    CMOS image sensors are devices that convert illumination signals (light intensity) into electronic signals. The goal of this thesis has been to analyze dominate noise sources in CMOS imagers and to improve the image quality by reducing the noise generated in the CMOS image sensor pixels.

  14. Effective FCM noise clustering algorithms in medical images.

    Science.gov (United States)

    Kannan, S R; Devi, R; Ramathilagam, S; Takezawa, K

    2013-02-01

    The main motivation of this paper is to introduce a class of robust non-Euclidean distance measures for the original data space to derive new objective function and thus clustering the non-Euclidean structures in data to enhance the robustness of the original clustering algorithms to reduce noise and outliers. The new objective functions of proposed algorithms are realized by incorporating the noise clustering concept into the entropy based fuzzy C-means algorithm with suitable noise distance which is employed to take the information about noisy data in the clustering process. This paper presents initial cluster prototypes using prototype initialization method, so that this work tries to obtain the final result with less number of iterations. To evaluate the performance of the proposed methods in reducing the noise level, experimental work has been carried out with a synthetic image which is corrupted by Gaussian noise. The superiority of the proposed methods has been examined through the experimental study on medical images. The experimental results show that the proposed algorithms perform significantly better than the standard existing algorithms. The accurate classification percentage of the proposed fuzzy C-means segmentation method is obtained using silhouette validity index.

  15. Noise reduction in selective computational ghost imaging using genetic algorithm

    Science.gov (United States)

    Zafari, Mohammad; Ahmadi-Kandjani, Sohrab; Kheradmand, Reza

    2017-03-01

    Recently, we have presented a selective computational ghost imaging (SCGI) method as an advanced technique for enhancing the security level of the encrypted ghost images. In this paper, we propose a modified method to improve the ghost image quality reconstructed by SCGI technique. The method is based on background subtraction using genetic algorithm (GA) which eliminates background noise and gives background-free ghost images. Analyzing the universal image quality index by using experimental data proves the advantage of this modification method. In particular, the calculated value of the image quality index for modified SCGI over 4225 realization shows an 11 times improvement with respect to SCGI technique. This improvement is 20 times in comparison to conventional CGI technique.

  16. Resolution and noise in ghost imaging with classical thermal light

    Institute of Scientific and Technical Information of China (English)

    Cheng Jing; Han Shen-Sheng; Yan Yi-Jing

    2006-01-01

    The resolution and classical noise in ghost imaging with a classical thermal light are investigated theoretically. For ghost imaging with a Gaussian Schell model source, the dependences of the resolution and noise on the spatial coherence of the source and the aperture in the imaging system are discussed and demonstrated by using numerical simulations.The results show that an incoherent source and a large aperture will lead to a good image quality and small noise.

  17. Sub-atom shot noise Faraday imaging of ultracold atom clouds

    CERN Document Server

    Kristensen, Mick A; Pedersen, Poul L; Klempt, Carsten; Sherson, Jacob F; Arlt, Jan J; Hilliard, Andrew J

    2016-01-01

    We demonstrate that a dispersive imaging technique based on the Faraday effect can measure the atom number in a large, ultracold atom cloud with a precision below the atom shot noise level. The minimally destructive character of the technique allows us to take multiple images of the same cloud, which enables sub-atom shot noise measurement precision of the atom number and allows for an in situ determination of the measurement precision. We have developed a noise model that quantitatively describes the noise contributions due to photon shot noise in the detected light and the noise associated with single atom loss. This model contains no free parameters and is calculated through an analysis of the fluctuations in the acquired images. For clouds containing $N \\sim 5 \\times 10^6$ atoms, we achieve a precision more than a factor of two below the atom shot noise level.

  18. Sub-atom shot noise Faraday imaging of ultracold atom clouds

    Science.gov (United States)

    Kristensen, M. A.; Gajdacz, M.; Pedersen, P. L.; Klempt, C.; Sherson, J. F.; Arlt, J. J.; Hilliard, A. J.

    2017-02-01

    We demonstrate that a dispersive imaging technique based on the Faraday effect can measure the atom number in a large, ultracold atom cloud with a precision below the atom shot noise level. The minimally destructive character of the technique allows us to take multiple images of the same cloud, which enables sub-atom shot noise measurement precision of the atom number and allows for an in situ determination of the measurement precision. We have developed a noise model that quantitatively describes the noise contributions due to photon shot noise in the detected light and the noise associated with single atom loss. This model contains no free parameters and is calculated through an analysis of the fluctuations in the acquired images. For clouds containing N∼ 5× {10}6 atoms, we achieve a precision more than a factor of two below the atom shot noise level.

  19. Existing Noise Level at Railway Stations in Malaysia

    Directory of Open Access Journals (Sweden)

    Shahidan Shahiron

    2017-01-01

    Full Text Available Railway transportation known as one of the most environmental friendly transportation mode. However, the significance problems of railway transportation are noise pollution and negatively impact the wellbeing of the whole community. Unfortunately, there has been lack of public awareness about the noise level produce by the railway transportation in Malaysia. This study investigates the noise level produced by railway transportation in Malaysia specifically by Keretapi Tanah Melayu Berhad (KTMB. Methods of collecting existing noise level at railway stations in Malaysia are briefly discussed in this study. The finding indicates that the noise level produced by the railway transportation in Malaysia which is by KTMB is considered as dangerous to human being and also exceed the noise limit that has been assigned by Department of Environment Ministry of Natural Resources and Environment of Malaysia. A better noise barrier and improved material should be developed to mitigate the existing noise level produced by railway transportations in Malaysia.

  20. Noise in laser speckle correlation and imaging techniques

    CERN Document Server

    Skipetrov, Sergey E; Cerbino, Roberto; Zakharov, Pavel; Weber, Bruno; Scheffold, Frank

    2010-01-01

    We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent pixels as well as to the effective time averaging (due to the finite sampling time) and spatial averaging (due to the finite pixel size). Our results provide a guide to estimation of noise level in such applications as the multi-speckle dynamic light scattering, time-resolved correlation spectroscopy, speckle visibility spectroscopy, laser speckle imaging etc.

  1. Improvising MSN and PSNR for Finger-Print Image noised by GAUSSIAN and SALT & PEPPER

    Directory of Open Access Journals (Sweden)

    Ashish kumar Dass

    2012-08-01

    Full Text Available Image de-noising is a vital concern in image processing. Out of different available method wavelet thresolding method is one of the important approaches for image de-noises. In this paper we propose an adaptive method of image de-noising in the wavelet sub-band domain assuming the images to be contaminated with noise based on threshold estimation for each sub-band. Under this framework the proposed technique estimates the threshold level by apply sub-band of each decomposition level. This paper entails the development of a new MATLAB function based on our algorithm. The experimental evaluation of our proposition reveals that our method removes noise more effectively than the in-built function provided by MATLAB .One of its applications for Fingerprint de-noise due to importance of fingerprint for day-to-day life especially in computer security purposes. Fingerprint acts as a vital role for user authentication as it is unique and not duplicated. Unfortunately allusion Fingerprints may get corrupted and polluted with noise during possession, transmission or retrieval from storage media. Many image processing algorithms such as pattern recognition need a clean fingerprint image to work effectively which in turn needs effective ways of de-noising such images. We apply our proposed algorithm and compare other traditional algorithms for different noises.

  2. BL_Wiener Denoising Method for Removal of Speckle Noise in Ultrasound Image

    Directory of Open Access Journals (Sweden)

    Suhaila Sari

    2015-02-01

    Full Text Available Medical imaging techniques are extremely important tools in medical diagnosis. One of these important imaging techniques is ultrasound imaging. However, during ultrasound image acquisition process, the quality of image can be degraded due to corruption by speckle noise. The enhancement of ultrasound images quality from the 2D ultrasound imaging machines is expected to provide medical practitioners more reliable medical images in their patients’ diagnosis. However, developing a denoising technique which could remove noise effectively without eliminating the image’s edges and details is still an ongoing issue. The objective of this paper is to develop a new method that is capable to remove speckle noise from the ultrasound image effectively. Therefore, in this paper we proposed the utilization of Bilateral Filter and Adaptive Wiener Filter (BL_Wiener denoising method for images corrupted by speckle noise. Bilateral Filter is a non-linear filter effective in removing noise, while Adaptive Wiener Filter balances the tradeoff between inverse filtering and noise smoothing by removing additive noise while inverting blurring. From our simulation results, it is found that the BL_Wiener method has improved between 0.89 [dB] to 3.35 [dB] in terms of PSNR for test images in different noise levels in comparison to conventional methods.

  3. A variational image restoration with spatially varying noise

    Science.gov (United States)

    Bao, Zheng; Bai, Hua; Liu, Ruihua; Shen, Chaomin

    2008-10-01

    The noise in natural images sometimes changes according to imaging mechanism or local image information. This is called spatially varying noise. It is obvious that classical variational denoising algorithms such as the Rudin-Osher-Fatemi model are not suitable for this kind of noise. We propose a variational method to remove this spatially varying noise based on the estimation of local variance for a given image, such that high noise regions are smoothed meanwhile the textures and certain details in low noise regions are preserved. Moreover, we give the proof of existence of the minimizer of our proposed functional. The experimental results show visual improvement and high signal-to-noise ratio over other variational denoising models.

  4. Ambient noise levels and detection threshold in Norway

    Science.gov (United States)

    Demuth, Andrea; Ottemöller, Lars; Keers, Henk

    2016-07-01

    Ambient seismic noise is caused by a number of sources in specific frequency bands. The quantification of ambient noise makes it possible to evaluate station and network performance. We evaluate noise levels in Norway from the 2013 data set of the Norwegian National Seismic Network as well as two temporary deployments. Apart from the station performance, we studied the geographical and temporal variations, and developed a local noise model for Norway. The microseism peaks related to the ocean are significant in Norway. We, therefore, investigated the relationship between oceanic weather conditions and noise levels. We find a correlation of low-frequency noise (0.125-0.25 Hz) with wave heights up to 900 km offshore. High (2-10 Hz) and intermediate (0.5-5 Hz) frequency noise correlates only up to 450 km offshore with wave heights. From a geographic perspective, stations in southern Norway show lower noise levels for low frequencies due to a larger distance to the dominant noise sources in the North Atlantic. Finally, we studied the influence of high-frequency noise levels on earthquake detectability and found that a noise level increase of 10 dB decreases the detectability by 0.5 magnitude units. This method provides a practical way to consider noise variations in detection maps.

  5. Kurtosis corrected sound pressure level as a noise metric for risk assessment of occupational noises.

    Science.gov (United States)

    Goley, G Steven; Song, Won Joon; Kim, Jay H

    2011-03-01

    Current noise guidelines use an energy-based noise metric to predict the risk of hearing loss, and thus ignore the effect of temporal characteristics of the noise. The practice is widely considered to underestimate the risk of a complex noise environment, where impulsive noises are embedded in a steady-state noise. A basic form for noise metrics is designed by combining the equivalent sound pressure level (SPL) and a temporal correction term defined as a function of kurtosis of the noise. Several noise metrics are developed by varying this basic form and evaluated utilizing existing chinchilla noise exposure data. It is shown that the kurtosis correction term significantly improves the correlation of the noise metric with the measured hearing losses in chinchillas. The average SPL of the frequency components of the noise that define the hearing loss with a kurtosis correction term is identified as the best noise metric among tested. One of the investigated metrics, the kurtosis-corrected A-weighted SPL, is applied to a human exposure study data as a preview of applying the metrics to human guidelines. The possibility of applying the noise metrics to human guidelines is discussed.

  6. Road Traffic Noise Level Assessment at an Institutional Area

    Directory of Open Access Journals (Sweden)

    Dev Swaroop

    2014-09-01

    Full Text Available Unplanned and rapid urbanization, industrialization, increasing number of vehicles, poor traffic management, poor road condition etc. are the major causes of higher noise levels in most of the Indian cities. Prolonged exposure to higher noise levels can lead to irreversible Noise Induced Hearing Loss (NIHL. Noise-induced hearing loss is contributing one-third to the total persons suffering from hearing loss in every country in the world. The present study aims at measuring the noise levels in the university campus to analyze the current situation and suggesting noise control measures to be adopted in University campus and along MMA Jauhar Marg. The numbers of vehicles were counted during November 17-21, 2012 and noise levels were measured at various pre decided locations. The traffic load in horizon years 2013, 2017, 2022, 2027 and 2032 on the MMA Jauhar Marg Road is predicted on the basis of observed traffic data and expected annual growth rate as 8.0% for pre Metro and 3.5% for post Metro. The noise levels were measured using Larson Davis Model 831 Class 1 Sound Level Meter on both sides of road at foot paths along MMA Jauhar Marg and at various receptor locations inside the different buildings in the university campus. Model RLS-90 is used for prediction of noise levels. The prediction of metro noise is carried out using statistical calculations. The combined noise levels were compared with standard criteria for silent zone and found on higher side. Installation of environment noise barrier is suggested as one of the noise control measure to be adopted along MMA Jauhar Marg and along metro viaduct to save students and staff from exposure of higher noise levels.

  7. Design considerations for a low-noise CMOS image sensor

    Science.gov (United States)

    González-Márquez, Ana; Charlet, Alexandre; Villegas, Alberto; Jiménez-Garrido, Francisco; Medeiro, Fernando; Domínguez-Castro, Rafael; Rodríguez-Vázquez, Ángel

    2015-03-01

    This paper reports a Low-Noise CMOS Image Sensor. Low-noise operation is achieved owing to the combination of a noise-enhanced pixel, the use of a two-step ADC architecture and the analysis, and the optimization thereof, of the noise contributed by the readout channel. The paper basically gathers the sensor architecture, the ADC converter architecture, the outcome of the noise analysis and some basic characterization data. The general low-noise design framework is discussed in the companion presentation.

  8. Comparison of Image Processing Techniques using Random Noise Radar

    Science.gov (United States)

    2014-03-27

    pseudo - random noise . The noise waveforms employed by the radar systems 9 are generally white and Gaussian, that is, the waveform’s power...2010. [5] Hardin, Joshua A. “Information Encoding on a Pseudo Random Noise Radar Waveform”, 2013. [6] Jackson, Julie A. “EENG 668/714 Advanced Radar ...COMPARISON OF IMAGE PROCESSING TECHNIQUES USING RANDOM NOISE RADAR THESIS Jesse Robert B. Cruz, Capt, USAF AFIT-ENG-14-M-22 DEPARTMENT OF THE

  9. On the loss-of-correlation due to PIV image noise

    Science.gov (United States)

    Scharnowski, Sven; Kähler, Christian J.

    2016-07-01

    The effect of image noise on the uncertainty of velocity fields measured with particle image velocimetry (PIV) is still an unsolved problem. Image noise reduces the correlation signal and thus affects the estimation of the particle image displacement. However, a systematic quantification of the effect of the noise level on the loss-of-correlation is missing. In this work, a new method is proposed to estimate the loss-of-correlation due to image noise F_{σ } from the autocorrelation function of PIV images. Furthermore, a new definition of the signal-to-noise ratio (SNR) for PIV images is suggested, which results in a bijective relation between F_{σ } and SNR. Based on the newly defined SNR, it becomes possible to estimate the signal level and the noise level itself. The presented method is very general because the estimation of F_{σ } and SNR works independently of various parameters, including the particle image intensity, the particle image density, the particle image size, the image noise distributions and the laser light-sheet profile. The findings lead to an extension of the fundamental PIV equation N=NI FI FO F_{Δ } and enable PIV users to optimize their measurement setup with respect to the image noise and not only based on the loss-of-correlation due to in-plane motion, out-of-plane motion and displacement gradients. Furthermore, the new definition of SNR allows for a characterization and comparison of PIV images. The new approaches are validated by using synthetic images, and the predictions are confirmed by using experimental data.

  10. Column-Parallel Correlated Multiple Sampling Circuits for CMOS Image Sensors and Their Noise Reduction Effects

    Directory of Open Access Journals (Sweden)

    Shoji Kawahito

    2010-10-01

    Full Text Available For low-noise complementary metal-oxide-semiconductor (CMOS image sensors, the reduction of pixel source follower noises is becoming very important. Column-parallel high-gain readout circuits are useful for low-noise CMOS image sensors. This paper presents column-parallel high-gain signal readout circuits, correlated multiple sampling (CMS circuits and their noise reduction effects. In the CMS, the gain of the noise cancelling is controlled by the number of samplings. It has a similar effect to that of an amplified CDS for the thermal noise but is a little more effective for 1/f and RTS noises. Two types of the CMS with simple integration and folding integration are proposed. In the folding integration, the output signal swing is suppressed by a negative feedback using a comparator and one-bit D-to-A converter. The CMS circuit using the folding integration technique allows to realize a very low-noise level while maintaining a wide dynamic range. The noise reduction effects of their circuits have been investigated with a noise analysis and an implementation of a 1Mpixel pinned photodiode CMOS image sensor. Using 16 samplings, dynamic range of 59.4 dB and noise level of 1.9 e- for the simple integration CMS and 75 dB and 2.2 e- for the folding integration CMS, respectively, are obtained.

  11. Column-Parallel Correlated Multiple Sampling Circuits for CMOS Image Sensors and Their Noise Reduction Effects

    Science.gov (United States)

    Suh, Sungho; Itoh, Shinya; Aoyama, Satoshi; Kawahito, Shoji

    2010-01-01

    For low-noise complementary metal-oxide-semiconductor (CMOS) image sensors, the reduction of pixel source follower noises is becoming very important. Column-parallel high-gain readout circuits are useful for low-noise CMOS image sensors. This paper presents column-parallel high-gain signal readout circuits, correlated multiple sampling (CMS) circuits and their noise reduction effects. In the CMS, the gain of the noise cancelling is controlled by the number of samplings. It has a similar effect to that of an amplified CDS for the thermal noise but is a little more effective for 1/f and RTS noises. Two types of the CMS with simple integration and folding integration are proposed. In the folding integration, the output signal swing is suppressed by a negative feedback using a comparator and one-bit D-to-A converter. The CMS circuit using the folding integration technique allows to realize a very low-noise level while maintaining a wide dynamic range. The noise reduction effects of their circuits have been investigated with a noise analysis and an implementation of a 1Mpixel pinned photodiode CMOS image sensor. Using 16 samplings, dynamic range of 59.4 dB and noise level of 1.9 e− for the simple integration CMS and 75 dB and 2.2 e− for the folding integration CMS, respectively, are obtained. PMID:22163400

  12. Noise level analysis in adult intensive care unit

    Directory of Open Access Journals (Sweden)

    Helen Katharine Christofel

    2016-01-01

    Full Text Available Objective: to analyze the noise level in adult intensive care unit. Methods: a quantitative study, in which the sound levels of the intensive care unit have been assessed by means of a decibel meter. Results: comparing the groups, there was a reduction in noise levels in both periods studied, but only in the afternoon there was a statistically significant difference (p<0.05. The health professionals pointed out that the unit had moderate noise, coming mainly from equipment and professionals. Conclusion: adjusting the ventilator alarms contributed to the reduction of noise levels in the unit, and there was the perception that it is a moderate noise environment, although the noise levels in decibels observed were above the recommended values.

  13. Noise-assisted correlation algorithm for suppressing noise-induced artifacts in ultrasonic Nakagami images.

    Science.gov (United States)

    Tsui, Po-Hsiang; Yeh, Chih-Kuang; Huang, Chih-Chung

    2012-05-01

    Ultrasonic Nakagami images can complement conventional B-mode images for scatterer characterization. White noise in anechoic areas leads to artifacts that affect the Nakagami image to characterize tissues. Artifact removal requires rejection of the white noise without deforming the backscattered waveform. This study proposes a noise-assisted correlation algorithm (NCA) and carries out simulations, phantom experiments, and clinical measurements to validate its feasibility and practicality. The simulation results show that the NCA can reject white noise in an anechoic area without any deformation of the backscattered waveforms. The results obtained from phantoms and tissues further demonstrate that the proposed NCA can suppress a Nakagami image artifact without changing the texture of the Nakagami image of the scattering background. The NCA is an essential algorithm to construct artifact-free Nakagami image for correctly reflecting scatterer properties of biological tissues.

  14. History Document Image Background Noise and Removal Methods

    Directory of Open Access Journals (Sweden)

    Ganchimeg.G

    2015-12-01

    Full Text Available It is common for archive libraries to provide public access to historical and ancient document image collections. It is common for such document images to require specialized processing in order to remove background noise and become more legible. Document images may be contaminated with noise during transmission, scanning or conversion to digital form. We can categorize noises by identifying their features and can search for similar patterns in a document image to choose appropriate methods for their removal. In this paper, we propose a hybrid binarization approach for improving the quality of old documents using a combination of global and local thresholding. This article also reviews noises that might appear in scanned document images and discusses some noise removal methods.

  15. Distinguishing the Noise and image structures for detecting the correction term and filtering the noise by using fuzzy rules

    Directory of Open Access Journals (Sweden)

    Sridevi.Ravada,

    2011-07-01

    Full Text Available A fuzzy filter is constructed from a set of fuzzy IF-THEN rules, these fuzzy rules come either from human experts or by matching input-output pairs .in this paper we propose a new fuzzy filter for the noise reduction of images corrupted with additive noise. here in this approach ,initially fuzzy derivatives for all eight directions that is N,E,W,S, NE,NW,SE,SW are calculated using “fuzzy IF-THEN rules “ and membership functions . Further the fuzzy derivative values obtained are used in the fuzzy smoothing for determining the correction term. Finally correction term can be added to the processed pixel value. Iteratively apply the fuzzy filter to reduce the noise and at each and every iteration membership function iscalculated based on the remaining noise level. A statistical model for the noise distribution can be incorporated to relate the homogeneity to the adaptation scheme of the membership functions.

  16. Robust image authentication in the presence of noise

    CERN Document Server

    2015-01-01

    This book addresses the problems that hinder image authentication in the presence of noise. It considers the advantages and disadvantages of existing algorithms for image authentication and shows new approaches and solutions for robust image authentication. The state of the art algorithms are compared and, furthermore, innovative approaches and algorithms are introduced. The introduced algorithms are applied to improve image authentication, watermarking and biometry.    Aside from presenting new directions and algorithms for robust image authentication in the presence of noise, as well as image correction, this book also:   Provides an overview of the state of the art algorithms for image authentication in the presence of noise and modifications, as well as a comparison of these algorithms, Presents novel algorithms for robust image authentication, whereby the image is tried to be corrected and authenticated, Examines different views for the solution of problems connected to image authentication in the pre...

  17. Plumbing noise: Pressure levels and perception in a luxury condominium

    Science.gov (United States)

    Watry, Derek

    2005-09-01

    A consulting project has recently been completed that addressed a number of noise concerns in a 9-unit, 20-year-old luxury condominium building in the San Francisco Bay Area. Among other tasks, the noise levels of four bathroom plumbing functions (flushing, showering, bath filling, bath draining) were measured in adjoining units and an inventory of noise concerns was collected. This paper reports the measured noise levels (nearly a 20-dBA range for every function!) and looks at the corresponding resident assessments not always clearly correlated with sound-pressure level.

  18. Measurement of Acceptable Noise Level with Background Music

    OpenAIRE

    Ahn, Hyun-Jung; Bahng, Junghwa; Lee, Jae Hee

    2015-01-01

    Background and Objectives Acceptable noise level (ANL) is a measure of the maximum background noise level (BNL) that a person is willing to tolerate while following a target story. Although researchers have used various sources of target sound in ANL measures, a limited type of background noise has been used. Extending the previous study of Gordon-Hickey & Moore (2007), the current study determined the effect of music genre and tempo on ANLs as possible factors affecting ANLs. We also investi...

  19. Low-Rank Decomposition Based Restoration of Compressed Images via Adaptive Noise Estimation.

    Science.gov (United States)

    Zhang, Xinfeng; Lin, Weisi; Xiong, Ruiqin; Liu, Xianming; Ma, Siwei; Gao, Wen

    2016-07-07

    Images coded at low bit rates in real-world applications usually suffer from significant compression noise, which significantly degrades the visual quality. Traditional denoising methods are not suitable for the content-dependent compression noise, which usually assume that noise is independent and with identical distribution. In this paper, we propose a unified framework of content-adaptive estimation and reduction for compression noise via low-rank decomposition of similar image patches. We first formulate the framework of compression noise reduction based upon low-rank decomposition. Compression noises are removed by soft-thresholding the singular values in singular value decomposition (SVD) of every group of similar image patches. For each group of similar patches, the thresholds are adaptively determined according to compression noise levels and singular values. We analyze the relationship of image statistical characteristics in spatial and transform domains, and estimate compression noise level for every group of similar patches from statistics in both domains jointly with quantization steps. Finally, quantization constraint is applied to estimated images to avoid over-smoothing. Extensive experimental results show that the proposed method not only improves the quality of compressed images obviously for post-processing, but are also helpful for computer vision tasks as a pre-processing method.

  20. Noise removal in multichannel image data by a parametric maximum noise fraction estimator

    DEFF Research Database (Denmark)

    Conradsen, Knut; Ersbøll, Bjarne Kjær; Nielsen, Allan Aasbjerg

    1991-01-01

    Some approaches to noise removal in multispectral imagery are presented. The primary contribution of the present work is the establishment of several ways of estimating the noise covariance matrix from image data and a comparison of the noise separation performances. A case study with Landsat MSS...... data demonstrates that the principal components are not sorted correctly in terms of visual image quality, whereas the minimum/maximum autocorrelation factors and the maximum noise fractions (MAFs) are. A case study with Landsat TM data shows an ordering which is consistent with the spatial wavelength...... in the components. The case studies indicate that a better noise separation is attained when using more complex noise models than the simple model implied by MAF analysis. (L.M.)...

  1. Analysis and Extension of the PCA Method, Estimating a Noise Curve from a Single Image

    Directory of Open Access Journals (Sweden)

    Miguel Colom

    2016-12-01

    Full Text Available In the article 'Image Noise Level Estimation by Principal Component Analysis', S. Pyatykh, J. Hesser, and L. Zheng propose a new method to estimate the variance of the noise in an image from the eigenvalues of the covariance matrix of the overlapping blocks of the noisy image. Instead of using all the patches of the noisy image, the authors propose an iterative strategy to adaptively choose the optimal set containing the patches with lowest variance. Although the method measures uniform Gaussian noise, it can be easily adapted to deal with signal-dependent noise, which is realistic with the Poisson noise model obtained by a CMOS or CCD device in a digital camera.

  2. Definition of 1992 Technology Aircraft Noise Levels and the Methodology for Assessing Airplane Noise Impact of Component Noise Reduction Concepts

    Science.gov (United States)

    Kumasaka, Henry A.; Martinez, Michael M.; Weir, Donald S.

    1996-01-01

    This report describes the methodology for assessing the impact of component noise reduction on total airplane system noise. The methodology is intended to be applied to the results of individual study elements of the NASA-Advanced Subsonic Technology (AST) Noise Reduction Program, which will address the development of noise reduction concepts for specific components. Program progress will be assessed in terms of noise reduction achieved, relative to baseline levels representative of 1992 technology airplane/engine design and performance. In this report, the 1992 technology reference levels are defined for assessment models based on four airplane sizes - an average business jet and three commercial transports: a small twin, a medium sized twin, and a large quad. Study results indicate that component changes defined as program final goals for nacelle treatment and engine/airframe source noise reduction would achieve from 6-7 EPNdB reduction of total airplane noise at FAR 36 Stage 3 noise certification conditions for all of the airplane noise assessment models.

  3. Technique Based on Image Pyramid and Bayes Rule for Noise Reduction in Unsupervised Change Detection

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-qiang; HUO hong; FANG Tao; ZHU Ju-lian; GE Wei-li

    2009-01-01

    In this paper, a technique based on image pyramid and Bayes rule for reducing noise effects in unsupervised change detection is proposed. By using Gaussian pyramid to process two multitemporal images respectively, two image pyramids are constructed. The difference pyramid images are obtained by point-by-point subtraction between the same level images of the two image pyramids. By resizing all difference pyramid images to the size of the original multitemporal image and then making product operator among them, a map being similar to the difference image is obtained. The difference image is generated by point-by-point subtraction between the two multitemporal images directly. At last, the Bayes rule is used to distinguish the changed pixels. Both synthetic and real data sets are used to evaluate the performance of the proposed technique. Experimental results show that the map from the proposed technique is more robust to noise than the difference image.

  4. Intrinsic Noise Level of Noise Cross-Correlation Functions and its Implication to Source Population of Ambient noises

    Science.gov (United States)

    Chen, Ying-Nien; Gung, Yuancheng; Chiao, Ling-Yun; Rhie, Junkee

    2017-01-01

    SUMMARYWe present a quantitative procedure to evaluate the intrinsic noise level (INL) of the noise cross-correlation function (NCF). The method is applied to realistic NCFs derived from the continuous data recorded by the seismic arrays in Taiwan and Korea. The obtained temporal evolution of NCF noise level follows fairly the prediction of the theoretical formulation, confirming the feasibility of the method. We then apply the obtained INL to the assessment of data quality and the source characteristics of ambient noise. We show that the INL-based signal-to-noise ratio provides an exact measure for the true noise level within the NCF and better resolving power for the NCF quality, and such measurement can be implemented to any time windows of the NCFs to evaluate the quality of overtones or coda waves. Moreover, since NCF amplitudes are influenced by both the population and excitation strengths of noises, while INL is primarily sensitive to the overall source population, with information from both measurements, we may better constrain the source characteristics of seismic ambient noises.

  5. Determination of noise pollution propagated from agricultural tractors and its driver’s noise exposure level

    Directory of Open Access Journals (Sweden)

    2012-09-01

    Full Text Available Introduction: Application of agricultural machineries such as tractor has been yielded a considerable development in different agricultural activities and productions. However, noticeable health problems such as noise pollution impact the users of these off-road vehicles. The purpose of this study was to determine the noise level induced by agricultural tractors and to evaluate the driver’s noise exposure level. .Material and Method: The sound pressure levels of three brands of tractor include John Deere, Ferguson and Romani were measured by sound level meter model Tes-1358. The characteristics of place for measuring tractors noise pollution were determined based on the ISO standard No 7216, 5131. The acquired data was analyzed using spss16 software. .Result: The results showed that the highest and the lowest noise level around the tractors were 83.8 dB (A and 73.9 dB (A for the John Deere and Romani, respectively. The effect of different transmission gears on the noise level of tractors was not statistically significant Pvalue>0.05. While, the effect of the tractor engine speeds on the noise level was statistically significant Pvalue<0.01. The exposure time of the most of drivers was frequently about 8 hour or more In this regards, the exposure levels of the tractor’s drivers to noise measured between 85-90 dB (A were higher than the Iranian occupational exposure limit (85 dB (A.Moreover, mean noise reduction rate of exsisting room which was used upon the typical tractor’s body was 9.5 dB in one octave band. .Conclusion: Application of standard cockpit and expansion mufflers can effectively reduce noise pollution emission and driver’s occupational exposure. Moreover, regular preventive maintenance and effective hearing conservation program including annual audiometry, hearing protection device, occupational health training for drivers must be implemented.

  6. Automatic exposure control systems designed to maintain constant image noise: effects on computed tomography dose and noise relative to clinically accepted technique charts.

    Science.gov (United States)

    Favazza, Christopher P; Yu, Lifeng; Leng, Shuai; Kofler, James M; McCollough, Cynthia H

    2015-01-01

    To compare computed tomography dose and noise arising from use of an automatic exposure control (AEC) system designed to maintain constant image noise as patient size varies with clinically accepted technique charts and AEC systems designed to vary image noise. A model was developed to describe tube current modulation as a function of patient thickness. Relative dose and noise values were calculated as patient width varied for AEC settings designed to yield constant or variable noise levels and were compared to empirically derived values used by our clinical practice. Phantom experiments were performed in which tube current was measured as a function of thickness using a constant-noise-based AEC system and the results were compared with clinical technique charts. For 12-, 20-, 28-, 44-, and 50-cm patient widths, the requirement of constant noise across patient size yielded relative doses of 5%, 14%, 38%, 260%, and 549% and relative noises of 435%, 267%, 163%, 61%, and 42%, respectively, as compared with our clinically used technique chart settings at each respective width. Experimental measurements showed that a constant noise-based AEC system yielded 175% relative noise for a 30-cm phantom and 206% relative dose for a 40-cm phantom compared with our clinical technique chart. Automatic exposure control systems that prescribe constant noise as patient size varies can yield excessive noise in small patients and excessive dose in obese patients compared with clinically accepted technique charts. Use of noise-level technique charts and tube current limits can mitigate these effects.

  7. Temporal pattern of acoustic imaging noise asymmetrically modulates activation in the auditory cortex.

    Science.gov (United States)

    Ranaweera, Ruwan D; Kwon, Minseok; Hu, Shuowen; Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2016-01-01

    This study investigated the hemisphere-specific effects of the temporal pattern of imaging related acoustic noise on auditory cortex activation. Hemodynamic responses (HDRs) to five temporal patterns of imaging noise corresponding to noise generated by unique combinations of imaging volume and effective repetition time (TR), were obtained using a stroboscopic event-related paradigm with extra-long (≥27.5 s) TR to minimize inter-acquisition effects. In addition to confirmation that fMRI responses in auditory cortex do not behave in a linear manner, temporal patterns of imaging noise were found to modulate both the shape and spatial extent of hemodynamic responses, with classically non-auditory areas exhibiting responses to longer duration noise conditions. Hemispheric analysis revealed the right primary auditory cortex to be more sensitive than the left to the presence of imaging related acoustic noise. Right primary auditory cortex responses were significantly larger during all the conditions. This asymmetry of response to imaging related acoustic noise could lead to different baseline activation levels during acquisition schemes using short TR, inducing an observed asymmetry in the responses to an intended acoustic stimulus through limitations of dynamic range, rather than due to differences in neuronal processing of the stimulus. These results emphasize the importance of accounting for the temporal pattern of the acoustic noise when comparing findings across different fMRI studies, especially those involving acoustic stimulation.

  8. REDUCTION OF CLASSROOM NOISE LEVELS USING GROUP CONTINGENCIES

    OpenAIRE

    Ring, Brandon M; Sigurdsson, Sigurdur O.; Eubanks, Sean L.; Silverman, Kenneth

    2014-01-01

    The therapeutic workplace is an employment-based abstinence reinforcement intervention for unemployed drug users where trainees receive on-the-job employment skills training in a classroom setting. The study is an extension of prior therapeutic workplace research, which suggested that trainees frequently violated noise standards. Participants received real-time graphed feedback of noise levels and had the opportunity to earn monetary group reinforcement for maintaining a low number of noise v...

  9. Noise and physical limits to maximum resolution of PET images

    Energy Technology Data Exchange (ETDEWEB)

    Herraiz, J.L.; Espana, S. [Dpto. Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Vicente, E.; Vaquero, J.J.; Desco, M. [Unidad de Medicina y Cirugia Experimental, Hospital GU ' Gregorio Maranon' , E-28007 Madrid (Spain); Udias, J.M. [Dpto. Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain)], E-mail: jose@nuc2.fis.ucm.es

    2007-10-01

    In this work we show that there is a limit for the maximum resolution achievable with a high resolution PET scanner, as well as for the best signal-to-noise ratio, which are ultimately related to the physical effects involved in the emission and detection of the radiation and thus they cannot be overcome with any particular reconstruction method. These effects prevent the spatial high frequency components of the imaged structures to be recorded by the scanner. Therefore, the information encoded in these high frequencies cannot be recovered by any reconstruction technique. Within this framework, we have determined the maximum resolution achievable for a given acquisition as a function of data statistics and scanner parameters, like the size of the crystals or the inter-crystal scatter. In particular, the noise level in the data as a limitation factor to yield high-resolution images in tomographs with small crystal sizes is outlined. These results have implications regarding how to decide the optimal number of voxels of the reconstructed image or how to design better PET scanners.

  10. Measurement of Noise Level in Enumeration Station in Rubber Industry

    Science.gov (United States)

    Rizkya, I.; Syahputri, K.; Sari, R. M.; Siregar, I.

    2017-03-01

    This research was conducted in companies engaged in the production of crumb rubber. In the rubber industry, the potential noise occurs in the enumeration station. Stations enumeration use machine and equipment that potentially generated noise. Noise can be defined as an unwanted sound because it does not fit the context of space and time so that may interfere with the comfort and human health. The noise level measured at random during the initial observation station enumeration is 101.8 dB. This value has exceeded the Threshold Limit Value (TLV) Kep-51 / MEN / 1999 and SNI No. 16-7063-2004 so research must be done to measure the level of noise in the enumeration station. Quantitative methods used in the study. Observations made with the calculation method of equivalent noise level. Observations were made on six measurement points for one shift for three days. The results showed the noise level over the Threshold Limit Value is equal to 85 dBA/8 hours. Based on the measurement results, the whole point of observation was far above the threshold Limit Value (TLV). The highest noise level equivalent is in the observation point 6 with a value of 102, 21 dB.

  11. Architectures for Low-noise CMOS Electronic Imaging

    Science.gov (United States)

    Kawahito, Shoji

    This chapter discusses various types of signal readout architectures for CMOS image sensors, implementing ultra-low-noise conversion of photo-generated charge packets into digital output values. It is based on a detailed analysis of the different noise sources in a CMOS imager, the noise responses of column noise cancelling circuits using correlated double sampling (CDS) and correlated multiple sampling (CMS) techniques and a noiseless signal readout technique using a precise digitizer. Finally, a practical example for the design of a CMOS image sensor with single-photon resolution is presented, and the technological requirements for meeting the condition for room-temperature readout noise of significantly less than 1 electron are discussed.

  12. Researches on the measurement of distribution image of radiated noise using focused beamforming

    Institute of Scientific and Technical Information of China (English)

    HUI Juan; HU Dan; HUI Junying; YIN Jingwei

    2008-01-01

    A method using focused beamforming to measure the distribution image (under-water image) of submarine and surface ship's noise sources is presented. Level linear array can measure the target image on water level, but the multi-path interference of underwater acoustic channel may affect the quality of it. Virtual time reversal mirror and virtual array can both solve the problem very well; they make the image with high resolution.

  13. High-order noise analysis for low dose iterative image reconstruction methods: ASIR, IRIS, and MBAI

    Science.gov (United States)

    Do, Synho; Singh, Sarabjeet; Kalra, Mannudeep K.; Karl, W. Clem; Brady, Thomas J.; Pien, Homer

    2011-03-01

    Iterative reconstruction techniques (IRTs) has been shown to suppress noise significantly in low dose CT imaging. However, medical doctors hesitate to accept this new technology because visual impression of IRT images are different from full-dose filtered back-projection (FBP) images. Most common noise measurements such as the mean and standard deviation of homogeneous region in the image that do not provide sufficient characterization of noise statistics when probability density function becomes non-Gaussian. In this study, we measure L-moments of intensity values of images acquired at 10% of normal dose and reconstructed by IRT methods of two state-of-art clinical scanners (i.e., GE HDCT and Siemens DSCT flash) by keeping dosage level identical to each other. The high- and low-dose scans (i.e., 10% of high dose) were acquired from each scanner and L-moments of noise patches were calculated for the comparison.

  14. Optimal Scale Edge Detection Utilizing Noise within Images

    Directory of Open Access Journals (Sweden)

    Adnan Khashman

    2003-04-01

    Full Text Available Edge detection techniques have common problems that include poor edge detection in low contrast images, speed of recognition and high computational cost. An efficient solution to the edge detection of objects in low to high contrast images is scale space analysis. However, this approach is time consuming and computationally expensive. These expenses can be marginally reduced if an optimal scale is found in scale space edge detection. This paper presents a new approach to detecting objects within images using noise within the images. The novel idea is based on selecting one optimal scale for the entire image at which scale space edge detection can be applied. The selection of an ideal scale is based on the hypothesis that "the optimal edge detection scale (ideal scale depends on the noise within an image". This paper aims at providing the experimental evidence on the relationship between the optimal scale and the noise within images.

  15. evaluation of the environmental noise levels in abuja municipality ...

    African Journals Online (AJOL)

    10-14. Noise pollution has been proven to aggravate chronic illnesses like hypertension and other cardiopulmonary diseases.8, 9 .... health hazard of different classes and magnitude ... sound levels in Abuja are fairly good in contrast to the .... Noise and Health 2012; 14(59): ... Information Technologies in Environmental.

  16. Bayesian Compressed Sensing with Unknown Measurement Noise Level

    DEFF Research Database (Denmark)

    Hansen, Thomas Lundgaard; Jørgensen, Peter Bjørn; Pedersen, Niels Lovmand

    2013-01-01

    In sparse Bayesian learning (SBL) approximate Bayesian inference is applied to find sparse estimates from observations corrupted by additive noise. Current literature only vaguely considers the case where the noise level is unknown a priori. We show that for most state-of-the-art reconstruction a...

  17. Cropping and noise resilient steganography algorithm using secret image sharing

    Science.gov (United States)

    Juarez-Sandoval, Oswaldo; Fierro-Radilla, Atoany; Espejel-Trujillo, Angelina; Nakano-Miyatake, Mariko; Perez-Meana, Hector

    2015-03-01

    This paper proposes an image steganography scheme, in which a secret image is hidden into a cover image using a secret image sharing (SIS) scheme. Taking advantage of the fault tolerant property of the (k,n)-threshold SIS, where using any k of n shares (k≤n), the secret data can be recovered without any ambiguity, the proposed steganography algorithm becomes resilient to cropping and impulsive noise contamination. Among many SIS schemes proposed until now, Lin and Chan's scheme is selected as SIS, due to its lossless recovery capability of a large amount of secret data. The proposed scheme is evaluated from several points of view, such as imperceptibility of the stegoimage respect to its original cover image, robustness of hidden data to cropping operation and impulsive noise contamination. The evaluation results show a high quality of the extracted secret image from the stegoimage when it suffered more than 20% cropping or high density noise contamination.

  18. Interferometric Imaging of Geostationary Satellites: Signal-to-Noise Considerations

    Science.gov (United States)

    2011-09-01

    and the extent to which they cover the necessary portions of the UV plane . Once the photon counting noise becomes smaller than the UV coverage noise, ad...satellites,” in Proc. SPIE 4091, Imaging Technology and Telescopes, J. W. Bilbro, J. B. Breckinridge, R. A. Carreras , S. R. Czyzak, M. J. Eckart, R. D...SPIE 4091, Imaging Technology and Telescopes, J. W. Bilbro, J. B. Breckinridge, R. A. Carreras , S. R. Czyzak, M. J. Eckart, R. D. Fiete, and P. S

  19. Noise Reduction Effect of Multiple-Sampling-Based Signal-Readout Circuits for Ultra-Low Noise CMOS Image Sensors

    OpenAIRE

    Shoji Kawahito; Min-Woong Seo

    2016-01-01

    This paper discusses the noise reduction effect of multiple-sampling-based signal readout circuits for implementing ultra-low-noise image sensors. The correlated multiple sampling (CMS) technique has recently become an important technology for high-gain column readout circuits in low-noise CMOS image sensors (CISs). This paper reveals how the column CMS circuits, together with a pixel having a high-conversion-gain charge detector and low-noise transistor, realizes deep sub-electron read noise...

  20. A Comparative Study of Removal Noise from Remote Sensing Image

    Directory of Open Access Journals (Sweden)

    Santosh Khamitkar

    2010-01-01

    Full Text Available This paper attempts to undertake the study of three types of noise such as Salt and Pepper (SPN, Random variation Impulse Noise (RVIN, Speckle (SPKN. Different noise densities have been removed between 10% to 60% by using five types of filters as Mean Filter (MF, Adaptive Wiener Filter (AWF, Gaussian Filter (GF, Standard Median Filter (SMF and Adaptive Median Filter (AMF. The same is applied to the Saturn remote sensing image and they are compared with one another. The comparative study is conducted with the help of Mean Square Errors (MSE and Peak-Signal to Noise Ratio (PSNR. So as to choose the base method for removal of noise from remote sensing image.

  1. A Comparative Study of Removal Noise from Remote Sensing Image

    CERN Document Server

    Al-amri, Salem Saleh; Khamitkar, S D

    2010-01-01

    This paper attempts to undertake the study of three types of noise such as Salt and Pepper (SPN), Random variation Impulse Noise (RVIN), Speckle (SPKN). Different noise densities have been removed between 10% to 60% by using five types of filters as Mean Filter (MF), Adaptive Wiener Filter (AWF), Gaussian Filter (GF), Standard Median Filter (SMF) and Adaptive Median Filter (AMF). The same is applied to the Saturn remote sensing image and they are compared with one another. The comparative study is conducted with the help of Mean Square Errors (MSE) and Peak-Signal to Noise Ratio (PSNR). So as to choose the base method for removal of noise from remote sensing image.

  2. ASSESSMENT OF WORK ZONE NOISE LEVELS AT A CEMENT ...

    African Journals Online (AJOL)

    Osondu

    2012-03-24

    Mar 24, 2012 ... factors affecting human health in today's ... Cement production is one of the major ... The offices and restaurant were considered as .... Figure 1 Classification of noise levels in different production sections during operation ...

  3. A Few Photons Among Many: Unmixing Signal and Noise for Photon-Efficient Active Imaging

    CERN Document Server

    Rapp, Joshua

    2016-01-01

    Conventional LIDAR systems require hundreds or thousands of photon detections to form accurate depth and reflectivity images. Recent photon-efficient computational imaging methods are remarkably effective with only 1.0 to 3.0 detected photons per pixel, but they are not demonstrated at signal-to-background ratio (SBR) below 1.0 because their imaging accuracies degrade significantly in the presence of high background noise. We introduce a new approach to depth and reflectivity estimation that focuses on unmixing contributions from signal and noise sources. At each pixel in an image, short-duration range gates are adaptively determined and applied to remove detections likely to be due to noise. For pixels with too few detections to perform this censoring accurately, we borrow data from neighboring pixels to improve depth estimates, where the neighborhood formation is also adaptive to scene content. Algorithm performance is demonstrated on experimental data at varying levels of noise. Results show improved perfo...

  4. Reducing Indoor Noise Levels Using People's Perception on Greenery

    Science.gov (United States)

    Mediastika, Christina E.; Binarti, Floriberta

    2013-12-01

    Employees working in cubicles of open-plan offices in Indonesia were studied in regard to their perception on the ability of indoor greenery to reduce noise levels. Sansevieria trifasciata and Scindapsus sp were used. Each was placed in the cubicle and noise levels were measured without plants, with Sansevieria, and with Scindapsus in place. The meters showed very insignificant difference. However, responses to surveys indicated a perception of lower noise in the presence of greenery. This seemed to be supported by prior knowledge and preconception and may be useful in creating a "quieter" indoor environment.

  5. Modeling hemodynamic responses in auditory cortex at 1.5 T using variable duration imaging acoustic noise.

    Science.gov (United States)

    Hu, Shuowen; Olulade, Olumide; Castillo, Javier Gonzalez; Santos, Joseph; Kim, Sungeun; Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2010-02-15

    A confound for functional magnetic resonance imaging (fMRI), especially for auditory studies, is the presence of imaging acoustic noise generated mainly as a byproduct of rapid gradient switching during volume acquisition and, to a lesser extent, the radiofrequency transmit. This work utilized a novel pulse sequence to present actual imaging acoustic noise for characterization of the induced hemodynamic responses and assessment of linearity in the primary auditory cortex with respect to noise duration. Results show that responses to brief duration (46 ms) imaging acoustic noise is highly nonlinear while responses to longer duration (>1 s) imaging acoustic noise becomes approximately linear, with the right primary auditory cortex exhibiting a higher degree of nonlinearity than the left for the investigated noise durations. This study also assessed the spatial extent of activation induced by imaging acoustic noise, showing that the use of modeled responses (specific to imaging acoustic noise) as the reference waveform revealed additional activations in the auditory cortex not observed with a canonical gamma variate reference waveform, suggesting an improvement in detection sensitivity for imaging acoustic noise-induced activity. Longer duration (1.5 s) imaging acoustic noise was observed to induce activity that expanded outwards from Heschl's gyrus to cover the superior temporal gyrus as well as parts of the middle temporal gyrus and insula, potentially affecting higher level acoustic processing.

  6. Median Filter Noise Reduction of Image and Backpropagation Neural Network Model for Cervical Cancer Classification

    Science.gov (United States)

    Wutsqa, D. U.; Marwah, M.

    2017-06-01

    In this paper, we consider spatial operation median filter to reduce the noise in the cervical images yielded by colposcopy tool. The backpropagation neural network (BPNN) model is applied to the colposcopy images to classify cervical cancer. The classification process requires an image extraction by using a gray level co-occurrence matrix (GLCM) method to obtain image features that are used as inputs of BPNN model. The advantage of noise reduction is evaluated by comparing the performances of BPNN models with and without spatial operation median filter. The experimental result shows that the spatial operation median filter can improve the accuracy of the BPNN model for cervical cancer classification.

  7. STRIPING NOISE REMOVAL OF IMAGES ACQUIRED BY CBERS 2 CCD CAMERA SENSOR

    Directory of Open Access Journals (Sweden)

    E. Amraei

    2014-10-01

    Full Text Available CCD Camera is a multi-spectral sensor that is carried by CBERS 2 satellite. Imaging technique in this sensor is push broom. In images acquired by the CCD Camera, some vertical striping noise can be seen. This is due to the detectors mismatch, inter detector variability, improper calibration of detectors and low signal-to-noise ratio. These noises are more profound in images acquired from the homogeneous surfaces, which are processed at level 2. However, the existence of these noises render the interpretation of the data and extracting information from these images difficult. In this work, spatial moment matching method is proposed to modify these images. In this method, the statistical moments such as mean and standard deviation of columns in each band are used to balance the statistical specifications of the detector array to those of reference values. After the removal of the noise, some periodic diagonal stripes remain in the image where their removal by using the aforementioned method seems impossible. Therefore, to omit them, frequency domain Butterworth notch filter was applied. Finally to evaluate the results, the image statistical moments such as the mean and standard deviation were deployed. The study proves the effectiveness of the method in noise removal.

  8. Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation

    Science.gov (United States)

    Blackman, Graham A.; Hall, Deborah A.

    2011-01-01

    Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

  9. Reducing the Effects of Background Noise during Auditory Functional Magnetic Resonance Imaging of Speech Processing: Qualitative and Quantitative Comparisons between Two Image Acquisition Schemes and Noise Cancellation

    Science.gov (United States)

    Blackman, Graham A.; Hall, Deborah A.

    2011-01-01

    Purpose: The intense sound generated during functional magnetic resonance imaging (fMRI) complicates studies of speech and hearing. This experiment evaluated the benefits of using active noise cancellation (ANC), which attenuates the level of the scanner sound at the participant's ear by up to 35 dB around the peak at 600 Hz. Method: Speech and…

  10. Reduction of noise in diffusion tensor images using anisotropic smoothing.

    Science.gov (United States)

    Ding, Zhaohua; Gore, John C; Anderson, Adam W

    2005-02-01

    To improve the accuracy of tissue structural and architectural characterization with diffusion tensor imaging, a novel smoothing technique is developed for reducing noise in diffusion tensor images. The technique extends the traditional anisotropic diffusion filtering method by allowing isotropic smoothing within homogeneous regions and anisotropic smoothing along structure boundaries. This is particularly useful for smoothing diffusion tensor images in which direction information contained in the tensor needs to be restored following noise corruption and preserved around tissue boundaries. The effectiveness of this technique is quantitatively studied with experiments on simulated and human in vivo diffusion tensor data. Illustrative results demonstrate that the anisotropic smoothing technique developed can significantly reduce the impact of noise on the direction as well as anisotropy measures of the diffusion tensor images.

  11. Lossless Astronomical Image Compression and the Effects of Random Noise

    Science.gov (United States)

    Pence, William

    2009-01-01

    In this paper we compare a variety of modern image compression methods on a large sample of astronomical images. We begin by demonstrating from first principles how the amount of noise in the image pixel values sets a theoretical upper limit on the lossless compression ratio of the image. We derive simple procedures for measuring the amount of noise in an image and for quantitatively predicting how much compression will be possible. We then compare the traditional technique of using the GZIP utility to externally compress the image, with a newer technique of dividing the image into tiles, and then compressing and storing each tile in a FITS binary table structure. This tiled-image compression technique offers a choice of other compression algorithms besides GZIP, some of which are much better suited to compressing astronomical images. Our tests on a large sample of images show that the Rice algorithm provides the best combination of speed and compression efficiency. In particular, Rice typically produces 1.5 times greater compression and provides much faster compression speed than GZIP. Floating point images generally contain too much noise to be effectively compressed with any lossless algorithm. We have developed a compression technique which discards some of the useless noise bits by quantizing the pixel values as scaled integers. The integer images can then be compressed by a factor of 4 or more. Our image compression and uncompression utilities (called fpack and funpack) that were used in this study are publicly available from the HEASARC web site.Users may run these stand-alone programs to compress and uncompress their own images.

  12. Estimating atmospheric parameters and reducing noise for multispectral imaging

    Science.gov (United States)

    Conger, James Lynn

    2014-02-25

    A method and system for estimating atmospheric radiance and transmittance. An atmospheric estimation system is divided into a first phase and a second phase. The first phase inputs an observed multispectral image and an initial estimate of the atmospheric radiance and transmittance for each spectral band and calculates the atmospheric radiance and transmittance for each spectral band, which can be used to generate a "corrected" multispectral image that is an estimate of the surface multispectral image. The second phase inputs the observed multispectral image and the surface multispectral image that was generated by the first phase and removes noise from the surface multispectral image by smoothing out change in average deviations of temperatures.

  13. Factors Affecting Noise Levels of High-Speed Handpieces

    Science.gov (United States)

    2012-06-01

    office communication and increase patient anxiety. Purpose: To determine if three noise-reducing techniques utilized in larger scale , non- dental...hearing loss may cause confusion, fear, and loneliness , and that sometimes hearing loss is accompanied by dizziness, which would be a handicap in the...employee noise exposures equal or exceed an 8- hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale (slow response) or

  14. Networking with noise at the molecular, cellular, and population level

    Science.gov (United States)

    Vilar, Jose

    2002-03-01

    The intrinsic stochastic nature of biochemical reactions affects enzymatic and transcriptional networks at different levels. Yet, cells are able to function effectively and consistently amidst such random fluctuations. I will discuss some molecular mechanisms that are able to reduce the intrinsic noise of chemical reactions, how suitable designs can make networks resistant to noise, and what strategies can be used by populations to achieve precise functions.

  15. LOW-NOISE PAVEMENT AS A WAY OF LIMITATION OF TRAFFIC NOISE LEVEL

    Directory of Open Access Journals (Sweden)

    Władysław Gardziejczyk

    2014-11-01

    Full Text Available Road surface can significantlyreduce the trafficnoise level. Depending on the characteristic of the upper surface layers the differences between the maximum rolling noise levels from passing vehicles to reach values about 10 dB (A. A special group is low-noise pavements characterized by the presence of voids above 15%. Application the porous asphalt layers or asphalt mixture type BBTM affects a significantreduction the width of land surrounded the roads where permissible equivalent sound level is exceeded. Such solutions in some cases can replace acoustic barriers. Road pavements with a higher content of voids require proper maintenance because their acoustic performances are reduced during operation.

  16. Perceptual Classification Images from Vernier Acuity Masked by Noise

    Science.gov (United States)

    Ahumada, A. J.; Null, Cynthia H. (Technical Monitor)

    1996-01-01

    Letting external noise rather than internal noise limit discrimination performance allows information to be extracted about the observer's stimulus classification rule. A perceptual classification image is the correlation over trials between the noise amplitude at a spatial location and the observer's responses. If, for example, the observer followed the rule of the ideal observer, the perceptual classification image would be an estimate of the ideal observer filter, the difference between the two unmasked images being discriminated. Perceptual classification images were estimated for a vernier discrimination task. The display screen had 48 pixels per degree horizontally and vertically. The no-offset image had a dark horizontal line of 4 pixels, a 1 pixel space, and 4 more dark pixels. Classification images were based on 1600 discrimination trials with the line contrast adjusted to keep the error rate near 25 percent. In the offset image, the second line was one pixel higher. Unlike the ideal observer filter (a horizontal dipole), the observer perceptual classification images are strongly oriented. Fourier transforms of the classification images had a peak amplitude near one cycle per degree and an orientation near 25 degrees. The spatial spread is much more than image blur predicts, and probably indicates the spatial position uncertainty in the task.

  17. Adaptive correction procedure for TVL1 image deblurring under impulse noise

    Science.gov (United States)

    Bai, Minru; Zhang, Xiongjun; Shao, Qianqian

    2016-08-01

    For the problem of image restoration of observed images corrupted by blur and impulse noise, the widely used TVL1 model may deviate from both the data-acquisition model and the prior model, especially for high noise levels. In order to seek a solution of high recovery quality beyond the reach of the TVL1 model, we propose an adaptive correction procedure for TVL1 image deblurring under impulse noise. Then, a proximal alternating direction method of multipliers (ADMM) is presented to solve the corrected TVL1 model and its convergence is also established under very mild conditions. It is verified by numerical experiments that our proposed approach outperforms the TVL1 model in terms of signal-to-noise ratio (SNR) values and visual quality, especially for high noise levels: it can handle salt-and-pepper noise as high as 90% and random-valued noise as high as 70%. In addition, a comparison with a state-of-the-art method, the two-phase method, demonstrates the superiority of the proposed approach.

  18. A maximum noise fraction transform with improved noise estimation for hyperspectral images

    Institute of Scientific and Technical Information of China (English)

    LIU Xiang; ZHANG Bing; GAO LianRu; CHEN DongMei

    2009-01-01

    Feature extraction is often performed to reduce spectral dimension of hyperspectral images before image classification.The maximum noise fraction (MNF) transform is one of the most commonly used spectral feature extraction methods.The spectral features in several bands of hyperspectral images are submerged by the noise.The MNF transform is advantageous over the principle component (PC) transform because it takes the noise information in the spatial domain into consideration.However,the experiments described in this paper demonstrate that classification accuracy is greatly influenced by the MNF transform when the ground objects are mixed together.The underlying mechanism of it is revealed and analyzed by mathematical theory.In order to improve the performance of classification after feature extraction when ground objects are mixed in hyperspectral images,a new MNF transform,with an Improved method of estimating hyperspectral Image noise covariance matrix (NCM),is presented.This improved MNF transform is applied to both the simulated data and real data.The results show that compared with the classical MNF transform,this new method enhanced the ability of feature extraction and increased classification accuracy.

  19. A hybrid algorithm for speckle noise reduction of ultrasound images.

    Science.gov (United States)

    Singh, Karamjeet; Ranade, Sukhjeet Kaur; Singh, Chandan

    2017-09-01

    Medical images are contaminated by multiplicative speckle noise which significantly reduce the contrast of ultrasound images and creates a negative effect on various image interpretation tasks. In this paper, we proposed a hybrid denoising approach which collaborate the both local and nonlocal information in an efficient manner. The proposed hybrid algorithm consist of three stages in which at first stage the use of local statistics in the form of guided filter is used to reduce the effect of speckle noise initially. Then, an improved speckle reducing bilateral filter (SRBF) is developed to further reduce the speckle noise from the medical images. Finally, to reconstruct the diffused edges we have used the efficient post-processing technique which jointly considered the advantages of both bilateral and nonlocal mean (NLM) filter for the attenuation of speckle noise efficiently. The performance of proposed hybrid algorithm is evaluated on synthetic, simulated and real ultrasound images. The experiments conducted on various test images demonstrate that our proposed hybrid approach outperforms the various traditional speckle reduction approaches included recently proposed NLM and optimized Bayesian-based NLM. The results of various quantitative, qualitative measures and by visual inspection of denoise synthetic and real ultrasound images demonstrate that the proposed hybrid algorithm have strong denoising capability and able to preserve the fine image details such as edge of a lesion better than previously developed methods for speckle noise reduction. The denoising and edge preserving capability of hybrid algorithm is far better than existing traditional and recently proposed speckle reduction (SR) filters. The success of proposed algorithm would help in building the lay foundation for inventing the hybrid algorithms for denoising of ultrasound images. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Noise Reduction Techniques and Scaling Effects towards Photon Counting CMOS Image Sensors

    Directory of Open Access Journals (Sweden)

    Assim Boukhayma

    2016-04-01

    Full Text Available This paper presents an overview of the read noise in CMOS image sensors (CISs based on four-transistors (4T pixels, column-level amplification and correlated multiple sampling. Starting from the input-referred noise analytical formula, process level optimizations, device choices and circuit techniques at the pixel and column level of the readout chain are derived and discussed. The noise reduction techniques that can be implemented at the column and pixel level are verified by transient noise simulations, measurement and results from recently-published low noise CIS. We show how recently-reported process refinement, leading to the reduction of the sense node capacitance, can be combined with an optimal in-pixel source follower design to reach a sub-0.3 \\(e^{-}_{rms}\\ read noise at room temperature. This paper also discusses the impact of technology scaling on the CIS read noise. It shows how designers can take advantage of scaling and how the Metal-Oxide-Semiconductor (MOS transistor gate leakage tunneling current appears as a challenging limitation. For this purpose, both simulation results of the gate leakage current and 1/f noise data reported from different foundries and technology nodes are used.

  1. Influence of barrier tops on noise levels: new BEM calculations

    DEFF Research Database (Denmark)

    Pigasse, Gilles; Kragh, Jørgen; Cutanda Henriquez, Vicente

    2012-01-01

    a complex geometry such as a threepanel top. The results show that the T-shaped barrier offers most noise reduction compared to the others. It can indeed bring up to 6.6 dB extra noise reduction at a position 40 m behind the barrier compared to a regular barrier. This study also shows that the noise......The Danish Road Directorate is currently investigating the possibility to optimise noise barriers by using specially shaped tops. The noise level at different positions behind the noise barrier has been calculated using the boundary element method with the help of the OpenBEM software....... The simulated situation is a barrier between a residential area and a motorway. The highway is modelled as a two-lane road and the sound levels are predicted at 10 m, 20 m and 40 m behind the barrier, respectively. Seven different types of barriers were tested including L-, T- and Y-tops as well as more...

  2. Adaptive nonlocal means filtering based on local noise level for CT denoising

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhoubo; Trzasko, Joshua D.; Lake, David S.; Blezek, Daniel J.; Manduca, Armando, E-mail: manduca.armando@mayo.edu [Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 (United States); Yu, Lifeng; Fletcher, Joel G.; McCollough, Cynthia H. [Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905 (United States)

    2014-01-15

    Purpose: To develop and evaluate an image-domain noise reduction method based on a modified nonlocal means (NLM) algorithm that is adaptive to local noise level of CT images and to implement this method in a time frame consistent with clinical workflow. Methods: A computationally efficient technique for local noise estimation directly from CT images was developed. A forward projection, based on a 2D fan-beam approximation, was used to generate the projection data, with a noise model incorporating the effects of the bowtie filter and automatic exposure control. The noise propagation from projection data to images was analytically derived. The analytical noise map was validated using repeated scans of a phantom. A 3D NLM denoising algorithm was modified to adapt its denoising strength locally based on this noise map. The performance of this adaptive NLM filter was evaluated in phantom studies in terms of in-plane and cross-plane high-contrast spatial resolution, noise power spectrum (NPS), subjective low-contrast spatial resolution using the American College of Radiology (ACR) accreditation phantom, and objective low-contrast spatial resolution using a channelized Hotelling model observer (CHO). Graphical processing units (GPU) implementation of this noise map calculation and the adaptive NLM filtering were developed to meet demands of clinical workflow. Adaptive NLM was piloted on lower dose scans in clinical practice. Results: The local noise level estimation matches the noise distribution determined from multiple repetitive scans of a phantom, demonstrated by small variations in the ratio map between the analytical noise map and the one calculated from repeated scans. The phantom studies demonstrated that the adaptive NLM filter can reduce noise substantially without degrading the high-contrast spatial resolution, as illustrated by modulation transfer function and slice sensitivity profile results. The NPS results show that adaptive NLM denoising preserves the

  3. Suppression of noise in SEM images using weighted local hysteresis smoothing filter.

    Science.gov (United States)

    Mazhari, Mohadeseh; Hasanzadeh, Reza P R

    2016-11-01

    It has been proven that Hysteresis Smoothing (HS) has several advantages for Scanning Electron Microscopy (SEM) image noise reduction. HS uses hysteresis thresholding to remove noise besides preserving important details of images. Determination of optimal threshold values (cursor width) plays an effective role in improving the performance of HS based filters. Recently, a novel local technique, named Local Adaptive Hysteresis Smoothing (LAHS), has been proposed to compute an optimal cursor width. In this paper, a new method is proposed to improve the performance of LAHS in noise reduction and detail preservation. In the proposed approach which is based on weighted averaging, local statistical characteristics of the image are used in order to modify the final values of estimated pixels by LAHS method. Proposed method is applied to SEM images corrupted by different levels of noise. Noise reduction and detail preservation performance of the proposed method is compared in both objective and subjective manners with other HS based filters. Experimental results demonstrate that the proposed method is successful in improving the performance of LAHS and also it achieves better performance in noise reduction besides detail preservation of SEM images in comparison with other HS based filters. SCANNING 38:634-643, 2016. © 2016 Wiley Periodicals, Inc.

  4. Anthropogenic noise alters bat activity levels and echolocation calls

    Directory of Open Access Journals (Sweden)

    Jessie P. Bunkley

    2015-01-01

    Full Text Available Negative impacts from anthropogenic noise are well documented for many wildlife taxa. Investigations of the effects of noise on bats however, have not been conducted outside of the laboratory. Bats that hunt arthropods rely on auditory information to forage. Part of this acoustic information can fall within the spectrum of anthropogenic noise, which can potentially interfere with signal reception and processing. Compressor stations associated with natural gas extraction produce broadband noise 24 hours a day, 365 days a year. With over half a million producing gas wells in the U.S. this infrastructure is a major source of noise pollution across the landscape. We conducted a ‘natural experiment’ in the second largest gas extraction field in the U.S. to investigate the potential effects of gas compressor station noise on the activity levels of the local bat assemblage. We used acoustic monitoring to compare the activity level (number of minutes in a night with a bat call of the bat assemblage at sites with compressor stations to sites lacking this infrastructure. We found that activity levels for the Brazilian free-tailed bat (Tadarida brasiliensis were 40% lower at loud compressor sites compared to quieter well pads, whereas the activity levels of four other species (Myotis californicus, M. cillolabrum, M. lucifugus, Parastrellus hesperus were not affected by noise. Furthermore, our results reveal that the assemblage of bat species emitting low frequency (35 kHz echolocation did not exhibit altered activity levels in noise. Lower activity levels of Brazilian free-tailed bats at loud sites indicate a potential reduction in habitat for this species. Additionally, a comparison of echolocation search calls produced by free-tailed bats at sites with and without compressor stations reveal that this species modifies its echolocation search calls in noise—producing longer calls with a narrower bandwidth. Call alterations might affect prey

  5. Fast Impulse Noise Removal from Highly Corrupted Images

    CERN Document Server

    Hosseini, Hossein

    2011-01-01

    In this paper, we suggest a general model for the fixed-valued impulse noise and propose a two-stage method for high density noise suppression while preserving the image details. In the first stage, we apply an iterative impulse detector, exploiting the image entropy, to identify the corrupted pixels and then employ an Adaptive Iterative Mean filter (AIM) to restore them. The filter is adaptive in terms of the number of iterations, which is different for each noisy pixel, according to their Euclidean distance from the nearest uncorrupted pixel. Experimental results show that the AIM filter is fast and outperforms the best existing techniques in both objective and subjective performance measures.

  6. Noise Removal From Microarray Images Using Maximum a Posteriori Based Bivariate Estimator

    Directory of Open Access Journals (Sweden)

    A.Sharmila Agnal

    2013-01-01

    Full Text Available Microarray Image contains information about thousands of genes in an organism and these images are affected by several types of noises. They affect the circular edges of spots and thus degrade the image quality. Hence noise removal is the first step of cDNA microarray image analysis for obtaining gene expression level and identifying the infected cells. The Dual Tree Complex Wavelet Transform (DT-CWT is preferred for denoising microarray images due to its properties like improved directional selectivity and near shift-invariance. In this paper, bivariate estimators namely Linear Minimum Mean Squared Error (LMMSE and Maximum A Posteriori (MAP derived by applying DT-CWT are used for denoising microarray images. Experimental results show that MAP based denoising method outperforms existing denoising techniques for microarray images.

  7. Self-reported sleep disturbances due to railway noise: exposure-response relationships for nighttime equivalent and maximum noise levels.

    Science.gov (United States)

    Aasvang, Gunn Marit; Moum, Torbjorn; Engdahl, Bo

    2008-07-01

    The objective of the present survey was to study self-reported sleep disturbances due to railway noise with respect to nighttime equivalent noise level (L(p,A,eq,night)) and maximum noise level (L(p,A,max)). A sample of 1349 people in and around Oslo in Norway exposed to railway noise was studied in a cross-sectional survey to obtain data on sleep disturbances, sleep problems due to noise, and personal characteristics including noise sensitivity. Individual noise exposure levels were determined outside of the bedroom facade, the most-exposed facade, and inside the respondents' bedrooms. The exposure-response relationships were analyzed by using logistic regression models, controlling for possible modifying factors including the number of noise events (train pass-by frequency). L(p,A,eq,night) and L(p,A,max) were significantly correlated, and the proportion of reported noise-induced sleep problems increased as both L(p,A,eq,night) and L(p,A,max) increased. Noise sensitivity, type of bedroom window, and pass-by frequency were significant factors affecting noise-induced sleep disturbances, in addition to the noise exposure level. Because about half of the study population did not use a bedroom at the most-exposed side of the house, the exposure-response curve obtained by using noise levels for the most-exposed facade underestimated noise-induced sleep disturbance for those who actually have their bedroom at the most-exposed facade.

  8. On noise in time-delay integration CMOS image sensors

    Science.gov (United States)

    Levski, Deyan; Choubey, Bhaskar

    2016-05-01

    Time delay integration sensors are of increasing interest in CMOS processes owing to their low cost, power and ability to integrate with other circuit readout blocks. This paper presents an analysis of the noise contributors in current day CMOS Time-Delay-Integration image sensors with various readout architectures. An analysis of charge versus voltage domain readout modes is presented, followed by a noise classification of the existing Analog Accumulator Readout (AAR) and Digital Accumulator Readout (DAR) schemes for TDI imaging. The analysis and classification of existing readout schemes include, pipelined charge transfer, buffered direct injection, voltage as well as current-mode analog accumulators and all-digital accumulator techniques. Time-Delay-Integration imaging modes in CMOS processes typically use an N-number of readout steps, equivalent to the number of TDI pixel stages. In CMOS TDI sensors, where voltage domain readout is used, the requirements over speed and noise of the ADC readout chain are increased due to accumulation of the dominant voltage readout and ADC noise with every stage N. Until this day, the latter is the primary reason for a leap-back of CMOS TDI sensors as compared to their CCD counterparts. Moreover, most commercial CMOS TDI implementations are still based on a charge-domain readout, mimicking a CCD-like operation mode. Thus, having a good understanding of each noise contributor in the signal chain, as well as its magnitude in different readout architectures, is vital for the design of future generation low-noise CMOS TDI image sensors based on a voltage domain readout. This paper gives a quantitative classification of all major noise sources for all popular implementations in the literature.

  9. Noise-induced bias for convolution-based interpolation in digital image correlation.

    Science.gov (United States)

    Su, Yong; Zhang, Qingchuan; Gao, Zeren; Xu, Xiaohai

    2016-01-25

    In digital image correlation (DIC), the noise-induced bias is significant if the noise level is high or the contrast of the image is low. However, existing methods for the estimation of the noise-induced bias are merely applicable to traditional interpolation methods such as linear and cubic interpolation, but are not applicable to generalized interpolation methods such as BSpline and OMOMS. Both traditional interpolation and generalized interpolation belong to convolution-based interpolation. Considering the widely use of generalized interpolation, this paper presents a theoretical analysis of noise-induced bias for convolution-based interpolation. A sinusoidal approximate formula for noise-induced bias is derived; this formula motivates an estimating strategy which is with speed, ease, and accuracy; furthermore, based on this formula, the mechanism of sophisticated interpolation methods generally reducing noise-induced bias is revealed. The validity of the theoretical analysis is established by both numerical simulations and actual subpixel translation experiment. Compared to existing methods, formulae provided by this paper are simpler, briefer, and more general. In addition, a more intuitionistic explanation of the cause of noise-induced bias is provided by quantitatively characterized the position-dependence of noise variability in the spatial domain.

  10. Passive synthetic aperture imaging with limited noise sources

    Science.gov (United States)

    Garnier, Josselin

    2016-09-01

    We consider a passive synthetic aperture imaging problem. A single moving receiver antenna records random signals generated by one or several distant noise sources and backscattered by one or several reflectors. The sources emit noise signals modeled by stationary random processes. The reflectors can be imaged by summing the autocorrelation functions of the received signals computed over successive time windows, corrected for Doppler factors and migrated by appropriate travel times. In particular, the Doppler effect plays an important role and it can be used for resolution enhancement. When the noise source positions are not known, the reflector can be localized with an accuracy proportional to the reciprocal of the noise bandwidth, even when only a very small number of sources are available. When the noise source positions are known, the reflector can be localized with a cross range resolution proportional to the carrier wavelength and inversely proportional to the length of the receiver trajectory (i.e. the synthetic aperture), and with a range resolution proportional to the reciprocal of the bandwidth, even with only one noise source.

  11. Image Denoising of Wavelet based Compressed Images Corrupted by Additive White Gaussian Noise

    Directory of Open Access Journals (Sweden)

    Shyam Lal

    2012-08-01

    Full Text Available In this study an efficient algorithm is proposed for removal of additive white Gaussian noise from compressed natural images in wavelet based domain. First, the natural image is compressed by discrete wavelet transform and then proposed hybrid filter is applied for image denoising of compressed images corrupted by Additive White Gaussian Noise (AWGN. The proposed hybrid filter (HMCD is combination of non-linear fourth order partial differential equation and bivariate shrinkage function. The proposed hybrid filter provides better results in term of noise suppression with keeping minimum edge blurring as compared to other existing image denoising techniques for wavelet based compressed images. Simulation and experimental results on benchmark test images demonstrate that the proposed hybrid filter attains competitive image denoising performances as compared with other state-of-the-art image denoising algorithms. It is more effective particularly for the highly corrupted images in wavelet based compressed domain.

  12. Image quality evaluation of iterative CT reconstruction algorithms: a perspective from spatial domain noise texture measures

    Science.gov (United States)

    Pachon, Jan H.; Yadava, Girijesh; Pal, Debashish; Hsieh, Jiang

    2012-03-01

    Non-linear iterative reconstruction (IR) algorithms have shown promising improvements in image quality at reduced dose levels. However, IR images sometimes may be perceived as having different image noise texture than traditional filtered back projection (FBP) reconstruction. Standard linear-systems-based image quality evaluation metrics are limited in characterizing such textural differences and non-linear image-quality vs. dose trade-off behavior, hence limited in predicting potential impact of such texture differences in diagnostic task. In an attempt to objectively characterize and measure dose dependent image noise texture and statistical properties of IR and FBP images, we have investigated higher order moments and Haralicks Gray Level Co-occurrence Matrices (GLCM) based texture features on phantom images reconstructed by an iterative and a traditional FBP method. In this study, the first 4 central order moments, and multiple texture features from Haralick GLCM in 4 directions at 6 different ROI sizes and four dose levels were computed. For resolution, noise and texture trade-off analysis, spatial frequency domain NPS and contrastdependent MTF were also computed. Preliminary results of the study indicate that higher order moments, along with spatial domain measures of energy, contrast, correlation, homogeneity, and entropy consistently capture the textural differences between FBP and IR as dose changes. These metrics may be useful in describing the perceptual differences in randomness, coarseness, contrast, and smoothness of images reconstructed by non-linear algorithms.

  13. Noise level analysis in buffer rod geometries for ultrasonic sensors.

    Science.gov (United States)

    Garcia-Alvarez, J; Yañez, Y; Prego, J L; Turo, A; Chavez, J A; Garcia, M J; Salazar, J

    2006-12-22

    This work presents an ultrasonic sensor for on-line batter monitoring with low-noise design considerations. The density and the compressibility of the batter vary as a function of mixing time and are strongly related to the quality of the final product. Traditionally, a batter sample of a fixed volume is removed and weighted in order to determine its density. This is a time consuming process. Benefits to the industry of on-line measuring techniques include better control of product quality, improving processing efficiencies and reduction in wastage. In this paper low-noise design considerations are accounted for an ultrasonic sensor based on a piezoceramic disk mounted between two reference buffer rods of acrylic resin to measure the acoustic impedance of the batter. Measuring the acoustic impedance changes of the batter its compressibility and density can be monitored. Spurious echoes generated at different parts of the buffer rods boundary strongly affect accuracy and reliability of the measurements, and are considered as noise. The influence of buffer rods geometry on noise level is studied using simulations and afterwards justified experimentally. Design aspects such as buffer rods length and radius, piezoceramic disk frequency and radius are discussed and their influence on noise level is shown. Finally, strategies for optimum geometry design of the ultrasonic sensor are given.

  14. The Noise Clinic: a Blind Image Denoising Algorithm

    Directory of Open Access Journals (Sweden)

    Marc Lebrun

    2015-01-01

    Full Text Available This paper describes the complete implementation of a blind image algorithm, that takes any digital image as input. In a first step the algorithm estimates a Signal and Frequency Dependent (SFD noise model. In a second step, the image is denoised by a multiscale adaptation of the Non-local Bayes denoising method. We focus here on a careful analysis of the denoising step and present a detailed discussion of the influence of its parameters. Extensive commented tests of the blind denoising algorithm are presented, on real JPEG images and scans of old photographs.

  15. Possibilities of reducing the noise level in the opencast exploitations of the Mecsek coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Kohegyi, I.; Hoffer, R.

    1988-01-01

    The noise level of different opencast exploitations was studied. It was stated that the producing equipment runs on a noise level higher than the admitted one. The noise level generated by new machinery is discussed. The noise conditions of transporting vehicles were also studied and in this relation the exposition to noise of drivers is also discussed. Suggestions are made how to decrease the noise level in general in the opencast mines and to develop a program for hearing protection.

  16. Variational approach for restoring blurred images with cauchy noise

    DEFF Research Database (Denmark)

    Sciacchitano, Federica; Dong, Yiqiu; Zeng, Tieyong

    2015-01-01

    model, we add a quadratic penalty term, which guarantees the uniqueness of the solution. Due to the convexity of our model, the primal dual algorithm is employed to solve the minimization problem. Experimental results show the effectiveness of the proposed method for simultaneously deblurring...... and denoising images corrupted by Cauchy noise. Comparison with other existing and well-known methods is provided as well....

  17. HOW TO KEEP SCHOOL NOISE AT THE RIGHT LEVEL.

    Science.gov (United States)

    MCKAY, RONALD L.

    DISCUSSES FACTORS TO BE CONSIDERED DURING SCHOOL PLANNING STAGES REGARDING NOISE LEVELS AND ACOUSTIC DESIGN IMPLICATIONS. FACTORS ARE--(1) A STAGE HOUSE IS DETRIMENTAL TO ORCHESTRAS, BANDS, CHORUSES, LECTURES, ASSEMBLIES, RECITALS, AND CERTAIN DRAMAS AND SPEECH-MUSIC PERFORMANCES. SUGGESTED IS AN AUDITORIUM WITH AUDIENCE AND PERFORMING PLATFORM…

  18. Effect of external classroom noise on schoolchildren's reading and mathematics performance: correlation of noise levels and gender.

    Science.gov (United States)

    Papanikolaou, M; Skenteris, N; Piperakis, S M

    2015-02-01

    The present study investigated the effect of low, medium, and high traffic road noise as well as irrelevant background speech noise on primary school children's reading and mathematical performance. A total of 676 participants (324 boys, 47.9% and 352 girls, 52.1%) of the 4th and 5th elementary classes participated in the project. The participants were enrolled in public primary schools from urban areas and had ages ranging from 9 to 10 years and from. Schools were selected on the basis of increasing levels of exposure to road traffic noise and then classified into three categories (Low noise: 55-66 dB, Medium noise: 67-77 dB, and High noise: 72-80 dB). We measured reading comprehension and mathematical skills in accordance with the national guidelines for elementary education, using a test designed specifically for the purpose of this study. On the one hand, children in low-level noise schools showed statistically significant differences from children in medium- and high-level noise schools in reading performance (plevel noise schools differed significantly from children in high-level noise schools but only in mathematics performance (p=0.001). Girls in general did better in reading score than boys, especially in schools with medium- and high-level noise. Finally the levels of noise and gender were found to be two independent factors.

  19. Sea Ice Deformation State From Synthetic Aperture Radar Imagery - Part II: Effects of Spatial Resolution and Noise Level

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Dall, Jørgen

    2008-01-01

    . The areal fraction at C-band remains constant. The retrieved average distance between deformation features increases both at C- and L-bands, as the image resolution gets coarser. The influence of noise becomes noticeable if its level is equal or larger than the average intensity backscattered from the level......C- and L-band airborne synthetic aperture radar (SAR) imagery acquired at like- and cross-polarization over sea ice under winter conditions is examined with the objective to study the discrimination between level ice and ice deformation features. High-resolution low-noise data were analysed....... The signal-to-noise ratio is varied between typical noise levels for airborne imagery and satellite data. Areal fraction of deformed ice and average deformation distance are determined for each image product. At L-band, the retrieved values of the areal fraction get larger as the image resolution is degraded...

  20. Interferometric SAR imaging by transmitting stepped frequency chaotic noise signals

    Science.gov (United States)

    Zhang, Yunhua; Gu, Xiang; Zhai, Wenshuai; Dong, Xiao; Shi, Xiaojin; Kang, Xueyan

    2015-10-01

    Noise radar has been applied in many fields since it was proposed more than 50 years ago. However, it has not been applied to interferometric SAR imaging yet as far as we know. This paper introduces our recent work on interferometric noise radar. An interferometric SAR system was developed which can transmit both chirp signal and chaotic noise signal (CNS) at multiple carrier frequencies. An airborne experiment with this system by transmitting both signals was carried out, and the data were processed to show the capability of interferometric SAR imaging with CNS. The results shows that although the interferometric phase quality of CNS is degraded due to the signal to noise ratio (SNR) is lower compared with that of chirp signal, we still can get satisfied DEM after multi-looking processing. Another work of this paper is to apply compressed sensing (CS) theory to the interferometric SAR imaging with CNS. The CS theory states that if a signal is sparse, then it can be accurately reconstructed with much less sampled data than that regularly required according to Nyquist Sampling Theory. To form a structured random matrix, if the transmitted signal is of fixed waveform, then random subsampling is needed. However, if the transmitted signal is of random waveform, then only uniform subsampling is needed. This is another advantage of noise signal. Both the interferometric phase images and the DEMs by regular method and by CS method are processed with results compared. It is shown that the degradation of interferometric phases due to subsampling is larger than that of amplitude image.

  1. Photonic microwave signals with zeptosecond level absolute timing noise

    CERN Document Server

    Xie, Xiaopeng; Nicolodi, Daniele; Giunta, Michele; Hänsel, Wolfgang; Lezius, Matthias; Joshi, Abhay; Datta, Shubhashish; Alexandre, Christophe; Lours, Michel; Tremblin, Pierre-Alain; Santarelli, Giorgio; Holzwarth, Ronald; Coq, Yann Le

    2016-01-01

    Photonic synthesis of radiofrequency revived the quest for unrivalled microwave purity by its seducing ability to convey the benefits of the optics to the microwave world. In this work, we perform a high-fidelity transfer of frequency stability between an optical reference and a microwave signal via a low-noise fiber-based frequency comb and cutting-edge photo-detection techniques. We demonstrate the generation of the purest microwave signal with a fractional frequency stability below 6.5 x 10^-16 at 1 s and a timing noise floor below 41 zs.Hz^-1/2 (phase noise below -173 dBc.Hz^-1 for a 12 GHz carrier). This outclasses existing sources and promises a new era for state-of-the-art microwave generation. The characterization is achieved by building two auxiliary low noise optoelectronic microwave reference and using a heterodyne cross-correlation scheme with lowermost detection noise. This unprecedented level of purity can impact domains such as radar systems, telecommunications and time-frequency metrology. Fur...

  2. Quantification of airport community noise impact in terms of noise levels, population density, and human subjective response

    Science.gov (United States)

    Deloach, R.

    1981-01-01

    The Fraction Impact Method (FIM), developed by the National Research Council (NRC) for assessing the amount and physiological effect of noise, is described. Here, the number of people exposed to a given level of noise is multiplied by a weighting factor that depends on noise level. It is pointed out that the Aircraft-noise Levels and Annoyance MOdel (ALAMO), recently developed at NASA Langley Research Center, can perform the NRC fractional impact calculations for given modes of operation at any U.S. airport. The sensitivity of these calculations to errors in estimates of population, noise level, and human subjective response is discussed. It is found that a change in source noise causes a substantially smaller change in contour area than would be predicted simply on the basis of inverse square law considerations. Another finding is that the impact calculations are generally less sensitive to source noise errors than to systematic errors in population or subjective response.

  3. [Comfort and noise level in infants with helmet interface].

    Science.gov (United States)

    Medina, A; Alvarez Fernández, P; Rey Galán, C; Álvarez Mendiola, P; Álvarez Blanco, S; Vivanco Allende, A

    2015-10-01

    To evaluate comfort and noise intensity using the COMFORT scale in infants who receive respiratory support with a helmet interface. An observational descriptive study was conducted on all infants (1 to 12 months of age) admitted to a PICU from November 1st 2013 to March 31st 2014 and who received non-invasive ventilation with a helmet interface. Tolerance to the interface was assessed by use of the COMFORT scale. The intensity of the noise to which the infants were exposed was measured with a TES1350A HIBOK 412 sound-level meter. Three measurements were made every day. Twenty seven patients with bronchiolitis (median age: 54 days; range: 10 to 256) were included. Median COMFORT score in the first day was 21 points (14 - 28). An increase in patient comfort was found with a gradual decrease in the scores, with a maximum reduction of 22% from the first hours (score of 22) to the fifth day (score of 18). The minimum sound intensity registered was 42dB, and the maximum was 78dB. Background noise intensity was associated with noise intensity in the helmet. No differences were observed in COMFORT score and noise intensity between ventilator devices. Helmet interface was well tolerated by infants. COMFORT score results are an indicator that infants were comfortable or very comfortable. The measured noise intensity was in the safe range permitted by World Health Organization. Copyright © 2014 Asociación Española de Pediatría. Published by Elsevier España, S.L.U. All rights reserved.

  4. Fourth-order partial differential equation noise removal on welding images

    Science.gov (United States)

    Halim, Suhaila Abd; Ibrahim, Arsmah; Sulong, Tuan Nurul Norazura Tuan; Manurung, Yupiter HP

    2015-10-01

    Partial differential equation (PDE) has become one of the important topics in mathematics and is widely used in various fields. It can be used for image denoising in the image analysis field. In this paper, a fourth-order PDE is discussed and implemented as a denoising method on digital images. The fourth-order PDE is solved computationally using finite difference approach and then implemented on a set of digital radiographic images with welding defects. The performance of the discretized model is evaluated using Peak Signal to Noise Ratio (PSNR). Simulation is carried out on the discretized model on different level of Gaussian noise in order to get the maximum PSNR value. The convergence criteria chosen to determine the number of iterations required is measured based on the highest PSNR value. Results obtained show that the fourth-order PDE model produced promising results as an image denoising tool compared with median filter.

  5. Fourth-order partial differential equation noise removal on welding images

    Energy Technology Data Exchange (ETDEWEB)

    Halim, Suhaila Abd; Ibrahim, Arsmah; Sulong, Tuan Nurul Norazura Tuan [Center of Mathematics Studies, Faculty of Computer and Mathematical Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Selangor. Malaysia (Malaysia); Manurung, Yupiter HP [Advanced Manufacturing Technology Center, Faculty of Mechanical Engineering, Universiti TEknologi MARA, 40450 Shah Alam, Selangor. Malaysia (Malaysia)

    2015-10-22

    Partial differential equation (PDE) has become one of the important topics in mathematics and is widely used in various fields. It can be used for image denoising in the image analysis field. In this paper, a fourth-order PDE is discussed and implemented as a denoising method on digital images. The fourth-order PDE is solved computationally using finite difference approach and then implemented on a set of digital radiographic images with welding defects. The performance of the discretized model is evaluated using Peak Signal to Noise Ratio (PSNR). Simulation is carried out on the discretized model on different level of Gaussian noise in order to get the maximum PSNR value. The convergence criteria chosen to determine the number of iterations required is measured based on the highest PSNR value. Results obtained show that the fourth-order PDE model produced promising results as an image denoising tool compared with median filter.

  6. Multislice CT angiography in aortic stent grafting: Relationship between image noise and body mass index

    Energy Technology Data Exchange (ETDEWEB)

    Sun Zhonghua [Discipline of Medical Imaging, Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth, Western Australia 6845 (Australia)]. E-mail: z.sun@curtin.edu.au

    2007-03-15

    Purpose: To investigate the correlation between image noise and body mass index (BMI) in multislice CT angiography (MSCT) for patients with abdominal aortic aneurysm (AAA) treated with endovascular stent grafts. Materials and methods: Seventeen patients who underwent MSCT following endovascular repair of AAA were included in the study. Image noise (standard deviation of the CT attenuation: S.D.) and signal to noise ratio (SNR) were plotted against BMI to demonstrate the correlation using a linear regression method. Image quality of 3D reconstructions was correlated to the SNR and BMI. Results: The r-value of linear regression between S.D. and BMI was 0.578 (p < 0.05), 0.835 and 0.802 (p < 0.001), respectively, at the level of renal artery, aortic aneurysm and common iliac artery. The r-value of linear regression between SNR and BMI was 0.332, 0.516 and 0.552 (p < 0.05), respectively, at above three levels. Image quality of 3D reconstructions was compromised in five patients and diagnosis was affected in two patients with BMI more than 30. Conclusion: A significant correlation was observed between image noise and BMI in MSCT angiography of endovascular repair of AAA. Our findings are valuable for optimisation of MSCT angiography scanning protocols and reduction of radiation dose in MSCT examinations.

  7. Effects of injected dose, BMI and scanner type on NECR and image noise in PET imaging.

    Science.gov (United States)

    Chang, Tingting; Chang, Guoping; Kohlmyer, Steve; Clark, John W; Rohren, Eric; Mawlawi, Osama R

    2011-08-21

    Noise equivalent count rate (NECR) and image noise are two different but related metrics that have been used to predict and assess image quality, respectively. The aim of this study is to investigate, using patient studies, the relationships between injected dose (ID), body mass index (BMI) and scanner type on NECR and image noise measurements in PET imaging. Two groups of 90 patients each were imaged on a GE DSTE and a DRX PET/CT scanner, respectively. The patients in each group were divided into nine subgroups according to three BMI (20-24.9, 25-29.9, 30-45 kg m(-2)) and three ID (296-444, 444-555, 555-740 MBq) ranges, resulting in ten patients/subgroup. All PET data were acquired in 3D mode and reconstructed using the VuePoint HD® fully 3D OSEM algorithm (2 iterations, 21(DRX) or 20 (DSTE) subsets). NECR and image noise measurements for bed positions covering the liver were calculated for each patient. NECR was calculated from the trues, randoms and scatter events recorded in the DICOM header of each patient study, while image noise was determined as the standard deviation of 50 non-neighboring voxels in the liver of each patient. A t-test compared the NECR and image noise for different scanners but with the same BMI and ID. An ANOVA test on the other hand was used to compare the results of patients with different BMI but the same ID and scanner type as well as different ID but the same BMI and scanner type. As expected the t-test showed a significant difference in NECR between the two scanners for all BMI and ID subgroups. However, contrary to what is expected no such findings were observed for image noise measurement. The ANOVA results showed a statistically significant difference in both NECR and image noise among the different BMI for each ID and scanner subgroup. However, there was no statistically significant difference in NECR and image noise across different ID for each BMI and scanner subgroup. Although the GE DRX PET/CT scanner has better count rate

  8. Effects of injected dose, BMI and scanner type on NECR and image noise in PET imaging

    Science.gov (United States)

    Chang, Tingting; Chang, Guoping; Kohlmyer, Steve; Clark, John W., Jr.; Rohren, Eric; Mawlawi, Osama R.

    2011-08-01

    Noise equivalent count rate (NECR) and image noise are two different but related metrics that have been used to predict and assess image quality, respectively. The aim of this study is to investigate, using patient studies, the relationships between injected dose (ID), body mass index (BMI) and scanner type on NECR and image noise measurements in PET imaging. Two groups of 90 patients each were imaged on a GE DSTE and a DRX PET/CT scanner, respectively. The patients in each group were divided into nine subgroups according to three BMI (20-24.9, 25-29.9, 30-45 kg m-2) and three ID (296-444, 444-555, 555-740 MBq) ranges, resulting in ten patients/subgroup. All PET data were acquired in 3D mode and reconstructed using the VuePoint HD® fully 3D OSEM algorithm (2 iterations, 21(DRX) or 20 (DSTE) subsets). NECR and image noise measurements for bed positions covering the liver were calculated for each patient. NECR was calculated from the trues, randoms and scatter events recorded in the DICOM header of each patient study, while image noise was determined as the standard deviation of 50 non-neighboring voxels in the liver of each patient. A t-test compared the NECR and image noise for different scanners but with the same BMI and ID. An ANOVA test on the other hand was used to compare the results of patients with different BMI but the same ID and scanner type as well as different ID but the same BMI and scanner type. As expected the t-test showed a significant difference in NECR between the two scanners for all BMI and ID subgroups. However, contrary to what is expected no such findings were observed for image noise measurement. The ANOVA results showed a statistically significant difference in both NECR and image noise among the different BMI for each ID and scanner subgroup. However, there was no statistically significant difference in NECR and image noise across different ID for each BMI and scanner subgroup. Although the GE DRX PET/CT scanner has better count rate

  9. Photonic microwave signals with zeptosecond-level absolute timing noise

    Science.gov (United States)

    Xie, Xiaopeng; Bouchand, Romain; Nicolodi, Daniele; Giunta, Michele; Hänsel, Wolfgang; Lezius, Matthias; Joshi, Abhay; Datta, Shubhashish; Alexandre, Christophe; Lours, Michel; Tremblin, Pierre-Alain; Santarelli, Giorgio; Holzwarth, Ronald; Le Coq, Yann

    2017-01-01

    Photonic synthesis of radiofrequency (RF) waveforms revived the quest for unrivalled microwave purity because of its ability to convey the benefits of optics to the microwave world. In this work, we perform a high-fidelity transfer of frequency stability between an optical reference and a microwave signal via a low-noise fibre-based frequency comb and cutting-edge photodetection techniques. We demonstrate the generation of the purest microwave signal with a fractional frequency stability below 6.5 × 10-16 at 1 s and a timing noise floor below 41 zs Hz-1/2 (phase noise below -173 dBc Hz-1 for a 12 GHz carrier). This outperforms existing sources and promises a new era for state-of-the-art microwave generation. The characterization is achieved through a heterodyne cross-correlation scheme with the lowermost detection noise. This unprecedented level of purity can impact domains such as radar systems, telecommunications and time-frequency metrology. The measurement methods developed here can benefit the characterization of a broad range of signals.

  10. Speckle Decorrelation and Dynamic Range in Speckle Noise Limited Imaging

    CERN Document Server

    Sivaramakrishnan, A; Hodge, P E; MacIntosh, B A; Sivaramakrishnan, Anand; Lloyd, James P.; Hodge, Philip E.; Macintosh, Bruce A.

    2002-01-01

    The useful dynamic range of an image in the diffraction limited regime is usually limited by speckles caused by residual phase errors in the optical system forming the image. The technique of speckle decorrelation involves introducing many independent realizations of additional phase error into a wavefront during one speckle lifetime, changing the instantaneous speckle pattern. A commonly held assumption is that this results in the speckles being `moved around' at the rate at which the additional phase screens are applied. The intention of this exercise is to smooth the speckles out into a more uniform background distribution during their persistence time, thereby enabling companion detection around bright stars to be photon noise limited rather than speckle-limited. We demonstrate analytically why this does not occur, and confirm this result with numerical simulations. We show that the original speckles must persist, and that the technique of speckle decorrelation merely adds more noise to the original speck...

  11. Speckle noise reduction in ultrasound images using a discrete wavelet transform-based image fusion technique.

    Science.gov (United States)

    Choi, Hyun Ho; Lee, Ju Hwan; Kim, Sung Min; Park, Sung Yun

    2015-01-01

    Here, the speckle noise in ultrasonic images is removed using an image fusion-based denoising method. To optimize the denoising performance, each discrete wavelet transform (DWT) and filtering technique was analyzed and compared. In addition, the performances were compared in order to derive the optimal input conditions. To evaluate the speckle noise removal performance, an image fusion algorithm was applied to the ultrasound images, and comparatively analyzed with the original image without the algorithm. As a result, applying DWT and filtering techniques caused information loss and noise characteristics, and did not represent the most significant noise reduction performance. Conversely, an image fusion method applying SRAD-original conditions preserved the key information in the original image, and the speckle noise was removed. Based on such characteristics, the input conditions of SRAD-original had the best denoising performance with the ultrasound images. From this study, the best denoising technique proposed based on the results was confirmed to have a high potential for clinical application.

  12. Measurement of Acceptable Noise Level with Background Music.

    Science.gov (United States)

    Ahn, Hyun-Jung; Bahng, Junghwa; Lee, Jae Hee

    2015-09-01

    Acceptable noise level (ANL) is a measure of the maximum background noise level (BNL) that a person is willing to tolerate while following a target story. Although researchers have used various sources of target sound in ANL measures, a limited type of background noise has been used. Extending the previous study of Gordon-Hickey & Moore (2007), the current study determined the effect of music genre and tempo on ANLs as possible factors affecting ANLs. We also investigated the relationships between individual ANLs and the familiarity of music samples and between music ANLs and subjective preference. Forty-one participants were seperated into two groups according to their ANLs, 29 low-ANL listeners and 12 high-ANL listeners. Using Korean ANL material, the individual ANLs were measured based on the listeners' most comfortable listening level and BNL. The ANLs were measured in six conditions, with different music tempo (fast, slow) and genre (K-pop, pop, classical) in a counterbalanced order. Overall, ANLs did not differ by the tempo of background music, but music genre significantly affected individual ANLs. We observed relatively higher ANLs with K-pop music and relatively lower ANLs with classical music. This tendency was similar in both low-ANL and high-ANL groups. However, the subjective ratings of music familiarity and preference affected ANLs differently for low-ANL and high-ANL groups. In contrast to the low-ANL listeners, the ANLs of the high-ANL listeners were significantly affected by music familiarity and preference. The genre of background music affected ANLs obtained using background music. The degree of music familiarity and preference appears to be associated with individual susceptibility to background music only for listeners who are greatly annoyed by background noise (high-ANL listeners).

  13. Secure Image Encryption Based On a Chua Chaotic Noise Generator

    Directory of Open Access Journals (Sweden)

    A. S. Andreatos

    2013-10-01

    Full Text Available This paper presents a secure image cryptography telecom system based on a Chua's circuit chaotic noise generator. A chaotic system based on synchronised Master–Slave Chua's circuits has been used as a chaotic true random number generator (CTRNG. Chaotic systems present unpredictable and complex behaviour. This characteristic, together with the dependence on the initial conditions as well as the tolerance of the circuit components, make CTRNGs ideal for cryptography. In the proposed system, the transmitter mixes an input image with chaotic noise produced by a CTRNG. Using thresholding techniques, the chaotic signal is converted to a true random bit sequence. The receiver must be able to reproduce exactly the same chaotic noise in order to subtract it from the received signal. This becomes possible with synchronisation between the two Chua's circuits: through the use of specific techniques, the trajectory of the Slave chaotic system can be bound to that of the Master circuit producing (almost identical behaviour. Additional blocks have been used in order to make the system highly parameterisable and robust against common attacks. The whole system is simulated in Matlab. Simulation results demonstrate satisfactory performance, as well as, robustness against cryptanalysis. The system works with both greyscale and colour jpg images.

  14. Multiregion level-set partitioning of synthetic aperture radar images.

    Science.gov (United States)

    Ben Ayed, Ismail; Mitiche, Amar; Belhadj, Ziad

    2005-05-01

    The purpose of this study is to investigate Synthetic Aperture Radar (SAR) image segmentation into a given but arbitrary number of gamma homogeneous regions via active contours and level sets. The segmentation of SAR images is a difficult problem due to the presence of speckle which can be modeled as strong, multiplicative noise. The proposed algorithm consists of evolving simple closed planar curves within an explicit correspondence between the interiors of curves and regions of segmentation to minimize a criterion containing a term of conformity of data to a speckle model of noise and a term of regularization. Results are shown on both synthetic and real images.

  15. A method for predicting DCT-based denoising efficiency for grayscale images corrupted by AWGN and additive spatially correlated noise

    Science.gov (United States)

    Rubel, Aleksey S.; Lukin, Vladimir V.; Egiazarian, Karen O.

    2015-03-01

    Results of denoising based on discrete cosine transform for a wide class of images corrupted by additive noise are obtained. Three types of noise are analyzed: additive white Gaussian noise and additive spatially correlated Gaussian noise with middle and high correlation levels. TID2013 image database and some additional images are taken as test images. Conventional DCT filter and BM3D are used as denoising techniques. Denoising efficiency is described by PSNR and PSNR-HVS-M metrics. Within hard-thresholding denoising mechanism, DCT-spectrum coefficient statistics are used to characterize images and, subsequently, denoising efficiency for them. Results of denoising efficiency are fitted for such statistics and efficient approximations are obtained. It is shown that the obtained approximations provide high accuracy of prediction of denoising efficiency.

  16. Mitigating noise in global manifold coordinates for hyperspectral image classification

    Science.gov (United States)

    Jin, Can; Bachmann, Charles M.

    2016-09-01

    Over the past decade, manifold and graph representations of hyperspectral imagery (HSI) have been explored widely in HSI applications. Among many data-driven approaches to deriving manifold coordinate representations including Isometric Mapping (ISOMAP), Local Linear Embedding (LLE), Laplacian Eigenmaps (LE), and Diffusion Kernels (DK), ISOMAP is the only global method that well represents the large scale nonlinear geometric structure of the data. In recent years, methods such as ENH-ISOMAP as well as its parallel computing accelerations makes ISOMAP practical for hyperspectral image dimensionality reduction. However, the noise problem in these methods has not been well addressed, which is critical to classification accuracy based on the manifold coordinates derived from these methods. While standard linear techniques to reduce the effects of noise can be applied as a preliminary step, these are based on global statistics and are applied globally across the entire data set, resulting in the risk of losing subtle nonlinear features before classification. To solve this problem, in this paper, we explore several approaches to modeling and mitigating noise in HSI in a local sense to improve the performance of the ENH-ISOMAP algorithm, aiming to reduce the noise effect on the manifold representations of the HSI. A new method to split data into local spectral subsets is introduced. Based on the local spectral subsets obtained with this method, a local noise model guided landmark selection scheme is proposed. In addition, a new robust adaptive neighborhood method using intrinsic dimensionality information to construct the k-Nearest Neighbor graph is introduced to increase the fidelity of the graph, based on the same framework of local spectral subsetting. The improved algorithm produces manifold coordinates with less noise, and shows a better classification accuracy using k-Nearest Neighbor classifier.

  17. Beyond the current noise limit in imaging through turbulent medium

    CERN Document Server

    Popowicz, A; Pollo, A; Smolka, B

    2015-01-01

    Shift-and-add is an approach employed to mitigate the phenomenon of resolution degradation in images acquired through a turbulent medium. Using this technique, a large number of consecutive short exposures is registered below the coherence time of the atmosphere or other blurring medium. The acquired images are shifted to the position of the brightest speckle and stacked together to obtain high-resolution and high signal-to-noise frame. In this paper we present a highly efficient method for determination of frames shifts, even if in a single frame the object cannot be distinguished from the background noise. The technique utilizes our custom genetic algorithm, which iteratively evolves a set of image shifts. We used the maximal energy of stacked images as an objective function for shifts estimation and validate the efficiency of the method on simulated and real images of simple and complex sources. Obtained results confirmed, that our proposed method allows for the recovery of spatial distribution of objects ...

  18. Evaluation of noise level at intensive care units in selected hospitals of Sanandaj

    Directory of Open Access Journals (Sweden)

    Nammam Ali Azadi

    2015-08-01

    Conclusion: We found the noise levels were always above the EPA thresholds at all three hospitals both during the day and night. It is recommended to train hospital officials and staffs for keeping noise levels to an acceptable level.

  19. Suppression of fixed pattern noise for infrared image system

    Science.gov (United States)

    Park, Changhan; Han, Jungsoo; Bae, Kyung-Hoon

    2008-04-01

    In this paper, we propose suppression of fixed pattern noise (FPN) and compensation of soft defect for improvement of object tracking in cooled staring infrared focal plane array (IRFPA) imaging system. FPN appears an observable image which applies to non-uniformity compensation (NUC) by temperature. Soft defect appears glittering black and white point by characteristics of non-uniformity for IR detector by time. This problem is very important because it happen serious problem for object tracking as well as degradation for image quality. Signal processing architecture in cooled staring IRFPA imaging system consists of three tables: low, normal, high temperature for reference gain and offset values. Proposed method operates two offset tables for each table. This is method which operates six term of temperature on the whole. Proposed method of soft defect compensation consists of three stages: (1) separates sub-image for an image, (2) decides a motion distribution of object between each sub-image, (3) analyzes for statistical characteristic from each stationary fixed pixel. Based on experimental results, the proposed method shows an improved image which suppresses FPN by change of temperature distribution from an observational image in real-time.

  20. Difference-Based Image Noise Modeling Using Skellam Distribution.

    Science.gov (United States)

    Hwang, Youngbae; Kim, Jun-Sik; Kweon, In So

    2012-07-01

    By the laws of quantum physics, pixel intensity does not have a true value, but should be a random variable. Contrary to the conventional assumptions, the distribution of intensity may not be an additive Gaussian. We propose to directly model the intensity difference and show its validity by an experimental comparison to the conventional additive model. As a model of the intensity difference, we present a Skellam distribution derived from the Poisson photon noise model. This modeling induces a linear relationship between intensity and Skellam parameters, while conventional variance computation methods do not yield any significant relationship between these parameters under natural illumination. The intensity-Skellam line is invariant to scene, illumination, and even most of camera parameters. We also propose practical methods to obtain the line using a color pattern and an arbitrary image under natural illumination. Because the Skellam parameters that can be obtained from this linearity determine a noise distribution for each intensity value, we can statistically determine whether any intensity difference is caused by an underlying signal difference or by noise. We demonstrate the effectiveness of this new noise model by applying it to practical applications of background subtraction and edge detection.

  1. A New Hybrid Fuzzy Intelligent Filter for Medical Image Noise Reduction

    OpenAIRE

    Somaye Aliakbari Dehkordi; Mohammad Ghasemzadeh; Vali Derhami

    2014-01-01

    Medical imaging comprises different imaging modalities and processes to image human body for diagnostic and treatment purposes and, therefore has an important role in the improvement of public health in all population groups. In this paper, we present an intelligent hybrid noise reduction filter which is based on Neuro-Fuzzy systems. It is especially beneficial in medical image noise reduction. First stage we feed the input image into four general noise reduction filters in parallel. These ge...

  2. Wavelet-based pavement image compression and noise reduction

    Science.gov (United States)

    Zhou, Jian; Huang, Peisen S.; Chiang, Fu-Pen

    2005-08-01

    For any automated distress inspection system, typically a huge number of pavement images are collected. Use of an appropriate image compression algorithm can save disk space, reduce the saving time, increase the inspection distance, and increase the processing speed. In this research, a modified EZW (Embedded Zero-tree Wavelet) coding method, which is an improved version of the widely used EZW coding method, is proposed. This method, unlike the two-pass approach used in the original EZW method, uses only one pass to encode both the coordinates and magnitudes of wavelet coefficients. An adaptive arithmetic encoding method is also implemented to encode four symbols assigned by the modified EZW into binary bits. By applying a thresholding technique to terminate the coding process, the modified EZW coding method can compress the image and reduce noise simultaneously. The new method is much simpler and faster. Experimental results also show that the compression ratio was increased one and one-half times compared to the EZW coding method. The compressed and de-noised data can be used to reconstruct wavelet coefficients for off-line pavement image processing such as distress classification and quantification.

  3. Noise removal in magnetic resonance diffusion tensor imaging.

    Science.gov (United States)

    Chen, Bin; Hsu, Edward W

    2005-08-01

    Although promising for visualizing the structure of ordered tissues, MR diffusion tensor imaging (DTI) has been hampered by long acquisition time and low spatial resolution associated with its inherently low signal-to-noise ratio (SNR). Moreover, the uncertainty in the DTI measurements has a direct impact on the accuracy of structural renderings such as fiber streamline tracking. Noise removal techniques can be used to improve the SNR of DTI without requiring additional acquisitions, albeit most low-pass filtering methods are accompanied by undesirable image blurring. In the present study, a modified vector-based partial-differential-equation (PDE) filtering formalism was implemented for smoothing DTI vector fields. Using an image residual-energy criterion to equate the degree of smoothing and error metrics empirically derived from DTI data to quantify the relative performances, the effectiveness in denoising DTI data is compared among image-based and vector-based PDE and fixed and adaptive low-pass k-space filtering. The results demonstrate that the edge-preservation feature of the PDE approach can be highly advantageous in enhancing DTI measurements, particularly for vector-based PDE filtering in applications relying on DTI directional information. These findings suggest a potential role for the postprocessing enhancement technique to improve the practical utility of DTI.

  4. Type of speech material affects Acceptable Noise Level test outcome

    Directory of Open Access Journals (Sweden)

    Xaver eKoch

    2016-02-01

    Full Text Available The Acceptable Noise Level (ANL test, in which individuals indicate what level of noise they are willing to put up with while following speech, has been used to guide hearing aid fitting decisions and has been found to relate to prospective hearing aid use. Unlike objective measures of speech perception ability, ANL outcome is not related to individual hearing loss or age, but rather reflects an individual's inherent acceptance of competing noise while listening to speech. As such, the measure may predict aspects of hearing aid success. Crucially, however, recent studies have questioned its repeatability (test-retest reliability. The first question for this study was whether the inconsistent results regarding the repeatability of the ANL test may be due to differences in speech material types used in previous studies. Second, it is unclear whether meaningfulness and semantic coherence of the speech modify ANL outcome. To investigate these questions, we compared ANLs obtained with three types of materials: the International Speech Test Signal (ISTS, which is non-meaningful and semantically non-coherent by definition, passages consisting of concatenated meaningful standard audiology sentences, and longer fragments taken from conversational speech. We included conversational speech as this type of speech material is most representative of everyday listening. Additionally, we investigated whether ANL outcomes, obtained with these three different speech materials, were associated with self-reported limitations due to hearing problems and listening effort in everyday life, as assessed by a questionnaire. ANL data were collected for 57 relatively good-hearing adult participants with an age range representative for hearing aid users. Results showed that meaningfulness, but not semantic coherence of the speech material affected ANL. Less noise was accepted for the non-meaningful ISTS signal than for the meaningful speech materials. ANL repeatability was

  5. Real-time implementation of optimized maximum noise fraction transform for feature extraction of hyperspectral images

    Science.gov (United States)

    Wu, Yuanfeng; Gao, Lianru; Zhang, Bing; Zhao, Haina; Li, Jun

    2014-01-01

    We present a parallel implementation of the optimized maximum noise fraction (G-OMNF) transform algorithm for feature extraction of hyperspectral images on commodity graphics processing units (GPUs). The proposed approach explored the algorithm data-level concurrency and optimized the computing flow. We first defined a three-dimensional grid, in which each thread calculates a sub-block data to easily facilitate the spatial and spectral neighborhood data searches in noise estimation, which is one of the most important steps involved in OMNF. Then, we optimized the processing flow and computed the noise covariance matrix before computing the image covariance matrix to reduce the original hyperspectral image data transmission. These optimization strategies can greatly improve the computing efficiency and can be applied to other feature extraction algorithms. The proposed parallel feature extraction algorithm was implemented on an Nvidia Tesla GPU using the compute unified device architecture and basic linear algebra subroutines library. Through the experiments on several real hyperspectral images, our GPU parallel implementation provides a significant speedup of the algorithm compared with the CPU implementation, especially for highly data parallelizable and arithmetically intensive algorithm parts, such as noise estimation. In order to further evaluate the effectiveness of G-OMNF, we used two different applications: spectral unmixing and classification for evaluation. Considering the sensor scanning rate and the data acquisition time, the proposed parallel implementation met the on-board real-time feature extraction.

  6. Subcutaneous Tissue Thickness is an Independent Predictor of Image Noise in Cardiac CT

    Energy Technology Data Exchange (ETDEWEB)

    Staniak, Henrique Lane; Sharovsky, Rodolfo [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil); Pereira, Alexandre Costa [Hospital das Clínicas - Universidade de São Paulo, São Paulo, SP (Brazil); Castro, Cláudio Campi de; Benseñor, Isabela M.; Lotufo, Paulo A. [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil); Faculdade de Medicina - Universidade de São Paulo, São Paulo, SP (Brazil); Bittencourt, Márcio Sommer, E-mail: msbittencourt@mail.harvard.edu [Hospital Universitário - Universidade de São Paulo, São Paulo, SP (Brazil)

    2014-01-15

    Few data on the definition of simple robust parameters to predict image noise in cardiac computed tomography (CT) exist. To evaluate the value of a simple measure of subcutaneous tissue as a predictor of image noise in cardiac CT. 86 patients underwent prospective ECG-gated coronary computed tomographic angiography (CTA) and coronary calcium scoring (CAC) with 120 kV and 150 mA. The image quality was objectively measured by the image noise in the aorta in the cardiac CTA, and low noise was defined as noise < 30HU. The chest anteroposterior diameter and lateral width, the image noise in the aorta and the skin-sternum (SS) thickness were measured as predictors of cardiac CTA noise. The association of the predictors and image noise was performed by using Pearson correlation. The mean radiation dose was 3.5 ± 1.5 mSv. The mean image noise in CT was 36.3 ± 8.5 HU, and the mean image noise in non-contrast scan was 17.7 ± 4.4 HU. All predictors were independently associated with cardiac CTA noise. The best predictors were SS thickness, with a correlation of 0.70 (p < 0.001), and noise in the non-contrast images, with a correlation of 0.73 (p < 0.001). When evaluating the ability to predict low image noise, the areas under the ROC curve for the non-contrast noise and for the SS thickness were 0.837 and 0.864, respectively. Both SS thickness and CAC noise are simple accurate predictors of cardiac CTA image noise. Those parameters can be incorporated in standard CT protocols to adequately adjust radiation exposure.

  7. Two Level DCT and Wavelet Packets Denoising Robust Image Watermarking

    Directory of Open Access Journals (Sweden)

    N.Koteswara Rao

    2014-01-01

    Full Text Available In this paper we present a low frequency watermarking scheme on gray level images, which is based on DCT transform and spread spectrum communications technique.The DCT of non overlapping 8x8 blocks of the host image is computed, then using each block DC coefficients we construct a low-resolution approximation image. We apply block based DCT on this approximation image, then a pseudo random noise sequence is added into its high frequencies. For detection, we extract the approximation image from the watermarked image, then the same pseudo random noise sequence is generated, and its correlation is computed with high frequencies of the watermarked approximation image. In our method, higher robustness is obtained because of embedding the watermark in low frequency. In addition, higher imperceptibility is gained by scattering the watermark's bit in different blocks. We evaluated the robustness of the proposed technique against many common attacks such as JPEG compression, additive Gaussian noise and median filter. Compared with related works, our method proved to be highly resistant in cases of compression and additive noise, while preserving high PSNR for the watermarked images.

  8. Dual energy contrast enhanced breast imaging optimization using contrast to noise ratio

    Science.gov (United States)

    Arvanitis, C. D.; Royle, G.; Speller, R.

    2007-03-01

    The properties of dual energy contrast enhanced breast imaging have been analyzed by imaging a 4 cm breast equivalent phantom consisting of adipose and glandular equivalent plastics. This phantom had superimposed another thin plastic which incorporated a 2 mm deep cylinder filled with iodinated contrast media. The iodine projected thicknesses used for this study was 3 mg/cm2. Low and high energy spectra that straddle the iodine K-edge were used. Critical parameters such as the energy spectra and exposure are discussed, along with post processing by means of nonlinear energy dependent function. The dual energy image was evaluated using the relative contrast to noise ratio of a 2.5 mm x 2.5 mm region of the image at the different iodine concentrations incorporating different breast composition with respect to the noniodinated areas. Optimum results were achieved when the low and high-energy images were used in such a way that relative contrast to noise ratio of the iodine with respect to the background tissue was maximum. A figure of merit suggests that higher noise levels can be tolerated at the benefit of lower exposure. Contrast media kinetics of a phantom incorporating a water flow of 20.4 ml/min through the plastic cylinder suggests that time domain imaging could be performed with this approach. The results suggest that optimization of dual energy contrast enhanced mammography has the potential to lead to the development of perfusion digital mammography.

  9. Imaging the Western Iberia Crustal Structure by Noise Analysis

    Science.gov (United States)

    Silveira, G. M.; Dias, N. A.; Custodio, S.; Kiselev, S.; Dündar, S.

    2014-12-01

    Portugal lies close to the Eurasian-African boundary, a region of tectonic regime transition from convergence in the Mediterranean to strike-slip in the Atlantic. Such broad convergence area, characterized by a slow rate of about 4.5-5.6 mm/yr, translates unto a scattered seismicity concentrated mainly in the offshore. Therefore, the irregular source-receiver geometry resulting from the inland seismic stations networks does not permit to derive high-resolution models of the Portuguese crustal structure using traditional passive seismology. Seismic interferometry/ambient noise surface-waves tomography allows imaging regions with a resolution that mainly depends on the seismic network coverage. Over the last decade, both Portuguese and Spanish permanent broadband (BB) seismic networks expanded significantly. This densification enabled to build a detailed image of the crustal structure of the Iberian Peninsula using ambient seismic noise. However, due to the existing network gaps towards west, the crustal image of Western Iberia is on the limit of resolution. The two years temporary deployment by the WILAS project contributed to fill those gaps and provide an excellent opportunity to study the Portuguese crustal structure. Dispersion measurements were computed for each pair of stations using empirical Green's functions generated by cross-correlating one-day-length seismic ambient-noise records. To improve the signal-to-noise ratio of the empirical Green functions computed from ambient noise records, we applied a phase cross-correlation method, followed by time-frequency domain phase weighted stack. Group-velocities were computed using the S-transform and we use the Fast Marching Surface Tomography algoritm to compute group velocity perturbation maps. Group velocities were then inverted as a function of depth to obtain S-wave velocity maps for diferent depths. The models will be compared with results from Ps receiver functions. The results obtained for the crust using

  10. Experimental analysis of image noise and interpolation bias in digital image correlation

    Science.gov (United States)

    Gao, Zeren; Xu, Xiaohai; Su, Yong; Zhang, Qingchuan

    2016-06-01

    The popularization of the digital image correlation (DIC) method has raised urgent needs to evaluate the accuracy of this method. However, there are still some problems to be solved. Among the problems, the effects of various factors, such as the image noise caused by the camera sensors, the employed interpolation algorithm, and the structure of the speckle patterns, have become a major concern. To experimentally measure the position-dependent systematic error (i.e. interpolation bias) caused by non-ideal interpolation algorithm is an important way to evaluate the quality of the speckle patterns in the correlation method, and remains unsolved. In this work, a novel, simple and convenient method is proposed to measure the interpolation bias. In the new method which can avoid the out-of-plane displacements and the mechanical errors of translation stages, integral-pixel shifts are applied to the image shown on the screen so that sub-pixel displacements can be realized in the images captured by the camera via proper experimental settings. Besides, the fluctuations of the image noise and the sub-pixel displacement errors caused by the image noise are experimentally analyzed by employing three types of cameras commonly used in the DIC measurements. Experimental results indicate that the fluctuations of the image noise are not only proportional to the image gray value, but also dependent on the type of the employed camera. On the basis of eliminating the image noise via the image averaging technique, high-precision interpolation bias curves more than one period are experimentally obtained by the proposed method.

  11. Improvement in DMSA imaging using adaptive noise reduction: an ROC analysis.

    Science.gov (United States)

    Lorimer, Lisa; Gemmell, Howard G; Sharp, Peter F; McKiddie, Fergus I; Staff, Roger T

    2012-11-01

    Dimercaptosuccinic acid imaging is the 'gold standard' for the detection of cortical defects and diagnosis of scarring of the kidneys. The Siemens planar processing package, which implements adaptive noise reduction using the Pixon algorithm, is designed to allow a reduction in image noise, enabling improved image quality and reduced acquisition time/injected activity. This study aimed to establish the level of improvement in image quality achievable using this algorithm. Images were acquired of a phantom simulating a single kidney with a range of defects of varying sizes, positions and contrasts. These images were processed using the Pixon processing software and shown to 12 observers (six experienced and six novices) who were asked to rate the images on a six-point scale depending on their confidence that a defect was present. The data were analysed using a receiver operating characteristic approach. Results showed that processed images significantly improved the performance of the experienced observers in terms of their sensitivity and specificity. Although novice observers showed significant increase in sensitivity when using the software, a significant decrease in specificity was also seen. This study concludes that the Pixon software can be used to improve the assessment of cortical defects in dimercaptosuccinic acid imaging by suitably trained observers.

  12. Subjective annoyance caused by indoor low-level and low frequency noise and control method

    Institute of Scientific and Technical Information of China (English)

    DI Guo-qing; ZHANG Bang-jun; SHANG Qi

    2005-01-01

    The influence of low-level noise has not been widely noticed. This paper discovered that low-level and low frequency noise(Aweighted equivalent level Leq < 45 dB) causes higher probability of subjective annoyance. The fuzzy mathematic principle was applied to deal with the threshold level of subjective annoyance from noise in this study; there is preferable relationship between the indoor noise and noise annoyance at low frequency noise level. Study indicated at the same centered noise level, the change of annoyance probability is mainly caused by the change of the frequency spectrum characteristic of the indoor noise. Under low noise level environment, without change of the medium-low frequency noise, the slight increase of medium-high frequency noise level with the help of noise sheltering effect can significantly reduce the noise annoyance. This discovery brings a new resolution on how to improve the environmental quality of working or living places. A noise control model is given in this study according to the acoustic analysis.

  13. Noise levels of dental equipment used in dental college of Damascus University

    OpenAIRE

    Mhd. Loutify Qsaibati; Ousama Ibrahim

    2014-01-01

    Background: In dental practical classes, the acoustic environment is characterized by high noise levels in relation to other teaching areas. The aims of this study were to measure noise levels produced during the different dental learning clinics, by equipments used in dental learning areas under different working conditions and by used and brand new handpieces under different working conditions. Materials and Methods: The noise levels were measured by using a noise level meter with a mic...

  14. Patient-specific minimum-dose imaging protocols for statistical image reconstruction in C-arm cone-beam CT using correlated noise injection

    Science.gov (United States)

    Wang, A. S.; Stayman, J. W.; Otake, Y.; Khanna, A. J.; Gallia, G. L.; Siewerdsen, J. H.

    2014-03-01

    Purpose: A new method for accurately portraying the impact of low-dose imaging techniques in C-arm cone-beam CT (CBCT) is presented and validated, allowing identification of minimum-dose protocols suitable to a given imaging task on a patient-specific basis in scenarios that require repeat intraoperative scans. Method: To accurately simulate lower-dose techniques and account for object-dependent noise levels (x-ray quantum noise and detector electronics noise) and correlations (detector blur), noise of the proper magnitude and correlation was injected into the projections from an initial CBCT acquired at the beginning of a procedure. The resulting noisy projections were then reconstructed to yield low-dose preview (LDP) images that accurately depict the image quality at any level of reduced dose in both filtered backprojection and statistical image reconstruction. Validation studies were conducted on a mobile C-arm, with the noise injection method applied to images of an anthropomorphic head phantom and cadaveric torso across a range of lower-dose techniques. Results: Comparison of preview and real CBCT images across a full range of techniques demonstrated accurate noise magnitude (within ~5%) and correlation (matching noise-power spectrum, NPS). Other image quality characteristics (e.g., spatial resolution, contrast, and artifacts associated with beam hardening and scatter) were also realistically presented at all levels of dose and across reconstruction methods, including statistical reconstruction. Conclusion: Generating low-dose preview images for a broad range of protocols gives a useful method to select minimum-dose techniques that accounts for complex factors of imaging task, patient-specific anatomy, and observer preference. The ability to accurately simulate the influence of low-dose acquisition in statistical reconstruction provides an especially valuable means of identifying low-dose limits in a manner that does not rely on a model for the nonlinear

  15. Medical Image De-Noising Schemes using Wavelet Transform with Fixed form Thresholding

    Directory of Open Access Journals (Sweden)

    Nadir Mustafa

    2015-10-01

    Full Text Available Medical Imaging is currently a hot area of bio-medical engineers, researchers and medical doctors as it is extensively used in diagnosing of human health and by health care institutes. The imaging equipment is the device, which is used for better image processing and highlighting the important features. These images are affected by random noise during acquisition, analyzing and transmission process. This condition results in the blurry image visible in low contrast. The Image De-noising System (IDs is used as a tool for removing image noise and preserving important data. Image de-noising is one of the most interesting research areas among researchers of technology-giants and academic institutions. For Criminal Identification Systems (CIS & Magnetic Resonance Imaging (MRI, IDs is more beneficial in the field of medical imaging. This paper proposes an algorithm for de-noising medical images using different types of wavelet transform, such as Haar, Daubechies, Symlets and Bi-orthogonal. In this paper noise image quality has been evaluated using filter assessment parameters like Peak Signal to Noise Ratio (PSNR, Mean Square Error (MSE and Variance, It has been observed to form the numerical results that, the presentation of proposed algorithm reduced the mean square error and achieved best value of peak signal to noise ratio (PSNR. In this paper, the wavelet based de-noising algorithm has been investigated on medical images along with threshold.

  16. Chest computed tomography using iterative reconstruction vs filtered back projection (Part 1): evaluation of image noise reduction in 32 patients

    Energy Technology Data Exchange (ETDEWEB)

    Pontana, Francois; Pagniez, Julien; Faivre, Jean-Baptiste; Remy, Jacques [Univ. Lille Nord de France, Department of Thoracic Imaging Hospital Calmette (EA 2694), Lille (France); Flohr, Thomas [Siemens HealthCare, Computed Tomography Division, Forchheim (Germany); Duhamel, Alain [Univ. Lille Nord de France, Department of Medical Statistics, Lille (France); Remy-Jardin, Martine [Univ. Lille Nord de France, Department of Thoracic Imaging Hospital Calmette (EA 2694), Lille (France); Hospital Calmette, Department of Thoracic Imaging, Lille cedex (France)

    2011-03-15

    To assess noise reduction achievable with an iterative reconstruction algorithm. 32 consecutive chest CT angiograms were reconstructed with regular filtered back projection (FBP) (Group 1) and an iterative reconstruction technique (IRIS) with 3 (Group 2a) and 5 (Group 2b) iterations. Objective image noise was significantly reduced in Group 2a and Group 2b compared with FBP (p < 0.0001). There was a significant reduction in the level of subjective image noise in Group 2a compared with Group 1 images (p < 0.003), further reinforced on Group 2b images (Group 2b vs Group 1; p < 0.0001) (Group 2b vs Group 2a; p = 0.0006). The overall image quality scores significantly improved on Group 2a images compared with Group 1 images (p = 0.0081) and on Group 2b images compared with Group 2a images (p < 0.0001). Comparative analysis of individual CT features of mild lung infiltration showed improved conspicuity of ground glass attenuation (p < 0.0001), ill-defined micronodules (p = 0.0351) and emphysematous lesions (p < 0.0001) on Group 2a images, further improved on Group 2b images for ground glass attenuation (p < 0.0001), and emphysematous lesions (p = 0.0087). Compared with regular FBP, iterative reconstructions enable significant reduction of image noise without loss of diagnostic information, thus having the potential to decrease radiation dose during chest CT examinations. (orig.)

  17. SU-E-I-09: The Impact of X-Ray Scattering On Image Noise for Dedicated Breast CT

    Energy Technology Data Exchange (ETDEWEB)

    Yang, K [Massachusetts General Hospital, Boston, MA (United States); Gazi, P [University of California, Davis, Sacramento, CA (United States); Boone, J [UC Davis Medical Center, Sacramento, CA (United States)

    2015-06-15

    Purpose: To quantify the impact of detected x-ray scatter on image noise in flat panel based dedicated breast CT systems and to determine the optimal scanning geometry given practical trade-offs between radiation dose and scatter reduction. Methods: Four different uniform polyethylene cylinders (104, 131, 156, and 184 mm in diameter) were scanned as the phantoms on a dedicated breast CT scanner developed in our laboratory. Both stationary projection imaging and rotational cone-beam CT imaging was performed. For each acquisition type, three different x-ray beam collimations were used (12, 24, and 109 mm measured at isocenter). The aim was to quantify image noise properties (pixel variance, SNR, and image NPS) under different levels of x-ray scatter, in order to optimize the scanning geometry. For both projection images and reconstructed CT images, individual pixel variance and NPS were determined and compared. Noise measurement from the CT images were also performed with different detector binning modes and reconstruction matrix sizes. Noise propagation was also tracked throughout the intermediate steps of cone-beam CT reconstruction, including the inverse-logarithmic process, Fourier-filtering before backprojection. Results: Image noise was lower in the presence of higher scatter levels. For the 184 mm polyethylene phantom, the image noise (measured in pixel variance) was ∼30% lower with full cone-beam acquisition compared to a narrow (12 mm) fan-beam acquisition. This trend is consistent across all phantom sizes and throughout all steps of CT image reconstruction. Conclusion: From purely a noise perspective, the cone-beam geometry (i.e. the full cone-angle acquisition) produces lower image noise compared to the lower-scatter fan-beam acquisition for breast CT. While these results are relevant in homogeneous phantoms, the full impact of scatter on noise in bCT should involve contrast-to-noise-ratio measurements in heterogeneous phantoms if the goal is to optimize

  18. Are the noise levels acceptable in a built environment like Hong Kong?

    Science.gov (United States)

    To, Wai Ming; Mak, Cheuk Ming; Chung, Wai Leung

    2015-01-01

    Governments all over the world have enacted environmental noise directives and noise control ordinances/acts to protect tranquility in residential areas. However, there is a lack of literature on the evaluation of whether the Acceptable Noise Levels (ANLs) stipulated in the directive/ordinance/act are actually achievable. The study aimed at measuring outdoor environmental noise levels in Hong Kong and identifying whether the measured noise levels are lower than the stipulated ANLs at 20 categories of residential areas. Data were gathered from a territory-wide noise survey. Outdoor noise measurements were conducted at 203 residential premises in urban areas, low-density residential areas, rural areas, and other areas. In total, 366 daytime hourly Leq outdoor noise levels, 362 nighttime hourly Leq outdoor noise levels, and 20 sets of daily, that is, 24 L(eq,1-)h outdoor noise levels were recorded. The mean daytime L(eq,1-h) values ranged 54.4-70.8 dBA, while the mean nighttime L(eq,1-h) values ranged 52.6-67.9 dBA. When the measured noise levels were compared with the stipulated ANLs, only three out of the 20 categories of areas had outdoor noise levels below ANLs during daytime. All other areas (and all areas during nighttime) were found to have outdoor noise levels at or above ANLs.

  19. Estimation of sufficient signal to noise ratio for texture analysis of magnetic resonance images

    Science.gov (United States)

    Savio, Sami; Harrison, Lara; Ryymin, Pertti; Dastidar, Prasun; Soimakallio, Seppo; Eskola, Hannu

    2011-03-01

    In this study, we have studied the effect of background noise on the texture analysis of muscle, bone marrow and fat tissues in 1.5 T magnetic resonance (MR) images using different statistical methods. Variable levels of noise were first added on 3-mm thick T2 weighted image slices of voluntary subjects to simulate several signal-to-noise ratio (SNR) levels. For each original and simulated image, the values for 264 texture parameters were calculated using MaZda, a texture analysis toolkit. We also determined Fisher coefficients based on the texture parameter values in order to enable high discrimination between different tissues. Linear discriminant analysis (LDA) and two different nearest neighbour (NN) methods were then applied for the texture parameters with the highest Fisher coefficient values. Several training and test sets were used to approximate the variation in the classification results. All the above-mentioned methods had the same classification accuracy, which in turn depended on the image SNR. We conclude that these tissues can be detected by texture analysis methods with a sufficient accuracy (90%) especially if SNR is at least 30-40 dB, even though the separation of different muscles remains a very challenging task.

  20. Investigation of noise levels generated by otologic drills.

    Science.gov (United States)

    Dalchow, Carsten V; Hagemeier, K C; Muenscher, A; Knecht, R; Kameier, F

    2013-02-01

    Drilling during temporal bone surgery may result in temporary or permanent noise-induced hearing loss or tinnitus. This has practical implications for both the patient and the surgeon. Different surgical drill devices, routinely used in temporal bone surgery, are examined referring to their emitted sound levels and sound transport. Two surgical drills were used on a brass tubing and a steel wire to simulate sound generation during temporal bone surgery. Overview measurements were performed on human cadaver in a medical laboratory. A set-up in a silent chamber was chosen to exclude external sound sources. The noise emissions and the vibration generated by a silver diamond bur and a cutting drill (Rose bur) were registered when used on a brass tubing and a solid steel wire with sound level meter and a non-contact laser vibrometer. The highest sound rate generated by the diamond burr did not exceed 63 dB(A) when used on a solid steel wire, whereas the cutting burr emitted 76 dB(A). Both drills produced lower sound levels on the brass tubing. Again the cutting burr topped the diamond burr with 68 dB(A) against 56 dB(A). The sound emission did not exceed 76 dB(A) outside a radius 4 cm around the drill location. In conclusion, sound emission generated by different surgical burs routinely used in temporal bone surgery is lower than expected. Still, within a small radius around those burs high sound pressure levels may be induced into surrounding structures such as ossicles, labyrinth, and cochlear. Still damage is feasible when using surgical drills for a longer time period close to sensitive structures.

  1. Quality-aware features-based noise level estimator for block matching and three-dimensional filtering algorithm

    Science.gov (United States)

    Xu, Shaoping; Hu, Lingyan; Yang, Xiaohui

    2016-01-01

    The performance of conventional denoising algorithms is usually controlled by one or several parameters whose optimal settings depend on the contents of the processed images and the characteristics of the noises. Among these parameters, noise level is a fundamental parameter that is always assumed to be known by most of the existing denoising algorithms (so-called nonblind denoising algorithms), which largely limits the applicability of these nonblind denoising algorithms in many applications. Moreover, these nonblind algorithms do not always achieve the best denoised images in visual quality even when fed with the actual noise level parameter. To address these shortcomings, in this paper we propose a new quality-aware features-based noise level estimator (NLE), which consists of quality-aware features extraction and optimal noise level parameter prediction. First, considering that image local contrast features convey important structural information that is closely related to image perceptual quality, we utilize the marginal statistics of two local contrast operators, i.e., the gradient magnitude and the Laplacian of Gaussian (LOG), to extract quality-aware features. The proposed quality-aware features have very low computational complexity, making them well suited for time-constrained applications. Then we propose a learning-based framework where the noise level parameter is estimated based on the quality-aware features. Based on the proposed NLE, we develop a blind block matching and three-dimensional filtering (BBM3D) denoising algorithm which is capable of effectively removing additive white Gaussian noise, even coupled with impulse noise. The noise level parameter of the BBM3D algorithm is automatically tuned according to the quality-aware features, guaranteeing the best performance. As such, the classical block matching and three-dimensional algorithm can be transformed into a blind one in an unsupervised manner. Experimental results demonstrate that the

  2. Poisson noise reduction from X-ray images by region classification and response median filtering

    Indian Academy of Sciences (India)

    THAKUR KIRTI; KADAM JITENDRA; SAPKAL ASHOK

    2017-06-01

    Medical imaging is perturbed with inherent noise such as speckle noise in ultrasound, Poisson noise in X-ray and Rician noise in MRI imaging. This paper focuses on X-ray image denoising problem. X-ray image quality could be improved by increasing dose value; however, this may result in cell death or similar kinds of issues. Therefore, image processing techniques are developed to minimise noise instead of increasing dose value for patient safety. In this paper, usage of modified Harris corner point detector to predict noisy pixels and responsive median filtering in spatial domain is proposed. Experimentation proved that the proposed work performs better than simple median filter and moving average (MA) filter. The results are very close to non-local means Poisson noise filter which is one of the current state-of-the-art methods. Benefits of the proposed work are simple noise prediction mechanism, good visual quality and less execution time.

  3. Adaptive anisotropic diffusion for noise reduction of phase images in Fourier domain Doppler optical coherence tomography.

    Science.gov (United States)

    Xia, Shaoyan; Huang, Yong; Peng, Shizhao; Wu, Yanfeng; Tan, Xiaodi

    2016-08-01

    Phase image in Fourier domain Doppler optical coherence tomography offers additional flow information of investigated samples, which provides valuable evidence towards accurate medical diagnosis. High quality phase images are thus desirable. We propose a noise reduction method for phase images by combining a synthetic noise estimation criteria based on local noise estimator (LNE) and distance median value (DMV) with anisotropic diffusion model. By identifying noise and signal pixels accurately and diffusing them with different coefficients respectively and adaptive iteration steps, we demonstrated the effectiveness of our proposed method in both phantom and mouse artery images. Comparison with other methods such as filtering method (mean, median filtering), wavelet method, probabilistic method and partial differential equation based methods in terms of peak signal-to-noise ratio (PSNR), equivalent number of looks (ENL) and contrast-to-noise ratio (CNR) showed the advantages of our method in reserving image energy and removing noise.

  4. Study of some parameters affecting noise level in textile spinning and weaving mills.

    Science.gov (United States)

    el-Dakhakhny, A A; Noweir, M H; Kamel, N R

    1975-01-01

    Noise was evaluated in six spinning and five weaving halls located in three textile mills in Egypt. Spindle speed (rpm) and loom speed (picks per minutes) were found to be important parameters affecting the noise level in these mills. Reduction of the number of spinning machines to five spindles per square meter of floor area will probably bring the noise level below the TLV. In the weaving departments, the decrease in the number of looms will not effectively reduce the noise level.

  5. Assessment of noise levels of the equipments used in the dental teaching institution, Bangalore

    OpenAIRE

    Sushi Kadanakuppe; Padma K Bhat; C Jyothi; C Ramegowda

    2011-01-01

    Context: In dental practical classes, the acoustic environment is characterized by high noise levels in relation to other teaching areas, due to the exaggerated noise produced by some of these devices and use of dental equipment by many users at the same time. Aims: To measure, analyze and compare noise levels of equipments among dental learning areas under different working conditions and also to measure and compare noise levels between used and brand new handpieces under different worki...

  6. Optimising threshold levels for information transmission in binary threshold networks: Independent multiplicative noise on each threshold

    Science.gov (United States)

    Zhou, Bingchang; McDonnell, Mark D.

    2015-02-01

    The problem of optimising the threshold levels in multilevel threshold system subject to multiplicative Gaussian and uniform noise is considered. Similar to previous results for additive noise, we find a bifurcation phenomenon in the optimal threshold values, as the noise intensity changes. This occurs when the number of threshold units is greater than one. We also study the optimal thresholds for combined additive and multiplicative Gaussian noise, and find that all threshold levels need to be identical to optimise the system when the additive noise intensity is a constant. However, this identical value is not equal to the signal mean, unlike the case of additive noise. When the multiplicative noise intensity is instead held constant, the optimal threshold levels are not all identical for small additive noise intensity but are all equal to zero for large additive noise intensity. The model and our results are potentially relevant for sensor network design and understanding neurobiological sensory neurons such as in the peripheral auditory system.

  7. De-noising of digital image correlation based on stationary wavelet transform

    Science.gov (United States)

    Guo, Xiang; Li, Yulong; Suo, Tao; Liang, Jin

    2017-03-01

    In this paper, a stationary wavelet transform (SWT) based method is proposed to de-noise the digital image with the light noise, and the SWT de-noise algorithm is presented after the analyzing of the light noise. By using the de-noise algorithm, the method was demonstrated to be capable of providing accurate DIC measurements in the light noise environment. The verification, comparative and realistic experiments were conducted using this method. The result indicate that the de-noise method can be applied to the full-field strain measurement under the light interference with a high accuracy and stability.

  8. Noise

    Science.gov (United States)

    Noise is all around you, from televisions and radios to lawn mowers and washing machines. Normally, you ... sensitive structures of the inner ear and cause noise-induced hearing loss. More than 30 million Americans ...

  9. De-Noising SPECT Images from a Typical Collimator Using Wavelet Transform

    Directory of Open Access Journals (Sweden)

    Farshid Babapour Mofrad

    2009-12-01

    Full Text Available Introduction: SPECT is a diagnostic imaging technique the main disadvantage of which is the existence of Poisson noise. So far, different methods have been used by scientists to improve SPECT images. The Wavelet Transform is a new method for de-noising which is widely used for noise reduction and quality enhancement of images. The purpose of this paper is evaluation of noise reduction in SPECT images by wavelet. Material and Methods: To calculate and simulate noise in images, it is common in nuclear medicine to use Monte Carlo techniques. The SIMIND software was used to simulate SPECT images in this research. The simulated and real images formed using the current typical (hexagonal collimator were de-noised by different types of wavelets. Results: The best type of wavelet was selected for SPECT images. The results demonstrated that the best type of wavelet in the simulated and real images increased Signal to Noise Ratio (SNR by 33% and 45% respectively. Also, Coefficient of Variation (CV decreased by 77% and 71% respectively, while Contrast of Recovery (CR was reduced by only 4% and 9% respectively. Conclusion: Comparing the results for real SPECT images in this paper with previously acquired results in real PET images, it can be concluded that the images of both nuclear medicine systems using Wavelet Transform differ in SNR and CR by only 5% and 7% respectively, and in CV by about 20%. Therefore, wavelet transform is applicable for nuclear medicine image de-noising.

  10. A Level Set Filter for Speckle Reduction in SAR Images

    OpenAIRE

    Huang Bo; Li Hongga; Huang Xiaoxia

    2010-01-01

    Despite much effort and significant progress in recent years, speckle removal for Synthetic Aperture Radar (SAR) image still is a challenging problem in image processing. Unlike the traditional noise filters, which are mainly based on local neighborhood statistical average or frequencies transform, in this paper, we propose a speckle reduction method based on the theory of level set, one form of curvature flow propagation. Firstly, based on partial differential equation, the Lee filter can b...

  11. Evaluation and analysis of noise levels at traffic intersections of Nagpur city, India.

    Science.gov (United States)

    Vijay, Ritesh; Popat, Rishabh; Pisode, Mayur; Sharma, Asheesh; Manoj, Kumar; Chakrabarti, T; Gupta, Rajesh

    2013-04-01

    The objective of the present study was to monitor and assess the noise levels at traffic intersections in Napgur city under heterogenic traffic activities. For this, traffic volume and noise level were measured at intersections on highways, major roads andring road during morning and evening peak hours. Traffic volume was categorized in light, medium and heavy vehicles while noise levels were measured for Lmin, Lmax, Leq , L10 and L90. Equivalent noise was observed in the range of 71.3 to 79.3 dB(A) at the traffic intersections. Due to heterogenic traffic conditions and activities at the intersection like honking, idling, gear noise, bearing noise, breaking noise, tyre-road noise and exhaust noise, no correlation was established between traffic volume and observed noise levels except West High Court road. A strong correlation was found at West High Court road due to controlled traffic flow and less impact of heavy vehicles. Impact of noisy vehicles on general traffic was also assessed at the traffic intersections based on noise pollution levels and traffic noise index. The study suggests that control measures are required at the traffic intersections to minimize noise pollution levels.

  12. Effects of reconstruction parameters on image noise and spatial resolution in cone-beam computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung-Wan; Lee, Chang-Lae; Cho, Hyo-Min; Park, Hye-Suk; Kim, Dae-Hong; Choi, Yu-Na; Kim, Hee-Joung [Yonsei University, Wonju (Korea, Republic of)

    2011-10-15

    CBCT (cone-beam computed tomography) is a promising modality in many medical applications due to the properties of fast volume coverage, lower radiation dose, easy hardware implementation, and higher spatial resolution. Recently, attention is being paid to the noise and resolution relationship for CBCT. In a CBCT system, image noise and spatial resolution play very important roles in image quality. However, there have not been many works to evaluate the relationship between the image noise and the spatial resolution in CBCT. In this study, we evaluated the effects of reconstruction parameters, such as the characteristics of the filter, the number of projections, and the voxel size, on the image noise and the spatial resolution in a CBCT system. The simulated projection data of a Catphan 600 phantom were reconstructed using the FDK (Feldkamp) algorithm. To evaluate the image noise and the spatial resolution, we calculated the COV (coefficient of variation) of the attenuation coefficient and the MTF (modulation transfer function) in axial images. Five reconstruction filters, Ram-Lak, Shepp-Logan, Cosine, Hamming, and Hann, were used to reconstruct the images. Different numbers of projections for a circular scan of 360 degrees and different voxel sizes were used to reconstruct the images to evaluate their effect on image noise and spatial resolution. The image noise given by the Hann filter was the lowest and the spatial resolution given by the Ram-Lak filter was the highest. The image noise was decreased as functions of the number of projections and the voxel size. The spatial resolution was increased as a function of the number of projections and decreased as a function of the voxel size. The results of this study show the relationship between the image noise and the spatial resolution in a CBCT system and the characteristics of the reconstruction factors for trade-off between the image noise and the spatial resolution. It can also provide information of the image

  13. Ultra-wideband noise radar imaging of cylindrical PEC objects using diffraction tomography

    Science.gov (United States)

    Shin, Hee Jung; Narayanan, Ram M.; Rangaswamy, Muralidhar

    2014-05-01

    In this paper, we show that a single transmission of a random noise waveform may not sufficient to obtain a successful tomographic image of an object. In order to overcome this shortcoming, multiple independent and identically distributed (iid) random noise waveforms over a frequency range from 8 to 10 GHz are transmitted to reconstruct the final image of various objects. Diffraction tomography theorem is applied for each noise waveform transmission so that the image of the multiple objects is reconstructed based on the backward scattered field at the end of each noise waveform transmission realization. After all iid noise waveforms are transmitted, the final tomographic image of the target is reconstructed by averaging all obtained images from multiple transmissions. Several numerical simulations in the spatial frequency domain are performed, and the successful tomographic image of the multiple cylindrical PEC objects is achieved after transmission of multiple iid ultra-wideband (UWB) random noise waveforms.

  14. Assessment of noise levels of the equipments used in the dental teaching institution, Bangalore

    Directory of Open Access Journals (Sweden)

    Sushi Kadanakuppe

    2011-01-01

    Full Text Available Context: In dental practical classes, the acoustic environment is characterized by high noise levels in relation to other teaching areas, due to the exaggerated noise produced by some of these devices and use of dental equipment by many users at the same time. Aims: To measure, analyze and compare noise levels of equipments among dental learning areas under different working conditions and also to measure and compare noise levels between used and brand new handpieces under different working conditions. Materials and Methods: Noise levels were measured and analyzed in different dental learning areas that included clinical, pre-clinical areas and laboratories selected as representatives of a variety of learning-teaching activities. The noise levels were determined using a precision noise level meter (CENTER® 325 IEC 651 TYPE II with a microphone. The mean of the maxima was determined. The data were collected, tabulated, and statistically analyzed using t tests. Results: The noise levels measured varied between 64 and 97 dB(A.The differences in sound levels when the equipment was merely turned on and during cutting operations and also between used and brand new equipments were recorded. The laboratory engines had the highest noise levels, whereas the noise levels in high-speed turbine handpieces and the low-speed contra angle handpieces were decreased. Conclusion: The noise levels detected in this study are considered to be close to the limit of risk of hearing loss.

  15. AN AMELIORATED DETECTION STATISTICS FOR ADAPTIVE MASK MEDIAN FILTRATION OF HEAVILY NOISED DIGITAL IMAGES

    Directory of Open Access Journals (Sweden)

    Geeta Hanji

    2016-11-01

    Full Text Available Noise reduction is an important area of research in image processing applications. The performance of the digital image noise filtering method primarily depends upon the accuracy of noise detection scheme. This paper presents an effective detector based, adaptive mask, median filtration of heavily noised digital images affected with fixed value (or salt and pepper impulse noise. The proposed filter presents a novel approach; an ameliorated Rank Ordered Absolute Deviation (ROAD statistics to judge whether the input pixel is noised or noise free. If a pixel is detected as corrupted, it is subjected to adaptive mask median filtration; otherwise, it is kept unchanged. Extensive experimental results and comparative performance evaluations demonstrate that the proposed filter outperforms the existing decision type, median based filters with powerful noise detectors in terms of objective performance measures and visual retrieviation accuracy.

  16. Assessment of ambient noise levels in the intensive care unit of a university hospital

    Directory of Open Access Journals (Sweden)

    Hatem O Qutub

    2009-01-01

    Conclusion : Some sources of environmental noise, such as the use of oxygen, suction equipment or respirators are unavoidable. Nevertheless, hospital ICUs should have measures to minimize the level of exposure to noise in the ICU. Further research in this area might focus on the noise level and other modifiable environmental stress factors in the ICU that affect patients as well as the staff.

  17. Dual adaptive statistical approach for quantitative noise reduction in photon-counting medical imaging: application to nuclear medicine images.

    Science.gov (United States)

    Hannequin, Pascal Paul

    2015-06-07

    Noise reduction in photon-counting images remains challenging, especially at low count levels. We have developed an original procedure which associates two complementary filters using a Wiener-derived approach. This approach combines two statistically adaptive filters into a dual-weighted (DW) filter. The first one, a statistically weighted adaptive (SWA) filter, replaces the central pixel of a sliding window with a statistically weighted sum of its neighbors. The second one, a statistical and heuristic noise extraction (extended) (SHINE-Ext) filter, performs a discrete cosine transformation (DCT) using sliding blocks. Each block is reconstructed using its significant components which are selected using tests derived from multiple linear regression (MLR). The two filters are weighted according to Wiener theory. This approach has been validated using a numerical phantom and a real planar Jaszczak phantom. It has also been illustrated using planar bone scintigraphy and myocardial single-photon emission computed tomography (SPECT) data. Performances of filters have been tested using mean normalized absolute error (MNAE) between the filtered images and the reference noiseless or high-count images.Results show that the proposed filters quantitatively decrease the MNAE in the images and then increase the signal-to-noise Ratio (SNR). This allows one to work with lower count images. The SHINE-Ext filter is well suited to high-size images and low-variance areas. DW filtering is efficient for low-size images and in high-variance areas. The relative proportion of eliminated noise generally decreases when count level increases. In practice, SHINE filtering alone is recommended when pixel spacing is less than one-quarter of the effective resolution of the system and/or the size of the objects of interest. It can also be used when the practical interest of high frequencies is low. In any case, DW filtering will be preferable.The proposed filters have been applied to nuclear

  18. Recent and long-term occupational noise exposure and salivary cortisol level

    DEFF Research Database (Denmark)

    Stokholm, Zara Ann; Hansen, Åse Marie; Grynderup, Matias Brødsgaard

    2014-01-01

    -term occupational noise exposure and cortisol level measured off work to assess a possible sustained HPA-axis effect. We included 501 industrial, finance, and service workers who were followed for 24h during work, leisure, and sleep. Ambient occupational noise exposure levels were recorded every 5s by personal...... and estimated the noise level at the ear. Salivary cortisol concentration was measured at 20.00h, the following day at awakening, and 30min after awakening on average 5, 14 and 14.5h after finishing work. The mean ambient noise exposure level was 79.9dB(A) [range: 55.0-98.9] and the mean estimated level...... observed no statistically significant exposure response relation between recent, or long-term ambient occupational noise exposure level and any cortisol parameter off work. This was neither the case for recent noise level at the ear. To conclude, neither recent nor long-term occupational noise exposure...

  19. Anomalously high noise levels in a fibre Bragg grating semiconductor laser

    Energy Technology Data Exchange (ETDEWEB)

    Kurnosov, V D; Kurnosov, K V [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation)

    2015-01-31

    Taking into account gain nonlinearity allows one to obtain anomalously high noise levels in a fibre Bragg grating laser diode. This paper examines the effect of the gain nonlinearity due to spectral hole burning on noise characteristics. (lasers)

  20. Potential of neuro-fuzzy methodology to estimate noise level of wind turbines

    Science.gov (United States)

    Nikolić, Vlastimir; Petković, Dalibor; Por, Lip Yee; Shamshirband, Shahaboddin; Zamani, Mazdak; Ćojbašić, Žarko; Motamedi, Shervin

    2016-01-01

    Wind turbines noise effect became large problem because of increasing of wind farms numbers since renewable energy becomes the most influential energy sources. However, wind turbine noise generation and propagation is not understandable in all aspects. Mechanical noise of wind turbines can be ignored since aerodynamic noise of wind turbine blades is the main source of the noise generation. Numerical simulations of the noise effects of the wind turbine can be very challenging task. Therefore in this article soft computing method is used to evaluate noise level of wind turbines. The main goal of the study is to estimate wind turbine noise in regard of wind speed at different heights and for different sound frequency. Adaptive neuro-fuzzy inference system (ANFIS) is used to estimate the wind turbine noise levels.

  1. Noise evaluation of Compton camera imaging for proton therapy

    Science.gov (United States)

    Ortega, P. G.; Torres-Espallardo, I.; Cerutti, F.; Ferrari, A.; Gillam, J. E.; Lacasta, C.; Llosá, G.; Oliver, J. F.; Sala, P. R.; Solevi, P.; Rafecas, M.

    2015-02-01

    Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of

  2. Noise evaluation of Compton camera imaging for proton therapy.

    Science.gov (United States)

    Ortega, P G; Torres-Espallardo, I; Cerutti, F; Ferrari, A; Gillam, J E; Lacasta, C; Llosá, G; Oliver, J F; Sala, P R; Solevi, P; Rafecas, M

    2015-03-07

    Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the reconstruction inverse problem. Jointly with prompt gamma, secondary neutrons and scattered photons, not strongly correlated with the dose map, can also reach the imaging detector and produce false events. These events deteriorate the image quality. Also, high intensity beams can produce particle accumulation in the camera, which lead to an increase of random coincidences, meaning events which gather measurements from different incoming particles. The noise scenario is expected to be different if double or triple events are used, and consequently, the reconstructed images can be affected differently by spurious data. The aim of the present work is to study the effect of false events in the reconstructed image, evaluating their impact in the determination of the beam particle ranges. A simulation study that includes misidentified events (neutrons and random coincidences) in the final image of a Compton Telescope for PT monitoring is presented. The complete chain of

  3. Radiation dose reduction in CT of the brain: can advanced noise filtering compensate for loss of image quality?

    Energy Technology Data Exchange (ETDEWEB)

    Siemund, Roger; Loeve, A.; Westen, D. van; Stenberg, L.; Petersen, C. (Dept. of Radiology, Lund Univ., Lund (Sweden); Center for Medical Imaging and Physiology, Skaane Univ. Hospital, Lund (Sweden)), email: roger.siemund@med.lu.se; Bjoerkman-Burtscher, I. M. (Dept. of Radiology, Lund Univ., Lund (Sweden); Center for Medical Imaging and Physiology, Skaane Univ. Hospital, Lund (Sweden); Lund Univ. Bioimaging Center, Lund (Sweden))

    2012-05-15

    Background: Computed tomography (CT) of the brain is performed with high local doses due to high demands on low contrast resolution. Advanced algorithms for noise reduction might be able to preserve critical image information when reducing radiation dose. Purpose: To evaluate the effect of advanced noise filtering on image quality in brain CT acquired with reduced radiation dose. Material and Methods: Thirty patients referred for non-enhanced CT of the brain were examined with two helical protocols: normal dose (ND, CTDIvol 57 mGy) and low dose (LD, CTDIvol 40 mGy) implying a 30% radiation dose reduction. Images from the LD examinations were also post processed with a noise reduction software with non-linear filters (SharpView CT), creating filtered low dose images (FLD) for each patient. The three image stacks for each patient were presented side by side in randomized order. Five radiologists, blinded for dose level and filtering, ranked these three axial image stacks (ND, LD, FLD) as best to poorest (1 to 3) regarding three image quality criteria. Measurements of mean Hounsfield units (HU) and standard deviation (SD) of the HU were calculated for large region of interest in the centrum semiovale as a measure for noise. Results: Ranking results in pooled data showed that the advanced noise filtering significantly improved the image quality in FLD as compared to LD images for all tested criteria. No significant differences in image quality were found between ND examinations and FLD. However, there was a notable inter-reader spread of the ranking. SD values were 15% higher for LD as compared to ND and FLD. Conclusion: The advanced noise filtering clearly improves image quality of CT examinations of the brain. This effect can be used to significantly lower radiation dose.

  4. Fractal dimension metric for quantifying noise texture of computed tomography images

    Science.gov (United States)

    Khobragade, P.; Fan, Jiahua; Rupcich, Franco; Crotty, Dominic J.; Gilat Schmidt, Taly

    2017-03-01

    This study investigated a fractal dimension algorithm for noise texture quantification in CT images. Quantifying noise in CT images is important for assessing image quality. Noise is typically quantified by calculating noise standard deviation and noise power spectrum (NPS). Different reconstruction kernels and iterative reconstruction approaches affect both the noise magnitude and noise texture. The shape of the NPS can be used as a noise texture descriptor. However, the NPS requires numerous images for calculation and is a vector quantity. This study proposes the metric of fractal dimension to quantify noise texture, because fractal dimension is a single scalar metric calculated from a small number of images. Fractal dimension measures the complexity of a pattern. In this study, the ACR CT phantom was scanned and images were reconstructed using filtered back-projection with three reconstruction kernels: bone, soft and standard. Regions of interest were extracted from the uniform section of the phantom for NPS and fractal dimension calculation. The results demonstrated a mean fractal dimension of 1.86 for soft kernel, 1.92 for standard kernel, and 2.16 for bone kernel. Increasing fractal dimension corresponded to shift in the NPS towards higher spatial frequencies and grainier noise appearance. Stable fractal dimension was calculated from two ROI's compared to more than 250 ROI's used for NPS calculation. The scalar fractal dimension metric may be a useful noise texture descriptor for evaluating or optimizing reconstruction algorithms.

  5. 3-Level DWT Image Watermarking Against Frequency and Geometrical Attacks

    Directory of Open Access Journals (Sweden)

    Asma Ahmad

    2014-11-01

    Full Text Available This paper introduces a robust image watermarking technique for the copyright protection. The proposed method is based on 3-level discrete wavelet transform (DWT. Encoded secret image using spiral scanning is hidden by alpha blending technique in LL sub bands. During embedding process, secret image is dispersed within LL band depending upon alpha value. Encoded secret images are extracted and decoded to recover the original secret image. The experimental results demonstrate that the watermarks generated with the proposed algorithm are invisible and the quality of watermarked image and the recovered image are improved. The scheme is found robust to various image processing attacks such as JPEG compression, Gaussian noise, blurring, median filtering and rotation.

  6. Evaluation and Analysis of Noise Level at High-Traffic Locations in Gusau, Nigeria

    Directory of Open Access Journals (Sweden)

    Jacob O. Ebozoje

    2013-12-01

    Full Text Available The measurement of noise levels at high-traffic intersections of Gusau town is reported in this work. Five high-traffic locations tagged LOC-A, LOC-B, LOC-C, LOC-D and LOC-E were selected and evaluated at different periods of the day using an MS6700 IEC 651, ANSI.Si.4 Type-2 Sound Level meter. Result analyses indicates that LOC-C has the highest noise level with LNP = 95 and TNI = 94, while LOC-B has the lowest noise level with LNP = 82 and TNI = 67. These noise levels imply that Gusau metropolis has an unacceptable noise level, well above the globally recommended levels of 60-65 dB(A and the national recommended level of 82 dB(A. The paper therefore makes recommendations on minimizing these intolerable noise levels with consequences for environmental and human health in the study location.

  7. Annoyance from Road Traffic, Trains, Airplanes and from Total Environmental Noise Levels.

    Science.gov (United States)

    Ragettli, Martina S; Goudreau, Sophie; Plante, Céline; Perron, Stéphane; Fournier, Michel; Smargiassi, Audrey

    2015-12-29

    There is a lack of studies assessing the exposure-response relationship between transportation noise and annoyance in North America. Our aims were to investigate the prevalence of noise annoyance induced by road traffic, trains and airplanes in relation to distance to transportation noise sources, and to total environmental noise levels in Montreal, Canada; annoyance was assessed as noise-induced disturbance. A telephone-based survey among 4336 persons aged >18 years was conducted. Exposure to total environmental noise (A-weighted outdoor noise levels-LAeq24h and day-evening-night equivalent noise levels-Lden) for each study participant was determined using a statistical noise model (land use regression-LUR) that is based on actual outdoor noise measurements. The proportion of the population annoyed by road traffic, airplane and train noise was 20.1%, 13.0% and 6.1%, respectively. As the distance to major roads, railways and the Montreal International Airport increased, the percentage of people disturbed and highly disturbed due to the corresponding traffic noise significantly decreased. When applying the statistical noise model we found a relationship between noise levels and disturbance from road traffic and total environmental noise, with Prevalence Proportion Ratios (PPR) for highly disturbed people of 1.10 (95% CI: 1.07-1.13) and 1.04 (1.02-1.06) per 1 dB(A) Lden, respectively. Our study provides the first comprehensive information on the relationship between transportation noise levels and disturbance in a Canadian city. LUR models are still in development and further studies on transportation noise induced annoyance are consequently needed, especially for sources other than road traffic.

  8. Impact of physiological noise correction on detecting blood oxygenation level-dependent contrast in the breast

    Science.gov (United States)

    Wallace, Tess E.; Manavaki, Roido; Graves, Martin J.; Patterson, Andrew J.; Gilbert, Fiona J.

    2017-01-01

    Physiological fluctuations are expected to be a dominant source of noise in blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) experiments to assess tumour oxygenation and angiogenesis. This work investigates the impact of various physiological noise regressors: retrospective image correction (RETROICOR), heart rate (HR) and respiratory volume per unit time (RVT), on signal variance and the detection of BOLD contrast in the breast in response to a modulated respiratory stimulus. BOLD MRI was performed at 3 T in ten volunteers at rest and during cycles of oxygen and carbogen gas breathing. RETROICOR was optimized using F-tests to determine which cardiac and respiratory phase terms accounted for a significant amount of signal variance. A nested regression analysis was performed to assess the effect of RETROICOR, HR and RVT on the model fit residuals, temporal signal-to-noise ratio, and BOLD activation parameters. The optimized RETROICOR model accounted for the largest amount of signal variance ( Δ R\\text{adj}2   =  3.3  ±  2.1%) and improved the detection of BOLD activation (P  =  0.002). Inclusion of HR and RVT regressors explained additional signal variance, but had a negative impact on activation parameter estimation (P  <  0.001). Fluctuations in HR and RVT appeared to be correlated with the stimulus and may contribute to apparent BOLD signal reactivity.

  9. A Convex Variational Model for Restoring Blurred Images with Multiplicative Noise

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Tieyong Zeng

    2013-01-01

    In this paper, a new variational model for restoring blurred images with multiplicative noise is proposed. Based on the statistical property of the noise, a quadratic penalty function technique is utilized in order to obtain a strictly convex model under a mild condition, which guarantees...... to multiplicative noise. A comparison with other methods is provided as well....

  10. Noise Levels in Two Emergency Departments Before and After the Introduction of Electronic Whiteboards

    DEFF Research Database (Denmark)

    Hertzum, Morten

    2013-01-01

    Purpose: Hospital work generates noise. This article investigates the noise level in emergency departments (EDs) to assess the need to address this aspect of the work environment and to investigate whether the replacement of dry-erase with electronic whiteboards lowers the noise level. Method......: In Study I we measured the noise level at the three coordination centres of an ED while it was still using dry-erase whiteboards and after it had switched to electronic whiteboards. In Study II we made similar noise measurements at another ED, supplemented with observation. Results: The median daily...... equivalent continuous noise levels were 60.0, 55.3, and 55.4 dB(A) at the three coordination centres in Study I and 56.5 dB(A) at the coordination centre in Study II. In both studies the noise levels were higher during workdays than weekends and higher during day and evening shifts than during night shifts...

  11. Bayesian Compressed Sensing with Unknown Measurement Noise Level

    DEFF Research Database (Denmark)

    Hansen, Thomas Lundgaard; Jørgensen, Peter Bjørn; Pedersen, Niels Lovmand

    2013-01-01

    algorithms based on the fast inference scheme noise precision estimation results in increased computational complexity and reconstruction error. We propose a three-layer hierarchical prior model which allows for the derivation of a fast inference algorithm that estimates the noise precision...

  12. Adaptive iterated function systems filter for images highly corrupted with fixed - Value impulse noise

    Science.gov (United States)

    Shanmugavadivu, P.; Eliahim Jeevaraj, P. S.

    2014-06-01

    The Adaptive Iterated Functions Systems (AIFS) Filter presented in this paper has an outstanding potential to attenuate the fixed-value impulse noise in images. This filter has two distinct phases namely noise detection and noise correction which uses Measure of Statistics and Iterated Function Systems (IFS) respectively. The performance of AIFS filter is assessed by three metrics namely, Peak Signal-to-Noise Ratio (PSNR), Mean Structural Similarity Index Matrix (MSSIM) and Human Visual Perception (HVP). The quantitative measures PSNR and MSSIM endorse the merit of this filter in terms of degree of noise suppression and details/edge preservation respectively, in comparison with the high performing filters reported in the recent literature. The qualitative measure HVP confirms the noise suppression ability of the devised filter. This computationally simple noise filter broadly finds application wherein the images are highly degraded by fixed-value impulse noise.

  13. Noise levels in the learning-teaching activities in a dental medicine school

    OpenAIRE

    Paula Andreia Matos; Carvalho, A.; João C. Sampaio Fernandes

    2002-01-01

    The noise levels made by clinical handpieces and laboratory engines are the main descriptors of acoustical comfort in learning spaces in a dental medicine school. Sound levels were measured in five types of classrooms and teaching laboratories at the University of Porto Dental Medicine School. Handpiece noise measurements were made while instruments were running free and during operations with cutting tools (tooth, metal and acrylic). Noise levels were determined using a precision sound level...

  14. Uncorrelated Phase Noise Analysis for Millimeter-Wave Radiometer Imager Frequency Synthesizer

    Directory of Open Access Journals (Sweden)

    Jin Zhang

    2013-09-01

    Full Text Available In this paper, a nontrivial uncorrelated phase noise analysis is proposed for frequency synthesizer of a passive millimeter-wave Synthetic Aperture Interferometric Radiometer (SAIR imager named BHU-2D-U designed for concealed weapon detections on human bodies with high imaging rates. This synthesizer provides local oscillators both for millimeter-wave front-ends and intermediate frequency IQ demodulators for the receivers. The influence of synthesizer uncorrelated phase noise in different offset frequency ranges on the visibility phase errors have been systematically investigated with phase noise mismatch requirements drawn. Integrated RMS phase error has been applied to establish uncorrelated phase noise requirements for visibility error control. Measurement results have proved that uncorrelated phase noise does exist among synthesizer output pairs, and the previously defined requirements are achieved with imaging results proposed. In conclusion, the uncorrelated phase noise effects on SAIR visibility errors have been concretized to phase noise design requirements, which have been realized by synthesizer design.

  15. PSO Algorithm based Adaptive Median Filter for Noise Removal in Image Processing Application

    Directory of Open Access Journals (Sweden)

    Ruby Verma

    2016-07-01

    Full Text Available A adaptive Switching median filter for salt and pepper noise removal based on genetic algorithm is presented. Proposed filter consist of two stages, a noise detector stage and a noise filtering stage. Particle swarm optimization seems to be effective for single objective problem. Noise Dictation stage works on it. In contrast to the standard median filter, the proposed algorithm generates the noise map of corrupted Image. Noise map gives information about the corrupted and non-corrupted pixels of Image. In filtering, filter calculates the median of uncorrupted neighbouring pixels and replaces the corrupted pixels. Extensive simulations are performed to validate the proposed filter. Simulated results show refinement both in Peak signal to noise ratio (PSNR and Image Quality Index value (IQI. Experimental results shown that proposed method is more effective than existing methods.

  16. [Equivalent continuous noise level in neonatal intensive care unit associated to burnout syndrome].

    Science.gov (United States)

    Garrido Galindo, A P; Camargo Caicedo, Y; Vélez-Pereira, A M

    2015-01-01

    Noise levels in neonatal intensive care units allow the appearance of symptoms associated with burnout such as stress, irritability, fatigue and emotional instability on health care personnel. The aim of this study was to evaluate the equivalent continuous noise levels in the neonatal intensive care unit and compare the results with noise levels associated with the occurrence of burnout syndrome on the care team. Continuous sampling was conducted for 20 days using a type I sound level meter on the unit. The maximum, the ninetieth percentile and the equivalent continuous noise level (Leq) values were recorded. Noise level is reported in the range of 51.4-77.6 decibels A (dBA) with an average of 64 dBA, 100.6 dBA maximum, and average background noise from 57.9 dBA. Noise levels exceed the standards suggested for neonatal intensive care units, are close to maximum values referred for noise exposure in the occupational standards and to noise levels associated with the onset of burnout; thus allowing to infer the probability of occurrence of high levels of noise present in the unit on the development of burnout in caregivers. Copyright © 2013 Elsevier España, S.L.U. y SEEIUC. All rights reserved.

  17. 信息动态%Analysis of the Noise and Signal-to-Noise of AOTF Imaging Spectrometer Based on EMCCD

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Imaging spectrometer based on acousto-optic tunable filter (AOTF) is a novel hyperspectral imaging system. In order to rectify the non-uniformity of radiation sensitivity on different waveband, especially the low signal-to-noise (SNR) in low-light conditions, the electron-multiplying CCD (EMCCD) sensor was proposed. The noise of AOTF imaging spectrometer was analyzed in both normal and EM modes of the CCD sensor with derived SNR calculating model which has been experimentally validated. On that basis, a new evaluation method of the dynamic range in EM mode and a novel method of calculating spectral radiance at the entrance aperture were adopted. The experimental result shows that the theoretic SNR models are fit, and better selection of EM mode is effective to improve the SNR and non-uniformity of radiation sensitivity in low light level conditions.

  18. Elimination of the Background Noise of the Decoded Image in Fresnel Zone Plate Scanning Holography

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A method of digitally high pass filtering in frequency domain is proposed to eliminate the background noise of the decoded image in Fresnel zone plate scanning holography. The high pass filter is designed as a circular stop, which should be suitable to suppressing the background noise significantly and remain much low frequency information of the object. The principle of high pass filtering is that the Fourier transform of the decoded image is multiplied with the high pass filter. Thus the frequency spectrum of the decoded image without the background noise is achieved. By inverse Fourier transform of the spectrum of the decoded image after multiplying operation, the decoded image without the background noise is obtained. Both of the computer simulations and the experimental results show that the contrast and the signal-to-noise ratio of the decoded image are significantly improved with digital filtering.

  19. Annoyance from Road Traffic, Trains, Airplanes and from Total Environmental Noise Levels

    Directory of Open Access Journals (Sweden)

    Martina S. Ragettli

    2015-12-01

    Full Text Available There is a lack of studies assessing the exposure-response relationship between transportation noise and annoyance in North America. Our aims were to investigate the prevalence of noise annoyance induced by road traffic, trains and airplanes in relation to distance to transportation noise sources, and to total environmental noise levels in Montreal, Canada; annoyance was assessed as noise-induced disturbance. A telephone-based survey among 4336 persons aged >18 years was conducted. Exposure to total environmental noise (A-weighted outdoor noise levels—LAeq24h and day-evening-night equivalent noise levels—Lden for each study participant was determined using a statistical noise model (land use regression—LUR that is based on actual outdoor noise measurements. The proportion of the population annoyed by road traffic, airplane and train noise was 20.1%, 13.0% and 6.1%, respectively. As the distance to major roads, railways and the Montreal International Airport increased, the percentage of people disturbed and highly disturbed due to the corresponding traffic noise significantly decreased. When applying the statistical noise model we found a relationship between noise levels and disturbance from road traffic and total environmental noise, with Prevalence Proportion Ratios (PPR for highly disturbed people of 1.10 (95% CI: 1.07–1.13 and 1.04 (1.02–1.06 per 1 dB(A Lden, respectively. Our study provides the first comprehensive information on the relationship between transportation noise levels and disturbance in a Canadian city. LUR models are still in development and further studies on transportation noise induced annoyance are consequently needed, especially for sources other than road traffic.

  20. Integration of speckle de-noising and image segmentation using Synthetic Aperture Radar image for flood extent extraction

    Indian Academy of Sciences (India)

    J Senthilnath; H Vikram Shenoy; Ritwik Rajendra; S N Omkar; V Mani; P G Diwakar

    2013-06-01

    Flood is one of the detrimental hydro-meteorological threats to mankind. This compels very efficient flood assessment models. In this paper, we propose remote sensing based flood assessment using Synthetic Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise has been reduced with the help of Lee, Frost and Gamma MAP filters. A performance comparison of these speckle removal filters is presented. From the results obtained, we deduce that the Gamma MAP is reliable. The selected Gamma MAP filtered image is segmented using Gray Level Co-occurrence Matrix (GLCM) and Mean Shift Segmentation (MSS). The GLCM is a texture analysis method that separates the image pixels into water and non-water groups based on their spectral feature whereas MSS is a gradient ascent method, here segmentation is carried out using spectral and spatial information. As test case, Kosi river flood is considered in our study. From the segmentation result of both these methods are comprehensively analysed and concluded that the MSS is efficient for flood mapping.

  1. Ambient and at-the-ear occupational noise exposure and serum lipid levels

    DEFF Research Database (Denmark)

    Arlien-Søborg, Mai C; Schmedes, Astrid S; Stokholm, Z A

    2016-01-01

    workers to obtain contrast in noise exposure levels. They provided a serum sample and wore portable dosimeters that every 5-s recorded ambient noise exposure levels during a 24-h period. We extracted measurements obtained during work and calculated the full-shift mean ambient noise level. For 331 workers......-the-ear occupational noise exposure and serum levels of total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, and triglycerides when accounting for well-established predictors of lipid levels. METHODS: This cross-sectional study included 424 industrial workers and 84 financial...

  2. Single Photon Counting Performance and Noise Analysis of CMOS SPAD-Based Image Sensors.

    Science.gov (United States)

    Dutton, Neale A W; Gyongy, Istvan; Parmesan, Luca; Henderson, Robert K

    2016-07-20

    SPAD-based solid state CMOS image sensors utilising analogue integrators have attained deep sub-electron read noise (DSERN) permitting single photon counting (SPC) imaging. A new method is proposed to determine the read noise in DSERN image sensors by evaluating the peak separation and width (PSW) of single photon peaks in a photon counting histogram (PCH). The technique is used to identify and analyse cumulative noise in analogue integrating SPC SPAD-based pixels. The DSERN of our SPAD image sensor is exploited to confirm recent multi-photon threshold quanta image sensor (QIS) theory. Finally, various single and multiple photon spatio-temporal oversampling techniques are reviewed.

  3. A method of using noise as a test pattern for determining image enhancement filters

    Energy Technology Data Exchange (ETDEWEB)

    Burgess, A.E. (Rochester Inst. of Tech., NY (United States)); Ghandeharian, H. (Stentor Canadian Network Management, Ottawa, ON (Canada))

    1994-08-01

    Many digitally based medical imaging systems include both reconstruction algorithms and additional image filters designed to enhance certain image features. The purpose of this note is to describe a simple procedure for determining the spatial frequency response of these proprietary enhancement filters. The technique uses image noise as a test pattern. The procedure consists of acquiring a small number of noise-only data sets of a uniform phantom and reconstructing the images using the different filters with repeated us of the noise data sets. A straightforward analysis then yields the enhancement filter frequency responses. (author).

  4. Impact of miscentering on patient dose and image noise in x-ray CT imaging : Phantom and clinical studies

    NARCIS (Netherlands)

    Habibzadeh, M. A.; Ay, M. R.; Asl, A. R. Kamali; Ghadiri, H.; Zaidi, H.

    The operation of the bowtie filter in x-ray CT is correct if the object being scanned is properly centered in the scanner's field-of-view. Otherwise, the dose delivered to the patient and image noise will deviate from optimal setting. We investigate the effect of miscentering on image noise and

  5. Impact of miscentering on patient dose and image noise in x-ray CT imaging : Phantom and clinical studies

    NARCIS (Netherlands)

    Habibzadeh, M. A.; Ay, M. R.; Asl, A. R. Kamali; Ghadiri, H.; Zaidi, H.

    2012-01-01

    The operation of the bowtie filter in x-ray CT is correct if the object being scanned is properly centered in the scanner's field-of-view. Otherwise, the dose delivered to the patient and image noise will deviate from optimal setting. We investigate the effect of miscentering on image noise and surf

  6. Error Analysis of Radar Coincidence Imaging in the Presence of Noise

    Directory of Open Access Journals (Sweden)

    Dai Qiang

    2014-10-01

    Full Text Available Radar coincidence imaging is a new method for high-resolution staring imaging. First, the mathematical model is constructed. Second, the theoretical error for radar coincidence imaging in the presence of noise is derived using the parametric imaging method. Third, the factors that affect the error are analyzed. Fourth, the sparse reconstruction algorithm is used to perform numerical simulations of radar coincidence imaging with different parameters. Finally, the effects of signal bandwidth, array configuration, size of the imaging unit, and target complexity on image error in the presence of noise are discussed. This study provides the theoretical framework for parameters selection and SNR requirements for radar coincidence imaging systems.

  7. Wavelet De-noising of Speech Using Singular Spectrum Analysis for Decomposition Level Selection

    Institute of Scientific and Technical Information of China (English)

    CAI Tie; ZHU Jie

    2007-01-01

    The problem of speech enhancement using threshold de-noising in wavelet domain was considered. The appropriate decomposition level is another key factor pertinent to de-noising performance. This paper proposed a new wavelet-based de-noising scheme that can improve the enhancement performance significantly in the presence of additive white Gaussian noise. The proposed algorithm can adaptively select the optimal decomposition level of wavelet transformation according to the characteristics of noisy speech. The experimental results demonstrate that this proposed algorithm outperforms the classical wavelet-based de-noising method and effectively improves the practicability of this kind of techniques.

  8. Predictive modelling of noise level generated during sawing of rocks by circular diamond sawblades

    Indian Academy of Sciences (India)

    Izzet Karakurt; Gokhan Aydin; Kerim Aydiner

    2013-06-01

    This paper presents an experimental and statistical study on noise level generated during of rock sawing by circular diamond sawblades. Influence of the operating variables and rock properties on the noise level are investigated and analysed. Statistical analyses are then employed and models are built for the prediction of noise levels depending on the operating variables and the rock properties. The derived models are validated through some statistical tests. It is found that increasing of peripheral speed, traverse speed and cutting depth result in an increase in noise levels. On the other hand, a decreasing trend for noise levels is initially observed with the increasing of flow rate of cooling fluid. It is also determined that there are moderate correlations between uniaxial compressive strength, density and noise levels. Furthermore, the modelling results reveal that the predictive models have high potentials as guidance for practical applications.

  9. Cluster signal-to-noise analysis for evaluation of the information content in an image.

    Science.gov (United States)

    Weerawanich, Warangkana; Shimizu, Mayumi; Takeshita, Yohei; Okamura, Kazutoshi; Yoshida, Shoko; Yoshiura, Kazunori

    2017-07-27

    To develop an observer-free method of analyzing image quality related to the observer performance in the detection task and 2) to analyze observer behavior patterns in the detection of small mass changes in CBCT images. Thirteen observers detected holes in a Teflon phantom in CBCT images. Using the same images, we developed a new method, cluster signal-to-noise analysis, to detect the holes by applying various cut-off values using ImageJ and reconstructing cluster signal-to-noise curves. We then evaluated the correlation between cluster signal-to-noise analysis and the observer performance test. We measured the background noise in each image to evaluate the relationship with false positive rates (FPRs) of the observers. Correlations between mean FPRs and intra- and inter-observer variations were also evaluated. Moreover, we calculated true positive rates (TPRs) and accuracies from background noise and evaluated their correlations with TPRs from observers. Cluster signal-to-noise curves were derived in cluster signal-to-noise analysis. They yield the detection of signals (true holes) related to noise (false holes). This method correlated highly with the observer performance test (R(2) = 0.9296). In noisy images, increasing background noise resulted in higher FPRs and larger intra- and inter-observer variations. TPRs and accuracies calculated from background noise had high correlation with actual TPRs from observers; R(2) was 0.9244 and 0.9338, respectively. Cluster signal-to-noise analysis can simulate the detection performance of observers and thus replace the observer performance test in the evaluation of image quality. Erroneous decision-making increased with increasing background noise.

  10. A new algorithm to reduce noise in microscopy images implemented with a simple program in python.

    Science.gov (United States)

    Papini, Alessio

    2012-03-01

    All microscopical images contain noise, increasing when (e.g., transmission electron microscope or light microscope) approaching the resolution limit. Many methods are available to reduce noise. One of the most commonly used is image averaging. We propose here to use the mode of pixel values. Simple Python programs process a given number of images, recorded consecutively from the same subject. The programs calculate the mode of the pixel values in a given position (a, b). The result is a new image containing in (a, b) the mode of the values. Therefore, the final pixel value corresponds to that read in at least two of the pixels in position (a, b). The application of the program on a set of images obtained by applying salt and pepper noise and GIMP hurl noise with 10-90% standard deviation showed that the mode performs better than averaging with three-eight images. The data suggest that the mode would be more efficient (in the sense of a lower number of recorded images to process to reduce noise below a given limit) for lower number of total noisy pixels and high standard deviation (as impulse noise and salt and pepper noise), while averaging would be more efficient when the number of varying pixels is high, and the standard deviation is low, as in many cases of Gaussian noise affected images. The two methods may be used serially. Copyright © 2011 Wiley Periodicals, Inc.

  11. Regularized Pre-image Estimation for Kernel PCA De-noising

    DEFF Research Database (Denmark)

    Abrahamsen, Trine Julie; Hansen, Lars Kai

    2011-01-01

    The main challenge in de-noising by kernel Principal Component Analysis (PCA) is the mapping of de-noised feature space points back into input space, also referred to as “the pre-image problem”. Since the feature space mapping is typically not bijective, pre-image estimation is inherently illposed...

  12. Spatial and Transform Domain Filtering Method for Image De-noising: A Review

    Directory of Open Access Journals (Sweden)

    Vandana Roy

    2013-09-01

    Full Text Available Present investigation reveals the quantum of work carried in the filtering methods for image de-noising. An image is often gets corrupted by various noises that are visible or invisible while being gathered, coded, acquired and transmitted. Noise influences various process parameters that may cause a quality problem for further image processing. De-noising of natural images is appears to be very simple however when considered under practical situations becomes complex. It has been cited by various author that parameter such as type and quantum of noise, image etc. through single algorithm or approach becomes cumbersome when results are optimized. In order to improve the quality of an image noise must be removed when the image is pre-processed and the important signal features like edge details should be retained as much as possible. The search on efficient image de-noising methods is still a valid challenge at the crossing of functional analysis and statistics. This paper reviews significant de-noising methods (spatial and transform domain method and their salient features and applications. One filter in each category has been taken in consideration to understand the characteristics of both spatial and transform domain filters.

  13. Industrial noise level study in a wheat processing factory in ilorin, nigeria

    Science.gov (United States)

    Ibrahim, I.; Ajao, K. R.; Aremu, S. A.

    2016-05-01

    An industrial process such as wheat processing generates significant noise which can cause adverse effects on workers and the general public. This study assessed the noise level at a wheat processing mill in Ilorin, Nigeria. A portable digital sound level meter HD600 manufactured by Extech Inc., USA was used to determine the noise level around various machines, sections and offices in the factory at pre-determined distances. Subjective assessment was also mode using a World Health Organization (WHO) standard questionnaire to obtain information regarding noise ratings, effect of noise on personnel and noise preventive measures. The result of the study shows that the highest noise of 99.4 dBA was recorded at a pressure blower when compared to other machines. WHO Class-4 hearing protector is recommended for workers on the shop floor and room acoustics should be upgraded to absorb some sounds transmitted to offices.

  14. Profiles of noise exposure levels in South African mining

    CSIR Research Space (South Africa)

    Edwards, A

    2011-05-01

    Full Text Available of personal noise exposure that could be accessed from the public domain and by the industry stakeholders be a priority. The inclusion of audiometric results in such a database would improve the prevention of NIHL and enable the monitoring of progress... in sand and gravel operators. /Mining Engineering/. 2008 Mar:50-57. 7. Mine Safety and Health Administration (MSHA) /Federal Register, 1999, ?Health Standards for Occupational Noise Exposure: Final Rule?/. Department of Labor, 30 CFR Parts 56 and 57...

  15. Quantum noise properties of CT images with anatomical textured backgrounds across reconstruction algorithms: FBP and SAFIRE

    Energy Technology Data Exchange (ETDEWEB)

    Solomon, Justin, E-mail: justin.solomon@duke.edu [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 (United States); Samei, Ehsan [Carl E. Ravin Advanced Imaging Laboratories, Department of Radiology, Duke University Medical Center, Durham, North Carolina 27705 and Departments of Biomedical Engineering and Electrical and Computer Engineering, Pratt School of Engineering, Duke University, Durham, North Carolina 27705 (United States)

    2014-09-15

    Purpose: Quantum noise properties of CT images are generally assessed using simple geometric phantoms with uniform backgrounds. Such phantoms may be inadequate when assessing nonlinear reconstruction or postprocessing algorithms. The purpose of this study was to design anatomically informed textured phantoms and use the phantoms to assess quantum noise properties across two clinically available reconstruction algorithms, filtered back projection (FBP) and sinogram affirmed iterative reconstruction (SAFIRE). Methods: Two phantoms were designed to represent lung and soft-tissue textures. The lung phantom included intricate vessel-like structures along with embedded nodules (spherical, lobulated, and spiculated). The soft tissue phantom was designed based on a three-dimensional clustered lumpy background with included low-contrast lesions (spherical and anthropomorphic). The phantoms were built using rapid prototyping (3D printing) technology and, along with a uniform phantom of similar size, were imaged on a Siemens SOMATOM Definition Flash CT scanner and reconstructed with FBP and SAFIRE. Fifty repeated acquisitions were acquired for each background type and noise was assessed by estimating pixel-value statistics, such as standard deviation (i.e., noise magnitude), autocorrelation, and noise power spectrum. Noise stationarity was also assessed by examining the spatial distribution of noise magnitude. The noise properties were compared across background types and between the two reconstruction algorithms. Results: In FBP and SAFIRE images, noise was globally nonstationary for all phantoms. In FBP images of all phantoms, and in SAFIRE images of the uniform phantom, noise appeared to be locally stationary (within a reasonably small region of interest). Noise was locally nonstationary in SAFIRE images of the textured phantoms with edge pixels showing higher noise magnitude compared to pixels in more homogenous regions. For pixels in uniform regions, noise magnitude was

  16. Using anisotropic diffusion equations in pixon domain for image de-noising

    DEFF Research Database (Denmark)

    Nadernejad, Ehsan; Forchhammer, Søren; Sharifzadeh, Sara

    2013-01-01

    Image enhancement is an essential phase in many image processing algorithms. In any image de-noising algorithm, it is a major concern to keep the interesting structures of the image. Such interesting structures in an image often correspond to the discontinuities in the image (edges). In this paper......, we propose a new algorithm for image de-noising using anisotropic diffusion equations in pixon domain. In this approach, diffusion equations are applied on the pixonal model of the image. The algorithm has been examined on a variety of standard images and the performance has been compared...... with algorithms known from the literature. The experimental results show that in comparison with the other existing methods, the proposed algorithm has a better performance in de-noising and preserving image edges....

  17. Improvement of material decomposition and image quality in dual-energy radiography by reducing image noise

    Science.gov (United States)

    Lee, D.; Kim, Y.-s.; Choi, S.; Lee, H.; Choi, S.; Jo, B. D.; Jeon, P.-H.; Kim, H.; Kim, D.; Kim, H.; Kim, H.-J.

    2016-08-01

    Although digital radiography has been widely used for screening human anatomical structures in clinical situations, it has several limitations due to anatomical overlapping. To resolve this problem, dual-energy imaging techniques, which provide a method for decomposing overlying anatomical structures, have been suggested as alternative imaging techniques. Previous studies have reported several dual-energy techniques, each resulting in different image qualities. In this study, we compared three dual-energy techniques: simple log subtraction (SLS), simple smoothing of a high-energy image (SSH), and anti-correlated noise reduction (ACNR) with respect to material thickness quantification and image quality. To evaluate dual-energy radiography, we conducted Monte Carlo simulation and experimental phantom studies. The Geant 4 Application for Tomographic Emission (GATE) v 6.0 and tungsten anode spectral model using interpolation polynomials (TASMIP) codes were used for simulation studies and digital radiography, and human chest phantoms were used for experimental studies. The results of the simulation study showed improved image contrast-to-noise ratio (CNR) and coefficient of variation (COV) values and bone thickness estimation accuracy by applying the ACNR and SSH methods. Furthermore, the chest phantom images showed better image quality with the SSH and ACNR methods compared to the SLS method. In particular, the bone texture characteristics were well-described by applying the SSH and ACNR methods. In conclusion, the SSH and ACNR methods improved the accuracy of material quantification and image quality in dual-energy radiography compared to SLS. Our results can contribute to better diagnostic capabilities of dual-energy images and accurate material quantification in various clinical situations.

  18. Appropriate patient selection at abdominal dual-energy CT using 80 kV: relationship between patient size, image noise, and image quality.

    Science.gov (United States)

    Guimarães, Luís S; Fletcher, Joel G; Harmsen, William S; Yu, Lifeng; Siddiki, Hassan; Melton, Zachary; Huprich, James E; Hough, David; Hartman, Robert; McCollough, Cynthia H

    2010-12-01

    To determine the computed tomographic (CT) detector configuration, patient size, and image noise limitations that will result in acceptable image quality of 80-kV images obtained at abdominal dual-energy CT. The Institutional Review Board approved this HIPAA-compliant retrospective study from archival material from patients consenting to the use of medical records for research purposes. A retrospective review of contrast material-enhanced abdominal dual-energy CT scans in 116 consecutive patients was performed. Three gastrointestinal radiologists noted detector configuration and graded image quality and artifacts at specified levels-midliver, midpancreas, midkidneys, and terminal ileum-by using two five-point scales. In addition, an organ-specific enhancement-to-noise ratio and background noise were measured in each patient. Patient size was measured by using the longest linear dimension at the level of interest, weight, lean body weight, body mass index, and body surface area. Detector configuration, patient sizes, and image noise levels that resulted in unacceptable image quality and artifact rankings (score of 4 or higher) were determined by using multivariate logistic regression. A 14 × 1.2-mm detector configuration resulted in fewer images with unacceptable quality than did the 64 × 0.6-mm configuration at all anatomic levels (P = .004, .01, and .02 for liver, pancreas, and kidneys, respectively). Image acceptability for the kidneys and ileum was significantly greater than that for the liver for all readers and detector configurations (P < .001). For the 14 × 1.2-mm detector configuration, patient longest linear dimensions yielding acceptable image quality across readers ranged from 34.9 to 35.8 cm at the four anatomic levels. An 80-kV abdominal CT can be performed with appropriate diagnostic quality in a substantial percentage of the population, but it is not recommended beyond the described patient size for each anatomic level. The 14 × 1.2-mm detector

  19. Impact of functional magnetic resonance imaging (fMRI) scanner noise on affective state and attentional performance.

    Science.gov (United States)

    Jacob, Shawna N; Shear, Paula K; Norris, Matthew; Smith, Matthew; Osterhage, Jeff; Strakowski, Stephen M; Cerullo, Michael; Fleck, David E; Lee, Jing-Huei; Eliassen, James C

    2015-01-01

    Previous research has shown that performance on cognitive tasks administered in the scanner can be altered by the scanner environment. There are no previous studies that have investigated the impact of scanner noise using a well-validated measure of affective change. The goal of this study was to determine whether performance on an affective attentional task or emotional response to the task would change in the presence of distracting acoustic noise, such as that encountered in a magnetic resonance imaging (MRI) environment. Thirty-four young adults with no self-reported history of neurologic disorder or mental illness completed three blocks of the affective Posner task outside of the scanner. The task was meant to induce frustration through monetary contingencies and rigged feedback. Participants completed a Self-Assessment Manikin at the end of each block to rate their mood, arousal level, and sense of dominance. During the task, half of the participants heard noise (recorded from a 4T MRI system), and half heard no noise. The affective Posner task led to significant reductions in mood and increases in arousal in healthy participants. The presence of scanner noise did not impact task performance; however, individuals in the noise group did report significantly poorer mood throughout the task. The results of the present study suggest that the acoustic qualities of MRI enhance frustration effects on an affective attentional task and that scanner noise may influence mood during similar functional magnetic resonance imaging (fMRI) tasks.

  20. Image mathematical morphology and image restoration application in detecting underground bin level

    Institute of Scientific and Technical Information of China (English)

    SUN Ji-ping; WU Bing

    2004-01-01

    By using image recognition technology, the underground bin level can be detdcted. The bin image is noised by vibration, atomy, backgroun and so on. The image restoration and image mathematical morphology were used based on neural network.A modified Hopfield network was presented for image restoration. The greed algorithm with n-simultaneous updates and apartially asynchronous algorithm were combined, improving convergence and avoiding synchronization penalties. Mathematical morphology was widely applicated in digital image processing. The basic idea of mathematical morphology is to use construction element measure image morphology for solving understand problem. Presented advanced Cellular neural network that forms MMCNN equation to be suit for mathematical morphology filter. It gave the theory of MMCNN dynamic extent and stable state. It was evidenced that arrived mathematical morphology filter through steady of dynamic precess in definite condition. The results of implementation were applied in detecting undergroug bin level.

  1. New decision-based trimmed median filter for high-density salt-and-pepper noise removal in images

    Science.gov (United States)

    Vijaykumar, Vaithiyam Rengarajan; Santhanamari, Guru

    2014-05-01

    A new switching-based trimmed median filter to remove high-density salt-and-pepper noise in digital images is proposed. Initially, a 3×3 sliding window is applied on each pixel in the noisy image. The minimum- and maximum-intensity values are trimmed, and the noisy pixels are detected based on the predefined threshold value. In the filtering stage, the noisy pixels are replaced by median value of uncorrupted pixels in the trimmed array. At very high noise density, if all the pixels in the sliding window are corrupted, then the proposed algorithm replaces noisy pixels by the midpoint of recently processed pixels. The experimental results for various test images show that the performance of the proposed algorithm is superior to the existing algorithms, namely SMF, WMF, CWMF, AMF, DBA, and MDBUTMF in terms of visual quality and edge preservation, even at noise levels as high as 95%.

  2. Noise reduction by frame averaging: a numerical simulation for portal imaging systems.

    Science.gov (United States)

    Swindell, W; Mosleh-Shirazi, M A

    1995-09-01

    We have studied the usefulness of both pre- and post-ADC frame summing for the purpose of reducing the effect of quantum noise and digitization noise in portal imaging systems. The study is based on the fluorescent-screen video-camera type of system. The study predicts the not-surprising result that provided the noise level at the ADC input is sufficiently large, the overall SNR can be increased by a factor of square root of M1M2, where M1 and M2 are the number of frames summed before and after the ADC. The study also predicts, somewhat unexpectedly, that there is an operating region in which increasing M1 actually decreases the SNR in the final image. To avoid this region M1 must be less than approximately 6 x 2(2B) (1 + -delta-1)1/2/(iaccf), where B is the number of ADC bits, -delta is the mean number of optical photons detected by the video camera per detected x-ray photon, iacc is the open-field number of detected x-ray photons per accelerator pulse per pixel, and f is the patient transmission factor. An equivalent statement is that the rms noise at the input to the ADC, sigma in, must exceed approximately 0.4q where q is the quantization interval of the ADC. It is possible that some systems operate in or close to this region. A second feature of this anomalous behavior is that the final image is not necessarily improved by increasing the number M2 of post-ADC-summed frames. For example, when sigma in/q = 0.2, there is no improvement in the overall rms error for M2 > 32.(ABSTRACT TRUNCATED AT 250 WORDS)

  3. Characterizing response to elemental unit of acoustic imaging noise: an FMRI study.

    Science.gov (United States)

    Tamer, Gregory G; Luh, Wen-Ming; Talavage, Thomas M

    2009-07-01

    Acoustic imaging noise produced during functional magnetic resonance imaging (fMRI) studies can hinder auditory fMRI research analysis by altering the properties of the acquired time-series data. Acoustic imaging noise can be especially confounding when estimating the time course of the hemodynamic response (HDR) in auditory event-related fMRI (fMRI) experiments. This study is motivated by the desire to establish a baseline function that can serve not only as a comparison to other quantities of acoustic imaging noise for determining how detrimental is one's experimental noise, but also as a foundation for a model that compensates for the response to acoustic imaging noise. Therefore, the amplitude and spatial extent of the HDR to the elemental unit of acoustic imaging noise (i.e., a single ping) associated with echoplanar acquisition were characterized and modeled. Results from this fMRI study at 1.5 T indicate that the group-averaged HDR in left and right auditory cortex to acoustic imaging noise (duration of 46 ms) has an estimated peak magnitude of 0.29% (right) to 0.48% (left) signal change from baseline, peaks between 3 and 5 s after stimulus presentation, and returns to baseline and remains within the noise range approximately 8 s after stimulus presentation.

  4. Speckle Noise Reduction for the Enhancement of Retinal Layers in Optical Coherence Tomography Images

    Directory of Open Access Journals (Sweden)

    Fereydoon Nowshiravan Rahatabad

    2015-09-01

    Full Text Available Introduction One of the most important pre-processing steps in optical coherence tomography (OCT is reducing speckle noise, resulting from multiple scattering of tissues, which degrades the quality of OCT images. Materials and Methods The present study focused on speckle noise reduction and edge detection techniques. Statistical filters with different masks and noise variances were applied on OCT and test images. Objective evaluation of both types of images was performed, using various image metrics such as peak signal-to-noise ratio (PSNR, root mean square error, correlation coefficient and elapsed time. For the purpose of recovery, Kuan filter was used as an input for edge enhancement. Also, a spatial filter was applied to improve image quality. Results The obtained results were presented as statistical tables and images. Based on statistical measures and visual quality of OCT images, Enhanced Lee filter (3×3 with a PSNR value of 43.6735 in low noise variance and Kuan filter (3×3 with a PSNR value of 37.2850 in high noise variance showed superior performance over other filters. Conclusion Based on the obtained results, by using speckle reduction filters such as Enhanced Lee and Kuan filters on OCT images, the number of compounded images, required to achieve a given image quality, could be reduced. Moreover, use of Kuan filters for promoting the edges allowed smoothing of speckle regions, while preserving image tissue texture.

  5. Analysis of noise pollution level in a University campus in South India

    Science.gov (United States)

    Thattai, D.; Sudarsan, J. S.; Sathyanathan, R.; Ramasamy, Visalatchi

    2017-07-01

    Noise comprises those sounds occurring around us that are not part of the environment under consideration. Noise is also a type of pollution and impacts on our health and wellness. The prevalence of noise is increasing in magnitude and severity because of growing population and urbanization. Noise pollution leads to many chronic and socially significant impacts. This study analyzes the level of noise at different points in SRM University. As the University encompasses a hospital also, it is more important to identify the sources of high noise levels and control them. As per Indian standards the desirable noise pollution for educational institutions and hospitals in daytime is 50 dbA. Noise levels were measured with a sound level meter at 19 points within the campus at three different timings (8-10 am, 12-2 pm, and 3-5 pm) over two cycles of measurements. The preliminary results show higher noise levels during morning and evening. Noise during Cycle 2 (latter half of semester) was 20% more compared to that of Cycle 1 (beginning of semester).

  6. A New Multi-Layered Fuzzy Image Filter for Removing Impulse Noise

    Directory of Open Access Journals (Sweden)

    Russel J Stonier

    2003-08-01

    Full Text Available In this paper we develop a fuzzy image .lter which consists of a multi-layered fuzzy structure based on the weighted fuzzy blend filter for the removal of noise from images heavily corrupted by impulse noise, while preserving the intricate details of the image. The introduction of multi-layered fuzzy systems substantially decreases the number of rules to be learnt. We then show how Evolutionary Algorithms (EAs can be used to effectively learn the fuzzy rules in each knowledge base. Results are presented for impulse noise corruption of the well-known 'Lena' image.

  7. Noise Reduction Technique for Images using Radial Basis Function Neural Networks

    Directory of Open Access Journals (Sweden)

    Sander Ali Khowaja

    2014-07-01

    Full Text Available This paper presents a NN (Neural Network based model for reducing the noise from images. This is a RBF (Radial Basis Function network which is used to reduce the effect of noise and blurring from the captured images. The proposed network calculates the mean MSE (Mean Square Error and PSNR (Peak Signal to Noise Ratio of the noisy images. The proposed network has also been successfully applied to medical images. The performance of the trained RBF network has been compared with the MLP (Multilayer Perceptron Network and it has been demonstrated that the performance of the RBF network is better than the MLP network.

  8. Restoration of Medical Images with Different Types of Noise; Restauracion de Imagenes Medicas con Diferentes Tipos de Ruido

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M. G.; Vidal, V.; Verdu, G.; Mayo, P.; Rodenas, F.

    2013-07-01

    In this paper, a method is proposed to reduce the Gaussian, speckle and impulsive noise. This filter, named PGMFDNL filter combines a nonlinear diffusion and fuzzy peer group. The proposed filter can effectively reduce image noise without any information about the noise present in the image. As a result, the proposed method obtains good performance in different types of noise.

  9. Methods For an Acceptable Traffic Noise Level Design

    Directory of Open Access Journals (Sweden)

    Zlatko Sviben

    2004-07-01

    Full Text Available Road noise disturbance on rough roads by means of loudnesssensor caused by wideband signal components with a significantimpact of tonal effects on smooth roads and in specificactions in driving lead to the annoyance of drivers. A systemicapproach has been applied for the sound quality estimation ofphysical properties of various noise sources and structuralvibroacoustic car properties and its components as an integratedparameter in car design for the purpose of the developmentand vehicle noise reduction. Simulation of the most importantcharacteristics of listening impressions was performedby modem systems of signal analysis together with the presentationof loudness, sharpness, and roughness as essential quantities.Optimization of the noise control measuring regarding vehiclesound was obtained by means of a simulation system withthe capability of the real time original sound filtering. Structuralanalysis was performed as an acoustic modal analysis on therear part and the car interior with the quantitative analysis ofsport and luxury car sounds. The possibility of active noise controlwas studied and examples are given for an application ofpsychoacoustic tools for car sound quality design. Sound qualitywas obtained by an observation of certain aspects, which areempirically or theoretically connected with the design. An experimentalsound synthesis with psychometrical measuring wasapplied. The sound quality of car interior is presented takinginto consideration the criteria of objectivity, reliability and validity.

  10. Theoretical investigation of the noise performance of active pixel imaging arrays based on polycrystalline silicon thin film transistors.

    Science.gov (United States)

    Koniczek, Martin; Antonuk, Larry E; El-Mohri, Youcef; Liang, Albert K; Zhao, Qihua

    2017-07-01

    Active matrix flat-panel imagers, which typically incorporate a pixelated array with one a-Si:H thin-film transistor (TFT) per pixel, have become ubiquitous by virtue of many advantages, including large monolithic construction, radiation tolerance, and high DQE. However, at low exposures such as those encountered in fluoroscopy, digital breast tomosynthesis and breast computed tomography, DQE is degraded due to the modest average signal generated per interacting x-ray relative to electronic additive noise levels of ~1000 e, or greater. A promising strategy for overcoming this limitation is to introduce an amplifier into each pixel, referred to as the active pixel (AP) concept. Such circuits provide in-pixel amplification prior to readout as well as facilitate correlated multiple sampling, enhancing signal-to-noise and restoring DQE at low exposures. In this study, a methodology for theoretically investigating the signal and noise performance of imaging array designs is introduced and applied to the case of AP circuits based on low-temperature polycrystalline silicon (poly-Si), a semiconductor suited to manufacture of large area, radiation tolerant arrays. Computer simulations employing an analog circuit simulator and performed in the temporal domain were used to investigate signal characteristics and major sources of electronic additive noise for various pixel amplifier designs. The noise sources include photodiode shot noise and resistor thermal noise, as well as TFT thermal and flicker noise. TFT signal behavior and flicker noise were parameterized from fits to measurements performed on individual poly-Si test TFTs. The performance of three single-stage and three two-stage pixel amplifier designs were investigated under conditions relevant to fluoroscopy. The study assumes a 20 × 20 cm(2) , 150 μm pitch array operated at 30 fps and coupled to a CsI:Tl x-ray converter. Noise simulations were performed as a function of operating conditions, including

  11. Switching Correlation and Noise Level in Pr(3+):YSO Crystal via Dressing Nonlinear Phase.

    Science.gov (United States)

    Ahmed, Irfan; Zhang, Zhaoyang; Wen, Feng; Zhang, Da; Li, Changbiao; Wang, Ruimin; Zhang, Yanpeng

    2016-09-21

    We propose and experimentally demonstrate that the intensity noise correlation and the noise level of intensity-difference and intensity-sum in Stokes and anti-Stokes channel can be well controlled by the relative nonlinear phase in spontaneous parametric four-wave mixing process. By modulating the relative nonlinear phase, including self-phase modulation and cross-phase modulation, switching the correlation into anti-correlation and the relative intensity noise level between the intensity-difference and intensity-sum are realized. We also show that the variation tendencies of the relative intensity noise level and the corresponding intensity fluctuations correlation are in accordance with each other.

  12. Reducing Indoor Noise Levels Using People’s Perception on Greenery

    OpenAIRE

    2013-01-01

    Employees working in cubicles of open-plan offices in Indonesia were studied in regard to their perception on the ability of indoor greenery to reduce noise levels. Sansevieria trifasciata and Scindapsus sp were used. Each was placed in the cubicle and noise levels were measured without plants, with Sansevieria, and with Scindapsus in place. The meters showed very insignificant difference. However, responses to surveys indicated a perception of lower noise in the presence...

  13. Switching Correlation and Noise Level in Pr3+:YSO Crystal via Dressing Nonlinear Phase

    OpenAIRE

    Irfan Ahmed; Zhaoyang Zhang; Feng Wen; Da Zhang; Changbiao Li; Ruimin Wang; Yanpeng Zhang

    2016-01-01

    We propose and experimentally demonstrate that the intensity noise correlation and the noise level of intensity-difference and intensity-sum in Stokes and anti-Stokes channel can be well controlled by the relative nonlinear phase in spontaneous parametric four-wave mixing process. By modulating the relative nonlinear phase, including self-phase modulation and cross-phase modulation, switching the correlation into anti-correlation and the relative intensity noise level between the intensity-di...

  14. Analysis of Proposed Noise Detection & Removal Technique in Degraded Fingerprint Images

    Science.gov (United States)

    Hamid, Ainul Azura Abdul; Rahim, Mohd Shafry Mohd; Al-Mazyad, Abdulaziz S.; Saba, Tanzila

    2015-12-01

    The quality of fingerprint images is important to ensure good performance of fingerprint recognition since recognition process depends heavily on the quality of fingerprint images. Fingerprint images obtained from the acquisition phase are either contaminated with noise or degraded due to poor quality machines. Several factors such as scars, moist in scanner and many more noises affect the quality of the images during scanning process. This paper performed an analysis and compared noise removal techniques reported in the literature for fingerprint images. We also implemented histogram equalization, median filter, Fourier transform, unsharp mask and grayscale enhancement techniques. The quality of enhanced images is measured by peak signal to noise ratio (PSNR) calculation for analysis and comparisons.

  15. CT urography in the urinary bladder: To compare excretory phase images using a low noise index and a high noise index with adaptive noise reduction filter

    Energy Technology Data Exchange (ETDEWEB)

    Takeyama, Nobuyuki; Hayashi, Takaki (Dept. of Radiology, Showa Univ. Fujigaoka Hospital, Yokohama (Japan)), email: momiji@mtc.biglobe.ne.jp; Ohgiya, Yoshimitsu (Dept. of Radiology, Showa Univ. School of Medicine, Tokyo (Japan)) (and others)

    2011-07-15

    Background: Although CT urography (CTU) is widely used for the evaluation of the entire urinary tract, the most important drawback is the radiation exposure. Purpose: To evaluate the effect of a noise reduction filter (NRF) using a phantom and to quantitatively and qualitatively compare excretory phase (EP) images using a low noise index (NI) with those using a high NI and postprocessing NRF (pNRF). Material and Methods: Each NI value was defined for a slice thickness of 5 mm, and reconstructed images with a slice thickness of 1.25 mm were assessed. Sixty patients who were at high risk of developing bladder tumors (BT) were divided into two groups according to whether their EP images were obtained using an NI of 9.88 (29 patients; group A) or an NI of 20 and pNRF (31 patients; group B). The CT dose index volume (CTDI{sub vol}) and the contrast-to-noise ratio (CNR) of the bladder with respect to the anterior pelvic fat were compared in both groups. Qualitative assessment of the urinary bladder for image noise, sharpness, streak artifacts, homogeneity, and the conspicuity of polypoid or sessile-shaped BTs with a short-axis diameter greater than 10 mm was performed using a 3-point scale. Results: The phantom study showed noise reduction of approximately 40% and 76% dose reduction between group A and group B. CTDI{sub vol} demonstrated a 73% reduction in group B (4.6 +- 1.1 mGy) compared with group A (16.9 +- 3.4 mGy). The CNR value was not significantly different (P = 0.60) between group A (16.1 +- 5.1) and group B (16.6 +- 7.6). Although group A was superior (P < 0.01) to group B with regard to image noise, other qualitative analyses did not show significant differences. Conclusion: EP images using a high NI and pNRF were quantitatively and qualitatively comparable to those using a low NI, except with regard to image noise

  16. Noise levels in primary schools of medium sized city in Greece.

    Science.gov (United States)

    Sarantopoulos, George; Lykoudis, Spyros; Kassomenos, Pavlos

    2014-06-01

    This study presents and evaluates noise levels recorded at 15 school complexes in order to describe the indoor as well as the outdoor acoustic environment of schools and gain insight on controlling factors. Noise levels at the roadside in front of the school, the schoolyard, and 41 classrooms, both occupied and unoccupied, were simultaneously and continuously recorded through the course of a daily timetable (08:20-13:10). The average speech noise level of teachers was separately measured for 1min periods. Indoor noise levels, in all cases, were much higher than internationally recommended values: LAeq,5min averaged 69.0dB in occupied classrooms, and 47.1dB in unoccupied ones. Average speech-to-noise ratio (SNR) was estimated to be 12.0dB(A) during teaching, whereas both indoor and outdoor noise levels were significantly elevated during break time and outdoor physical-educational activities. Corresponding measurements of indoor and outdoor noise suggest that noise from the outside (road and schoolyard) affects the background noise level in the classrooms, however in varying degrees, depending on the specific layout and road traffic characteristics. Using double glazing diminishes this effect.

  17. Non-uniform noise spatial distribution in CT myocardial perfusion and a potential solution: statistical image reconstruction

    Science.gov (United States)

    Thériault Lauzier, Pascal; Tang, Jie; Chen, Guang-Hong

    2012-03-01

    Myocardial perfusion scans are an important tool in the assessment of myocardial viability following an infarction. Cardiac perfusion analysis using CT datasets is limited by the presence of so-called partial scan artifacts. These artifacts are due to variations in beam hardening and scatter between different short-scan angular ranges. In this research, another angular range dependent effect is investigated: non-uniform noise spatial distribution. Images reconstructed using filtered backprojection (FBP) are subject to this effect. Statistical image reconstruction (SIR) is proposed as a potential solution. A numerical phantom with added Poisson noise was simulated and two swines were scanned in vivo to study the effect of FBP and SIR on the spatial uniformity of the noise distribution. It was demonstrated that images reconstructed using FBP often show variations in noise on the order of 50% between different time frames. This variation is mitigated to about 10% using SIR. The noise level is also reduced by a factor of 2 in SIR images. Finally, it is demonstrated that the measurement of quantitative perfusion metrics are generally more accurate when SIR is used instead of FBP.

  18. Study on traffic noise level of Sylhet by multiple regression analysis associated with health hazards

    Directory of Open Access Journals (Sweden)

    J. B. Alam, M. Jobair Bin Alam, M. M. Rahman, A. K. Dikshit, S. K. Khan

    Full Text Available The study reports the level of traffic-induced noise pollution in Sylhet City. For this purpose noise levels have been measured at thirty-seven major locations of the city from 7 am to 11 pm during the working days. It was observed that at all the locations the level of noise remains far above the acceptable limit for all the time. The noise level on the main road near residential area, hospital area and educational area were above the recommended level (65dBA. It was found that the predictive equations are in 60-70% correlated with the measured noise level. The study suggests that vulnerable institutions like school and hospital should be located about 60m away from the roadside unless any special arrangement to alleviate sound is used.

  19. Kalman-median Compound Filter for Gaussian and Impulse Noise Reduction on Digital Images

    OpenAIRE

    山森, 一人; 山田, 義治; 相川, 勝

    2013-01-01

    This paper proposes an image restoration method from degraded images which include additive gaussian noise and impulse noise. This method tries to achieve image restoration by using combination of canonical state space model kalman filter and median filter. Kalman filter estimates internal state of a dynamic system based on system model. The canonical state space models are described by two equations; state equation that expresses a transition process of the region including the focusing pixe...

  20. A Denoising Scheme for Randomly Clustered Noise Removal in ICCD Sensing Image

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-01-01

    Full Text Available An Intensified Charge-Coupled Device (ICCD image is captured by the ICCD image sensor in extremely low-light conditions. Its noise has two distinctive characteristics. (a Different from the independent identically distributed (i.i.d. noise in natural image, the noise in the ICCD sensing image is spatially clustered, which induces unexpected structure information; (b The pattern of the clustered noise is formed randomly. In this paper, we propose a denoising scheme to remove the randomly clustered noise in the ICCD sensing image. First, we decompose the image into non-overlapped patches and classify them into flat patches and structure patches according to if real structure information is included. Then, two denoising algorithms are designed for them, respectively. For each flat patch, we simulate multiple similar patches for it in pseudo-time domain and remove its noise by averaging all the simulated patches, considering that the structure information induced by the noise varies randomly over time. For each structure patch, we design a structure-preserved sparse coding algorithm to reconstruct the real structure information. It reconstructs each patch by describing it as a weighted summation of its neighboring patches and incorporating the weights into the sparse representation of the current patch. Based on all the reconstructed patches, we generate a reconstructed image. After that, we repeat the whole process by changing relevant parameters, considering that blocking artifacts exist in a single reconstructed image. Finally, we obtain the reconstructed image by merging all the generated images into one. Experiments are conducted on an ICCD sensing image dataset, which verifies its subjective performance in removing the randomly clustered noise and preserving the real structure information in the ICCD sensing image.

  1. A Denoising Scheme for Randomly Clustered Noise Removal in ICCD Sensing Image.

    Science.gov (United States)

    Wang, Fei; Wang, Yibin; Yang, Meng; Zhang, Xuetao; Zheng, Nanning

    2017-01-26

    An Intensified Charge-Coupled Device (ICCD) image is captured by the ICCD image sensor in extremely low-light conditions. Its noise has two distinctive characteristics. (a) Different from the independent identically distributed (i.i.d.) noise in natural image, the noise in the ICCD sensing image is spatially clustered, which induces unexpected structure information; (b) The pattern of the clustered noise is formed randomly. In this paper, we propose a denoising scheme to remove the randomly clustered noise in the ICCD sensing image. First, we decompose the image into non-overlapped patches and classify them into flat patches and structure patches according to if real structure information is included. Then, two denoising algorithms are designed for them, respectively. For each flat patch, we simulate multiple similar patches for it in pseudo-time domain and remove its noise by averaging all the simulated patches, considering that the structure information induced by the noise varies randomly over time. For each structure patch, we design a structure-preserved sparse coding algorithm to reconstruct the real structure information. It reconstructs each patch by describing it as a weighted summation of its neighboring patches and incorporating the weights into the sparse representation of the current patch. Based on all the reconstructed patches, we generate a reconstructed image. After that, we repeat the whole process by changing relevant parameters, considering that blocking artifacts exist in a single reconstructed image. Finally, we obtain the reconstructed image by merging all the generated images into one. Experiments are conducted on an ICCD sensing image dataset, which verifies its subjective performance in removing the randomly clustered noise and preserving the real structure information in the ICCD sensing image.

  2. A noise level prediction method based on electro-mechanical frequency response function for capacitors.

    Science.gov (United States)

    Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao

    2013-01-01

    The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

  3. Reduction of Classroom Noise Levels Using Group Contingencies

    Science.gov (United States)

    Ring, Brandon M.; Sigurdsson, Sigurdur O.; Eubanks, Sean L.; Silverman, Kenneth

    2014-01-01

    The therapeutic workplace is an employment-based abstinence reinforcement intervention for unemployed drug users where trainees receive on-the-job employment skills training in a classroom setting. The study is an extension of prior therapeutic workplace research, which suggested that trainees frequently violated noise standards. Participants…

  4. Ultrawideband Noise Radar Imaging of Impenetrable Cylindrical Objects Using Diffraction Tomography

    Directory of Open Access Journals (Sweden)

    Hee Jung Shin

    2014-01-01

    Full Text Available Ultrawideband (UWB waveforms achieve excellent spatial resolution for better characterization of targets in tomographic imaging applications compared to narrowband waveforms. In this paper, two-dimensional tomographic images of multiple scattering objects are successfully obtained using the diffraction tomography approach by transmitting multiple independent and identically distributed (iid UWB random noise waveforms. The feasibility of using a random noise waveform for tomography is investigated by formulating a white Gaussian noise (WGN model using spectral estimation. The analytical formulation of object image formation using random noise waveforms is established based on the backward scattering, and several numerical diffraction tomography simulations are performed in the spatial frequency domain to validate the analytical results by reconstructing the tomographic images of scattering objects. The final image of the object based on multiple transmitted noise waveforms is reconstructed by averaging individually formed images which compares very well with the image created using the traditional Gaussian pulse. Pixel difference-based measure is used to analyze and estimate the image quality of the final reconstructed tomographic image under various signal-to-noise ratio (SNR conditions. Also, preliminary experiment setup and measurement results are presented to assess the validation of simulation results.

  5. Nonlinear Image Restoration in Confocal Microscopy : Stability under Noise

    NARCIS (Netherlands)

    Roerdink, J.B.T.M.

    1995-01-01

    In this paper we study the noise stability of iterative algorithms developed for attenuation correction in Fluorescence Confocal Microscopy using FT methods. In each iteration the convolution of the previous estimate is computed. It turns out that the estimators are robust to noise perturbation.

  6. Nonlinear Image Restoration in Confocal Microscopy : Stability under Noise

    NARCIS (Netherlands)

    Roerdink, J.B.T.M.

    1995-01-01

    In this paper we study the noise stability of iterative algorithms developed for attenuation correction in Fluorescence Confocal Microscopy using FT methods. In each iteration the convolution of the previous estimate is computed. It turns out that the estimators are robust to noise perturbation.

  7. Cascaded systems analysis of noise reduction algorithms in dual-energy imaging.

    Science.gov (United States)

    Richard, Samuel; Siewerdsen, Jeffrey H

    2008-02-01

    An important aspect of dual-energy (DE) x-ray image decomposition is the incorporation of noise reduction techniques to mitigate the amplification of quantum noise. This article extends cascaded systems analysis of imaging performance to DE imaging systems incorporating linear noise reduction algorithms. A general analytical formulation of linear DE decomposition is derived, with weighted log subtraction and several previously reported noise reduction algorithms emerging as special cases. The DE image noise-power spectrum (NPS) and modulation transfer function (MTF) demonstrate that noise reduction algorithms impart significant, nontrivial effects on the spatial-frequency-dependent transfer characteristics which do not cancel out of the noise-equivalent quanta (NEQ). Theoretical predictions were validated in comparison to the measured NPS and MTF. The resulting NEQ was integrated with spatial-frequency-dependent task functions to yield the detectability index, d', for evaluation of DE imaging performance using different decomposition algorithms. For a 3 mm lung nodule detection task, the detectability index varied from d' 2.5 (i.e., nodule clearly visible) for "anti-correlated noise reduction" (ACNR) or "simple-smoothing of the high-energy image" (SSH) algorithms applied to soft-tissue or bone-only decompositions, respectively. Optimal dose allocation (A*, the fraction of total dose delivered in the low-energy projection) was also found to depend on the choice of noise reduction technique. At fixed total dose, multi-function optimization suggested a significant increase in optimal dose allocation from A* = 0.32 for conventional log subtraction to A* = 0.79 for ACNR and SSH in soft-tissue and bone-only decompositions, respectively. Cascaded systems analysis extended to the general formulation of DE image decomposition provided an objective means of investigating DE imaging performance across a broad range of acquisition and decomposition algorithms in a manner that

  8. Estimating the level of dynamical noise in time series by using fractal dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Sase, Takumi, E-mail: sase@sat.t.u-tokyo.ac.jp [Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 153-8505 (Japan); Ramírez, Jonatán Peña [CONACYT Research Fellow, Center for Scientific Research and Higher Education at Ensenada (CICESE), Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860, Ensenada, Baja California (Mexico); Kitajo, Keiichi [BSI-Toyota Collaboration Center, RIKEN Brain Science Institute, Wako, Saitama 351-0198 (Japan); Aihara, Kazuyuki; Hirata, Yoshito [Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 153-8505 (Japan); Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan)

    2016-03-11

    We present a method for estimating the dynamical noise level of a ‘short’ time series even if the dynamical system is unknown. The proposed method estimates the level of dynamical noise by calculating the fractal dimensions of the time series. Additionally, the method is applied to EEG data to demonstrate its possible effectiveness as an indicator of temporal changes in the level of dynamical noise. - Highlights: • A dynamical noise level estimator for time series is proposed. • The estimator does not need any information about the dynamics generating the time series. • The estimator is based on a novel definition of time series dimension (TSD). • It is demonstrated that there exists a monotonic relationship between the • TSD and the level of dynamical noise. • We apply the proposed method to human electroencephalographic data.

  9. Image quality evaluation of virtual monoenergetic spectral images obtained in two types of dual energy CT based on noise level%两种双能CT技术虚拟单能谱图像的噪声比较研究

    Institute of Scientific and Technical Information of China (English)

    周旸; 曾勇明; 周密; 高志梅; 孙静坤

    2016-01-01

    Objective To investigate the image quality difference of the virtual monochromatic spectral(VMS) images synthesized from fast kilovoltage switching and dual-source dual-energy CT for a given radiation dose. Methods A plurality of disposable syringes containing 15 mg/ml iodine contrast agent and saline were placed on the surface of the male anthropomorphic phantom consisting ofhead neck and torso, GE HD750 gemstone spectral imaging and Siemens Somatom Definition Flash dual energy CT protocols were performed on the phantom for a same dose(volume CT dose index 6.52 mGy), and VMS images (40, 60, 70, 80, 100, 120, 140 keV) were reconstructed and obtained(VMSkV switching and VMSdual-source image), respectively. The objective image noise, iodine signal noise ratio(SNR), iodine contrast noise ratio (CNR) and CT values were measured. The results were analyzed using the paired t test and ANOVA. Results All VMS iodine CT values were gradually decreased with the increasing of keV , and iodine CT values on VMSdual-source images were greater than on VMSkV switching images(P<0.05), VMSkV switching iodine CT values in descending order from the head , chest, abdomen at less than 100 keV,while most VMSdual-source iodine CT values were highest on chest(P<0.05). VMSdual-source and VMSkV switching image noise were highest at 40 keV and successively raised from the head, chest , abdomen. VMSkV switching image noise gradually decreased with the increase of keV in the range of 40 to 70 keV , gradually increased up to the trough after 70 keV from 80 keV gradually decreased, while VMSdual-source image noise was lowest at 70 keV or 80 keV , and then with the keV increased gradually increased. Image noise on VMSkV switching images in the range of 40 to 100 keV were higher than that on VMSdual-source images and lower in the range of 100 to 140 keV at most part(P<0.05). VMSdual-source and VMSkV switching iodine SNR were highest at 40 keV or 60 keV,SNR on VMSdual-source images are greater than

  10. Effects of pedagogical ideology on the perceived loudness and noise levels in preschools.

    Science.gov (United States)

    Jonsdottir, Valdis; Rantala, Leena M; Oskarsson, Gudmundur Kr; Sala, Eeva

    2015-01-01

    High activity noise levels that result in detrimental effects on speech communication have been measured in preschools. To find out if different pedagogical ideologies affect the perceived loudness and levels of noise, a questionnaire study inquiring about the experience of loudness and voice symptoms was carried out in Iceland in eight private preschools, called "Hjalli model", and in six public preschools. Noise levels were also measured in the preschools. Background variables (stress level, age, length of working career, education, smoking, and number of children per teacher) were also analyzed in order to determine how much they contributed toward voice symptoms and the experience of noisiness. Results indicate that pedagogical ideology is a significant factor for predicting noise and its consequences. Teachers in the preschool with tighter pedagogical control of discipline (the "Hjalli model") experienced lower activity noise loudness than teachers in the preschool with a more relaxed control of behavior (public preschool). Lower noise levels were also measured in the "Hjalli model" preschool and fewer "Hjalli model" teachers reported voice symptoms. Public preschool teachers experienced more stress than "Hjalli model" teachers and the stress level was, indeed, the background variable that best explained the voice symptoms and the teacher's perception of a noisy environment. Discipline, structure, and organization in the type of activity predicted the activity noise level better than the number of children in the group. Results indicate that pedagogical ideology is a significant factor for predicting self-reported noise and its consequences.

  11. Effects of broadband noise on cortical evoked auditory responses at different loudness levels in young adults.

    Science.gov (United States)

    Sharma, Mridula; Purdy, Suzanne C; Munro, Kevin J; Sawaya, Kathleen; Peter, Varghese

    2014-03-26

    Young adults with no history of hearing concerns were tested to investigate their /da/-evoked cortical auditory evoked potentials (P1-N1-P2) recorded from 32 scalp electrodes in the presence and absence of noise at three different loudness levels (soft, comfortable, and loud), at a fixed signal-to-noise ratio (+3 dB). P1 peak latency significantly increased at soft and loud levels, and N1 and P2 latencies increased at all three levels in the presence of noise, compared with the quiet condition. P1 amplitude was significantly larger in quiet than in noise conditions at the loudest level. N1 amplitude was larger in quiet than in noise for the soft level only. P2 amplitude was reduced in the presence of noise to a similar degree at all loudness levels. The differential effects of noise on P1, N1, and P2 suggest differences in auditory processes underlying these peaks. The combination of level and signal-to-noise ratio should be considered when using cortical auditory evoked potentials as an electrophysiological indicator of degraded speech processing.

  12. Noise calculation model and analysis of high-gain readout circuits for CMOS image sensors

    Science.gov (United States)

    Kawahito, Shoji; Itoh, Shinya

    2008-02-01

    A thermal noise calculation model of high-gain switched-capacitor column noise cancellers for CMOS image sensors is presented. In the high-gain noise canceller with a single noise cancelling stage, the reset noise of the readout circuits dominates the noise at high gain. Using the double-stage architecture using a switched-capacitor gain stage and a sample-and-hold stage using two sampling capacitors, the reset noise of the gain stage can be cancelled. The resulting input referred thermal noise power of high-gain double-stage switched-capacitor noise canceller is revealed to be proportional to (g_a/g_s)/GC_L where g_a, G and C_L are the transconductance, gain and output capacitance of the amplifier, respectively, and g_s is the output conductance of an in-pixel source follower. An important contribution of the proposed noise calculation formula is the inclusion of the influence of the transconductance ratio of the amplifier to that of the source follower. For low-noise design, it is important that the transconductance of the amplifier used in the noise canceller is minimized under the condition of meeting the required response time of the switched capacitor amplifier which is inversely proportional to the cutoff angular frequency.

  13. Level, peculiarities and effects of coal mine noise on pit workers. [correlation between noise intensity and hearing impairment

    Science.gov (United States)

    Darlea, I. G.; Bitir, P.; Coculescu, M.

    1974-01-01

    There exists a correlation between noise intensity and spectrum and degree of hearing impairment in the different professional categories in the pit. Most affected are dross miners and drillers. In these, the first degree of hypoacusia sets in within the first five years of exposure. Deafness begins at a frequency of 4,000 Hz, but often enough (20%) at 2,000 Hz as well, progressively evolving through the classical stages if exposure to noise continues. In the coal bearing basins investigated, the noise level is, on the whole, 31.2%, but the conventional zone is not involved by more than 6.3%. Technological and medical measures are proposed for the purpose of avoiding these troubles in the future.

  14. A Novel Image Segmentation Algorithm Based on Neutrosophic Filtering and Level Set

    Directory of Open Access Journals (Sweden)

    Yanhui Guo

    2016-03-01

    Full Text Available Image segmentation is an important step in image processing and analysis, pattern recognition, and machine vision. A few of algorithms based on level set have been proposed for image segmentation in the last twenty years. However, these methods are time consuming, and sometime fail to extract the correct regions especially for noisy images. Recently, neutrosophic set (NS theory has been applied to image processing for noisy images with indeterminant information. In this paper, a novel image segmentation approach is proposed based on the filter in NS and level set theory. At first, the image is transformed into NS domain, which is described by three membership sets (T, I and F. Then, a filter is newly defined and employed to reduce the indeterminacy of the image. Finally, a level set algorithm is used in the image after filtering operation for image segmentation. Experiments have been conducted using different images. The results demonstrate that the proposed method can segment the images effectively and accurately. It is especially able to remove the noise effect and extract the correct regions on both the noise-free images and the images with different levels of noise.

  15. SPECKLE NOISE FILTERING FOR ULTRASOUND IMAGES OF COMMON CAROTID ARTERY: A REVIEW

    Directory of Open Access Journals (Sweden)

    D. Sasikala

    2014-05-01

    Full Text Available Speckle is modeled as a signal dependent noise, which tends to reduce the image resolution and contrast, thereby reducing the diagnostic values of the ultrasound imaging modality. Reduction of speckle noise is one of the most important processes to increase the quality of biomedical images. Filters are used to improve the quality of ultrasound images by removing the noise. This paper compares the performance of the thresholding technique Bayes Shrink in despeckling the medical ultrasound images with other classical speckle reduction filters like Lee, Frost, Median, Kaun, Wavelet Bayes, Anisotropic diffusion and Wavelet. The performance of these filters is analyzed by the statistical measures such as Peak Signal-to Noise Ratio, Mean Square Error and Equivalent Number of Looks. To produce a better quality resolution picture, the filter should have high Peak Signal to Noise Ratio, low Mean Square Error, high Equivalent Number of Looks. The results obtained are presented in the form of filtered images, statistical tables and graphs. Finally, the best filter has been recommended based on the statistical and experimental results. From the results obtained Lee and Frost filter outperforms the other mentioned filters in terms of high PSNR and low MSE for high variance of noise where as anisotropic diffusion filter outperforms with high PSNR and low MSE with maximum ENL for low variance values of noise.

  16. Noise analysis for near field 3-D FM-CW radar imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Sheen, David M.

    2015-06-19

    Near field radar imaging systems are used for several applications including concealed weapon detection in airports and other high-security venues. Despite the near-field operation, phase noise and thermal noise can limit the performance in several ways including reduction in system sensitivity and reduction of image dynamic range. In this paper, the effects of thermal noise, phase noise, and processing gain are analyzed in the context of a near field 3-D FM-CW imaging radar as might be used for concealed weapon detection. In addition to traditional frequency domain analysis, a time-domain simulation is employed to graphically demonstrate the effect of these noise sources on a fast-chirping FM-CW system.

  17. Total Variation Regularization Algorithms for Images Corrupted with Different Noise Models: A Review

    Directory of Open Access Journals (Sweden)

    Paul Rodríguez

    2013-01-01

    Full Text Available Total Variation (TV regularization has evolved from an image denoising method for images corrupted with Gaussian noise into a more general technique for inverse problems such as deblurring, blind deconvolution, and inpainting, which also encompasses the Impulse, Poisson, Speckle, and mixed noise models. This paper focuses on giving a summary of the most relevant TV numerical algorithms for solving the restoration problem for grayscale/color images corrupted with several noise models, that is, Gaussian, Salt & Pepper, Poisson, and Speckle (Gamma noise models as well as for the mixed noise scenarios, such the mixed Gaussian and impulse model. We also include the description of the maximum a posteriori (MAP estimator for each model as well as a summary of general optimization procedures that are typically used to solve the TV problem.

  18. Analysis of optical amplifier noise in coherent optical communication systems with optical image rejection receivers

    DEFF Research Database (Denmark)

    Jørgensen, Bo Foged; Mikkelsen, Benny; Mahon, Cathal J.

    1992-01-01

    performance. Two types of optical image rejection receivers are investigated: a novel, all-optical configuration and the conventional, microwave-based configuration. The analysis shows that local oscillator-spontaneous emission beat noise (LO-SP), signal-spontaneous emission beat noise (S-SP), and spontaneous......A detailed theoretical analysis of optical amplifier noise in coherent optical communication systems with heterodyne receivers is presented. The analysis quantifies in particular how optical image rejection receiver configurations reduce the influence of optical amplifier noise on system......-spontaneous beat noise (SP-SP) can all be reduced by 3 dB, thereby doubling the dynamic range of the optical amplifier. A 2.5-dB improvement in dynamic range has been demonstrated experimentally with the all-optical image rejection configuration. The implications of the increased dynamic range thus obtained...

  19. Quantitative appraisal for noise reduction in digital holographic phase imaging.

    Science.gov (United States)

    Montresor, Silvio; Picart, Pascal

    2016-06-27

    This paper discusses on a quantitative comparison of the performances of different advanced algorithms for phase data de-noising. In order to quantify the performances, several criteria are proposed: the gain in the signal-to-noise ratio, the Q index, the standard deviation of the phase error, and the signal to distortion ratio. The proposed methodology to investigate de-noising algorithms is based on the use of a realistic simulation of noise-corrupted phase data. A database including 25 fringe patterns divided into 5 patterns and 5 different signal-to-noise ratios was generated to evaluate the selected de-noising algorithms. A total of 34 algorithms divided into different families were evaluated. Quantitative appraisal leads to ranking within the considered criteria. A fairly good correlation between the signal-to-noise ratio gain and the quality index has been observed. There exists an anti-correlation between the phase error and the quality index which indicates that the phase errors are mainly structural distortions in the fringe pattern. Experimental results are thoroughly discussed in the paper.

  20. Lateral facilitation--no effect on the target noise level.

    Science.gov (United States)

    Katkov, Mikhail; Sagi, Dov

    2010-11-23

    The detection threshold of a centrally placed Gabor target is reduced in the presence of aligned high-contrast Gabor patches that are optimally spaced from the target (Polat & Sagi, 1993). Here we determined whether threshold reduction is due to signal enhancement or to decreased signal response variability (internal noise), using a recently developed analysis for a Signal Detection Theory (SDT)-based contrast-identification paradigm (Katkov, Tsodyks, & Sagi, 2007a). We found that flankers did not affect internal noise, but instead caused increased target response when collinear with it, in agreement with the lateral facilitation effect. Based on these results, we concluded that lateral facilitation can be explained by signal enhancement only, and that uncertainty-based models do not provide a satisfactory description of the data.

  1. A switching median filter with boundary discriminative noise detection for extremely corrupted images.

    Science.gov (United States)

    Ng, Pei-Eng; Ma, Kai-Kuang

    2006-06-01

    A novel switching median filter incorporating with a powerful impulse noise detection method, called the boundary discriminative noise detection (BDND), is proposed in this paper for effectively denoising extremely corrupted images. To determine whether the current pixel is corrupted, the proposed BDND algorithm first classifies the pixels of a localized window, centering on the current pixel, into three groups--lower intensity impulse noise, uncorrupted pixels, and higher intensity impulse noise. The center pixel will then be considered as "uncorrupted," provided that it belongs to the "uncorrupted" pixel group, or "corrupted." For that, two boundaries that discriminate these three groups require to be accurately determined for yielding a very high noise detection accuracy--in our case, achieving zero miss-detection rate while maintaining a fairly low false-alarm rate, even up to 70% noise corruption. Four noise models are considered for performance evaluation. Extensive simulation results conducted on both monochrome and color images under a wide range (from 10% to 90%) of noise corruption clearly show that our proposed switching median filter substantially outperforms all existing median-based filters, in terms of suppressing impulse noise while preserving image details, and yet, the proposed BDND is algorithmically simple, suitable for real-time implementation and application.

  2. Imaging resolution signal-to-noise ratio in transverse phase amplification from classical information theory

    Energy Technology Data Exchange (ETDEWEB)

    French, Doug [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)], E-mail: french@purdue.edu; Huang Zun; Pao, H.-Y.; Jovanovic, Igor [School of Nuclear Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2009-03-02

    A quantum phase amplifier operated in the spatial domain can improve the signal-to-noise ratio in imaging beyond the classical limit. The scaling of the signal-to-noise ratio with the gain of the quantum phase amplifier is derived from classical information theory.

  3. Assessment of noise levels in clinical and laboratory areas of dental teaching institution, Ahmedabad

    Directory of Open Access Journals (Sweden)

    Sujal M Parkar

    2014-01-01

    Full Text Available Aim: To measure and assess the noise levels produced by different dental equipments. Materials and Methods: Measurement of the noise level was performed in preclinics, clinics, and dental laboratory of different departments of Ahmedabad Dental College and Hospital. The noise levels were determined using a Mini sound meter (CEM USA, which was placed at the dentist′s and laboratory technician′s ear level and at a distance of 1 m from a main noise source. The level of noise was measured in decibel (dB while the instruments were at maximum running speed. Results: In dental laboratory, the nosiest dental equipment was gypsum lathe trimmer with the noise level ranging from 87.36 to 98.3 dB. In preclinical area, the sound produced by low-speed air-rotor ranges from 66.68 to 69.28 dB. In clinical areas, the highest noise produced was by high-speed air-rotor (73.36 to 81.8 dB. The noise created by suction pump when in contact with mucosa was in range from 73.1 to 80.32 dB. The noise levels generated during cutting were significantly higher (P < 0.05 than those of noncutting, which was proved in the course of the measurements. Conclusion: At the end of the study it can be concluded that the sound levels are below that causes damage to the human ear (85 dB. However, dental technicians and other personnel working all day in noisy laboratories could be at risk of Noise-Induced Hearing Loss if they did not choose not to wear ear protection.

  4. Comparing the performance of different ultrasonic images enhancement for speckle noise reduction in ultrasound images using techniques: a preference study

    Science.gov (United States)

    Rana, Md. Shohel; Sarker, Kaushik; Bhuiyan, Touhid; Hassan, Md. Maruf

    2017-06-01

    Diagnostic ultrasound (US) is an important tool in today's sophisticated medical diagnostics. Nearly every medical discipline benefits itself from this relatively inexpensive method that provides a view of the inner organs of the human body without exposing the patient to any harmful radiations. Medical diagnostic images are usually corrupted by noise during their acquisition and most of the noise is speckle noise. To solve this problem, instead of using adaptive filters which are widely used, No-Local Means based filters have been used to de-noise the images. Ultrasound images of four organs such as Abdomen, Ortho, Liver, Kidney, Brest and Prostrate of a Human body have been used and applied comparative analysis study to find out the output. These images were taken from Siemens SONOLINE G60 S System and the output was compared by matrices like SNR, RMSE, PSNR IMGQ and SSIM. The significance and compared results were shown in a tabular format.

  5. Noise levels in the learning-teaching activities in a dental medicine school

    Science.gov (United States)

    Matos, Andreia; Carvalho, Antonio P. O.; Fernandes, Joao C. S.

    2002-11-01

    The noise levels made by different clinical handpieces and laboratory engines are considered to be the main descriptors of acoustical comfort in learning spaces in a dental medicine school. Sound levels were measured in five types of classrooms and teaching laboratories at the University of Porto Dental Medicine School. Handpiece noise measurements were made while instruments were running free and during operations with cutting tools (tooth, metal, and acrylic). Noise levels were determined using a precision sound level meter, which was positioned at ear level and also at one-meter distance from the operator. Some of the handpieces were brand new and the others had a few years of use. The sound levels encountered were between 60 and 99 dB(A) and were compared with the noise limits in A-weighted sound pressure level for mechanical equipments installed in educational buildings included in the Portuguese Noise Code and in other European countries codes. The daily personal noise exposure levels (LEP,d) of the students and professors were calculated to be between 85 and 90 dB(A) and were compared with the European legal limits. Some noise limits for this type of environment are proposed and suggestions for the improvement of the acoustical environment are given.

  6. Environmental noise levels affect the activity budget of the Florida manatee

    Science.gov (United States)

    Miksis-Olds, Jennifer L.; Donaghay, Percy L.; Miller, James H.; Tyack, Peter L.

    2005-09-01

    Manatees inhabit coastal bays, lagoons, and estuaries because they are dependent on the aquatic vegetation that grows in shallow waters. Food requirements force manatees to occupy the same areas in which human activities are the greatest. Noise produced from human activities has the potential to affect these animals by eliciting responses ranging from mild behavioral changes to extreme aversion. This study quantifies the behavioral responses of manatees to both changing levels of ambient noise and transient noise sources. Results indicate that elevated environmental noise levels do affect the overall activity budget of this species. The proportion of time manatees spend feeding, milling, and traveling in critical habitats changed as a function of noise level. More time was spent in the directed, goal-oriented behaviors of feeding and traveling, while less time was spent milling when noise levels were highest. The animals also responded to the transient noise of approaching vessels with changes in behavioral state and movements out of the geographical area. This suggests that manatees detect and respond to changes in environmental noise levels. Whether these changes legally constitute harassment and produce biologically significant effects need to be addressed with hypothesis-driven experiments and long-term monitoring. [For Animal Bioacoustics Best Student Paper Award.

  7. IMPROVING DISPLACEMENT SIGNAL-TO-NOISE RATIO FOR LOW-SIGNAL RADIATION FORCE ELASTICITY IMAGING USING BAYESIAN TECHNIQUES

    Science.gov (United States)

    Dumont, Douglas M.; Walsh, Kristy M.; Byram, Brett C.

    2017-01-01

    Radiation force-based elasticity imaging is currently being investigated as a possible diagnostic modality for a number of clinical tasks, including liver fibrosis staging and the characterization of cardiovascular tissue. In this study, we evaluate the relationship between peak displacement magnitude and image quality and propose using a Bayesian estimator to overcome the challenge of obtaining viable data in low displacement signal environments. Displacement data quality were quantified for two common radiation force-based applications, acoustic radiation force impulse imaging, which measures the displacement within the region of excitation, and shear wave elasticity imaging, which measures displacements outside the region of excitation. Performance as a function of peak displacement magnitude for acoustic radiation force impulse imaging was assessed in simulations and lesion phantoms by quantifying signal-to-noise ratio (SNR) and contrast-to-noise ratio for varying peak displacement magnitudes. Overall performance for shear wave elasticity imaging was assessed in ex vivo chicken breast samples by measuring the displacement SNR as a function of distance from the excitation source. The results show that for any given displacement magnitude level, the Bayesian estimator can increase the SNR by approximately 9 dB over normalized cross-correlation and the contrast-to-noise ratio by a factor of two. We conclude from the results that a Bayesian estimator may be useful for increasing data quality in SNR-limited imaging environments. PMID:27157861

  8. A New Hybrid Fuzzy Intelligent Filter for Medical Image Noise Reduction

    Directory of Open Access Journals (Sweden)

    Somaye Aliakbari Dehkordi

    2014-10-01

    Full Text Available Medical imaging comprises different imaging modalities and processes to image human body for diagnostic and treatment purposes and, therefore has an important role in the improvement of public health in all population groups. In this paper, we present an intelligent hybrid noise reduction filter which is based on Neuro-Fuzzy systems. It is especially beneficial in medical image noise reduction. First stage we feed the input image into four general noise reduction filters in parallel. These general filters are: mean filter, median filter, weighted median filter and the adaptive median filter. At the second stage we give the output of the above filters as input into a Neuro-Fuzzy system. As expected, the ability of Neuro-Fuzzy systems in encoding human knowledge and using non-deterministic knowledge, allow us to achieve much more noise reduction from the input images. We implement the proposed method and use it for reduction of noise from a set of medical images affected with high noise density. Experimental results show that the idea is considerably effective.

  9. Result Analysis of Blur and Noise on Image Denoising based on PDE

    Directory of Open Access Journals (Sweden)

    Meenal Jain

    2012-12-01

    Full Text Available The effect of noise on image is still a challenging problem for researchers. Image Denoising has remained a fundamental problem in the field of image processing. Wavelets give a superior performance in image denoising due to properties such as sparsity and multi resolution structure. Many of the previous research use the basic noise reduction through image blurring. Blurring can be done locally, as in the Gaussian smoothing model or in anisotropic filtering; by calculus of variations; or in the frequency domain, such as Weiner filters. In this paper we proposed an image denoising method using partial differential equation. In our proposed approach we proposed three different approaches first is for blur, second is for noise and finally for blur and noise. These approaches are compared by Average absolute difference, signal to noise ratio (SNR, peak signal to noise ratio (PSNR, Image Fidelity and Mean square error. So we can achieve better result on different scenario. We also compare our result on the basis of the above five parameters and the result is better in comparison to the traditional technique.

  10. A practical exposure-equivalent metric for instrumentation noise in x-ray imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Yadava, G K; Kuhls-Gilcrist, A T; Rudin, S; Patel, V K; Hoffmann, K R; Bednarek, D R [Toshiba Stroke Research Center, State University of New York at Buffalo, Buffalo, NY 14214 (United States)

    2008-09-21

    The performance of high-sensitivity x-ray imagers may be limited by additive instrumentation noise rather than by quantum noise when operated at the low exposure rates used in fluoroscopic procedures. The equipment-invasive instrumentation noise measures (in terms of electrons) are generally difficult to make and are potentially not as helpful in clinical practice as would be a direct radiological representation of such noise that may be determined in the field. In this work, we define a clinically relevant representation for instrumentation noise in terms of noise-equivalent detector entrance exposure, termed the instrumentation noise-equivalent exposure (INEE), which can be determined through experimental measurements of noise-variance or signal-to-noise ratio (SNR). The INEE was measured for various detectors, thus demonstrating its usefulness in terms of providing information about the effective operating range of the various detectors. A simulation study is presented to demonstrate the robustness of this metric against post-processing, and its dependence on inherent detector blur. These studies suggest that the INEE may be a practical gauge to determine and compare the range of quantum-limited performance for clinical x-ray detectors of different design, with the implication that detector performance at exposures below the INEE will be instrumentation-noise limited rather than quantum-noise limited.

  11. Contrast-to-noise in X-ray differential phase contrast imaging

    NARCIS (Netherlands)

    Engel, K.J.; Geller, D.; Koehler, T.; Martens, G.; Schusser, S.; Vogtmeier, G.; Roessl, E.

    2011-01-01

    A quantitative theory for the contrast-to-noise ratio (CNR) in differential phase contrast imaging (DPCI) is proposed and compared to that of images derived from classical absorption contrast imaging (ACI). Most prominently, the CNR for DPCI contains the reciprocal of thespatial wavelength to be ima

  12. SU-E-QI-17: Dependence of 3D/4D PET Quantitative Image Features On Noise

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, J; Budzevich, M; Zhang, G; Latifi, K; Dilling, T; Balagurunathan, Y; Gu, Y; Grove, O; Feygelman, V; Gillies, R; Moros, E; Lee, H. [Moffitt Cancer Center, Tampa, FL (United States)

    2014-06-15

    Purpose: Quantitative imaging is a fast evolving discipline where a large number of features are extracted from images; i.e., radiomics. Some features have been shown to have diagnostic, prognostic and predictive value. However, they are sensitive to acquisition and processing factors; e.g., noise. In this study noise was added to positron emission tomography (PET) images to determine how features were affected by noise. Methods: Three levels of Gaussian noise were added to 8 lung cancer patients PET images acquired in 3D mode (static) and using respiratory tracking (4D); for the latter images from one of 10 phases were used. A total of 62 features: 14 shape, 19 intensity (1stO), 18 GLCM textures (2ndO; from grey level co-occurrence matrices) and 11 RLM textures (2ndO; from run-length matrices) features were extracted from segmented tumors. Dimensions of GLCM were 256×256, calculated using 3D images with a step size of 1 voxel in 13 directions. Grey levels were binned into 256 levels for RLM and features were calculated in all 13 directions. Results: Feature variation generally increased with noise. Shape features were the most stable while RLM were the most unstable. Intensity and GLCM features performed well; the latter being more robust. The most stable 1stO features were compactness, maximum and minimum length, standard deviation, root-mean-squared, I30, V10-V90, and entropy. The most stable 2ndO features were entropy, sum-average, sum-entropy, difference-average, difference-variance, difference-entropy, information-correlation-2, short-run-emphasis, long-run-emphasis, and run-percentage. In general, features computed from images from one of the phases of 4D scans were more stable than from 3D scans. Conclusion: This study shows the need to characterize image features carefully before they are used in research and medical applications. It also shows that the performance of features, and thereby feature selection, may be assessed in part by noise analysis.

  13. Studies on assessment of traffic noise level in Aurangabad city, India

    Directory of Open Access Journals (Sweden)

    B J Bhosale

    2010-01-01

    Full Text Available With the rapid rate of urbanization of Aurangabad city due to the expanding industrialization, the problem of noise pollution has become a concern for urban dwellers and government authority too. Noise pollution due to vehicular traffic is one of the growing environmental problems of urban centers. The study deals with the assessment of traffic noise levels in Aurangabad city. With respect to the total number of vehicles passing the road in unit time, which was surveyed by direct count method, six different sites from Aurangabad city, viz., Nagar Naka, Kranti Chowk, CIDCO bus stand, Railway station area, Dhoot Hospital and Baba petrol pump were selected to study the vehicular noise level. Noise measurements were carried out at these six locations on both working day and holiday during the peak traffic hours, i.e. 8:00 a.m. - 11:a.m., 1:00 p.m. - 4:00 p.m. and 5:00 p.m. - 8:00 p.m., in the morning, afternoon and evening sessions, respectively, after 5 minutes time interval. The noise level was monitored using noise level meter. The results obtained from this investigation showed that the Nagar Naka, Kranti chowk and CIDCO bus stand area have dense traffic zones when compared with the Railway station area, Dhoot Hospital and Baba petrol pump. The minimum and the maximum noise levels are 74 and 86 dB, respectively, on working day and 70 and 81 dB, respectively, on holiday. The measured noise level values exceed the prescribed noise level.

  14. A real-time noise filtering strategy for photon counting 3D imaging lidar.

    Science.gov (United States)

    Zhang, Zijing; Zhao, Yuan; Zhang, Yong; Wu, Long; Su, Jianzhong

    2013-04-22

    For a direct-detection 3D imaging lidar, the use of Geiger mode avalanche photodiode (Gm-APD) could greatly enhance the detection sensitivity of the lidar system since each range measurement requires a single detected photon. Furthermore, Gm-APD offers significant advantages in reducing the size, mass, power and complexity of the system. However the inevitable noise, including the background noise, the dark count noise and so on, remains a significant challenge to obtain a clear 3D image of the target of interest. This paper presents a smart strategy, which can filter out false alarms in the stage of acquisition of raw time of flight (TOF) data and obtain a clear 3D image in real time. As a result, a clear 3D image is taken from the experimental system despite the background noise of the sunny day.

  15. STUDY ON NOISE LEVEL GENERATED BY HUMAN ACTIVITIES IN SIBIU CITY, ROMANIA

    Directory of Open Access Journals (Sweden)

    Cristina STANCA-MOISE

    2014-10-01

    Full Text Available In this paper I have proposed an analysis and monitoring of the noise sources in the open spaces of air traffic, rail and car in Sibiu. From centralizing data obtained from the analysis of the measurements performed with equipment noise levels, we concluded that the noise and vibration produced by means of Transportation (air, road, rail can affect human health if they exceed limits. Noise is present and part of our lives and always a source of pollution as any of modern man is not conscious.

  16. Does the acceptable noise level (ANL) predict hearing-aid use?

    DEFF Research Database (Denmark)

    Olsen, Steen Østergaard; Brännström, K Jonas

    2014-01-01

    OBJECTIVE: It has been suggested that individuals have an inherent acceptance of noise in the presence of speech, and that different acceptance of noise results in different hearing-aid (HA) use. The acceptable noise level (ANL) has been proposed for measurement of this property. It has been...... reviewed journals as well as a number of papers from trade journals, posters and oral presentations from audiology conventions. CONCLUSIONS: An inherent acceptance of noise in the presence of speech may exist, but no method for precise measurement of ANL is available. The ANL model for prediction of HA use...

  17. Reduction of CMOS Image Sensor Read Noise to Enable Photon Counting.

    Science.gov (United States)

    Guidash, Michael; Ma, Jiaju; Vogelsang, Thomas; Endsley, Jay

    2016-04-09

    Recent activity in photon counting CMOS image sensors (CIS) has been directed to reduction of read noise. Many approaches and methods have been reported. This work is focused on providing sub 1 e(-) read noise by design and operation of the binary and small signal readout of photon counting CIS. Compensation of transfer gate feed-through was used to provide substantially reduced CDS time and source follower (SF) bandwidth. SF read noise was reduced by a factor of 3 with this method. This method can be applied broadly to CIS devices to reduce the read noise for small signals to enable use as a photon counting sensor.

  18. Two-level system noise reduction for Microwave Kinetic Inductance Detectors

    CERN Document Server

    Noroozian, Omid; Zmuidzinas, Jonas; LeDuc, Henry G; Mazin, Benjamin A

    2009-01-01

    Noise performance is one of the most crucial aspects of any detector. Superconducting Microwave Kinetic Inductance Detectors (MKIDs) have an "excess" frequency noise that shows up as a small time dependent jitter of the resonance frequency characterized by the frequency noise power spectrum measured in units of Hz^2/Hz. Recent studies have shown that this noise almost certainly originates from a surface layer of two-level system (TLS) defects on the metallization or substrate. Fluctuation of these TLSs introduces noise in the resonator due to coupling of the TLS electric dipole moments to the resonator's electric field. Motivated by a semi-empirical quantitative theory of this noise mechanism, we have designed and tested new resonator geometries in which the high-field "capacitive" portion of the CPW resonator is replaced by an interdigitated capacitor (IDC) structure with 10 - 20 micron electrode spacing, as compared to the 2 micron spacing used for our more conventional CPW resonators. Measurements show tha...

  19. Study of traffic noise levels at various heights of a 39-story building

    Science.gov (United States)

    Norman L. Meyerson

    1977-01-01

    Comparative measurements of exterior noise levels made at floors 3, 14, 26, and 37 of a high-rise apartment tower, when presented as a statistical distribution of percent exceedance vs. decibels, show the nature of the influence of local traffic at the low floors compared to the influence of an area source at the high floors. The open window penalty to interior noise...

  20. Transitions between levels of a quantum bouncer induced by a noise-like perturbation

    Science.gov (United States)

    Codau, C.; Nesvizhevsky, V. V.; Fertl, M.; Pignol, G.; Protasov, K. V.

    2012-06-01

    The probability of transition between levels of a quantum bouncer, induced by a noise-like perturbation, is calculated. The results are applied to two sources of noise (vibrations and mirror surface waviness) which might play an important role in future GRANIT experiment, aiming at precision studies of/with the neutron quantum bouncer.

  1. Transitions between levels of a quantum bouncer induced by a noise-like perturbation

    CERN Document Server

    Codau, C; Fertl, M; Pignol, G; Protasov, K V

    2012-01-01

    The probability of transition between levels of a quantum bouncer, induced by a noise-like perturbation, is calculated. The results are applied to two sources of noise (vibrations and mirror surface waviness) which might play an important role in future GRANIT experiment, aiming at precision studies of/with the neutron quantum bouncer.

  2. Transitions between levels of a quantum bouncer induced by a noise-like perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Codau, C.; Nesvizhevsky, V.V. [ILL, 6 rue Jules Horowitz, Grenoble F-38042 (France); Fertl, M. [ILL, 6 rue Jules Horowitz, Grenoble F-38042 (France); Paul Scherrer Institut, 5232 Villigen (Switzerland); Pignol, G., E-mail: guillaume.pignol@lpsc.in2p3.fr [Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph Fourier-CNRS/IN2P3-INPG, Grenoble (France); Protasov, K.V. [Laboratoire de Physique Subatomique et de Cosmologie, Universite Joseph Fourier-CNRS/IN2P3-INPG, Grenoble (France)

    2012-06-11

    The probability of transition between levels of a quantum bouncer, induced by a noise-like perturbation, is calculated. The results are applied to two sources of noise (vibrations and mirror surface waviness) which might play an important role in future GRANIT experiment, aiming at precision studies of/with the neutron quantum bouncer.

  3. Removing Noises Induced by Gamma Radiation in Cerenkov Luminescence Imaging Using a Temporal Median Filter

    Science.gov (United States)

    Li, Yang; Zhan, Yonghua; Kang, Fei; Wang, Jing

    2016-01-01

    Cerenkov luminescence imaging (CLI) can provide information of medical radionuclides used in nuclear imaging based on Cerenkov radiation, which makes it possible for optical means to image clinical radionuclide labeled probes. However, the exceptionally weak Cerenkov luminescence (CL) from Cerenkov radiation is susceptible to lots of impulse noises introduced by high energy gamma rays generating from the decays of radionuclides. In this work, a temporal median filter is proposed to remove this kind of impulse noises. Unlike traditional CLI collecting a single CL image with long exposure time and smoothing it using median filter, the proposed method captures a temporal sequence of CL images with shorter exposure time and employs a temporal median filter to smooth a temporal sequence of pixels. Results of in vivo experiments demonstrated that the proposed temporal median method can effectively remove random pulse noises induced by gamma radiation and achieve a robust CLI image. PMID:27648450

  4. Removing Noises Induced by Gamma Radiation in Cerenkov Luminescence Imaging Using a Temporal Median Filter

    Directory of Open Access Journals (Sweden)

    Xu Cao

    2016-01-01

    Full Text Available Cerenkov luminescence imaging (CLI can provide information of medical radionuclides used in nuclear imaging based on Cerenkov radiation, which makes it possible for optical means to image clinical radionuclide labeled probes. However, the exceptionally weak Cerenkov luminescence (CL from Cerenkov radiation is susceptible to lots of impulse noises introduced by high energy gamma rays generating from the decays of radionuclides. In this work, a temporal median filter is proposed to remove this kind of impulse noises. Unlike traditional CLI collecting a single CL image with long exposure time and smoothing it using median filter, the proposed method captures a temporal sequence of CL images with shorter exposure time and employs a temporal median filter to smooth a temporal sequence of pixels. Results of in vivo experiments demonstrated that the proposed temporal median method can effectively remove random pulse noises induced by gamma radiation and achieve a robust CLI image.

  5. Effects of photon noise on speckle image reconstruction with the Knox-Thompson algorithm. [in astronomy

    Science.gov (United States)

    Nisenson, P.; Papaliolios, C.

    1983-01-01

    An analysis of the effects of photon noise on astronomical speckle image reconstruction using the Knox-Thompson algorithm is presented. It is shown that the quantities resulting from the speckle average arre biased, but that the biases are easily estimated and compensated. Calculations are also made of the convergence rate for the speckle average as a function of the source brightness. An illustration of the effects of photon noise on the image recovery process is included.

  6. A Fast Switching Filter for Impulsive Noise Removal from Color Images

    CERN Document Server

    Celebi, M Emre; Uddin, Bakhtiyar; Aslandogan, Y Alp; 10.2352/J.ImagingSci.Technol.(2007)51:2(155)

    2010-01-01

    In this paper, we present a fast switching filter for impulsive noise removal from color images. The filter exploits the HSL color space, and is based on the peer group concept, which allows for the fast detection of noise in a neighborhood without resorting to pairwise distance computations between each pixel. Experiments on large set of diverse images demonstrate that the proposed approach is not only extremely fast, but also gives excellent results in comparison to various state-of-the-art filters.

  7. Hybrid Denoising Method for Removal of Mixed Noise in Medical Images

    Directory of Open Access Journals (Sweden)

    J UMAMAHESWARI, Dr.G.RADHAMANI

    2012-05-01

    Full Text Available Nowadays, Digital image acquisition and processing techniques plays a very important role in current day medical diagnosis. During the acquisition process, there could be distortions in the images, which will negatively affect the diagnosis images. In this paper a new technique based on the hybridization of wavelet filter and center weighted median filters is proposed for denoising multiple noise (Gaussian and Impulse images. The model is experimented on standard Digital Imaging and Communications in Medicine (DICOM images and the performances are evaluated in terms of peak signal to noise ratio (PSNR, Mean Absolute Error (MAE, Universal Image Quality Index (UQI and Evaluation Time (ET. Results prove that utilization of center weighted median filters in combination with wavelet thresholding filters on DICOM images deteriorates the performance. The proposed filter gives suitable results on the basis of PSNR, MSE, UQI and ET. In addition, the proposed filter gives nearly uniform and consistent results on all the test images.

  8. Preferred listening levels of mobile phone programs when considering subway interior noise

    Directory of Open Access Journals (Sweden)

    Jyaehyoung Yu

    2016-01-01

    Full Text Available Today, people listen to music loud using personal listening devices. Although a majority of studies have reported that the high volume played on these listening devices produces a latent risk of hearing problems, there is a lack of studies on "double noise exposures" such as environmental noise plus recreational noise. The present study measures the preferred listening levels of a mobile phone program with subway interior noise for 74 normal-hearing participants in five age groups (ranging from 20s to 60s. The speakers presented the subway interior noise at 73.45 dB, while each subject listened to three application programs [Digital Multimedia Broadcasting (DMB, music, game] for 30 min using a tablet personal computer with an earphone. The participants′ earphone volume levels were analyzed using a sound level meter and a 2cc coupler. Overall, the results showed that those in their 20s listened to the three programs significantly louder with DMB set at significantly higher volume levels than for the other programs. Higher volume levels were needed for middle frequency compared to the lower and higher frequencies. We concluded that any potential risk of noise-induced hearing loss for mobile phone users should be communicated when users listen regularly, although the volume level was not high enough that the users felt uncomfortable. When considering individual listening habits on mobile phones, further study to predict total accumulated environmental noise is still needed.

  9. Modeling signal-to-noise ratio of otoacoustic emissions in workers exposed to different industrial noise levels

    Directory of Open Access Journals (Sweden)

    Parvin Nassiri

    2016-01-01

    Full Text Available Introduction: Noise is considered as the most common cause of harmful physical effects in the workplace. A sound that is generated from within the inner ear is known as an otoacoustic emission (OAE. Distortion-product otoacoustic emissions (DPOAEs assess evoked emission and hearing capacity. The aim of this study was to assess the signal-to-noise ratio in different frequencies and at different times of the shift work in workers exposed to various levels of noise. It was also aimed to provide a statistical model for signal-to-noise ratio (SNR of OAEs in different frequencies based on the two variables of sound pressure level (SPL and exposure time. Materials and Methods: This case–control study was conducted on 45 workers during autumn 2014. The workers were divided into three groups based on the level of noise exposure. The SNR was measured in frequencies of 1000, 2000, 3000, 4000, and 6000 Hz in both ears, and in three different time intervals during the shift work. According to the inclusion criterion, SNR of 6 dB or greater was included in the study. The analysis was performed using repeated measurements of analysis of variance, spearman correlation coefficient, and paired samples t-test. Results: The results showed that there was no statistically significant difference between the three exposed groups in terms of the mean values of SNR (P > 0.05. Only in signal pressure levels of 88 dBA with an interval time of 10:30–11:00 AM, there was a statistically significant difference between the right and left ears with the mean SNR values of 3000 frequency (P = 0.038. The SPL had a significant effect on the SNR in both the right and left ears (P = 0.023, P = 0.041. The effect of the duration of measurement on the SNR was statistically significant in both the right and left ears (P = 0.027, P < 0.001. Conclusion: The findings of this study demonstrated that after noise exposure during the shift, SNR of OAEs reduced from the

  10. [A new wavelet image de-noising method based on new threshold function].

    Science.gov (United States)

    Xing, Guoquan; Ye, Huashan; Zhang, Yuxia; Yan, Yu

    2013-08-01

    In order to improve image de-noising effect,a new threshold function de-noising method based on wavelet analysis was proposed, which can overcome the continuity problem of the hard-threshold function, and eliminate the constant deviation of the soft one by constructing a new threshold function. Experimental results showed that the new threshold function could obtain higher peak signal to noise ratio (PSNR) in image de-nosing. A better denoising effect could be obtained compared with the hard-threshold function, the soft one, the semi-soft one, the cubic polynomial interpolation semi-soft one, and the asymptotic semi-soft one.

  11. Method of recognizing the high-speed railway noise barriers based on the distance image

    Science.gov (United States)

    Ma, Le; Shao, Shuangyun; Feng, Qibo; Liu, Bingqian; Kim, Chol Ryong

    2016-10-01

    The damage or lack of the noise barriers is one of the important hidden troubles endangering the safety of high-speed railway. In order to obtain the vibration information of the noise barriers, the online detection systems based on laser vision were proposed. The systems capture images of the laser stripe on the noise barriers and export data files containing distance information between the detection systems on the train and the noise barriers. The vibration status or damage of the noise barriers can be estimated depending on the distance information. In this paper, we focused on the method of separating the area of noise barrier from the background automatically. The test results showed that the proposed method is in good efficiency and accuracy.

  12. The Relationship between Vessel Traffic and Noise Levels Received by Killer Whales (Orcinus orca.

    Directory of Open Access Journals (Sweden)

    Juliana Houghton

    Full Text Available Whale watching has become increasingly popular as an ecotourism activity around the globe and is beneficial for environmental education and local economies. Southern Resident killer whales (Orcinus orca comprise an endangered population that is frequently observed by a large whale watching fleet in the inland waters of Washington state and British Columbia. One of the factors identified as a risk to recovery for the population is the effect of vessels and associated noise. An examination of the effects of vessels and associated noise on whale behavior utilized novel equipment to address limitations of previous studies. Digital acoustic recording tags (DTAGs measured the noise levels the tagged whales received while laser positioning systems allowed collection of geo-referenced data for tagged whales and all vessels within 1000 m of the tagged whale. The objective of the current study was to compare vessel data and DTAG recordings to relate vessel traffic to the ambient noise received by tagged whales. Two analyses were conducted, one including all recording intervals, and one that excluded intervals when only the research vessel was present. For all data, significant predictors of noise levels were length (inverse relationship, number of propellers, and vessel speed, but only 15% of the variation in noise was explained by this model. When research-vessel-only intervals were excluded, vessel speed was the only significant predictor of noise levels, and explained 42% of the variation. Simple linear regressions (ignoring covariates found that average vessel speed and number of propellers were the only significant correlates with noise levels. We conclude that vessel speed is the most important predictor of noise levels received by whales in this study. Thus, measures that reduce vessel speed in the vicinity of killer whales would reduce noise exposure in this population.

  13. The relationship between vessel traffic and noise levels received by killer whales (Orcinus orca)

    Science.gov (United States)

    Houghton, Juliana; Holt, Marla M.; Giles, Deborah A.; Hanson, M. Bradley; Emmons, Candice K.; Hogan, Jeffrey T.; Branch, Trevor A.; VanBlaricom, Glenn R.

    2015-01-01

    Whale watching has become increasingly popular as an ecotourism activity around the globe and is beneficial for environmental education and local economies. Southern Resident killer whales (Orcinus orca) comprise an endangered population that is frequently observed by a large whale watching fleet in the inland waters of Washington state and British Columbia. One of the factors identified as a risk to recovery for the population is the effect of vessels and associated noise. An examination of the effects of vessels and associated noise on whale behavior utilized novel equipment to address limitations of previous studies. Digital acoustic recording tags (DTAGs) measured the noise levels the tagged whales received while laser positioning systems allowed collection of geo-referenced data for tagged whales and all vessels within 1000 m of the tagged whale. The objective of the current study was to compare vessel data and DTAG recordings to relate vessel traffic to the ambient noise received by tagged whales. Two analyses were conducted, one including all recording intervals, and one that excluded intervals when only the research vessel was present. For all data, significant predictors of noise levels were length (inverse relationship), number of propellers, and vessel speed, but only 15% of the variation in noise was explained by this model. When research-vessel-only intervals were excluded, vessel speed was the only significant predictor of noise levels, and explained 42% of the variation. Simple linear regressions (ignoring covariates) found that average vessel speed and number of propellers were the only significant correlates with noise levels. We conclude that vessel speed is the most important predictor of noise levels received by whales in this study. Thus, measures that reduce vessel speed in the vicinity of killer whales would reduce noise exposure in this population.

  14. Prediction and comparison of noise levels from ground and elevated flare systems

    Energy Technology Data Exchange (ETDEWEB)

    Obasi, E. [Stantec Consulting Ltd., Surrey, BC (Canada)

    2009-07-01

    Flaring is a process to dispose of hydrocarbons during clean-up, emergency shut downs or dispose a small volume waste streams of mixed gasses that cannot easily or safely be separated. This presentation discussed flaring as a noise issue. It focused on flaring noise characterization; flare noise modeling; flare sound power levels; and flare sound pressure level comparison at a distance of 1.5 km. The presentation included a photograph of flaring at a gas plant in Nigeria. The presentation listed some of the potential health effects associated with long term exposure to excessive noise, such as hearing loss; headaches; stress; fatigue; sleep disturbance; and high blood pressure. Companies flare gas to dispose waste gases in a safe and reliable manner through combustion and to depressurize gas lines during maintenance and emergencies. This presentation also discussed ground and elevated flares; components of flare noise characterization; and key factors affecting flare noise. A model to predict flaring noise was also presented. It demonstrated that at the same gas mass flow rate, the noise level from elevated flare stacks are significantly higher than ground flares. tabs., figs.

  15. More noise, please: How cultural overprinting in the urban environment can be exploited for improved subsurface imaging (Invited)

    Science.gov (United States)

    Weiss, C. J.

    2009-12-01

    A long standing issue for geophysical imaging methods revolves around the proper treatment of "noise": Defining what noise is; separating "noise" for "signal"; filtering and suppressing noise; and recently, challenging the prevailing view that noise is a nuisance to see if, instead, it may contribute favorably toward improving subsurface imaging fidelity. This last point is particularly relevant to geophysical imaging in the urban environment where noise sources are abundant, complex, and logistical constraints on geophysical field procedures prohibit a crude "turning up the volume" approach to simply drown out the noise with powerful sources of electromagnetic and seismic energy. In this contribution I explore the concept passive geophysical imaging which uses uncorrelated ambient noise as the source of geophysical imaging energy to be used in the urban environment. Examples will be presented from seismic and ground penetrating radar methods, in addition to new theoretical results bearing on the feasibility of low-frequency electromagnetic induction techniques.

  16. Rician noise reduction in magnetic resonance images using adaptive non-local mean and guided image filtering

    Science.gov (United States)

    Mahmood, Muhammad Tariq; Chu, Yeon-Ho; Choi, Young-Kyu

    2016-06-01

    This paper proposes a Rician noise reduction method for magnetic resonance (MR) images. The proposed method is based on adaptive non-local mean and guided image filtering techniques. In the first phase, a guidance image is obtained from the noisy image through an adaptive non-local mean filter. Sobel operators are applied to compute the strength of edges which is further used to control the spread of the kernel in non-local mean filtering. In the second phase, the noisy and the guidance images are provided to the guided image filter as input to restore the noise-free image. The improved performance of the proposed method is investigated using the simulated and real data sets of MR images. Its performance is also compared with the previously proposed state-of-the art methods. Comparative analysis demonstrates the superiority of the proposed scheme over the existing approaches.

  17. The use of wavelet filters for reducing noise in posterior fossa Computed Tomography images

    Energy Technology Data Exchange (ETDEWEB)

    Pita-Machado, Reinado [Centro de Ingeniería Clínica. Guacalote y Circunvalación, Santa Clara 50200 (Cuba); Perez-Diaz, Marlen, E-mail: mperez@uclv.edu.cu; Lorenzo-Ginori, Juan V., E-mail: mperez@uclv.edu.cu; Bravo-Pino, Rolando, E-mail: mperez@uclv.edu.cu [Centro de Estudios de Electrónica y Tecnologías de la Información (CEETI), Universidad Central Marta Abreu de las Villas, Carretera a Camajuaní, km. 5 1/2 Santa Clara 54830 (Cuba)

    2014-11-07

    Wavelet transform based de-noising like wavelet shrinkage, gives the good results in CT. This procedure affects very little the spatial resolution. Some applications are reconstruction methods, while others are a posteriori de-noising methods. De-noising after reconstruction is very difficult because the noise is non-stationary and has unknown distribution. Therefore, methods which work on the sinogram-space don’t have this problem, because they always work over a known noise distribution at this point. On the other hand, the posterior fossa in a head CT is a very complex region for physicians, because it is commonly affected by artifacts and noise which are not eliminated during the reconstruction procedure. This can leads to some false positive evaluations. The purpose of our present work is to compare different wavelet shrinkage de-noising filters to reduce noise, particularly in images of the posterior fossa within CT scans in the sinogram-space. This work describes an experimental search for the best wavelets, to reduce Poisson noise in Computed Tomography (CT) scans. Results showed that de-noising with wavelet filters improved the quality of posterior fossa region in terms of an increased CNR, without noticeable structural distortions.

  18. Relationship between container ship underwater noise levels and ship design, operational and oceanographic conditions

    Science.gov (United States)

    McKenna, Megan F.; Wiggins, Sean M.; Hildebrand, John A.

    2013-05-01

    Low-frequency ocean ambient noise is dominated by noise from commercial ships, yet understanding how individual ships contribute deserves further investigation. This study develops and evaluates statistical models of container ship noise in relation to design characteristics, operational conditions, and oceanographic settings. Five-hundred ship passages and nineteen covariates were used to build generalized additive models. Opportunistic acoustic measurements of ships transiting offshore California were collected using seafloor acoustic recorders. A 5-10 dB range in broadband source level was found for ships depending on the transit conditions. For a ship recorded multiple times traveling at different speeds, cumulative noise was lowest at 8 knots, 65% reduction in operational speed. Models with highest predictive power, in order of selection, included ship speed, size, and time of year. Uncertainty in source depth and propagation affected model fit. These results provide insight on the conditions that produce higher levels of underwater noise from container ships.

  19. Influence of music and music preference on acceptable noise levels in listeners with normal hearing.

    Science.gov (United States)

    Gordon-Hickey, Susan; Moore, Robert E

    2007-05-01

    Acceptable noise level (ANL) is defined as the maximum level of background noise that an individual is willing to accept while listening to speech. The type of background noise does not affect ANL results with the possible exception of music. The purpose of this study was to determine if ANL for music was different from ANL for twelve-talker babble and investigate if there was a correlation between ANL for music samples and preference for those music samples. Results demonstrated that ANL for music tended to be better than ANL for twelve-talker babble, indicating listeners were more willing to accept music as a background noise than speech babble. The results further demonstrated that ANL for the music samples were not correlated with preference for the music samples, indicating that ANL for music was not related to music preference. Therefore, music appeared to be processed differently as a background noise than twelve-talker babble.

  20. Noise levels at critical points in the municipality of Guadalajara, Jalisco, Mexico

    Science.gov (United States)

    Figueroa, Arturo; Garcia, Jesus; Macias, Jorge; Orozco, Martha; Garcia, Javier; Delgadillo, Alan

    2002-11-01

    Studies of acoustic conditions are planning tools on which we can diagnose the problem of noise pollution in the cities. The first study on noise pollution made in the city was made by the University of Guadalajara in 1995 and updated in 1998 covering with measuring points the city center. This paper discusses the problem of noise pollution by motor vehicles at critical points and covers a total of 105 points. The study also analyzes the problem of noise pollution base on the community annoyance from which a regulation policy should derive. Results of the study show that the most critical points are located within zone 1 (center) where Leq levels within the range of 70-85 dB were found. Such levels exceed by far the international standard of 65 dB as recommended for ambient noise by the World Health Organization.

  1. Relationship between lighting and noise levels and productivity of the occupants in automotive assembly industry.

    Science.gov (United States)

    Akbari, Jafar; Dehghan, Habibollah; Azmoon, Hiva; Forouharmajd, Farhad

    2013-01-01

    Work environment affects human productivity and his performance. The aims of this study were to investigate the effects of lighting and noise levels on human productivity in the automotive assembly industry. Subjects were 181 workers from different parts of an automobile assembly industry. Illuminance (Lx) at the height of 30 inches from the surface of work station and noise (dBA) were locally measured. Also human productivity by the Goldsmith and Hersey scale (1980) was measured. Data were analyzed by using SPSS v20 Pearson correlation coefficient. The results showed that the relationship between noise level and human productivity is negative and significant (P 0.05). Based on the results, in assembly tasks, noise has a negative impact on human productivity, and lighting does not affect this. So, in order to increase employee productivity, noise control and reduction to less than the standard values (less than 85 dB) is necessary.

  2. Security against jamming and noise exclusion in imaging

    Science.gov (United States)

    Roga, Wojciech; Jeffers, John

    2016-09-01

    We describe a protocol by which an imaging system could be protected against jamming by a malevolent party. Our protocol not only allows recognition of the jamming, but also allows for the recovery of the true image from the jammed one. We apply the method to jamming of quantum ghost imaging, for which the jamming detection probability is increased when the imaging light is entangled. The method can also be used to provide image recovery in general noisy environments.

  3. Effect of background noise on neuronal coding of interaural level difference cues in rat inferior colliculus

    Science.gov (United States)

    Mokri, Yasamin; Worland, Kate; Ford, Mark; Rajan, Ramesh

    2015-01-01

    Humans can accurately localize sounds even in unfavourable signal-to-noise conditions. To investigate the neural mechanisms underlying this, we studied the effect of background wide-band noise on neural sensitivity to variations in interaural level difference (ILD), the predominant cue for sound localization in azimuth for high-frequency sounds, at the characteristic frequency of cells in rat inferior colliculus (IC). Binaural noise at high levels generally resulted in suppression of responses (55.8%), but at lower levels resulted in enhancement (34.8%) as well as suppression (30.3%). When recording conditions permitted, we then examined if any binaural noise effects were related to selective noise effects at each of the two ears, which we interpreted in light of well-known differences in input type (excitation and inhibition) from each ear shaping particular forms of ILD sensitivity in the IC. At high signal-to-noise ratios (SNR), in most ILD functions (41%), the effect of background noise appeared to be due to effects on inputs from both ears, while for a large percentage (35.8%) appeared to be accounted for by effects on excitatory input. However, as SNR decreased, change in excitation became the dominant contributor to the change due to binaural background noise (63.6%). These novel findings shed light on the IC neural mechanisms for sound localization in the presence of continuous background noise. They also suggest that some effects of background noise on encoding of sound location reported to be emergent in upstream auditory areas can also be observed at the level of the midbrain. PMID:25865218

  4. Effect of background noise on neuronal coding of interaural level difference cues in rat inferior colliculus.

    Science.gov (United States)

    Mokri, Yasamin; Worland, Kate; Ford, Mark; Rajan, Ramesh

    2015-07-01

    Humans can accurately localize sounds even in unfavourable signal-to-noise conditions. To investigate the neural mechanisms underlying this, we studied the effect of background wide-band noise on neural sensitivity to variations in interaural level difference (ILD), the predominant cue for sound localization in azimuth for high-frequency sounds, at the characteristic frequency of cells in rat inferior colliculus (IC). Binaural noise at high levels generally resulted in suppression of responses (55.8%), but at lower levels resulted in enhancement (34.8%) as well as suppression (30.3%). When recording conditions permitted, we then examined if any binaural noise effects were related to selective noise effects at each of the two ears, which we interpreted in light of well-known differences in input type (excitation and inhibition) from each ear shaping particular forms of ILD sensitivity in the IC. At high signal-to-noise ratios (SNR), in most ILD functions (41%), the effect of background noise appeared to be due to effects on inputs from both ears, while for a large percentage (35.8%) appeared to be accounted for by effects on excitatory input. However, as SNR decreased, change in excitation became the dominant contributor to the change due to binaural background noise (63.6%). These novel findings shed light on the IC neural mechanisms for sound localization in the presence of continuous background noise. They also suggest that some effects of background noise on encoding of sound location reported to be emergent in upstream auditory areas can also be observed at the level of the midbrain.

  5. A simple experimental procedure to quantify image noise in the context of strain measurements at the microscale using DIC and SEM images

    Directory of Open Access Journals (Sweden)

    Bornert M.

    2010-06-01

    Full Text Available Image noise is an important factor that influences the accuracy of strain field measurements by means of digital image correlation and scanning electron microscope (SEM imaging. We propose a new model to quantify the SEM image noise, which extends the classical photon noise model by taking into account the brightness setup in SEM imaging. Furthermore, we apply this model to investigate the impact of different SEM setting parameters on image noise, such as detector, dwell time, spot size, and pressure in the SEM chamber in the context of low vacuum imaging.

  6. Filtering images contaminated with pep and salt type noise with pulse-coupled neural networks

    Institute of Scientific and Technical Information of China (English)

    ZHANG Junying; LU Zhijun; SHI Lin; DONG Jiyang; SHI Meihong

    2005-01-01

    Pulse coupled neural network (PCNN) has a specific feature that the fire of one neuron can capture its adjacent neurons to fire due to their spatial proximity and intensity similarity. In this paper, it is indicated that this feature itself is a very good mechanism for image filtering when the image is damaged with pep and salt (PAS) type noise. An adaptive filtering method, in which the noisy pixels are first located and then filtered based on the output of the PCNN, is presented. The threshold function of a neuron in the PCNN is designed when it is used for filtering random PAS and extreme PAS noise contaminated image respectively. The filtered image has no distortion for noisy pixels and only less mistiness for non-noisy pixels, compared with the conventional window-based filtering method. Excellent experimental results show great effectiveness and efficiency of the proposed method, especially for heavy-noise contaminated images.

  7. On the efficiency of techniques for the reduction of impulsive noise in astronomical images

    CERN Document Server

    Popowicz, A; Blachowicz, T; Orlov, V; Smolka, B

    2016-01-01

    The impulsive noise in astronomical images originates from various sources. It develops as a result of thermal generation in pixels, collision of cosmic rays with image sensor or may be induced by high readout voltage in Electron Multiplying CCD (EMCCD). It is usually efficiently removed by employing the dark frames or by averaging several exposures. Unfortunately, there are some circumstances, when either the observed objects or positions of impulsive pixels evolve and therefore each obtained image has to be filtered independently. In this article we present an overview of impulsive noise filtering methods and compare their efficiency for the purpose of astronomical image enhancement. The employed set of noise templates consists of dark frames obtained from CCD and EMCCD cameras working on ground and in space. The experiments conducted on synthetic and real images, allowed for drawing numerous conclusions about the usefulness of several filtering methods for various: (1) widths of stellar profiles, (2) signa...

  8. Direct Estimate of Cirrus Noise in Herschel Hi-GAL Images

    CERN Document Server

    Martin, P G; Roy, A; Bernard, J -P; Molinari, S; Billot, N; Brunt, C; Calzoletti, L; DiGiorgio, A M; Elia, D; Faustini, F; Joncas, G; Mottram, J C; Natoli, P; Noriega-Crespo, A; Paladini, R; Robitaille, J F; Strafella, F; Traficante, A; Veneziani, M

    2010-01-01

    In Herschel images of the Galactic plane and many star forming regions, a major factor limiting our ability to extract faint compact sources is cirrus confusion noise, operationally defined as the "statistical error to be expected in photometric measurements due to confusion in a background of fluctuating surface brightness". The histogram of the flux densities of extracted sources shows a distinctive faint-end cutoff below which the catalog suffers from incompleteness and the flux densities become unreliable. This empirical cutoff should be closely related to the estimated cirrus noise and we show that this is the case. We compute the cirrus noise directly, both on Herschel images from which the bright sources have been removed and on simulated images of cirrus with statistically similar fluctuations. We connect these direct estimates with those from power spectrum analysis, which has been used extensively to predict the cirrus noise and provides insight into how it depends on various statistical properties ...

  9. Image Deconvolution Under Poisson Noise Using Sparse Representations and Proximal Thresholding Iteration

    CERN Document Server

    Dupé, François-Xavier; Starck, Jean Luc

    2008-01-01

    We propose an image deconvolution algorithm when the data is contaminated by Poisson noise. The image to restore is assumed to be sparsely represented in a dictionary of waveforms such as the wavelet or curvelet transform. Our key innovations are: First, we handle the Poisson noise properly by using the Anscombe variance stabilizing transform leading to a non-linear degradation equation with additive Gaussian noise. Second, the deconvolution problem is formulated as the minimization of a convex functional with a data-fidelity term reflecting the noise properties, and a non-smooth sparsity-promoting penalties over the image representation coefficients (e.g. l1-norm). Third, a fast iterative backward-forward splitting algorithm is proposed to solve the minimization problem. We derive existence and uniqueness conditions of the solution, and establish convergence of the iterative algorithm. Experimental results are carried out to show the striking benefits gained from taking into account the Poisson statistics of...

  10. Sleep Disturbance from Road Traffic, Railways, Airplanes and from Total Environmental Noise Levels in Montreal

    Directory of Open Access Journals (Sweden)

    Stéphane Perron

    2016-08-01

    Full Text Available The objective of our study was to measure the impact of transportation-related noise and total environmental noise on sleep disturbance for the residents of Montreal, Canada. A telephone-based survey on noise-related sleep disturbance among 4336 persons aged 18 years and over was conducted. LNight for each study participant was estimated using a land use regression (LUR model. Distance of the respondent’s residence to the nearest transportation noise source was also used as an indicator of noise exposure. The proportion of the population whose sleep was disturbed by outdoor environmental noise in the past 4 weeks was 12.4%. The proportion of those affected by road traffic, airplane and railway noise was 4.2%, 1.5% and 1.1%, respectively. We observed an increased prevalence in sleep disturbance for those exposed to both rail and road noise when compared for those exposed to road only. We did not observe an increased prevalence in sleep disturbance for those that were both exposed to road and planes when compared to those exposed to road or planes only. We developed regression models to assess the marginal proportion of sleep disturbance as a function of estimated LNight and distance to transportation noise sources. In our models, sleep disturbance increased with proximity to transportation noise sources (railway, airplane and road traffic and with increasing LNight values. Our study provides a quantitative estimate of the association between total environmental noise levels estimated using an LUR model and sleep disturbance from transportation noise.

  11. Minimize the Percentage of Noise in Biomedical Images Using Neural Networks

    Directory of Open Access Journals (Sweden)

    Abdul Khader Jilani Saudagar

    2014-01-01

    Full Text Available The overall goal of the research is to improve the quality of biomedical image for telemedicine with minimum percentages of noise in the retrieved image and to take less computation time. The novelty of this technique lies in the implementation of spectral coding for biomedical images using neural networks in order to accomplish the above objectives. This work is in continuity of an ongoing research project aimed at developing a system for efficient image compression approach for telemedicine in Saudi Arabia. We compare the efficiency of this technique against existing image compression techniques, namely, JPEG2000, in terms of compression ratio, peak signal to noise ratio (PSNR, and computation time. To our knowledge, the research is the primary in providing a comparative study with other techniques used in the compression of biomedical images. This work explores and tests biomedical images such as X-rays, computed tomography (CT, magnetic resonance imaging (MRI, and positron emission tomography (PET.

  12. Minimize the percentage of noise in biomedical images using neural networks.

    Science.gov (United States)

    Saudagar, Abdul Khader Jilani

    2014-01-01

    The overall goal of the research is to improve the quality of biomedical image for telemedicine with minimum percentages of noise in the retrieved image and to take less computation time. The novelty of this technique lies in the implementation of spectral coding for biomedical images using neural networks in order to accomplish the above objectives. This work is in continuity of an ongoing research project aimed at developing a system for efficient image compression approach for telemedicine in Saudi Arabia. We compare the efficiency of this technique against existing image compression techniques, namely, JPEG2000, in terms of compression ratio, peak signal to noise ratio (PSNR), and computation time. To our knowledge, the research is the primary in providing a comparative study with other techniques used in the compression of biomedical images. This work explores and tests biomedical images such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET).

  13. Identification and removal of laser-induced noise in photoacoustic imaging using singular value decomposition.

    Science.gov (United States)

    Hill, Emma R; Xia, Wenfeng; Clarkson, Matthew J; Desjardins, Adrien E

    2017-01-01

    Singular value decomposition (SVD) was used to identify and remove laser-induced noise in photoacoustic images acquired with a clinical ultrasound scanner. This noise, which was prominent in the radiofrequency data acquired in parallel from multiple transducer elements, was induced by the excitation light source. It was modelled by truncating the SVD matrices so that only the first few largest singular value components were retained, and subtracted prior to image reconstruction. The dependency of the signal amplitude and the number of the largest singular value components used for noise modeling was investigated for different photoacoustic source geometries. Validation was performed with simulated data and measured noise, and with photoacoustic images acquired from the human forearm and finger in vivo using L14-5/38 and L40-8/12 linear array clinical imaging probes. The use of only one singular value component was found to be sufficient to achieve near-complete removal of laser-induced noise from reconstructed images. This method has strong potential to increase image quality for a wide range of photoacoustic imaging systems with parallel data acquisition.

  14. Noise reduction of cDNA microarray images using complex wavelets.

    Science.gov (United States)

    Howlader, Tamanna; Chaubey, Yogendra P

    2010-08-01

    Noise reduction is an essential step of cDNA microarray image analysis for obtaining better-quality gene expression measurements. Wavelet-based denoising methods have shown significant success in traditional image processing. The complex wavelet transform (CWT) is preferred to the classical discrete wavelet transform for denoising of microarray images due to its improved directional selectivity for better representation of the circular edges of spots and near shift-invariance property. Existing CWT-based denoising methods are not efficient for microarray image processing because they fail to take into account the signal as well as noise correlations that exist between red and green channel images. In this paper, two bivariate estimators are developed for the CWT-based denoising of microarray images using the standard maximum a posteriori and linear minimum mean squared error estimation criteria. The proposed denoising methods are capable of taking into account both the interchannel signal and noise correlations. Significance of the proposed denoising methods is assessed by examining the effect of noise reduction on the estimation of the log-intensity ratio. Extensive experimentations are carried out to show that the proposed methods provide better noise reduction of microarray images leading to more accurate estimation of the log-intensity ratios as compared to the other CWT-based denoising methods.

  15. Noise-Coupled Image Rejection Architecture of Complex Bandpass ΔΣAD Modulator

    Science.gov (United States)

    San, Hao; Kobayashi, Haruo

    This paper proposes a new realization technique of image rejection function by noise-coupling architecture, which is used for a complex bandpass ΔΣAD modulator. The complex bandpass ΔΣAD modulator processes just input I and Q signals, not image signals, and the AD conversion can be realized with low power dissipation. It realizes an asymmetric noise-shaped spectra, which is desirable for such low-IF receiver applications. However, the performance of the complex bandpass ΔΣAD modulator suffers from the mismatch between internal analog I and Q paths. I/Q path mismatch causes an image signal, and the quantization noise of the mirror image band aliases into the desired signal band, which degrades the SQNDR (Signal to Quantization Noise and Distortion Ratio) of the modulator. In our proposed modulator architecture, an extra notch for image rejection is realized by noise-coupled topology. We just add some passive capacitors and switches to the modulator; the additional integrator circuit composed of an operational amplifier in the conventional image rejection realization is not necessary. Therefore, the performance of the complex modulator can be effectively raised without additional power dissipation. We have performed simulation with MATLAB to confirm the validity of the proposed architecture. The simulation results show that the proposed architecture can achieve the realization of image-rejection effectively, and improve the SQNDR of the complex bandpass ΔΣAD modulator.

  16. Application of input amplitude masks in image encryption with spatially incoherent illumination for increase of decrypted images signal-to-noise ratio

    Science.gov (United States)

    Cheremkhin, Pavel A.; Evtikhiev, Nikolay N.; Krasnov, Vitaly V.; Molodtsov, Dmitriy Y.; Rodin, Vladislav G.; Shifrina, Anna V.

    2016-04-01

    The majority of existing methods of optical encryption use not only light intensity distribution, easily registered with photosensors, but also its phase distribution. This provides best encryption strength for fixed quantities of elements and phase levels in a mask. Downsides are holographic registration scheme used in order to register not only light intensity distribution but also its phase distribution and speckle noise occurring due to coherent illumination. That factors lead to very poor decryption quality when it comes from computer simulations to optical implementations. Method of optical encryption with spatially incoherent illumination does not have drawbacks inherent to coherent systems, however, as only light intensity distribution is considered, mean value of image to be encrypted is always above zero which leads to intensive zero spatial frequency peak in image spectrum. Therefore, in case of spatially incoherent illumination, image spectrum, as well as encryption key spectrum, cannot be white. If encryption is based on convolution operation, no matter coherent light used or not, Fourier spectrum amplitude distribution of encryption key should overlap Fourier spectrum amplitude distribution of image to be encrypted otherwise loss of information is unavoidable. Another factor affecting decrypted image quality is original image spectrum. Usually, most part of image energy is concentrated in area of low frequencies. Consequently, only this area in encrypted image contains information about original image, while other areas contain only noise. We propose to use additional encoding of input scene to increase size of the area containing useful information. This provides increase of signal-to-noise ratio in encrypted image and consequentially increases quality of decrypted images. Results of computer simulations of test images optical encryption with spatially incoherent illumination and additional input amplitude masks are presented.

  17. A Monte Carlo simulator for noise analysis of avalanche photodiode pixels in low-light image sensing

    Science.gov (United States)

    Resetar, Tomislav; Süss, Andreas; Vermandere, Elke; Karpiak, Bogdan; Puers, Robert; Van Hoof, Chris

    2016-03-01

    Noise performance of avalanche photodiodes in light detection is typically described by the excessive noise factor, taking into account only the increase of the variance of the output electron count distribution with respect to the input. This approach is attractive since the excessive noise factor, together with the avalanche gain, can easily be included into the signal-to-noise ratio expression of the complete detection chain. For low-light applications down to single-photon counting, that description is typically not sufficient since one is also interested in the higher moments of the output distribution. Analytical derivation of the output electron count distributions of avalanche photodiodes is typically possible only for very simple electric field profile approximations, which is often not a sufficient description of reality. This work presents a Monte Carlo simulator for numerical prediction of the output distribution that can be applied to any arbitrary electric field profile as well as any light absorption profile and therefore serve as a useful tool for device design and optimization. Comparison with the standard McIntyre theory is provided for a constant field profile showing good agreement. Furthermore, the presented method is used to predict the avalanche noise performance of the recently presented pinned avalanche photodiode pixel (PAPD) with the electric field profile extracted from a finite-element simulation. The pixel is aiming for improvements in high-speed and low-light level image detection in minimally-modified CMOS image sensor technology.

  18. Mixed Gaussian-Impulse Noise Image Restoration Via Total Variation

    Science.gov (United States)

    2012-05-01

    pp. 402–407. [12] L. Rudin , S. Osher, and E. Fatemi, “Nonlinear total vari- ation based noise removal algorithms.,” Physica D. Non- lin. Phenomena...variation regularization in positron emission tomography,” UCLA CAM Report 98-48, 1998, CAM Report 98-48, UCLA. [16] S. Osher, N. Paragios, L. Rudin , and P

  19. Airfoil Self-Noise - Investigation with Particle Image Velocimetry

    NARCIS (Netherlands)

    Pröbsting, S.

    2015-01-01

    Noise generated aerodynamically by the airflow over a lifting surface is often of concern for applications as diverse as air and ground transportation, heating, ventilation, air-conditioning systems, and wind turbines. The thesis describes the application of advanced optical flow measurements techni

  20. Low-noise heterodyne receiver for electron cyclotron emission imaging and microwave imaging reflectometry

    Science.gov (United States)

    Tobias, B.; Domier, C. W.; Luhmann, N. C.; Luo, C.; Mamidanna, M.; Phan, T.; Pham, A.-V.; Wang, Y.

    2016-11-01

    The critical component enabling electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) to resolve 2D and 3D electron temperature and density perturbations is the heterodyne imaging array that collects and downconverts radiated emission and/or reflected signals (50-150 GHz) to an intermediate frequency (IF) band (e.g. 0.1-18 GHz) that can be transmitted by a shielded coaxial cable for further filtering and detection. New circuitry has been developed for this task, integrating gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs) mounted on a liquid crystal polymer (LCP) substrate. The improved topology significantly increases electromagnetic shielding from out-of-band interference, leads to 10× improvement in the signal-to-noise ratio, and dramatic cost savings through integration. The current design, optimized for reflectometry and edge radiometry on mid-sized tokamaks, has demonstrated >20 dB conversion gain in upper V-band (60-75 GHz). Implementation of the circuit in a multi-channel electron cyclotron emission imaging (ECEI) array will improve the diagnosis of edge-localized modes and fluctuations of the high-confinement, or H-mode, pedestal.

  1. Measurement of SQUID noise levels for SuperCDMS SNOLAB detectors - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Maxwell [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-27

    SuperCDMS SNOLAB is a second generation direct dark matter search. In the SuperCDMS SNOLAB experiment, detectors are able to pick up from signals from dark matter nuclear recoil interactions which occur inside the bulk of the detectors. These interactions produce both phonon and charge signals. HEMTs read out charge signals whereas TES are used to detect phonon signals which are then read out by SQUID amplifiers. SQUID amplifiers must add negligible noise to the TES intrinsic noise which has been previously measured and is approximately 50pA/√Hz down to 100Hz for ease of signal distinguishability in dark matter nuclear interactions. The intrinsic noise level of the SQUID was tested in the SLAC 300mK fridge and determined to provide adequately low levels of noise with a floor of approximately 3pA/√Hz. Furthermore, a 10x amplifier was tested for addition of extraneous noise. This noise was investigated with and without this amplifier, and it was found that it did not add a significant amount of noise to the intrinsic SQUID noise.

  2. Aircraft noise exposure affects rat behavior, plasma norepinephrine levels, and cell morphology of the temporal lobe*

    Science.gov (United States)

    Di, Guo-qing; Zhou, Bing; Li, Zheng-guang; Lin, Qi-li

    2011-01-01

    In order to investigate the physiological effects of airport noise exposure on organisms, in this study, we exposed Sprague-Dawley rats in soundproof chambers to previously recorded aircraft-related noise for 65 d. For comparison, we also used unexposed control rats. Noise was arranged according to aircraft flight schedules and was adjusted to its weighted equivalent continuous perceived noise levels (L WECPN) of 75 and 80 dB for the two experimental groups. We examined rat behaviors through an open field test and measured the concentrations of plasma norepinephrine (NE) by high performance liquid chromatography-fluorimetric detection (HPLC-FLD). We also examined the morphologies of neurons and synapses in the temporal lobe by transmission electron microscopy (TEM). Our results showed that rats exposed to airport noise of 80 dB had significantly lower line crossing number (P<0.05) and significantly longer center area duration (P<0.05) than control animals. After 29 d of airport noise exposure, the concentration of plasma NE of exposed rats was significantly higher than that of the control group (P<0.05). We also determined that the neuron and synapsis of the temporal lobe of rats showed signs of damage after aircraft noise of 80 dB exposure for 65 d. In conclusion, exposing rats to long-term aircraft noise affects their behaviors, plasma NE levels, and cell morphology of the temporal lobe. PMID:22135145

  3. Aircraft noise exposure affects rat behavior, plasma norepinephrine levels, and cell morphology of the temporal lobe

    Institute of Scientific and Technical Information of China (English)

    Guo-qing DI; Bing ZHOU; Zheng-guang; LI, Qi-li LIN

    2011-01-01

    In order to investigate the physiological effects of airport noise exposure on organisms,in this study,we exposed Sprague-Dawley rats in soundproof chambers to previously recorded aircraft-related noise for 65 d.For comparison,we also used unexposed control rats.Noise was arranged according to aircraft flight schedules and was adjusted to its weighted equivalent continuous perceived noise levels (LwEcPN) of 75 and 80 dB for the two experimental groups.We examined rat behaviors through an open field test and measured the concentrations of plasma norepinephrine (NE) by high performance liquid chromatography-fluorimetric detection (HPLC-FLD).We also examined the morphologies of neurons and synapses in the temporal lobe by transmission electron microscopy (TEM).Our results showed that rats exposed to airport noise of 80 dB had significantly lower line crossing number (P<0.05) and significantly longer center area duration (P<0.05) than control animals.After 29 d of airport noise exposure,the concentration of plasma NE of exposed rats was significantly higher than that of the control group (P<0.05).We also determined that the neuron and synapsis of the temporal lobe of rats showed signs of damage after aircraft noise of 80 dB exposure for 65 d.In conclusion,exposing rats to long-term aircraft noise affects their behaviors,plasma NE levels,and cell morphology of the temporal lobe.

  4. Tomographic imaging with ultra-wideband noise radar using time-domain data

    Science.gov (United States)

    Shin, Hee Jung; Narayanan, Ram M.; Rangaswamy, Muralidhar

    2013-05-01

    This paper investigates the feasibility of using a noise waveform in an ultra-wideband (UWB) radar system for two-dimensional tomographic imaging of a stationary object with a multistatic tomographic geometry. Multiple UWB transmitters and receivers are positioned along each side of the imaging area. We perform several numerical simulations in time-domain, and the successful imaging of the target is achieved by visual inspection of the formed images.

  5. Reduced image noise at low-dose multidetector CT of the abdomen with prior image constrained compressed sensing algorithm.

    Science.gov (United States)

    Lubner, Meghan G; Pickhardt, Perry J; Tang, Jie; Chen, Guang-Hong

    2011-07-01

    To assess the effect of prior image constrained compressed sensing (PICCS) on noise reduction and image quality at low-dose computed tomography (CT). This HIPAA-compliant institutional review board-approved retrospective study was performed by using DICOM CT colonography data sets obtained in 20 adult patients. Informed consent was waived. Low-dose CT colonography was performed with 64-detector CT by using the standard protocol with mean effective dose per series of 3.06 mSv (range, 1.4-7.7 mSv). PICCS was applied to standard filtered back-projection (FBP) series. For FBP and PICCS series, mean and standard deviation (SD) of attenuation were obtained with 100-mm(2) circular region of interest (ROI) at six sites (240 soft-tissue, colonic gas, and subcutaneous fat measurements). Two abdominal radiologists reviewed two- and three-dimensional CT colonography displays and graded image quality with a five-point scale. Phantom studies were performed to compare spatial resolution and image quality between FBP and PICCS. Mean image noise and image quality scores were calculated and compared for clinical and phantom data sets. Bland-Altman, generalized estimating equation regression model, and Student t tests were used to obtain limits of agreement and to compare noise ratios and subjective image quality. Mean SD of attenuation (image noise) for ROIs was 38.0 for FBP and 12.2 for PICCS, corresponding to a noise-reduction factor of 3.1 (P < .001). Average noise reduction was 3.3 for soft tissue, 2.8 for air, and 3.0 for fat attenuation. Attenuation did not substantially change between FBP and PICCS images. Average two-dimensional image quality was 2.45 for FBP and 3.4 for PICCS (P < .001). Average three-dimensional image quality at three sites in the colon was 3.5 for FBP and 3.7 for PICCS (P = .34). Phantom data sets revealed no loss of spatial resolution in a line phantom and reduced noise in a liver tumor phantom when PICCS was compared with FBP. Application of PICCS to

  6. The relative importance of noise level and number of events on human reactions to noise: Community survey findings and study methods

    Science.gov (United States)

    Fields, J. M.

    1980-01-01

    The data from seven surveys of community response to environmental noise are reanalyzed to assess the relative influence of peak noise levels and the numbers of noise events on human response. The surveys do not agree on the value of the tradeoff between the effects of noise level and numbers of events. The value of the tradeoff cannot be confidently specified in any survey because the tradeoff estimate may have a large standard error of estimate and because the tradeoff estimate may be seriously biased by unknown noise measurement errors. Some evidence suggests a decrease in annoyance with very high numbers of noise events but this evidence is not strong enough to lead to the rejection of the conventionally accepted assumption that annoyance is related to a log transformation of the number of noise events.

  7. A Level Set Filter for Speckle Reduction in SAR Images

    Directory of Open Access Journals (Sweden)

    Xiaoxia Huang

    2010-01-01

    Full Text Available Despite much effort and significant progress in recent years, speckle removal for Synthetic Aperture Radar (SAR image still is a challenging problem in image processing. Unlike the traditional noise filters, which are mainly based on local neighborhood statistical average or frequencies transform, in this paper, we propose a speckle reduction method based on the theory of level set, one form of curvature flow propagation. Firstly, based on partial differential equation, the Lee filter can be cast as a formulation of anisotropic diffusion function; furthermore, we continued to deduce it into a level set formulation. Level set flow into the method allows the front interface to propagate naturally with topological changes, where the speed is proportional to the curvature of the intensity contours in an image. Hence, small speckle will disappear quickly, while large scale interfaces will be slow to evolve. Secondly, for preserving finer detailed structures in images when smoothing the speckle, the evolution is switched between minimum or maximum curvature speed depending on the scale of speckle. The proposed method has been illustrated by experiments on simulation image and ERS-2 SAR images under different circumstances. Its advantages over the traditional speckle reduction filter approaches have also been demonstrated.

  8. A Level Set Filter for Speckle Reduction in SAR Images

    Science.gov (United States)

    Li, Hongga; Huang, Bo; Huang, Xiaoxia

    2010-12-01

    Despite much effort and significant progress in recent years, speckle removal for Synthetic Aperture Radar (SAR) image still is a challenging problem in image processing. Unlike the traditional noise filters, which are mainly based on local neighborhood statistical average or frequencies transform, in this paper, we propose a speckle reduction method based on the theory of level set, one form of curvature flow propagation. Firstly, based on partial differential equation, the Lee filter can be cast as a formulation of anisotropic diffusion function; furthermore, we continued to deduce it into a level set formulation. Level set flow into the method allows the front interface to propagate naturally with topological changes, where the speed is proportional to the curvature of the intensity contours in an image. Hence, small speckle will disappear quickly, while large scale interfaces will be slow to evolve. Secondly, for preserving finer detailed structures in images when smoothing the speckle, the evolution is switched between minimum or maximum curvature speed depending on the scale of speckle. The proposed method has been illustrated by experiments on simulation image and ERS-2 SAR images under different circumstances. Its advantages over the traditional speckle reduction filter approaches have also been demonstrated.

  9. A review on noise suppression and aberration compensation in holographic particle image velocimetry

    Directory of Open Access Journals (Sweden)

    K.F. Tamrin

    2016-12-01

    Full Text Available Understanding three-dimensional (3D fluid flow behaviour is undeniably crucial in improving performance and efficiency in a wide range of applications in engineering and medical fields. Holographic particle image velocimetry (HPIV is a potential tool to probe and characterize complex flow dynamics since it is a truly three-dimensional three-component measurement technique. The technique relies on the coherent light scattered by small seeding particles that are assumed to faithfully follow the flow for subsequent reconstruction of the same the event afterward. However, extraction of useful 3D displacement data from these particle images is usually aggravated by noise and aberration which are inherent within the optical system. Noise and aberration have been considered as major hurdles in HPIV in obtaining accurate particle image identification and its corresponding 3D position. Major contributions to noise include zero-order diffraction, out-of-focus particles, virtual image and emulsion grain scattering. Noise suppression is crucial to ensure that particle image can be distinctly differentiated from background noise while aberration compensation forms particle image with high integrity. This paper reviews a number of HPIV configurations that have been proposed to address these issues, summarizes the key findings and outlines a basis for follow-on research.

  10. Development of a noise reduction filter algorithm for pediatric body images in multidetector CT.

    Science.gov (United States)

    Nishimaru, Eiji; Ichikawa, Katsuhiro; Okita, Izumi; Tomoshige, Yukihiro; Kurokawa, Takehiro; Nakamura, Yuko; Suzuki, Masayuki

    2010-12-01

    Recently, several types of post-processing image filter which was designed to reduce noise allowing a corresponding dose reduction in CT images have been proposed and these were reported to be useful for noise reduction of CT images of adult patients. However, these have not been reported on adaptation for pediatric patients. Because they are not very effective with small (<20 cm) display fields of view, they could not be used for pediatric (e.g., premature babies and infants) body CT images. In order to solve this restriction, we have developed a new noise reduction filter algorithm which can be applicable for pediatric body CT images. This algorithm is based on a three-dimensional post processing, in which output pixel values are calculated by multi-directional, one-dimensional median filters on original volumetric datasets. The processed directions were selected except in in-plane (axial plane) direction, and consequently the in-plane spatial resolution was not affected by the filter. Also, in other directions, the spatial resolutions including slice thickness were almost maintained due to a characteristic of non-linear filtering of the median filter. From the results of phantom studies, the proposed algorithm could reduce standard deviation values as a noise index by up to 30% without affecting the spatial resolution of all directions, and therefore, contrast-to-noise ratio was improved by up to 30%. This newly developed filter algorithm will be useful for the diagnosis and radiation dose reduction of pediatric body CT images.

  11. Noise level measurement, a new method to evaluate effectiveness of sedation in pediatric dentistry.

    Science.gov (United States)

    Sabouri, A Sassan; Firoozabadi, Farshid; Carlin, Drew; Creighton, Paul; Raczka, Michelle; Joshi, Prashant; Heard, Christopher

    2014-12-01

    Pediatric dentists perform moderate sedation frequently to facilitate dental treatment in uncooperative children. Assessing the depth and quality of sedation is an important factor in the clinical utilization of moderate sedation. We aimed to determine if the level of noise, created by the children who are undergoing moderate sedation during dental procedures, could be used as a nonsubjective measurement of the depth of sedation and compare it to the Ohio State Behavior Rating Score (OSBRS). Following Institutional Review Board approval and after receiving informed consent, we studied 51 children with a mean age of 4.2 years and average weight of 18.5 kg, who were undergoing restorative or extractive dental procedures, requiring moderate sedation. Sedation efficacy was assessed using OSBRS at several stages of the procedure. The noise level was measured by using a NoisePRO logging device to record the noise level at a rate of every second throughout the procedure. The depth of sedation assessed by OSBRS during the operative procedure was significantly correlated with noise level. The act of administering the local anesthesia and the operative procedure itself were two phases of the encounter that were significantly associated with higher OSBRS as well as noise levels. Measurement of noise level can be used as an effective guide to quantify the depth of sedation at different stages of the dental procedure. It is a nonsubjective and continuous measurement, which could be useful in clinical practice for the administration of moderate sedation during dental procedures. By using noise level analysis we are able to determine successful, poor, and failed sedation outcome. Copyright © 2014. Published by Elsevier B.V.

  12. Comparing Loudness Tolerance and Acceptable Noise Level in Listeners With Hearing Loss.

    Science.gov (United States)

    Franklin, Clifford A; White, Letitia J; Franklin, Thomas C; Livengood, Lindsay G

    2016-08-01

    The present study was a follow-up investigation to a previous study exploring the relationship between listeners' loudness tolerance and listeners' acceptable noise level among normally hearing adults. The present study compared the same two measures, but data were obtained from listeners with hearing loss; 12 adults with sensorineural hearing loss participated in a loudness tolerance measure using a scaling technique initially established for setting hearing aid output limits, in addition to an acceptable noise level measure. The acceptable noise level procedure used in this study quantified the listeners' acceptance of background noise while listening to speech. As with the research involving listeners with normal hearing, the Pearson correlation procedure indicated a lack of any statistically significant correlation between the two measures.

  13. Clutter noise reduction for phased array imaging using frequency-spatial polarity coherence

    Science.gov (United States)

    Gongzhang, Rui; Gachagan, Anthony; Xiao, Bo

    2015-03-01

    A number of materials used in industry exhibit highly-scattering properties which can reduce the performance of conventional ultrasonic NDE approaches. Moving Bandwidth Polarity Thresholding (MBPT) is a robust frequency diversity based algorithm for scatter noise reduction in single A-scan waveforms, using sign coherence across a range of frequency bands to reduce grain noise and improve Signal to Noise Ratio. Importantly, for this approach to be extended to array applications, spatial variation of noise characteristics must also be considered. This paper presents a new spatial-frequency diversity based algorithm for array imaging, extended from MBPT. Each A-scan in the full matrix capture array dataset is partitioned into a serial of overlapped frequency bands and then undergoes polarity thresholding to generate sign-only coefficients indicating possible flaw locations within each selected band. These coefficients are synthesized to form a coefficient matrix using a delay and sum approach in each frequency band. Matrices produced across the frequency bands are then summed to generate a weighting matrix, which can be applied on any conventional image. A 5MHz linear array has been used to acquire data from both austenitic steel and high nickel alloy (HNA) samples to validate the proposed algorithm. Background noise is significantly suppressed for both samples after applying this approach. Importantly, three side drilled holes and the back wall of the HNA sample are clearly enhanced in the processed image, with a mean 133% Contrast to Noise Ratio improvement when compared to a conventional TFM image.

  14. Input Space Regularization Stabilizes Pre-images for Kernel PCA De-noising

    DEFF Research Database (Denmark)

    Abrahamsen, Trine Julie; Hansen, Lars Kai

    2009-01-01

    Solution of the pre-image problem is key to efficient nonlinear de-noising using kernel Principal Component Analysis. Pre-image estimation is inherently ill-posed for typical kernels used in applications and consequently the most widely used estimation schemes lack stability. For de...

  15. Background Noise Removal in Ultrasonic B-scan Images Using Iterative Statistical Techniques

    NARCIS (Netherlands)

    Wells, I.; Charlton, P. C.; Mosey, S.; Donne, K. E.

    2008-01-01

    The interpretation of ultrasonic B-scan images can be a time-consuming process and its success depends on operator skills and experience. Removal of the image background will potentially improve its quality and hence improve operator diagnosis. An automatic background noise removal algorithm is prop

  16. Noise Equivalent Counts Based Emission Image Reconstruction Algorithm of Tomographic Gamma Scanning

    CERN Document Server

    Wang, Ke; Feng, Wei; Han, Dong

    2014-01-01

    Tomographic Gamma Scanning (TGS) is a technique used to assay the nuclide distribution and radioactivity in nuclear waste drums. Both transmission and emission scans are performed in TGS and the transmission image is used for the attenuation correction in emission reconstructions. The error of the transmission image, which is not considered by the existing reconstruction algorithms, negatively affects the final results. An emission reconstruction method based on Noise Equivalent Counts (NEC) is presented. Noises from the attenuation image are concentrated to the projection data to apply the NEC Maximum-Likelihood Expectation-Maximization algorithm. Experiments are performed to verify the effectiveness of the proposed method.

  17. QR code based noise-free optical encryption and decryption of a gray scale image

    Science.gov (United States)

    Jiao, Shuming; Zou, Wenbin; Li, Xia

    2017-03-01

    In optical encryption systems, speckle noise is one major challenge in obtaining high quality decrypted images. This problem can be addressed by employing a QR code based noise-free scheme. Previous works have been conducted for optically encrypting a few characters or a short expression employing QR codes. This paper proposes a practical scheme for optically encrypting and decrypting a gray-scale image based on QR codes for the first time. The proposed scheme is compatible with common QR code generators and readers. Numerical simulation results reveal the proposed method can encrypt and decrypt an input image correctly.

  18. Noise-Compensating Algebraic Reconstruction for a Rotational Modulation Gamma-Ray Imager

    CERN Document Server

    Budden, B; Cherry, M L

    2010-01-01

    Imaging in the hard X-ray/gamma ray spectrum requires techniques which involve the spatial or temporal modulation of incident photons. A deconvolution of the observed data is then implemented to reconstruct an image of the object scene. In practice, noise in the data contributes to poor quality in the reconstructed image. The use of statistical deconvolution techniques is a common practice in astronomical and medical physics applications to compensate for this noise. In the case of the Rotational Modulator (RM), however, an algebraic technique is required to achieve "super-resolution". We present the RM and the advantages it offers over more traditional approaches, and describe an image reconstruction technique based on an algebraic solution with compensation for noise.

  19. Effect of explosive noise on gastrointestinal transit and plasma levels of polypeptide hormones

    Institute of Scientific and Technical Information of China (English)

    Zhen-Bin Mu; Yu-Xin Huang; Bao-Min Zhao; Zhen-Xiong Liu; Bing-Hua Zhang; Qing-Li Wang

    2006-01-01

    AIM: To investigate the effect of firing noise on gastrointestinal transit and probe its mechanism by measuring the levels of plasma polypeptide hormones.METHODS: Atotal of 64 SD rats were randomly divided into a control group and three stimulating groups. Firing noise of different intensity by sub-machine guns was used as inflicting factor. The effect of firing noise on liquid substance gastrointestinal transit and solid substance gastrointestinal transit was observed by measuring the ratio of carbon powder suspension transmitting and barium sticks transmitting respectively.Plasma levels of polypeptide hormones were measured by radio-immunoassay.RESULTS: The noise accelerated gastrointestinal transit of solid food by more than 80 db;and accelerated gastrointestinal transit of liquid food significantly by more than 120 db. Meantime, plasma levels of plasma motilin (MTL)(157.47±16.08; 151.90±17.08), somatostatin (SS)(513.97±88.77; 458.25±104.30), substance P (SP)(115.52±20.70; 110.28±19.96) and vasoactive intestinal peptide (VIP) (214.21±63.17; 251.76±97.24)remarkably changed also.CONCLUSION: Within a certain intensity range,the firing noise changes the levels of rat plasma gastrointestinal hormones, but the gastrointestinal transit is still normal. Beyond the range, the noise induces plasma hormone levels disturbance and gastrointestinal transit disorder.

  20. Effect of Training Class Label Noise on Classification Performances for Land Cover Mapping with Satellite Image Time Series

    Directory of Open Access Journals (Sweden)

    Charlotte Pelletier

    2017-02-01

    Full Text Available Supervised classification systems used for land cover mapping require accurate reference databases. These reference data come generally from different sources such as field measurements, thematic maps, or aerial photographs. Due to misregistration, update delay, or land cover complexity, they may contain class label noise, i.e., a wrong label assignment. This study aims at evaluating the impact of mislabeled training data on classification performances for land cover mapping. Particularly, it addresses the random and systematic label noise problem for the classification of high resolution satellite image time series. Experiments are carried out on synthetic and real datasets with two traditional classifiers: Support Vector Machines (SVM and Random Forests (RF. A synthetic dataset has been designed for this study, simulating vegetation profiles over one year. The real dataset is composed of Landsat-8 and SPOT-4 images acquired during one year in the south of France. The results show that both classifiers are little influenced for low random noise levels up to 25%–30%, but their performances drop down for higher noise levels. Different classification configurations are tested by increasing the number of classes, using different input feature vectors, and changing the number of training instances. Algorithm complexities are also analyzed. The RF classifier achieves high robustness to random and systematic label noise for all the tested configurations; whereas the SVM classifier is more sensitive to the kernel choice and to the input feature vectors. Finally, this work reveals that the cross-validation procedure is impacted by the presence of class label noise.

  1. Noise-Assisted Quantum Electron Transfer in Multi-Level Donor-Acceptor System

    CERN Document Server

    Gurvitz, Shmuel; Berman, Gennady P

    2014-01-01

    We analytically and numerically study noise-assisted quantum electron transfer (ET) in bio-complexes consisting of a single-level electron donor and an acceptor which is modeled by many electron energy levels. Interactions are included between the donor and the acceptor energy levels and with the protein environment, which is modeled by a diagonal classical noise acting on all donor and acceptor energy levels. Different regions of parameters characterizing (i) the number of the acceptor levels, (ii) the acceptor "band-width", and (iii) the amplitude of noise and its correlation time are considered. Under some conditions, we derive analytical expressions for the ET rate and efficiency, which reveal the coarse-grain features. We obtain equal occupation of all levels at large times, independently of the structure of the acceptor band. We discuss the multi-scale regime of the acceptor population, and the accompanying effect of quantum coherent oscillations, which are analogous to those observed in experiments on ...

  2. Image-based Water Level Measurement Method under Stained Ruler

    Institute of Scientific and Technical Information of China (English)

    Jae-do KIM; Young-joon HAN; Hern-soo HAHN

    2010-01-01

    This paper proposes the water level measuring method based on the image,while the ruler used to indicate the water level is stained.The contamination of the ruler weakens or eliminates many features which are required for the image processing.However,the feature of the color difference between the ruler and the water surface are firmer on the environmental change compare to the other features.As the color differences are embossed,only the region of the ruler is limited to eliminate the noise,and the average image is produced by using several continuous frames.A histogram is then produced based on the height axis of the produced intensity average image.Local peaks and local valleys are detected,and the section between the peak and valley which have the greatest change is looked for.The valley point at this very moment is used to detect the water level.The detected water level is then converted to the actual water level by using the mapping table.The proposed method is compared to the ultrasonic based method to evaluate its accuracy and efficiency on the various contaminated environments.

  3. Suppression of Mixed Noise in the Similar Images by Using Adaptive LMS L-filters

    Directory of Open Access Journals (Sweden)

    S. Marchevsky

    2000-12-01

    Full Text Available In this paper, several adaptive least mean squares (LMSlocation-invariant filter (L-filter modifications will be described.These filters are based on linear combination of order statistics. Theadaptive L-filters are able to adapt well to variety of noiseprobability distribution, including impulsive noise. They also performwell in the case of nonstationary signals and, therefore, they aresuitable for image processing, too. Following this L-filter property,applications of the adaptive LMS L-filters for filteringtwo-dimensional static images degraded by mixed noise consisting ofadditive Gaussian white noise and impulsive noise will be presented inthis paper. Based on conveniently selected experiments intent on imagefiltering, the properties of a several adaptive L-filters modificationswill be demonstrated and compared. It will follow from experimentresults, that the L-filter modification called signal-dependent LMSL-filter yields the best results.

  4. The impact of noise level on students' learning performance at state elementary school in Medan

    Science.gov (United States)

    Buchari, Matondang, Nazaruddin

    2017-06-01

    This study was conducted to determine the level and impact of noise on pupils' learning performance that was observed through a survey at State Elementary School (SDN 060882), which is located on the corner of Abdullah Lubis Street and Pattimura Medan Street. The study was done by measuring the noise level using the Threshold Limit Value (TLV) by taking 24 locations as the measurement points. The results indicated that the noise levels exceeded the standard TLV >55 dBA as regulated in the Decree of the Minister of Environment No. KEP/48/MENLH/11/1996. According to the data processing, the noise level at school was 70.79 dBA. The classrooms were classified into noisy zones based on the Noise Mapping. Those in Red Zone which noise level were in the range of (69-75 dBA) were Class IIIa, Class IVb, and Class VI. In addition, those in Yellow Zone which were in the range of (65-69 dBA) were Class II, Class IIIa, Class IVa and Class V. The noise brought the physiological impact in the forms of dizziness that had the highest percentage of 22% and emotional and uncomfortable feeling of 21%; the communication impact of teacher's explanation disturbance of 22%; and Pupils' learning performance was evidenced to decline of 22%. Some improvements are suggested to reduce the noise such as the reposition of windows, acoustic material to cover the classrooms' wall, and bamboo trees or grasses as the barried around the school area.

  5. Determination of the level of noise in nurseries and pre-schools and the teachers′ level of annoyance

    Directory of Open Access Journals (Sweden)

    Ozan Gokdogan

    2016-01-01

    Full Text Available Objective: The aim of this article is to determine the level of noise in nurseries and pre-schools and also to compare measured levels with standard levels and evaluate the teachers’ level of annoyance. Materials and Methods: The level of noise was measured in three different schools. A total of 162 students, whose ages were between 3 and 6 years, and 12 teachers were included the study. Every age groups’ level of noise was measured during sleeping, gaming, and eating activity. In addition, teachers’ annoyance was assessed in different age groups. Results: The 4- to 6-year-old groups were found to have higher level of sounds than 3-year-old group. Eating period was found to be the highest level of sound whereas sleeping was found the lowest. Furthermore, teachers’ annoyance was found higher as the age decreased. Conclusion: Nurseries and pre-schools have noisy environment both for the students and the teachers. High level of noise, which has bad effects on health, is a public health problem. Both the students’ families and teachers must be aware of this annoying situation.

  6. Cortisol level decreases natural killer cell activity among women with aircraft noise

    Directory of Open Access Journals (Sweden)

    Hartono Hartono

    2016-02-01

    Full Text Available One of the impacts of exposure to noise is stress. Natural killer (NK cells are one of the leukocyte subsets that are responsive to physiological and psychological stress. The objective of the present research was to determine the relationship between cortisol levels and NK cell activity among women with aircraft noise stress in the area of Adi Sumarmo Airport, Solo. This study was an analytical survey with a cross sectional design. The number of subjects was 39, who were divided into 3 groups of 13 subjects each. Groups 1 to 3 were exposed to noise levels of 92.29 dB, 71.79 dB and 52.17 dB, respectively. The sample was taken using simple random sampling. The data were analyzed by Pearson correlation test and Anova followed by post hoc test using LSD test. The Anova test showed that there were significant differences in circulating cortisol levels among all groups (p = 0.018. The Pearson correlation test showed that there was a positive association between circulating cortisol levels and the number of NK cells (r = 0.547; p< 0.05 and a negative association between circulating cortisol levels and NK cell activity (r = - 0.578; p < 0.05. This study indicated that cortisol levels decreased NK cell activity among women with exposure to aircraft noise. Women who experienced aircraft noise stress showed increased cortisol levels and decreased NK cells activity.

  7. Extracting fingerprint of wireless devices based on phase noise and multiple level wavelet decomposition

    Science.gov (United States)

    Zhao, Weichen; Sun, Zhuo; Kong, Song

    2016-10-01

    Wireless devices can be identified by the fingerprint extracted from the signal transmitted, which is useful in wireless communication security and other fields. This paper presents a method that extracts fingerprint based on phase noise of signal and multiple level wavelet decomposition. The phase of signal will be extracted first and then decomposed by multiple level wavelet decomposition. The statistic value of each wavelet coefficient vector is utilized for constructing fingerprint. Besides, the relationship between wavelet decomposition level and recognition accuracy is simulated. And advertised decomposition level is revealed as well. Compared with previous methods, our method is simpler and the accuracy of recognition remains high when Signal Noise Ratio (SNR) is low.

  8. A Simple Approach to Determine Noise Frequency of Boiler Drum Level

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper proposed a simple approach to determine noise frequency of boiler drum level in order to improve control performance. Based on analysis of uncertainty of drum level, the redundant oscillation component of signal, noise is ascribed to the surface wave of drum water. According to the characteristic of surface wave, a new method was proposed to determine noise's frequency band. By gradually removing the lowest frequency component of signal, the variance of remained component is calculated and observed. An apparent turning point was found and the corresponding critical frequcncy was determined. With this result a low-pass filter was designed to separate noise component. Finally validation is conducted by comparing the proposed method and conventional ones. Results show the accuracy and simpleness of the proposed method.

  9. X-ray imaging using avalanche multiplication in amorphous selenium: investigation of depth dependent avalanche noise.

    Science.gov (United States)

    Hunt, D C; Tanioka, Kenkichi; Rowlands, J A

    2007-03-01

    The past decade has seen the swift development of the flat-panel detector (FPD), also known as the active matrix flat-panel imager, for digital radiography. This new technology is applicable to other modalities, such as fluoroscopy, which require the acquisition of multiple images, but could benefit from some improvements. In such applications where more than one image is acquired less radiation is available to form each image and amplifier noise becomes a serious problem. Avalanche multiplication in amorphous selenium (a-Se) can provide the necessary amplification prior to read out so as to reduce the effect of electronic noise of the FPD. However, in direct conversion detectors avalanche multiplication can lead to a new source of gain fluctuation noise called depth dependent avalanche noise. A theoretical model was developed to understand depth dependent avalanche noise. Experiments were performed on a direct imaging system implementing avalanche multiplication in a layer of a-Se to validate the theory. For parameters appropriate for a diagnostic imaging FPD for fluoroscopy the detective quantum efficiency (DQE) was found to drop by as much as 50% with increasing electric field, as predicted by the theoretical model. This drop in DQE can be eliminated by separating the collection and avalanche regions. For example by having a region of low electric field where x rays are absorbed and converted into charge that then drifts into a region of high electric field where the x-ray generated charge undergoes avalanche multiplication. This means quantum noise limited direct conversion FPD for low exposure imaging techniques are a possibility.

  10. A weighted dictionary learning model for denoising images corrupted by mixed noise.

    Science.gov (United States)

    Liu, Jun; Tai, Xue-Cheng; Huang, Haiyang; Huan, Zhongdan

    2013-03-01

    This paper proposes a general weighted l(2)-l(0) norms energy minimization model to remove mixed noise such as Gaussian-Gaussian mixture, impulse noise, and Gaussian-impulse noise from the images. The approach is built upon maximum likelihood estimation framework and sparse representations over a trained dictionary. Rather than optimizing the likelihood functional derived from a mixture distribution, we present a new weighting data fidelity function, which has the same minimizer as the original likelihood functional but is much easier to optimize. The weighting function in the model can be determined by the algorithm itself, and it plays a role of noise detection in terms of the different estimated noise parameters. By incorporating the sparse regularization of small image patches, the proposed method can efficiently remove a variety of mixed or single noise while preserving the image textures well. In addition, a modified K-SVD algorithm is designed to address the weighted rank-one approximation. The experimental results demonstrate its better performance compared with some existing methods.

  11. Fuzzy techniques for noise removal in image sequences and interval-valued fuzzy mathematical morphology

    OpenAIRE

    Mélange, Tom

    2010-01-01

    Image sequences play an important role in today's world. They provide us a lot of information. Videos are for example used for traffic observations, surveillance systems, autonomous navigation and so on. Due to bad acquisition, transmission or recording, the sequences are however usually corrupted by noise, which hampers the functioning of many image processing techniques. A preprocessing module to filter the images often becomes necessary. After an introduction to fuzzy set theory and ...

  12. A Variational Level Set Model Combined with FCMS for Image Clustering Segmentation

    Directory of Open Access Journals (Sweden)

    Liming Tang

    2014-01-01

    Full Text Available The fuzzy C means clustering algorithm with spatial constraint (FCMS is effective for image segmentation. However, it lacks essential smoothing constraints to the cluster boundaries and enough robustness to the noise. Samson et al. proposed a variational level set model for image clustering segmentation, which can get the smooth cluster boundaries and closed cluster regions due to the use of level set scheme. However it is very sensitive to the noise since it is actually a hard C means clustering model. In this paper, based on Samson’s work, we propose a new variational level set model combined with FCMS for image clustering segmentation. Compared with FCMS clustering, the proposed model can get smooth cluster boundaries and closed cluster regions due to the use of level set scheme. In addition, a block-based energy is incorporated into the energy functional, which enables the proposed model to be more robust to the noise than FCMS clustering and Samson’s model. Some experiments on the synthetic and real images are performed to assess the performance of the proposed model. Compared with some classical image segmentation models, the proposed model has a better performance for the images contaminated by different noise levels.

  13. A noise level prediction method based on electro-mechanical frequency response function for capacitors.

    Directory of Open Access Journals (Sweden)

    Lingyu Zhu

    Full Text Available The capacitors in high-voltage direct-current (HVDC converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

  14. On the influence of noise correlations in measurement data on basis image noise in dual-energylike x-ray imaging.

    Science.gov (United States)

    Roessl, Ewald; Ziegler, Andy; Proksa, Roland

    2007-03-01

    In conventional dual-energy systems, two transmission measurements with distinct spectral characteristics are performed. These measurements are used to obtain the line integrals of two basis material densities. Usually, the measurement process is such that the two measured signals can be treated as independent and therefore uncorrelated. Recently, however, a readout system for x-ray detectors has been introduced for which this is no longer the case. The readout electronics is designed to obtain simultaneous measurements of the total number of photons N and the total energy E they deposit in the sensor material. Practically, this is realized by a signal replication and separate counting and integrating processing units. Since the quantities N and E are (electronically) derived from one and the same physical sensor signal, they are statistically correlated. Nevertheless, the pair N and E can be used to perform a dual-energy processing following the well-known approach by Alvarez and Macovski. Formally, this means that N is to be identified with the first dual-energy measurement M1 and E with the second measurement M2. In the presence of input correlations between M1 = N and M2 = E, however, the corresponding analytic expressions for the basis image noise have to be modified. The main observation made in this paper is that for positively correlated data, as is the case for the simultaneous counting and integrating device mentioned above, the basis image noise is suppressed through the influence of the covariance between the two signals. We extend the previously published relations for the basis image noise to the case where the original measurements are not independent and illustrate the importance of the input correlations by comparing dual-energy basis image noise resulting from the device mentioned above and a device measuring the photon numbers and the deposited energies consecutively.

  15. Image processing methods for noise reduction in the TJ-II Thomson Scattering diagnostic

    Energy Technology Data Exchange (ETDEWEB)

    Dormido-Canto, S., E-mail: sebas@dia.uned.es [Departamento de Informatica y Automatica, UNED, Madrid 28040 (Spain); Farias, G. [Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Vega, J.; Pastor, I. [Asociacion EURATOM/CIEMAT para Fusion, Madrid 28040 (Spain)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We describe an approach in order to reduce or mitigate the stray-light on the images and show the exceptional results. Black-Right-Pointing-Pointer We analyze the parameters to take account in the proposed process. Black-Right-Pointing-Pointer We report a simplified exampled in order to explain the proposed process. - Abstract: The Thomsom Scattering diagnostic of the TJ-II stellarator provides temperature and density profiles. The CCD camera acquires images corrupted with noise that, in some cases, can produce unreliable profiles. The main source of noise is the so-called stray-light. In this paper we describe an approach that allows mitigation of the effects that stray-light has on the images: extraction regions with connected-components. In addition, the robustness and effectiveness of the noise reduction technique is validated in two ways: (1) supervised classification and (2) comparison of electron temperature profiles.

  16. Accounting for anatomical noise in search-capable model observers for planar nuclear imaging.

    Science.gov (United States)

    Sen, Anando; Gifford, Howard C

    2016-01-01

    Model observers intended to predict the diagnostic performance of human observers should account for the effects of both quantum and anatomical noise. We compared the abilities of several visual-search (VS) and scanning Hotelling-type models to account for anatomical noise in a localization receiver operating characteristic (LROC) study involving simulated nuclear medicine images. Our VS observer invoked a two-stage process of search and analysis. The images featured lesions in the prostate and pelvic lymph nodes. Lesion contrast and the geometric resolution and sensitivity of the imaging collimator were the study variables. A set of anthropomorphic mathematical phantoms was imaged with an analytic projector based on eight parallel-hole collimators with different sensitivity and resolution properties. The LROC study was conducted with human observers and the channelized nonprewhitening, channelized Hotelling (CH) and VS model observers. The CH observer was applied in a "background-known-statistically" protocol while the VS observer performed a quasi-background-known-exactly task. Both of these models were applied with and without internal noise in the decision variables. A perceptual search threshold was also tested with the VS observer. The model observers without inefficiencies failed to mimic the average performance trend for the humans. The CH and VS observers with internal noise matched the humans primarily at low collimator sensitivities. With both internal noise and the search threshold, the VS observer attained quantitative agreement with the human observers. Computational efficiency is an important advantage of the VS observer.

  17. Noise from Two-Level Systems in Superconducting Resonators

    Science.gov (United States)

    Neill, C.; Barends, R.; Chen, Y.; Chiaro, B.; Jeffrey, E.; Kelly, J.; Mariantoni, M.; Megrant, A.; Mutus, J.; Ohya, S.; Sank, D.; Vainsencher, A.; Wenner, J.; White, T.; Cleland, A. N.; Martinis, J. M.

    2013-03-01

    Two-level systems (TLSs) present in amorphous dielectrics and surface interfaces are a significant source of decoherence in superconducting qubits. Linear microwave resonators offer a valuable instrument for characterizing the strongly power-dependent response of these TLSs. Using quarter-wavelength coplanar waveguide resonators, we monitored the microwave response of the resonator at a single near-resonant frequency versus time at varying microwave drive powers. We observe a time dependent variation of the resonator's internal dissipation and resonance frequency. The amplitude of these variations saturates with power in a manner similar to loss from TLSs. These results provide a means for quantifying the number and distribution of TLSs.

  18. Anatomical noise in contrast-enhanced digital mammography. Part II. Dual-energy imaging

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Melissa L.; Yaffe, Martin J. [Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5, Canada and Department of Medical Biophysics, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada); Mainprize, James G. [Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada); Carton, Ann-Katherine; Saab-Puong, Sylvie; Iordache, Răzvan; Muller, Serge [GE Healthcare, 283 rue de la Minière, Buc 78530 (France); Jong, Roberta A. [Breast Imaging, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada); Dromain, Clarisse [Department of Radiology, Institut Gustave Roussy, 39 rue Camille Desmoulin, Villejuif 94805 (France)

    2013-08-15

    Purpose: Dual-energy (DE) contrast-enhanced digital mammography (CEDM) uses an iodinated contrast agent in combination with digital mammography (DM) to evaluate lesions on the basis of tumor angiogenesis. In DE imaging, low-energy (LE) and high-energy (HE) images are acquired after contrast administration and their logarithms are subtracted to cancel the appearance of normal breast tissue. Often there is incomplete signal cancellation in the subtracted images, creating a background “clutter” that can impair lesion detection. This is the second component of a two-part report on anatomical noise in CEDM. In Part I the authors characterized the anatomical noise for single-energy (SE) temporal subtraction CEDM by a power law, with model parameters α and β. In this work the authors quantify the anatomical noise in DE CEDM clinical images and compare this with the noise in SE CEDM. The influence on the anatomical noise of the presence of iodine in the breast, the timing of imaging postcontrast administration, and the x-ray energy used for acquisition are each evaluated.Methods: The power law parameters, α and β, were measured from unprocessed LE and HE images and from DE subtracted images to quantify the anatomical noise. A total of 98 DE CEDM cases acquired in a previous clinical pilot study were assessed. Conventional DM images from 75 of the women were evaluated for comparison with DE CEDM. The influence of the imaging technique on anatomical noise was determined from an analysis of differences between the power law parameters as measured in DM, LE, HE, and DE subtracted images for each subject.Results: In DE CEDM, weighted image subtraction lowers β to about 1.1 from 3.2 and 3.1 in LE and HE unprocessed images, respectively. The presence of iodine has a small but significant effect in LE images, reducing β by about 0.07 compared to DM, with α unchanged. Increasing the x-ray energy, from that typical in DM to a HE beam, significantly decreases α by about 2

  19. Modeling reaction noise with a desired accuracy by using the X level approach reaction noise estimator (XARNES) method.

    Science.gov (United States)

    Konkoli, Zoran

    2012-07-21

    A novel computational method for modeling reaction noise characteristics has been suggested. The method can be classified as a moment closure method. The approach is based on the concept of correlation forms which are used for describing spatially extended many body problems where particle numbers change in space and time. In here, it was shown how the formalism of spatially extended correlation forms can be adapted to study well mixed reaction systems. Stochastic fluctuations in particle numbers are described by selectively capturing correlation effects up to the desired order, ξ. The method is referred to as the ξ-level Approximation Reaction Noise Estimator method (XARNES). For example, the ξ=1 description is equivalent to the mean field theory (first-order effects), the ξ=2 case corresponds to the previously developed PARNES method (pair effects), etc. The main idea is that inclusion of higher order correlation effects should lead to better (more accurate) results. Several models were used to test the method, two versions of a simple complex formation model, the Michaelis-Menten model of enzymatic kinetics, the smallest bistable reaction network, a gene expression network with negative feedback, and a random large network. It was explicitly demonstrated that increase in ξ indeed improves accuracy in all cases investigated. The approach has been implemented as automatic software using the Mathematica programming language. The user only needs to input reaction rates, stoichiometry coefficients, and the desired level of computation ξ.

  20. Noise evaluation of Compton camera imaging for proton therapy

    CERN Document Server

    Ortega, P G; Cerutti, F; Ferrari, A; Gillam, J E; Lacasta, C; Llosá, G; Oliver, J F; Sala, P R; Solevi, P; Rafecas, M

    2015-01-01

    Compton Cameras emerged as an alternative for real-time dose monitoring techniques for Particle Therapy (PT), based on the detection of prompt-gammas. As a consequence of the Compton scattering process, the gamma origin point can be restricted onto the surface of a cone (Compton cone). Through image reconstruction techniques, the distribution of the gamma emitters can be estimated, using cone-surfaces backprojections of the Compton cones through the image space, along with more sophisticated statistical methods to improve the image quality. To calculate the Compton cone required for image reconstruction, either two interactions, the last being photoelectric absorption, or three scatter interactions are needed. Because of the high energy of the photons in PT the first option might not be adequate, as the photon is not absorbed in general. However, the second option is less efficient. That is the reason to resort to spectral reconstructions, where the incoming γ energy is considered as a variable in the recons...

  1. Phase-aligned multiple spin-echo averaging: a simple way to improve signal-to-noise ratio of in vivo mouse spinal cord diffusion tensor image.

    Science.gov (United States)

    Tu, Tsang-Wei; Budde, Matthew D; Xie, Mingqiang; Chen, Ying-Jr; Wang, Qing; Quirk, James D; Song, Sheng-Kwei

    2014-12-01

    To improve signal-noise-ratio of in vivo mouse spinal cord diffusion tensor imaging using-phase aligned multiple spin-echo technique. In vivo mouse spinal cord diffusion tensor imaging maps generated by multiple spin-echo and conventional spin-echo diffusion weighting were examined to demonstrate the efficacy of multiple spin-echo diffusion sequence to improve image quality and throughput. Effects of signal averaging using complex, magnitude and phased images from multiple spin-echo diffusion weighting were also assessed. Bayesian probability theory was used to generate phased images by moving the coherent signals to the real channel to eliminate the effect of phase variation between echoes while preserving the Gaussian noise distribution. Signal averaging of phased multiple spin-echo images potentially solves both the phase incoherence problem and the bias of the elevated Rician noise distribution in magnitude image. The proposed signal averaging with Bayesian phase-aligned multiple spin-echo images approach was compared to the conventional spin-echo data acquired with doubling the scan time. The diffusion tensor imaging parameters were compared in the mouse contusion spinal cord injury. Significance level (p-value) and effect size (Cohen's d) were reported between the control and contused spinal cord to inspect the sensitivity of each approach in detecting white matter pathology. Compared to the spin-echo image, the signal-noise-ratio increased to 1.84-fold using the phased image averaging and to 1.30-fold using magnitude image averaging in the spinal cord white matter. Multiple spin-echo phased image averaging showed improved image quality of the mouse spinal cord among the tested methods. Diffusion tensor imaging metrics obtained from multiple spin-echo phased images using three echoes and two averages closely agreed with those derived by spin-echo magnitude data with four averages (two times more in acquisition time). The phased image averaging correctly

  2. Modeling the behavior of signal-to-noise ratio for repeated snapshot imaging

    CERN Document Server

    Li, Junhui; Yang, Dongyue; Wu, Guohua; Yin, Longfei; Guo, Hong

    2016-01-01

    For imaging of static object by the means of sequential repeated independent measurements, a theoretical modeling of the behavior of signal-to-noise ratio (SNR) with varying number of measurement is developed, based on the information capacity of optical imaging systems. Experimental veritification of imaging using pseudo-thermal light source is implemented, for both the direct average of multiple measurements, and the image reconstructed by second order fluctuation correlation (SFC) which is closely related to ghost imaging. Successful curve fitting of data measured under different conditions verifies the model.

  3. Simultaneous Measurement and Analysis of Noise Levels in Flexible and Rigid Pavements

    Directory of Open Access Journals (Sweden)

    Hakan Yıldırım

    2014-06-01

    Full Text Available Although concrete roads have been used worldwide for years, the same improvement could not exist in Turkey and therefore, bituminous (hot mix asphalt roads were preferred instead.In this paper, the vastly built HMA (Hot Mix Asphalt roads and rarely preferred concrete roads were compared based on their level of noise. For this purpose, the concrete road at the length of 2 kilometers between Afyonkarahisar and Emirdag; also the transition point to the HMA road (which continues after the concrete road was observed.Both concrete and HMA road ends of this transition point was equipped with a noise measurement device and a camera was installed separately for providing minimum level of noise interference. Consequently, change in the noise levels depending on the building material of roads was recorded simultaneously. These factors was analysed and various models related to the sort of coating was provided. At this stage, the distance between set up points was kept as short as possible in order to prevent different results in the density of traffic and also in the flow rate.Result of various measurements and analysis provided the noise levels of concrete roads being 4 dB(A less than HMA roads in the comparison based on the same level of vehicle composition and traffic flow. Encouraging the construction of concrete roads in our country is emphasized accordingly.

  4. PERFORMANCE ANALYSIS OF IMAGE DENOISING WITH WAVELET THRESHOLDING METHODS FOR DIFFERENT LEVELS OF DECOMPOSITION

    Directory of Open Access Journals (Sweden)

    Anutam

    2014-10-01

    Full Text Available Image Denoising is an important part of diverse image processing and computer vision problems. The important property of a good image denoising model is that it should completely remove noise as far as possible as well as preserve edges. One of the most powerful and perspective approaches in this area is image denoising using discrete wavelet transform (DWT. In this paper, comparison of various Wavelets at different decomposition levels has been done. As number of levels increased, Peak Signal to Noise Ratio (PSNR of image gets decreased whereas Mean Absolute Error (MAE and Mean Square Error (MSE get increased . A comparison of filters and various wavelet based methods has also been carried out to denoise the image. The simulation results reveal that wavelet based Bayes shrinkage method outperforms other methods.

  5. Influence of sinogram affirmed iterative reconstruction of CT data on image noise characteristics and low-contrast detectability: an objective approach.

    Directory of Open Access Journals (Sweden)

    Christian von Falck

    Full Text Available OBJECTIVES: To utilize a novel objective approach combining a software phantom and an image quality metric to systematically evaluate the influence of sinogram affirmed iterative reconstruction (SAFIRE of multidetector computed tomography (MDCT data on image noise characteristics and low-contrast detectability (LCD. MATERIALS AND METHODS: A low-contrast and a high-contrast phantom were examined on a 128-slice scanner at different dose levels. The datasets were reconstructed using filtered back projection (FBP and SAFIRE and virtual low-contrast lesions (-20HU were inserted. LCD was evaluated using the multiscale structural similarity index (MS-SIM*. Image noise texture and spatial resolution were objectively evaluated. RESULTS: The use of SAFIRE led to an improvement of LCD for all dose levels and lesions sizes. The relative improvement of LCD was inversely related to the dose level, declining from 208%(±37%, 259%(±30% and 309%(±35% at 25mAs to 106%(±6%, 119%(±9% and 123%(±8% at 200mAs for SAFIRE filter strengths of 1, 3 and 5 (p<0.05. SAFIRE reached at least the LCD of FBP at a relative dose of 50%. There was no statistically significant difference in spatial resolution. The use of SAFIRE led to coarser image noise granularity. CONCLUSION: A novel objective approach combining a software phantom and the MS-SSIM* image quality metric was used to analyze the detectability of virtual low-contrast lesions against the background of image noise as created using SAFIRE in comparison to filtered back-projection. We found, that image noise characteristics using SAFIRE at 50% dose were comparable to the use of FBP at 100% dose with respect to lesion detectability. The unfamiliar imaging appearance of iteratively reconstructed datasets may in part be explained by a different, coarser noise characteristic as demonstrated by a granulometric analysis.

  6. Rabi noise spectroscopy of individual two-level tunneling defects

    Science.gov (United States)

    Matityahu, Shlomi; Lisenfeld, Jürgen; Bilmes, Alexander; Shnirman, Alexander; Weiss, Georg; Ustinov, Alexey V.; Schechter, Moshe

    2017-06-01

    Understanding the nature of two-level tunneling defects is important for minimizing their disruptive effects in various nanodevices. By exploiting the resonant coupling of these defects to a superconducting qubit, one can probe and coherently manipulate them individually. In this work, we utilize a phase qubit to induce Rabi oscillations of single tunneling defects and measure their dephasing rates as a function of the defect's asymmetry energy, which is tuned by an applied strain. The dephasing rates scale quadratically with the external strain and are inversely proportional to the Rabi frequency. These results are analyzed and explained within a model of interacting defects, in which pure dephasing of coherent high-frequency (gigahertz) defects is caused by interaction with incoherent low-frequency thermally excited defects. Our analysis sets an upper bound for the relaxation rates of thermally excited defects interacting strongly with strain fields.

  7. Computed Tomography Image Origin Identification based on Original Sensor Pattern Noise and 3D Image Reconstruction Algorithm Footprints.

    Science.gov (United States)

    Duan, Yuping; Bouslimi, Dalel; Yang, Guanyu; Shu, Huazhong; Coatrieux, Gouenou

    2016-06-08

    In this paper, we focus on the "blind" identification of the Computed Tomography (CT) scanner that has produced a CT image. To do so, we propose a set of noise features derived from the image chain acquisition and which can be used as CT-Scanner footprint. Basically, we propose two approaches. The first one aims at identifying a CT-Scanner based on an Original Sensor Pattern Noise (OSPN) that is intrinsic to the X-ray detectors. The second one identifies an acquisition system based on the way this noise is modified by its 3D image reconstruction algorithm. As these reconstruction algorithms are manufacturer dependent and kept secret, our features are used as input to train an SVM based classifier so as to discriminate acquisition systems. Experiments conducted on images issued from 15 different CT-Scanner models of 4 distinct manufacturers demonstrate that our system identifies the origin of one CT image with a detection rate of at least 94% and that it achieves better performance than Sensor Pattern Noise (SPN) based strategy proposed for general public camera devices.

  8. Combination therapy using antioxidants and low level laser therapy (LLLT) on noise induced hearing loss (NIHL)

    Science.gov (United States)

    Chang, So-Young; Lim, Sung Kyu; Lee, Min young; Chung, Phil-Sang; Jung, Jae-Yun; Rhee, Chung-Ku

    2016-02-01

    One of the most common factors that cause hearing disorders is noise trauma. Noise is an increasing hazard and it is pervasive, which makes it difficult to take precautions and prevent noise-induced hearing loss (NIHL). The prevalence of hearing loss among factory workers to be 42 %[1]. Ocupational noise induced hearing loss (ONIHL) continues to be a significant occupational hazard. ONIHL is permanent and may cause significant disability, for which there currently exists no cure, but is largely preventable. More than 30 million Americans are potentially exposed to hazardous noise levels in occupations such as transportation, construction, and coal mining, as well as recreationally. In the mainstream setting, exposure avoidance strategies aimed to reduce the incidence of ONIHL remain the focus of public health and occupational medicine approaches[2]. In military conditions this is most often caused by such things as explosions, blasts, or loud noises from vehicles ranging from 100 to 140 dB[3] and military weapons generating approximately 140-185 dB peak sound pressure levels[4].

  9. Entropy-Based Method of Choosing the Decomposition Level in Wavelet Threshold De-noising

    Directory of Open Access Journals (Sweden)

    Yan-Fang Sang

    2010-06-01

    Full Text Available In this paper, the energy distributions of various noises following normal, log-normal and Pearson-III distributions are first described quantitatively using the wavelet energy entropy (WEE, and the results are compared and discussed. Then, on the basis of these analytic results, a method for use in choosing the decomposition level (DL in wavelet threshold de-noising (WTD is put forward. Finally, the performance of the proposed method is verified by analysis of both synthetic and observed series. Analytic results indicate that the proposed method is easy to operate and suitable for various signals. Moreover, contrary to traditional white noise testing which depends on “autocorrelations”, the proposed method uses energy distributions to distinguish real signals and noise in noisy series, therefore the chosen DL is reliable, and the WTD results of time series can be improved.

  10. Pink Noise in Rowing Ergometer Performance and the Role of Skill Level.

    Science.gov (United States)

    Den Hartigh, Ruud J R; Cox, Ralf F A; Gernigon, Christophe; Van Yperen, Nico W; Van Geert, Paul L C

    2015-10-01

    The aim of this study was to examine (1) the temporal structures of variation in rowers’ (natural) ergometer strokes to make inferences about the underlying motor organization, and (2) the relation between these temporal structures and skill level. Four high-skilled and five lower-skilled rowers completed 550 strokes on a rowing ergometer. Detrended Fluctuation Analysis was used to quantify the temporal structure of the intervals between force peaks. Results showed that the temporal structure differed from random, and revealed prominent patterns of pink noise for each rower. Furthermore, the high-skilled rowers demonstrated more pink noise than the lower-skilled rowers. The presence of pink noise suggeststhat rowing performance emerges from the coordination among interacting component processes across multiple time scales. The difference in noise pattern between high-skilled and lower-skilled athletes indicates that the complexity of athletes’ motor organization is a potential key characteristic of elite performance.

  11. Impact of Anthropogenic Noise on Aquatic Animals: From Single Species to Community-Level Effects.

    Science.gov (United States)

    Sabet, Saeed Shafiei; Neo, Yik Yaw; Slabbekoorn, Hans

    2016-01-01

    Anthropogenic noise underwater is on the rise and may affect aquatic animals of marine and freshwater ecosystems. Many recent studies concern some sort of impact assessment of a single species. Few studies addressed the noise impact on species interactions underwater, whereas there are some studies that address community-level impact but only on land in air. Key processes such as predator-prey or competitor interactions may be affected by the masking of auditory cues, noise-related disturbance, or attentional interference. Noise-associated changes in these interactions can cause shifts in species abundance and modify communities, leading to fundamental ecosystem changes. To gain further insight into the mechanism and generality of earlier findings, we investigated the impact on both a predator and a prey species in captivity, zebrafish (Danio rerio) preying on waterfleas (Daphnia magna).

  12. Image simulation and a model of noise power spectra across a range of mammographic beam qualities

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, Alistair, E-mail: alistairmackenzie@nhs.net; Dance, David R.; Young, Kenneth C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Diaz, Oliver [Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom and Computer Vision and Robotics Research Institute, University of Girona, Girona 17071 (Spain)

    2014-12-15

    Purpose: The aim of this work is to create a model to predict the noise power spectra (NPS) for a range of mammographic radiographic factors. The noise model was necessary to degrade images acquired on one system to match the image quality of different systems for a range of beam qualities. Methods: Five detectors and x-ray systems [Hologic Selenia (ASEh), Carestream computed radiography CR900 (CRc), GE Essential (CSI), Carestream NIP (NIPc), and Siemens Inspiration (ASEs)] were characterized for this study. The signal transfer property was measured as the pixel value against absorbed energy per unit area (E) at a reference beam quality of 28 kV, Mo/Mo or 29 kV, W/Rh with 45 mm polymethyl methacrylate (PMMA) at the tube head. The contributions of the three noise sources (electronic, quantum, and structure) to the NPS were calculated by fitting a quadratic at each spatial frequency of the NPS against E. A quantum noise correction factor which was dependent on beam quality was quantified using a set of images acquired over a range of radiographic factors with different thicknesses of PMMA. The noise model was tested for images acquired at 26 kV, Mo/Mo with 20 mm PMMA and 34 kV, Mo/Rh with 70 mm PMMA for three detectors (ASEh, CRc, and CSI) over a range of exposures. The NPS were modeled with and without the noise correction factor and compared with the measured NPS. A previous method for adapting an image to appear as if acquired on a different system was modified to allow the reference beam quality to be different from the beam quality of the image. The method was validated by adapting the ASEh flat field images with two thicknesses of PMMA (20 and 70 mm) to appear with the imaging characteristics of the CSI and CRc systems. Results: The quantum noise correction factor rises with higher beam qualities, except for CR systems at high spatial frequencies, where a flat response was found against mean photon energy. This is due to the dominance of secondary quantum noise

  13. Comparison of the Effect of Noise Levels on Stress Response in Two Different Operation Groups in an Orthopedic Surgery Room

    Directory of Open Access Journals (Sweden)

    Hasibe Baytan Yildiz

    2016-09-01

    Full Text Available Aim: The aim of this randomized, single-blinded study was to evaluate the effects of noise on hemodynamic and neuroendocrine stress response by measuring the level of noise in the surgery rooms of patients undergoing knee operations under neuroaxial anesthesia. Gerec ve Yontem: We compared patient responses from two groups of patients: those undergoing knee operations in a surgery room where the noise level (measured in decibels is high, and those undergoing meniscus operations in a surgery room with lower noise levels. The STAI, the State-Trait Anxiety Inventory (STAI-1, and the anxiety test (STAI-2wereperformed at preoperative and postoperative periods. 20 ml of blood sample was taken for basal, intraoperative 30th minute, and postoperative 1st hour measurements. Systolic, diastolic, and mean arterial blood pressures were found to be higher in the high noise level group. ACTH levels were increased during the early postoperative period and became normal during the late postoperative period in the high noise level group whereas ACTH levels were significantly decreased in the low-noise level group. Basal cortisol levels were significantly higher in the high noise level group. HCRP, an inflammatory response mediator was found to be decreased in both groups. Early and late blood glucose levels were significantly higher in the high noise group. There was a greater increase in early and late blood glucose levels in the high noise group. In the postoperative period, although the state-trait anxiety inventory (STAI-2 levels being higher in patients subject to noisier environment determines how people feel independent of the conditions and state they are in, this result made us consider that the noise the patients were subjected to in the intraoperative period may cause a stress response. Discussion: As a result we believe that standard noise levels should be achieved by reducing the factors causing high noise levels in the operating room. This will

  14. Influence of age and sex on hearing threshold levels in workers exposed to different intensity levels of occupational noise

    Energy Technology Data Exchange (ETDEWEB)

    Szanto, C.; Ionescu, M.

    1983-01-01

    The influence of age, sex and duration of exposure on hearing threshold level (HTL) was assessed in male and female workers exposed to occupational noise. The noise intensities were of 84 and 98 dB(A) continuous equivalent level. Large differences were noted between males and females exposed to 98 dB(A) as well as between males exposed to 98 and 83 dB(A). We concluded that exposure to 98 dB(A) accelerates the evolution of hearing loss, this trend being more pronounced in males. The 83-dB(A) intensity apparently induces a hearing loss above the values due to socioacusis. To evaluate the noxious effect of noise, the HTLs obtained in the group exposed to 98 and 83-dB(A) were compared to those of the non-exposed group of Royster and Thomas. The highest difference was found in males exposed to 98 dB(A).

  15. Noise Reduction of Welding Defect Image Based on NSCT and Anisotropic Diffusion

    Institute of Scientific and Technical Information of China (English)

    吴一全; 万红; 叶志龙; 刚铁

    2014-01-01

    In order to reduce noise effectively in the welding defect image and preserve the minutiae information, a noise reduction method of welding defect image based on nonsubsampled contourlet transform (NSCT) and anisot-ropic diffusion is proposed. Firstly, an X-ray welding defect image is decomposed by NSCT. Then total variation (TV) model and Catte_PM model are used for the obtained low-pass component and band-pass components, respec-tively. Finally, the denoised image is synthesized by inverse NSCT. Experimental results show that, compared with the hybrid method of wavelet threshold shrinkage with TV diffusion, the method combining NSCT with P_Laplace diffu-sion, and the method combining contourlet with TV model and adaptive contrast diffusion, the proposed method has a great improvement in the aspects of subjective visual effect, peak signal-to-noise ratio (PSNR) and mean-square error (MSE). Noise is suppressed more effectively and the minutiae information is preserved better in the image.

  16. ℓ0TV: A new method for image restoration in the presence of impulse noise

    KAUST Repository

    Yuan, Ganzhao

    2015-06-02

    Total Variation (TV) is an effective and popular prior model in the field of regularization-based image processing. This paper focuses on TV for image restoration in the presence of impulse noise. This type of noise frequently arises in data acquisition and transmission due to many reasons, e.g. a faulty sensor or analog-to-digital converter errors. Removing this noise is an important task in image restoration. State-of-the-art methods such as Adaptive Outlier Pursuit(AOP), which is based on TV with L02-norm data fidelity, only give sub-optimal performance. In this paper, we propose a new method, called L0T V -PADMM, which solves the TV-based restoration problem with L0-norm data fidelity. To effectively deal with the resulting non-convex nonsmooth optimization problem, we first reformulate it as an equivalent MPEC (Mathematical Program with Equilibrium Constraints), and then solve it using a proximal Alternating Direction Method of Multipliers (PADMM). Our L0TV-PADMM method finds a desirable solution to the original L0-norm optimization problem and is proven to be convergent under mild conditions. We apply L0TV-PADMM to the problems of image denoising and deblurring in the presence of impulse noise. Our extensive experiments demonstrate that L0TV-PADMM outperforms state-of-the-art image restoration methods.

  17. Measurements of the communication noise level on the internal roads of the manufacturing metallurgical enterprise

    Directory of Open Access Journals (Sweden)

    B. Gajdzik

    2012-07-01

    Full Text Available This publication shows the results of measurements of the noise level emitted by the motor trucks on the internal roads of the steelworks. The distribution of the metallurgical products with the use of trucks is, next to the rail transport, one of the main logistic forms of products delivery to the customer. The research was conducted on one of the busiest internal roads of metallurgical enterprise ArcelorMittal Poland in Dąbrowa Górnicza. The enterprise conducts the whole production cycle and is the biggest steel producer in Poland. On the premises of the steelworks there were five points of measurements marked where the noise level is measured and the results were compared with the acceptable noise levels defined in the norms.

  18. A region finding method to remove the noise from the images of the human hand gesture recognition system

    Science.gov (United States)

    Khan, Muhammad Jibran; Mahmood, Waqas

    2015-12-01

    The performance of the human hand gesture recognition systems depends on the quality of the images presented to the system. Since these systems work in real time environment the images may be corrupted by some environmental noise. By removing the noise the performance of the system can be enhanced. So far different noise removal methods have been presented in many researches to eliminate the noise but all have its own limitations. We have presented a region finding method to deal with the environmental noise that gives better results and enhances the performance of the human hand gesture recognition systems so that the recognition rate of the system can be improved.

  19. School cafeteria noise-The impact of room acoustics and speech intelligibility on children's voice levels

    Science.gov (United States)

    Bridger, Joseph F.

    2002-05-01

    The impact of room acoustics and speech intelligibility conditions of different school cafeterias on the voice levels of children is examined. Methods of evaluating cafeteria designs and predicting noise levels are discussed. Children are shown to modify their voice levels with changes in speech intelligibility like adults. Reverberation and signal to noise ratio are the important acoustical factors affecting speech intelligibility. Children have much more difficulty than adults in conditions where noise and reverberation are present. To evaluate the relationship of voice level and speech intelligibility, a database of real sound levels and room acoustics data was generated from measurements and data recorded during visits to a variety of existing cafeterias under different occupancy conditions. The effects of speech intelligibility and room acoustics on childrens voice levels are demonstrated. A new method is presented for predicting speech intelligibility conditions and resulting noise levels for the design of new cafeterias and renovation of existing facilities. Measurements are provided for an existing school cafeteria before and after new room acoustics treatments were added. This will be helpful for acousticians, architects, school systems, regulatory agencies, and Parent Teacher Associations to create less noisy cafeteria environments.

  20. Rock drills used in South African mines: a comparative study of noise and vibration levels

    Energy Technology Data Exchange (ETDEWEB)

    J.I. Phillips; P.S. Heyns; G. Nelson [National Health Laboratory Service, Johannesburg (South Africa). National Institute for Occupational Health

    2007-07-01

    The study compared the noise and vibration levels associated with three hand-held rock drills (pneumatic, hydraulic and electric) currently used in South African mines, and a prototype acoustically shielded self-propelled rock drill. Equivalent A-weighted sound pressure levels were recorded on a geometrical grid, using Rion NL-11 and NL-14 sound level meters. Vibration measurements were conducted on the pneumatic, hydraulic and electric drills in accordance with the ISO 5349-1 (2001) international standard on human exposure to hand-transmitted vibration, using a Brel and Kjaer UA0894 hand adaptor. PCB Piezo accelerometers were used to measure vibration in three orthogonal directions. No vibration measurements were conducted on the self-propelled drill. All four drills emitted noise exceeding 85 dB(A). The pneumatic drill reached levels of up to 114 dB(A), while the shielded self-propelled drill almost complied with the 85 dB(A) 8 h exposure limit. Vibration levels of up to 31 m s{sup -2} were recorded. These levels greatly exceed recommended and legislated levels. Significant engineering advances will need to be made in the manufacture of rock drills to impact on noise induced hearing loss and hand arm vibration syndrome. Isolating the operator from the drill, as for the self-propelled drill, addresses the problems of both vibration and noise exposure, and is a possible direction for future development.

  1. Assessment of noise level in sundry processing and manufacturing industries in Ilorin metropolis, Nigeria.

    Science.gov (United States)

    Oyedepo, Olayinka S; Saadu, Abdullahi A

    2010-03-01

    In this work, noise level in five selected processing and manufacturing industries in Ilorin are evaluated and compared. Emphasis is given to noise emitted by individual industrial machinery from the selected industries. Event L(Aeq) and L(N) cycles were studied to identify the noisy machines and to generate baseline data. Findings show that hammer mill machine from mineral-bearing rock-crushing mills produced the highest average noise [98.4 dB(A)], an electric generator 1 [95.6 dB(A)] from the soft drink bottling industry, an electric generator [97.7 dB(A)] from the beer brewing and bottling industry, a vacuum pump [93.1 dB(A)] from the tobacco making industry, and an electric generator 2 [94.1 dB(A)] from the mattress-making industry. The highest and lowest average noise exposure levels are recorded in mineral-bearing rock-crushing mills [93.16 dB(A)] and the mattress making industry [84.69 dB(A)], respectively. The study shows that, at 95% confidence level, there is significant difference (P industries surveyed. The percentages of machines that emit noise above Federal Environmental Protection Agency and Occupational Safety and Health Administration recommendations [90 dB(A)] are from the soft drink bottling industry (83.3%), the beer brewing and bottling industry (42.9%), the tobacco making industry (71.4%), the mattress making industry (11.1%), and minerals crushing mills (87.5%). In the past 20 years, the noise levels in the soft drink bottling industry were reduced by 0.58 dB(A), and those of the beer brewing and bottling industry were reduced by 9.66 dB(A). However, that of the mattress making industry increased by 2.69 dB(A). On average, the noise level in these industries has been reduced by 2.52 dB(A). The results of this study show that the noise control measures put in place have significant impacts on the noise exposure level in the industries surveyed.

  2. Noise level in intensive care units of a public university hospital in Santa Marta (Colombia).

    Science.gov (United States)

    Garrido Galindo, A P; Camargo Caicedo, Y; Vélez-Pereira, A M

    2016-10-01

    To evaluate the noise level in adult, pediatric and neonatal intensive care units of a university hospital in the city of Santa Marta (Colombia). A descriptive, observational, non-interventional study with follow-up over time was carried out. Continuous sampling was conducted for 20 days for each unit using a type i sound level meter, filter frequency in A weighting and Fast mode. We recorded the maximum values, the 90th percentile as background noise, and the continuous noise level. The mean hourly levels in the adult unit varied between 57.40±1.14-63.47±2.13dBA, with a maximum between 71.55±2.32-77.22±1.94dBA, and a background noise between 53.51±1.16-60.26±2.10dBA; in the pediatric unit the mean hourly levels varied between 57.07±3.07-65.72±2.46dBA, with a maximum of 68.69±3.57-79.06±2.34dBA, and a background noise between 53.33±3.54-61.96±2.85dBA; the neonatal unit in turn presented mean hourly values between 59.54±2.41-65.33±1.77dBA, with a maximum value between 67.20±2.13-77.65±3.74dBA, and a background noise between 55.02±2.03-58.70±1.95dBA. Analysis of variance revealed a significant difference between the hourly values and between the different units, with the time of day exhibiting a greater influence. The type of unit affects the noise levels in intensive care units, the pediatric unit showing the highest values and the adult unit the lowest values. However, the parameter exerting the greatest influence upon noise level is the time of day, with higher levels in the morning and evening, and lower levels at night and in the early morning. Copyright © 2015 Elsevier España, S.L.U. y SEMICYUC. All rights reserved.

  3. Therapy imaging: a signal-to-noise analysis of metal plate/film detectors.

    Science.gov (United States)

    Munro, P; Rawlinson, J A; Fenster, A

    1987-01-01

    We have measured the modulation transfer functions [MTF (f)'s] and the noise power spectra [NPS (f)] of therapy x-ray detectors irradiated by 60Co, 6- and 18-MV radiotherapy beams. Using these quantities, we have calculated the noise-equivalent quanta [NEQ (f)] and the detective quantum efficiency [DQE (f)] to quantitate the limitations of therapy detectors. The detectors consisted of film or fluorescent screen-film combinations in contact with copper, lead, or tungsten metal plates. The resolution of the detectors was found to be comparable to fluorescent screen-film combinations used in diagnostic radiology, however, the signal-to-noise ratio [SNR (f)] of the detectors was limited due to film granularity. We conclude that improved images can be obtained by using alternative detector systems which have less noise or film granularity.

  4. Noise-Produced Patterns in Images Constructed from Magnetic Flux Leakage Data

    CERN Document Server

    Pimenova, Anastasiya V; Levesley, Jeremy; Elkington, Peter; Bacciarelli, Mark

    2015-01-01

    Magnetic flux leakage measurements help identify the position, size and shape of corrosion-related defects in steel casings used to protect boreholes drilled into oil and gas reservoirs. Images constructed from magnetic flux leakage data contain patterns related to noise inherent in the method. We investigate the patterns and their scaling properties for the case of delta-correlated input noise, and consider the implications for the method's ability to resolve defects. The analytical evaluation of the noise-produced patterns is made possible by model reduction facilitated by large-scale approximation. With appropriate modification, the approach can be employed to analyze noise-produced patterns in other situations where the data of interest are not measured directly, but are related to the measured data by a complex linear transform involving integrations with respect to spatial coordinates.

  5. TU-F-CAMPUS-I-04: Head-Only Asymmetric Gradient System Evaluation: ACR Image Quality and Acoustic Noise

    Energy Technology Data Exchange (ETDEWEB)

    Weavers, P; Shu, Y; Tao, S; Bernstein, M [Mayo Clinic, Rochester, Minnesota (United States); Lee, S; Piel, J; Foo, T [GE Global Research, Niskayuna, NY (United States); Mathieu, J-B [GE Healthcare, Florence, SC (Italy)

    2015-06-15

    Purpose: A high-performance head-only magnetic resonance imaging gradient system with an acquisition volume of 26 cm employing an asymmetric design for the transverse coils has been developed. It is able to reach a magnitude of 85 mT/m at a slew rate of 700 T/m/s, but operated at 80 mT/m and 500 T/m/s for this test. A challenge resulting from this asymmetric design is that the gradient nonlinearly exhibits both odd- and even-ordered terms, and as the full imaging field of view is often used, the nonlinearity is pronounced. The purpose of this work is to show the system can produce clinically useful images after an on-site gradient nonlinearity calibration and correction, and show that acoustic noise levels fall within non-significant risk (NSR) limits for standard clinical pulse sequences. Methods: The head-only gradient system was inserted into a standard 3T wide-bore scanner without acoustic damping. The ACR phantom was scanned in an 8-channel receive-only head coil and the standard American College of Radiology (ACR) MRI quality control (QC) test was performed. Acoustic noise levels were measured for several standard pulse sequences. Results: Images acquired with the head-only gradient system passed all ACR MR image quality tests; Both even and odd-order gradient distortion correction terms were required for the asymmetric gradients to pass. Acoustic noise measurements were within FDA NSR guidelines of 99 dBA (with assumed 20 dBA hearing protection) A-weighted and 140 dB for peak for all but one sequence. Note the gradient system was installed without any shroud or acoustic batting. We expect final system integration to greatly reduce noise experienced by the patient. Conclusion: A high-performance head-only asymmetric gradient system operating at 80 mT/m and 500 T/m/s conforms to FDA acoustic noise limits in all but one case, and passes all the ACR MR image quality control tests. This work was supported in part by the NIH grant 5R01EB010065.

  6. Signal-to-noise performance analysis of streak tube imaging lidar systems. I. Cascaded model.

    Science.gov (United States)

    Yang, Hongru; Wu, Lei; Wang, Xiaopeng; Chen, Chao; Yu, Bing; Yang, Bin; Yuan, Liang; Wu, Lipeng; Xue, Zhanli; Li, Gaoping; Wu, Baoning

    2012-12-20

    Streak tube imaging lidar (STIL) is an active imaging system using a pulsed laser transmitter and a streak tube receiver to produce 3D range and intensity imagery. The STIL has recently attracted a great deal of interest and attention due to its advantages of wide azimuth field-of-view, high range and angle resolution, and high frame rate. This work investigates the signal-to-noise performance of STIL systems. A theoretical model for characterizing the signal-to-noise performance of the STIL system with an internal or external intensified streak tube receiver is presented, based on the linear cascaded systems theory of signal and noise propagation. The STIL system is decomposed into a series of cascaded imaging chains whose signal and noise transfer properties are described by the general (or the spatial-frequency dependent) noise factors (NFs). Expressions for the general NFs of the cascaded chains (or the main components) in the STIL system are derived. The work presented here is useful for the design and evaluation of STIL systems.

  7. Reduction of noise in medullary renograms from dynamic MR images

    NARCIS (Netherlands)

    Giele, ELW; de Priester, JA; Blom, JA; den Boer, JA; van Engelshoven, JMA; Hasman, A

    2000-01-01

    Dynamic magnetic resonance images of the kidney can be used to acquire separate renograms of the cortex and medulla, A high-quality cortical renogram can be determined directly from a region of interest (ROI) placed in the cortex. Due to partial volume effects, part of the signal from a ROI placed i

  8. Imaging crustal structure using local earthquake and ambient noise tomography in North Texas

    Science.gov (United States)

    Sufri, O.; DeShon, H. R.; Scales, M. M.; Hayward, C.; Magnani, M. B.

    2016-12-01

    North Texas, including the Dallas-Fort Worth metroplex, has experienced an increase in seismicity rate since 2008 and these events have been linked, to varying degrees of certainty, to wastewater injection in the Ordovician Ellenburger Formation, deposited on top of the crystalline basement. We focus here on local earthquake and ambient noise tomography approaches to imaging the subsurface velocity heterogeneity associated with the larger and better-recorded North Texas sequence: the Azle-Reno, the Irving-Dallas, and the M4 Venus earthquake sequences. The 2013-2014 Azle-Reno sequence generated 27 felt earthquakes (M2.1-3.6) between November 2013 and January 2014, although earthquake rates at lower magnitude levels (M0-2) during the same time window were highly variable. The most recent set of Azle-Reno earthquakes occurred in December 2015, following a nearby M3.0 event near Haslet. SMU and collaborators currently operate 30 seismic stations in the basin. In addition, SMU and Nodal Seismic collaborated to deploy a dense network of 10 Hz single-component (vertical) sensors over the Azle-Reno earthquakes source zone. Ten days of continuous data were acquired between February 25 and March 8, 2014. We present results of double-difference local earthquake tomography and ambient noise tomography using the local network and the nodal datasets. Ambient noise tomography allows us to obtain higher resolution near surface structure and group velocity maps to complement the Vp, Vs and Vp/Vs images provided by the local earthquake dataset. Local earthquake tomography results for the Irving-Dallas and Venus (Johnson County) seismicity will also be presented. The Fort Worth basin deepens from west-to-east, and we hypothesize that large NE-SW trending basement faults, some of which have been reactivated since 2008, compartmentalize the subsurface. Exploring similarities and differences in velocity heterogeneities in the Ellenburger formation, and the crystalline basement using

  9. Roughness preserving filter design to remove spatial noise from stereoscopic skin images for stable haptic rendering.

    Science.gov (United States)

    Lee, K; Kim, M; Lee, O; Kim, K

    2017-08-01

    A problem in skin rendering with haptic feedback is the reconstruction of accurate 3D skin surfaces from stereo skin images to be used for touch interactions. This problem also encompasses the issue of how to accurately remove haptic spatial noise caused by the construction of disparity maps from stereo skin images, while minimizing the loss of the original skin roughness for cloning real tough textures without errors. Since the haptic device is very sensitive to high frequencies, even small amounts of noise can cause serious system errors including mechanical oscillations and unexpected exerting forces. Therefore, there is a need to develop a noise removal algorithm that preserves haptic roughness. A new algorithm for a roughness preserving filter (RPF) that adaptively removes spatial noise, is proposed. The algorithm uses the disparity control parameter (λ) and noise control parameter (k), obtained from singular value decomposition of a disparity map. The parameter k determines the amount of noise to be removed, and the optimum value of k is automatically chosen based on a threshold of gradient angles of roughness (Ra ). The RPF algorithm was implemented and verified with three real skin images. Evaluation criteria include preserved roughness quality and removed noise. Mean squared error (MSE), peak signal to noise ratio (PSNR), and objective roughness measures Ra and Rq were used for evaluation, and the results were compared against a median filter. The results show that the proposed RPF algorithm is a promising technology for removing noise and retaining maximized roughness, which guarantees stable haptic rendering for skin roughness. The proposed RPF is a promising technology because it allows for any stereo image to be filtered without the risk of losing the original roughness. In addition, the algorithm runs automatically for any given stereo skin image with relation to the disparity parameter λ, and the roughness parameters Ra or Rq are given priority

  10. An exploratory survey of noise levels associated with a 100kW wind turbine

    Science.gov (United States)

    Balombin, J. R.

    1980-01-01

    Noise measurements of a 125-foot diameter, 100 kW wind turbine are presented. The data include measurements as functions of distance from the turbine and directivity angle and cover a frequency range from 1 Hz to several kHz. Potential community impact is discussed in terms of A-weighted noise levels relative to background levels, and the intrasonic spectral content. Finally, the change in the sound power spectrum associated with a change in the rotor speed in described. The acoustic impact of this size wind turbine is judged to be minimal.

  11. The Relationship between Personality Type and Acceptable Noise Levels: A Pilot Study.

    Science.gov (United States)

    Franklin, Cliff; Johnson, Laura V; White, Letitia; Franklin, Clay; Smith-Olinde, Laura

    2013-01-01

    Objectives. This study examined the relationship between acceptable noise level (ANL) and personality. ANL is the difference between a person's most comfortable level for speech and the loudest level of background noise they are willing to accept while listening to speech. Design. Forty young adults with normal hearing participated. ANLs were measured and two personality tests (Big Five Inventory, Myers-Briggs Type Indicator) were administered. Results. The analysis revealed a correlation between ANL and the openness and conscientious personality dimensions from the Big Five Inventory; no correlation emerged between ANL and the Myers-Briggs personality types. Conclusions. Lower ANLs are correlated with full-time hearing aid use and the openness personality dimension; higher ANLs are correlated with part-time or hearing aid nonuse and the conscientious personality dimension. Current data suggest that those more open to new experiences may accept more noise and possibly be good hearing aid candidates, while those more conscientious may accept less noise and reject hearing aids, based on their unwillingness to accept background noise. Knowing something about a person's personality type may help audiologists determine if their patients will likely be good candidates for hearing aids.

  12. Noise levels of a track-laying tractor during field operations in the vineyard

    Directory of Open Access Journals (Sweden)

    Pietro Catania

    2013-09-01

    Full Text Available Noise in agriculture is one of the risk factors to be taken into account in the assessment of the health and safety of workers; in particular, it is known that the tractor is a source of high noise. The Italian Low Decree 81/2008 defined the requirements for assessing and managing noise risk identifying a number of procedures to be adopted at different noise levels to limit workers exposure. This paper concerns the analysis of the noise risk arising from the use of a tracklaying tractor during field operations carried out in the vineyard. The objective of this study was to evaluate the noise level that comes close to the ear of the operator driving the tractor measuring the values of equivalent sound level (Leq(A and peak sound pressure (LCpk. We considered four options related to the same tractor coupled with the following tools to perform some farming operations: rototilling, chisel plough, flail mowers and vibro farmer. We considered three test conditions: T1 in flat (slope 0%, T2 uphill and T3 downhill (both 30% slope. The instrument used for the measurements is a precision integrating portable sound level meter, class 1, model HD2110L by Delta OHM, Italy. Each survey lasted 2 minutes, with an interval of measurement equal to 0.5 s. The tests were performed in compliance with the standards ISO 9612 and ISO 9432. The results show that the measured sound levels exceed the limits allowed by the regulations in almost all the test conditions; values exceeding the threshold limit of 80 dB(A were recorded coming up to a maximum value of 92.8 dB(A for flail mowers in test T1. When limits imposed by the regulations are exceeded, the operator is obliged to wear the appropriate Personal Protective Equipment.

  13. The influence of hologram aperture on speckle noise in the reconstructed image of digital holography and its reduction

    Science.gov (United States)

    Cai, Xiao-ou; Wang, Hui

    2008-01-01

    Based on the whole process of the recording and reconstruction of digital holography, we study the formation cause of speckle noise in its reconstructed image and acquire the conclusion that the small size of hologram aperture diffraction aggravates the speckle noise of reconstructed image and the speckle noise has been one of primary noise sources in the reconstruction process. In order to reduce the speckle noise resulting from little hologram aperture diffraction, we set an appropriate aperture function matching the recording parameter and aperture size of hologram and deconvolve the reconstructed image with it. The validity has been proved in theory and experiment. Therefore, it offers a brand-new thought and practical way to reduce the speckle noise in the reconstructed image of digital holography.

  14. Fuzzy peer groups for reducing mixed gaussian-impulse noise from color images.

    Science.gov (United States)

    Morillas, Samuel; Gregori, Valentín; Hervas, Antonio

    2009-07-01

    The peer group of an image pixel is a pixel similarity-based concept which has been successfully used to devise image denoising methods. However, since it is difficult to define the pixel similarity in a crisp way, we propose to represent this similarity in fuzzy terms. In this paper, we introduce the fuzzy peer group concept, which extends the peer group concept in the fuzzy setting. A fuzzy peer group will be defined as a fuzzy set that takes a peer group as support set and where the membership degree of each peer group member will be given by its fuzzy similarity with respect to the pixel under processing. The fuzzy peer group of each image pixel will be determined by means of a novel fuzzy logic-based procedure. We use the fuzzy peer group concept to design a two-step color image filter cascading a fuzzy rule-based switching impulse noise filter by a fuzzy average filtering over the fuzzy peer group. Both steps use the same fuzzy peer group, which leads to computational savings. The proposed filter is able to efficiently suppress both Gaussian noise and impulse noise, as well as mixed Gaussian-impulse noise. Experimental results are provided to show that the proposed filter achieves a promising performance.

  15. WAVELET TECHNIQUE RECOVERING IMAGE BLURRED BY MIXED GAUSSIAN AND SALT-PEPPER NOISE

    Institute of Scientific and Technical Information of China (English)

    Hu Junquan; Huang Daren; Wang Zhenwu; Zhang Zeyin

    2003-01-01

    In this paper, we propose a new method to removing the mixed Gaussian and salt-pepper noise based on wavelet. To estimate outlier, A scheme called max-min method is adopted after DWT. Experimental results show that this method is more effective than common image restoration methods, such as Median filter, center weighted median filter.

  16. Noise temperature improvement for magnetic fusion plasma millimeter wave imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Lai, J.; Domier, C. W.; Luhmann, N. C. [Department of Electrical and Computer Engineering, University of California at Davis, Davis, California 95616 (United States)

    2014-03-15

    Significant progress has been made in the imaging and visualization of magnetohydrodynamic and microturbulence phenomena in magnetic fusion plasmas [B. Tobias et al., Plasma Fusion Res. 6, 2106042 (2011)]. Of particular importance have been microwave electron cyclotron emission imaging and microwave imaging reflectometry systems for imaging T{sub e} and n{sub e} fluctuations. These instruments have employed heterodyne receiver arrays with Schottky diode mixer elements directly connected to individual antennas. Consequently, the noise temperature has been strongly determined by the conversion loss with typical noise temperatures of ∼60 000 K. However, this can be significantly improved by making use of recent advances in Monolithic Microwave Integrated Circuit chip low noise amplifiers to insert a pre-amplifier in front of the Schottky diode mixer element. In a proof-of-principle design at V-Band (50–75 GHz), significant improvement of noise temperature from the current 60 000 K to measured 4000 K has been obtained.

  17. Underwater radiated noise levels of a research icebreaker in the central Arctic Ocean.

    Science.gov (United States)

    Roth, Ethan H; Schmidt, Val; Hildebrand, John A; Wiggins, Sean M

    2013-04-01

    U.S. Coast Guard Cutter Healy's underwater radiated noise signature was characterized in the central Arctic Ocean during different types of ice-breaking operations. Propulsion modes included transit in variable ice cover, breaking heavy ice with backing-and-ramming maneuvers, and dynamic positioning with the bow thruster in operation. Compared to open-water transit, Healy's noise signature increased approximately 10 dB between 20 Hz and 2 kHz when breaking ice. The highest noise levels resulted while the ship was engaged in backing-and-ramming maneuvers, owing to cavitation when operating the propellers astern or in opposing directions. In frequency bands centered near 10, 50, and 100 Hz, source levels reached 190-200 dB re: 1 μPa at 1 m (full octave band) during ice-breaking operations.

  18. How to coadd images? II. A coaddition image that is optimal for any purpose in the background dominated noise limit

    CERN Document Server

    Zackay, Barak

    2015-01-01

    Image coaddition is one of the most basic operations that astronomers perform. In Paper~I, we presented the optimal ways to coadd images in order to detect faint sources and to perfrom flux measurements under the assumption that the noise is approximately Gaussian. Here, we build on these results and derive from first principles a coaddition technique which is optimal for any hypothesis testing and measurement (e.g., source detection, flux or shape measurements and star/galaxy separation), in the background-noise-dominated case. This method has several important properties. The pixels of the resulting coadd image are uncorrelated. This image preserves all the information (from the original individual images) on all spatial frequencies. Any hypothesis testing or measurement that can be done on all the individual images simultaneously, can be done on the coadded image without any loss of information. The PSF of this image is typically as narrow, or narrower than the PSF of the best image in the ensemble. Moreov...

  19. Do hearing threshold levels in workers of the furniture industry reflect their exposure to noise?

    Directory of Open Access Journals (Sweden)

    Małgorzata Pawlaczyk-Łuszczyńska

    2016-06-01

    Full Text Available Background: The aim of the study was to analyze the hearing status of employees of a furniture factory with respect to their exposure to noise and the presence of additional risk factors of noise-induced hearing loss (NIHL. Material and Methods: Noise measurements, questionnaire survey and assessment of hearing, using pure tone audiometry, were carried out in 50 male workers, aged 20–57 years, directly employed in the manufacture of furniture. The actual workers’ hearing threshold levels (HTLs were compared with the predictions calculated according to PN-ISO 1999:2000 based on age, gender and noise exposure. Results: Workers under study were exposed to noise at daily noise exposure levels of 82.7–94.8 dB (mean: 90.9 dB for a period of 3–14 years. In all subjects, mean HTL at 500 Hz, 1000 Hz, 2000 Hz and 4000 Hz did not exceed 25 dB. Nevertheless, high frequency notches were found in 11% of audiograms. The actual workers’ HTLs at 3000–6000 Hz were similar to those predicted using PN-ISO 1999:2000. There were statistical significant differences between HTLs in subgroups of people with higher (> 78 mm Hg and lower (≤ 78 mm Hg diastolic blood pressure, smokers and non-smokers, and those working with organic solvents. Hearing loss was more evident in subjects affected by the additional risk factors specified above. Conclusions: The results confirm the need to consider, in addition to noise, also some other NIHL risk factors, such as tobacco smoking, elevated blood pressure, and co-exposure to organic solvents when estimating the risk of NIHL and developing the hearing conservation programs for workers. Med Pr 2016;67(3:337–351

  20. Noise levels in Southern California Integrated GPS Network (SCIGN) data; Preliminary results

    Science.gov (United States)

    Langbein, J.; Heflin, M. B.; Hurst, K.; Kedar, S.; Herring, T.; King, N. E.; Prawirodirdjo, L.

    2002-12-01

    Quantifying the noise levels in GPS data is a necessary for estimating station velocities and their uncertainties. The estimate of velocity uncertainty is particularly sensitive to the noise model used to characterize the time-series at its lowest frequencies. Previous published analysis (Zhang et. al, 1997 and Mao et. al, 1999) of noise levels in GPS data indicated that the flicker noise (1/f where f is frequency) best represent the temporal correlations at low frequencies in GPS station position time-series. On the other hand, analysis of high precision EDM data (Langbein and Johnson, 1995) show temporal correlations at low frequencies that is consistent with a random-walk (1/{f2}). It is believed that localized monument wobble is the cause for the random-walk. With the more recent GPS solutions that use data from a regional network and, as a consequence of resolving the ambiguity in GPS phase data, these solutions have better precision than those used in the published results. To test whether random-walk could be a component of the GPS data, time series of GPS data processed by JPL using GIPSY-OASIS II are examined. These data are from a subset of SCIGN for which the ambiguities have been resolved and a local reference frame has been defined. Preliminary analysis indicates that either flicker or a wide-band, seasonal noise is present. In addition, it is possible to place an upper bound on the amount of random-walk noise in the SCIGN data since these data span enough time and the recent data have less flicker noise than the published solutions.

  1. Modeling of interior noise levels in large combustion turbine power stations

    Energy Technology Data Exchange (ETDEWEB)

    Hedeen, R.A. [GE Global Research, Niskayuna, NY (United States); Loud, R.L. [GE Energy, Schenectady, NY (United States)

    2007-07-01

    A study was conducted to predict noise emissions from power generating stations. In particular, the SoundPLAN4 ray-tracing program originally designed for exterior environmental noise propagation analysis, was used to predict the sound levels coming from inside combustion turbines and combined-cycle power plants. Although exterior sound levels are of interest due to their propagation into nearby communities, interior sound levels are important because of their influence on occupational noise exposure. Most regulations are concerned with an 85 dBA, 8 hour exposure. Therefore, plant designers, operators, and owners must be able to predict and control the areas in their plants where these regulations must be considered. In this study, the Raynoise 5 program was also used to analyze sound propagation. The ray-trace model considered the known sound power levels of the major pieces of equipment and was able to predict the sound distribution through the turbine hall with acceptable accuracy. The models used in this study were suitable for both compliance evaluation and noise target optimization of the individual power train components. It was concluded that the location and arrangement of the power train, off-base skids, and stand-alone equipment can be altered to control the sound level in desired areas of the plant. 7 refs., 4 figs.

  2. Intelligibility of speech in noise at high presentation levels: effects of hearing loss and frequency region.

    Science.gov (United States)

    Summers, Van; Cord, Mary T

    2007-08-01

    These experiments examined how high presentation levels influence speech recognition for high- and low-frequency stimuli in noise. Normally hearing (NH) and hearing-impaired (HI) listeners were tested. In Experiment 1, high- and low-frequency bandwidths yielding 70%-correct word recognition in quiet were determined at levels associated with broadband speech at 75 dB SPL. In Experiment 2, broadband and band-limited sentences (based on passbands measured in Experiment 1) were presented at this level in speech-shaped noise filtered to the same frequency bandwidths as targets. Noise levels were adjusted to produce approximately 30%-correct word recognition. Frequency bandwidths and signal-to-noise ratios supporting criterion performance in Experiment 2 were tested at 75, 87.5, and 100 dB SPL in Experiment 3. Performance tended to decrease as levels increased. For NH listeners, this "rollover" effect was greater for high-frequency and broadband materials than for low-frequency stimuli. For HI listeners, the 75- to 87.5-dB increase improved signal audibility for high-frequency stimuli and rollover was not observed. However, the 87.5- to 100-dB increase produced qualitatively similar results for both groups: scores decreased most for high-frequency stimuli and least for low-frequency materials. Predictions of speech intelligibility by quantitative methods such as the Speech Intelligibility Index may be improved if rollover effects are modeled as frequency dependent.

  3. Cat Swarm Optimization Based Functional Link Artificial Neural Network Filter for Gaussian Noise Removal from Computed Tomography Images

    OpenAIRE

    Kumar, M.; Mishra, S K; S S Sahu

    2016-01-01

    Gaussian noise is one of the dominant noises, which degrades the quality of acquired Computed Tomography (CT) image data. It creates difficulties in pathological identification or diagnosis of any disease. Gaussian noise elimination is desirable to improve the clarity of a CT image for clinical, diagnostic, and postprocessing applications. This paper proposes an evolutionary nonlinear adaptive filter approach, using Cat Swarm Functional Link Artificial Neural Network (CS-FLANN) to remove the ...

  4. A Hybrid Method of medical Image Restoration with Gaussian and Impulsive Noise; Un Metodo Hibrido de Restauracion de Images Medidas con Ruido Gausino e Impulsivo

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, M. G.; Vidal, V.; Verdu, G.; Mayo, P.; Rodenas, F.

    2011-07-01

    The noise removal techniques to restore noisy images is currently an important issue, for example, medical images obtained by X-ray computed tomography in noise due to the use of a small number of projections present noise of different types. In this paper we analyze and evaluate two techniques that separately each behaves efficiently for the removal of Gaussian and impulsive noise respectively, and combined to form a hybrid approach obtains very good performance with respect to quality in most different types of noise.

  5. Noise property of a four-level system in vee + ladder configuration

    Science.gov (United States)

    Ming, Ying; Liu, Hong-Yu; Yang, Rong-Can

    2016-11-01

    We present the results of a theoretical study of the output amplitude noises of a four-level atomic system in vee + ladder configuration. The difference and connection of electromagnetically induced transparency and Autler-Townes splitting effects are investigated theoretically. The output amplitude noise of the probe field of two effects were compared, the quantum properties of the input field of the thin medium and the thick medium under Autler-Townes splitting or electromagnetically induced transparency (EIT) condition are maintained, the higher fidelity is obtained in the storage of the thick medium under the condition of EIT in non-classical states. The noise characteristics of the squeezed vacuum field after four-level coherent medium are studied; the noise of the output field is lowest when the detection light is far away from detuning. The double split of EIT window was made by the dynamic Stark splitting on the ground state of control field, the quantum properties of the input field in the strong-control field and strong-coupling field were maintained. The output noise spectrum is divided with the increase in the field strength, the maximum output squeezing is far away from the resonance.

  6. Relationship between Lighting and Noise Levels and Productivity of the Occupants in Automotive Assembly Industry

    Directory of Open Access Journals (Sweden)

    Jafar Akbari

    2013-01-01

    Full Text Available Work environment affects human productivity and his performance. The aims of this study were to investigate the effects of lighting and noise levels on human productivity in the automotive assembly industry. Method. Subjects were 181 workers from different parts of an automobile assembly industry. Illuminance (Lx at the height of 30 inches from the surface of work station and noise (dBA were locally measured. Also human productivity by the Goldsmith and Hersey scale (1980 was measured. Data were analyzed by using SPSS v20 Pearson correlation coefficient. Results. The results showed that the relationship between noise level and human productivity is negative and significant (, , but there was no significant relationship between lighting and human productivity (. Conclusion. Based on the results, in assembly tasks, noise has a negative impact on human productivity, and lighting does not affect this. So, in order to increase employee productivity, noise control and reduction to less than the standard values (less than 85 dB is necessary.

  7. Equivalent noise level response to number of vehicles: a comparison between a high traffic flow and low traffic flow highway in Klang Valley, Malaysia

    OpenAIRE

    Halim, Herni; Abdullah, Ramdzani

    2014-01-01

    HIGHLIGHTS Highway traffic noise is a serious problem in Malaysia Heavy traffic flow highway recorded higher noise level compared to low traffic flow Noise level stabilized at certain number of vehicles on the road i.e above 500 vehicles. Although much research on road traffic noise has found that noise level increase are influenced by driver behavior and source-receiver distance, little attention has been paid to the relationship between noise level and total number of vehicles...

  8. Image Filtering Driven by Level Curves

    Science.gov (United States)

    Rajwade, Ajit; Banerjee, Arunava; Rangarajan, Anand

    This paper presents an approach to image filtering that is driven by the properties of the iso-valued level curves of the image and their relationship with one another. We explore the relationship of our algorithm to existing probabilistically driven filtering methods such as those based on kernel density estimation, local-mode finding and mean-shift. Extensive experimental results on filtering gray-scale images, color images, gray-scale video and chromaticity fields are presented. In contrast to existing probabilistic methods, in our approach, the selection of the parameter that prevents diffusion across the edge is robustly decoupled from the smoothing of the density itself. Furthermore, our method is observed to produce better filtering results for the same settings of parameters for the filter window size and the edge definition.

  9. Noise minimization via deep submicron system-on-chip integration in megapixel CMOS imaging sensors

    Science.gov (United States)

    Kozlowski, L. J.

    2006-03-01

    Infrared sensor designers have long maximized S/N ratio by employing pixel-based amplification in conjunction with supplemental noise suppression. Instead, we suppress photodiode noise using novel SoC implementation with simple three transistor pixel; supporting SoC components include a feedback amplifier having elements distributed amongst the pixel and column buffer, a tapered reset clock waveform, and reset timing generator. The tapered reset method does not swell pixel area, compel processing of the correlated reset and signal values, or require additional memory. Integrated in a 2.1 M pixel imager developed for generating high definition television, random noise is ˜8e-at video rates to 225 MHz. Random noise of ˜30e-would otherwise he predicted for the 5 μm 5 μm pixels having 5.5 fF detector capacitance with negligible image lag. Minimum sensor S/N ratio is 52 dB with 1920 by 1080 progressive readout at 60 Hz, 72 Hz and 90 Hz. Fixed pattern noise is <2 DN via on-chip signal processing.

  10. Robust boundary detection of left ventricles on ultrasound images using ASM-level set method.

    Science.gov (United States)

    Zhang, Yaonan; Gao, Yuan; Li, Hong; Teng, Yueyang; Kang, Yan

    2015-01-01

    Level set method has been widely used in medical image analysis, but it has difficulties when being used in the segmentation of left ventricular (LV) boundaries on echocardiography images because the boundaries are not very distinguish, and the signal-to-noise ratio of echocardiography images is not very high. In this paper, we introduce the Active Shape Model (ASM) into the traditional level set method to enforce shape constraints. It improves the accuracy of boundary detection and makes the evolution more efficient. The experiments conducted on the real cardiac ultrasound image sequences show a positive and promising result.

  11. Compressed sensing for reduction of noise and artefacts in direct PET image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Dominik; Israel, Ina; Schneider, Magdalena; Samnick, Samuel [Wuerzburg Univ. (Germany). Dept. of Nuclear Medicine; Basse-Luesebrink, Thomas C.; Kampf, Thomas; Jakob, Peter M. [Wuerzburg Univ. (Germany). Dept. of Experimental Physics 5; Fischer, Andre [Wuerzburg Univ. (Germany). Inst. of Radiology

    2014-03-01

    Aim: Image reconstruction in positron emission tomography (PET) can be performed using either direct or iterative methods. Direct reconstruction methods need a short reconstruction time. However, for data containing few counts, they often result in poor visual images with high noise and reconstruction artefacts. Iterative reconstruction methods such as ordered subset expectation maximization (OSEM) can lead to overestimation of activity in cold regions distorting quantitative analysis. The present work investigates the possibilities to reduce noise and reconstruction artefacts of direct reconstruction methods using compressed sensing (CS). Materials and methods: Raw data are generated either using Monte Carlo simulations using GATE or are taken from PET measurements with a Siemens Inveon small-animal PET scanner. The fully sampled dataset was reconstructed using filtered backprojection (FBP) and reduced in Fourier space by multiplication with an incoherently undersampled sampling pattern, followed by an additional reconstruction with CS. Different sampling patterns are used and an average of the reconstructions is taken. The images are compared to the results of an OSEM reconstruction and quantified using signal-to-noise ratio (SNR). Results: The application of the proposed CS post-processing technique clearly improves the image contrast. Dependent on the undersampling factor, noise and artefacts are reduced resulting in an SNR that is increased up to 3.4-fold. For short acquisition times with low count statistics the SNR of the CS reconstructed image exceeds the SNR of the OSEM reconstruction. Conclusion: Especially for low count data, the proposed CS-based post-processing method applied to FBP reconstructed PET images enhances the image quality significantly. (orig.)

  12. [Novel method of noise power spectrum measurement for computed tomography images with adaptive iterative reconstruction method].

    Science.gov (United States)

    Nishimaru, Eiji; Ichikawa, Katsuhiro; Hara, Takanori; Terakawa, Shoichi; Yokomachi, Kazushi; Fujioka, Chikako; Kiguchi, Masao; Ishifuro, Minoru

    2012-01-01

    Adaptive iterative reconstruction techniques (IRs) can decrease image noise in computed tomography (CT) and are expected to contribute to reduction of the radiation dose. To evaluate the performance of IRs, the conventional two-dimensional (2D) noise power spectrum (NPS) is widely used. However, when an IR provides an NPS value drop at all spatial frequency (which is similar to NPS changes by dose increase), the conventional method cannot evaluate the correct noise property because the conventional method does not correspond to the volume data natures of CT images. The purpose of our study was to develop a new method for NPS measurements that can be adapted to IRs. Our method utilized thick multi-planar reconstruction (MPR) images. The thick images are generally made by averaging CT volume data in a direction perpendicular to a MPR plane (e.g. z-direction for axial MPR plane). By using this averaging technique as a cutter for 3D-NPS, we can obtain adequate 2D-extracted NPS (eNPS) from 3D NPS. We applied this method to IR images generated with adaptive iterative dose reduction 3D (AIDR-3D, Toshiba) to investigate the validity of our method. A water phantom with 24 cm-diameters was scanned at 120 kV and 200 mAs with a 320-row CT (Acquilion One, Toshiba). From the results of study, the adequate thickness of MPR images for eNPS was more than 25.0 mm. Our new NPS measurement method utilizing thick MPR images was accurate and effective for evaluating noise reduction effects of IRs.

  13. Ensemble Empirical Mode Decomposition: Image Data Analysis with White-noise Reflection

    Directory of Open Access Journals (Sweden)

    M. Kopecký

    2010-01-01

    Full Text Available During the last decade, Zhaohua Wu and Norden E. Huang announced a new improvement of the original Empirical Mode Decomposition method (EMD. Ensemble Empirical Mode Decomposition and its abbreviation EEMD represents a major improvement with great versatility and robustness in noisy data filtering. EEMD consists of sifting and making an ensemble of a white noise-added signal, and treats the mean value as the final true result. This is due to the use of a finite, not infinitesimal, amplitude of white noise which forces the ensemble to exhaust all possible solutions in the sifting process. These steps collate signals of different scale in a proper intrinsic mode function (IMF dictated by the dyadic filter bank. As EEMD is a time–space analysis method, the added white noise is averaged out with a sufficient number of trials. Here, the only persistent part that survives the averaging process is the signal component (original data, which is then treated as the true and more physically meaningful answer. The main purpose of adding white noise was to provide a uniform reference frame in the time–frequency space. The added noise collates the portion of the signal of comparable scale in a single IMF. Image data taken as time series is a non-stationary and nonlinear process to which the new proposed EEMD method can be fitted out. This paper reviews the new approach of using EEMD and demonstrates its use on the example of image data analysis, making use of some advantages of the statistical characteristics of white noise. This approach helps to deal with omnipresent noise.

  14. A median-Gaussian filtering framework for Moiré pattern noise removal from X-ray microscopy image.

    Science.gov (United States)

    Wei, Zhouping; Wang, Jian; Nichol, Helen; Wiebe, Sheldon; Chapman, Dean

    2012-02-01

    Moiré pattern noise in Scanning Transmission X-ray Microscopy (STXM) imaging introduces significant errors in qualitative and quantitative image analysis. Due to the complex origin of the noise, it is difficult to avoid Moiré pattern noise during the image data acquisition stage. In this paper, we introduce a post-processing method for filtering Moiré pattern noise from STXM images. This method includes a semi-automatic detection of the spectral peaks in the Fourier amplitude spectrum by using a local median filter, and elimination of the spectral noise peaks using a Gaussian notch filter. The proposed median-Gaussian filtering framework shows good results for STXM images with the size of power of two, if such parameters as threshold, sizes of the median and Gaussian filters, and size of the low frequency window, have been properly selected.

  15. Load influence on gear noise. [mathematical model for determining acoustic pressure level as function of load

    Science.gov (United States)

    Merticaru, V.

    1974-01-01

    An original mathematical model is proposed to derive equations for calculation of gear noise. These equations permit the acoustic pressure level to be determined as a function of load. Application of this method to three parallel gears is reported. The logical calculation scheme is given, as well as the results obtained.

  16. Relationship between Acceptable Noise Level and the Abbreviated Profile of Hearing Aid Benefit

    Science.gov (United States)

    Freyaldenhoven, Melinda C.; Nabelek, Anna K.; Tampas, Joanna W.

    2008-01-01

    Purpose: This study investigated the relationship between acceptable noise levels (ANLs) and the Abbreviated Profile of Hearing Aid Benefit (APHAB; R. M. Cox & G. C. Alexander, 1995). This study further examined the APHAB's ability to predict hearing aid use. Method: ANL and APHAB data were collected for 191 listeners with impaired hearing,…

  17. Acceptance Noise Level: Effects of the Speech Signal, Babble, and Listener Language

    Science.gov (United States)

    Shi, Lu-Feng; Azcona, Gabrielly; Buten, Lupe

    2015-01-01

    Purpose: The acceptable noise level (ANL) measure has gained much research/clinical interest in recent years. The present study examined how the characteristics of the speech signal and the babble used in the measure may affect the ANL in listeners with different native languages. Method: Fifteen English monolingual, 16 Russian-English bilingual,…

  18. Totally confined explosive welding. [apparatus to reduce noise level and protect personnel during explosive bonding

    Science.gov (United States)

    Bement, L. J. (Inventor)

    1974-01-01

    A method and associated apparatus for confining the undesirable by-products and limiting noise of explosive welding are discussed. The apparatus consists fo a simple enclosure into which the explosive is placed and within which the explosion occurs. The shape of the enclosure, the placement of the explosive, and the manner in which the enclosure is placed upon the material to be welded determine the force of the explosion transmitted to the proposed bond area. The explosion is totally confined within the enclosure thus reducing the noise level and preventing debris from being strewn about to contaminate the weld area or create personnel hazards.

  19. Effect of external pressure environment on the internal noise level due to a source inside a cylindrical tank

    Science.gov (United States)

    Clevenson, S. A.; Roussos, L. A.

    1984-01-01

    A small cylindrical tank was used to study the effect on the noise environment within a tank of conditions of atmospheric (sea level) pressure or vacuum environments on the exterior. Experimentally determined absorption coefficients were used to calculate transmission loss, transmissibility coefficients and the sound pressure (noise) level differences in the interior. The noise level differences were also measured directly for the two exterior environments and compared to various analytical approximations with limited agreement. Trend study curves indicated that if the tank transmission loss is above 25 dB, the difference in interior noise level between the vacuum and ambient pressure conditions are less than 2 dB.

  20. Application of the local similarity filter for the suppression of multiplicative noise in medical ultrasound images

    Science.gov (United States)

    Kusnik, Damian; Smolka, Bogdan; Cyganek, Boguslaw

    2016-04-01

    In this paper we address the problem of the reduction of multiplicative noise in digital images. This kind of image distortion, also known as speckle noise, severely decreases the quality of medical ultrasound images and therefore their effective enhancement and restoration is of vital importance for proper visual inspection and quantitative measurements. The structure of the proposed Pixel-Patch Similarity Filter (PPSF) is a weighted average of pixels in a processing block and the weights are determined calculating the sum of squared differences between the mean of a patch and the intensities of pixels of the local window at the block center. The structure of the proposed design is similar to the bilateral and non-local means filters, however we neglect the topographic distance between pixels, which decreases substantially its computational complexity. The new technique was evaluated on standard gray scale test images contaminated with multiplicative noise modelled using Gaussian and uniform distribution. Its efficiency was also assessed utilizing a set of simulated ultrasonographic images distorted by means of the Field II simulation software and real ultrasound images of a finger joint. The comparison with the state-of-the-art techniques revealed very high efficiency of the proposed filtering framework, especially for strongly degraded images. Visually, the homogeneous areas are smoother, while image edges and small details are better preserved. The experiments have shown that satisfactory results were obtained with patches consisting of only 9 samples belonging to a relatively small processing block of 7x7 pixels, which ensures low computational complexity of the proposed denoising scheme and allows its application in real-time image processing scenarios.

  1. The effects of ipsilateral, contralateral, and bilateral broadband noise on the mid-level hump in intensity discrimination.

    Science.gov (United States)

    Roverud, Elin; Strickland, Elizabeth A

    2015-11-01

    Previous psychoacoustical and physiological studies indicate that the medial olivocochlear reflex (MOCR), a bilateral, sound-evoked reflex, may lead to improved sound intensity discrimination in background noise. The MOCR can decrease the range of basilar-membrane compression and can counteract effects of neural adaptation from background noise. However, the contribution of these processes to intensity discrimination is not well understood. This study examined the effect of ipsilateral, contralateral, and bilateral noise on the "mid-level hump." The mid-level hump refers to intensity discrimination Weber fractions (WFs) measured for short-duration, high-frequency tones which are poorer at mid levels than at lower or higher levels. The mid-level hump WFs may reflect a limitation due to basilar-membrane compression, and thus may be decreased by the MOCR. The noise was either short (50 ms) or long (150 ms), with the long noise intended to elicit the sluggish MOCR. For a tone in quiet, mid-level hump WFs improved with ipsilateral noise for most listeners, but not with contralateral noise. For a tone in ipsilateral noise, WFs improved with contralateral noise for most listeners, but only when both noises were long. These results are consistent with MOCR-induced WF improvements, possibly via decreases in effects of compression and neural adaptation.

  2. Locally homogenized and de-noised vector fields for cardiac fiber tracking in DT-MRI images

    Science.gov (United States)

    Akhbardeh, Alireza; Vadakkumpadan, Fijoy; Bayer, Jason; Trayanova, Natalia A.

    2009-02-01

    In this study we develop a methodology to accurately extract and visualize cardiac microstructure from experimental Diffusion Tensor (DT) data. First, a test model was constructed using an image-based model generation technique on Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) data. These images were derived from a dataset having 122x122x500 um3 voxel resolution. De-noising and image enhancement was applied to this high-resolution dataset to clearly define anatomical boundaries within the images. The myocardial tissue was segmented from structural images using edge detection, region growing, and level set thresholding. The primary eigenvector of the diffusion tensor for each voxel, which represents the longitudinal direction of the fiber, was calculated to generate a vector field. Then an advanced locally regularizing nonlinear anisotropic filter, termed Perona-Malik (PEM), was used to regularize this vector field to eliminate imaging artifacts inherent to DT-MRI from volume averaging of the tissue with the surrounding medium. Finally, the vector field was streamlined to visualize fibers within the segmented myocardial tissue to compare the results with unfiltered data. With this technique, we were able to recover locally regularized (homogenized) fibers with a high accuracy by applying the PEM regularization technique, particularly on anatomical surfaces where imaging artifacts were most apparent. This approach not only aides in the visualization of noisy complex 3D vector fields obtained from DT-MRI, but also eliminates volume averaging artifacts to provide a realistic cardiac microstructure for use in electrophysiological modeling studies.

  3. Reducing visitor noise levels at Muir Woods National Monument using experimental management.

    Science.gov (United States)

    Stack, David W; Peter, Newman; Manning, Robert E; Fristrup, Kurt M

    2011-03-01

    Noise impacts resources and visitor experience in many protected natural areas, and visitors can be the dominant source of noise. This experimental study tested the efficacy and acceptability of signs asking visitors to be quiet at Muir Woods National Monument, California. Signs declaring a "quiet zone" (at the park's Cathedral Grove) or a "quiet day" (throughout the park) were posted on a randomized schedule that included control days (no signs). Visitor surveys were conducted to measure the cognitive and behavioral responses of visitors to the signs and test the acceptability of these management practices to visitors. Visitors were highly supportive of these management practices and reported that they consciously limited the amount of noise they produced. Sound level measurements showed substantial decreases on days when signs were posted.

  4. High levels of sound pressure: acoustic reflex thresholds and auditory complaints of workers with noise exposure

    Directory of Open Access Journals (Sweden)

    Alexandre Scalli Mathias Duarte

    2015-08-01

    Full Text Available INTRODUCTION: The clinical evaluation of subjects with occupational noise exposure has been difficult due to the discrepancy between auditory complaints and auditory test results. This study aimed to evaluate the contralateral acoustic reflex thresholds of workers exposed to high levels of noise, and to compare these results to the subjects' auditory complaints.METHODS: This clinical retrospective study evaluated 364 workers between 1998 and 2005; their contralateral acoustic reflexes were compared to auditory complaints, age, and noise exposure time by chi-squared, Fisher's, and Spearman's tests.RESULTS: The workers' age ranged from 18 to 50 years (mean = 39.6, and noise exposure time from one to 38 years (mean = 17.3. We found that 15.1% (55 of the workers had bilateral hearing loss, 38.5% (140 had bilateral tinnitus, 52.8% (192 had abnormal sensitivity to loud sounds, and 47.2% (172 had speech recognition impairment. The variables hearing loss, speech recognition impairment, tinnitus, age group, and noise exposure time did not show relationship with acoustic reflex thresholds; however, all complaints demonstrated a statistically significant relationship with Metz recruitment at 3000 and 4000 Hz bilaterally.CONCLUSION: There was no significance relationship between auditory complaints and acoustic reflexes.

  5. Measuring the levels of noise at the İstanbul Atatürk Airport and comparisons with model simulations.

    Science.gov (United States)

    Sari, Deniz; Ozkurt, Nesimi; Akdag, Ali; Kutukoglu, Murat; Gurarslan, Aliye

    2014-06-01

    Airport noise and its impact on the surrounding areas are major issues in the aviation industry. The İstanbul Atatürk Airport is a major global airport with passenger numbers increasing rapidly per annum. The noise levels for day, evening and night times were modeled around the İstanbul Atatürk Airport according to the European Noise Directive using the actual data records for the year 2011. The "ECAC Doc. 29-Interim" method was used for the computation of the aircraft traffic noise. In the setting the noise model for the local airport topography was taken into consideration together with the noise source data, the airport loadings, features of aircraft and actual air traffic data. Model results were compared with long-term noise measurement values for calibration. According to calibration results, classifications of the aircraft type and flight tracks were revised. For noise model validation, the daily noise measurements at four additional locations were used during the verification period. The input data was re-edited only for these periods and the model was validated. A successful model performance was obtained in several zones around the airport. The validated noise model of the İstanbul Atatürk Airport can be now utilized both for determining the noise levels in the future and for producing new strategies which are about the land use planning, operational considerations for the air traffic management and the noise abatement procedures.

  6. Listening level of music through headphones in train car noise environments.

    Science.gov (United States)

    Shimokura, Ryota; Soeta, Yoshiharu

    2012-09-01

    Although portable music devices are useful for passing time on trains, exposure to music using headphones for long periods carries the risk of damaging hearing acuity. The aim of this study is to examine the listening level of music through headphones in the noisy environment of a train car. Eight subjects adjusted the volume to an optimum level (L(music)) in a simulated noisy train car environment. In Experiment I, the effects of noise level (L(train)) and type of train noise (rolling, squealing, impact, and resonance) were examined. Spectral and temporal characteristics were found to be different according to the train noise type. In Experiment II, the effects of L(train) and type of music (five vocal and five instrumental music) were examined. Each music type had a different pitch strength and spectral centroid, and each was evaluated by φ(1) and W(φ(0)), respectively. These were classified as factors of the autocorrelation function (ACF) of the music. Results showed that L(music) increased as L(train) increased in both experiments, while the type of music greatly influenced L(music). The type of train noise, however, only slightly influenced L(music). L(music) can be estimated using L(train) and the ACF factors φ(1) and W(φ(0)).

  7. Integrated Spectral Low Noise Image Sensor with Nanowire Polarization Filters for Low Contrast Imaging

    Science.gov (United States)

    2015-11-05

    filters and investigate their integration with the spectral image sensors. In addition, I will investigate image processing algorithms that will take...are composed of a 2D grid of heterogeneous imaging sensors. Current polarization imaging employ four different pixelated polarization filters ... filters and investigate their integration with the spectral image sensors. In addition, I will investigate image processing algorithms that will take

  8. A Comparative Land Use-Based Analysis of Noise Pollution Levels in Selected Urban Centers of Nigeria.

    Science.gov (United States)

    Baloye, David O; Palamuleni, Lobina G

    2015-09-29

    Growth in the commercialization, mobility and urbanization of human settlements across the globe has greatly exposed world urban population to potentially harmful noise levels. The situation is more disturbing in developing countries like Nigeria, where there are no sacrosanct noise laws and regulations. This study characterized noise pollution levels in Ibadan and Ile-Ife, two urban areas of Southwestern Nigeria that have experienced significant increases in population and land use activities. Eight hundred noise measurements, taken at 20 different positions in the morning, afternoon, and evening of carefully selected weekdays, in each urban area, were used for this study. Findings put the average noise levels in the urban centers at between 53 dB(A) and 89 dB (A), a far cry from the World Health Organization (WHO) permissible limits in all the land use types, with highest noise pollution levels recorded for transportation, commercial, residential and educational land use types. The result of the one-way ANOVA test carried out on the dependent variable noise and fixed factor land use types reveals a statistically significant mean noise levels across the study area (F(3,34) = 15.13, p = 0.000). The study underscores noise pollution monitoring and the urgent need to control urban noise pollution with appropriate and effective policies.

  9. What is the influence of background noise and exercise on the listening levels of iPod users?

    Science.gov (United States)

    Hodgetts, William; Szarko, Ryan; Rieger, Jana

    2009-12-01

    The widespread use of portable listening devices (PLDs) has increased concern about the potential for hearing impairment caused by their use. The current study investigated the effects of external noise and exercise on the use of PLDs. The 24 participants listened to the same song on an iPod during rest-in-quiet, rest-in-noise, and exercise-in-noise conditions. Preferred listening levels (PLLs) were recorded and participants' maximum noise doses were calculated. Participants selected significantly higher listening levels in both noise conditions than in the quiet condition. The variability of volume selection was reduced significantly in the noise conditions. The maximum daily noise dose would have been exceeded by seven participants in the rest-in-noise condition and by eight in the exercise-in-noise condition compared to one participant in the rest-in-quiet condition. These results indicated that increased background noise causes individuals to increase the volume on their PLDs to potentially dangerous levels and that increased noise alone was not the only factor affecting the participants as the addition of exercise induced even further increases in PLLs.

  10. The subjective importance of noise spectral content

    Science.gov (United States)

    Baxter, Donald; Phillips, Jonathan; Denman, Hugh

    2014-01-01

    This paper presents secondary Standard Quality Scale (SQS2) rankings in overall quality JNDs for a subjective analysis of the 3 axes of noise, amplitude, spectral content, and noise type, based on the ISO 20462 softcopy ruler protocol. For the initial pilot study, a Python noise simulation model was created to generate the matrix of noise masks for the softcopy ruler base images with different levels of noise, different low pass filter noise bandwidths and different band pass filter center frequencies, and 3 different types of noise: luma only, chroma only, and luma and chroma combined. Based on the lessons learned, the full subjective experiment, involving 27 observers from Google, NVIDIA and STMicroelectronics was modified to incorporate a wider set of base image scenes, and the removal of band pass filtered noise masks to ease observer fatigue. Good correlation was observed with the Aptina subjective noise study. The absence of tone mapping in the noise simulation model visibly reduced the contrast at high levels of noise, due to the clipping of the high levels of noise near black and white. Under the 34-inch viewing distance, no significant difference was found between the luma only noise masks and the combined luma and chroma noise masks. This was not the intuitive expectation. Two of the base images with large uniform areas, `restaurant' and `no parking', were found to be consistently more sensitive to noise than the texture rich scenes. Two key conclusions are (1) there are fundamentally different sensitivities to noise on a flat patch versus noise in real images and (2) magnification of an image accentuates visual noise in a way that is non-representative of typical noise reduction algorithms generating the same output frequency. Analysis of our experimental noise masks applied to a synthetic Macbeth ColorChecker Chart confirmed the color-dependent nature of the visibility of luma and chroma noise.

  11. 苹果采摘机器人夜间图像降噪算法%De-noising algorithm of night vision image for apple harvesting robot

    Institute of Scientific and Technical Information of China (English)

    贾伟宽; 赵德安; 阮承治; 沈甜; 陈玉; 姬伟

    2015-01-01

    captured, the noises are analyzed through the difference image method, and the type of noise is determined to be mixed noise. The main part of mixed noise is Gaussian noise, accompanied by some salt-pepper noise. Aiming at the problem of Gaussian noise removal, the theory of independent component analysis (ICA) is introduced into the de-noising method for night vision image. The ICA algorithm mostly uses gradient iterative solver, so it has some defects, such as easily trapped in local minimum, slow convergence speed. All of these defects lead to the following phenomena easily, such as the unthoroughness in the de-noising and the long running time. In order to overcome these defects, particle swarm optimization (PSO) algorithm is used to optimize the ICA, further to establish an optimized ICA de-noising method based on PSO (PSO-ICA), applied in night vision image, hoping to minimize noise pollution and improving the operating efficiency of de-noising method. Using the standard Lenna image and apple image captured under nature light, by the simulation experiments, these 2 pictures are added with the Gaussian noise with the variance of 0.05 and the salt-pepper noise with the P value of 0.05, respectively. Compared with the average filtering method and ICA de-noising method, the results show that the de-noising effect of PSO-ICA algorithm is the most ideal. Using peak signal-to-noise ratio (PSNR) to do difference test, the result shows that, under 0.05 significant level, 3 de-noising methods show significant difference. Using different apple night vision images captured to do experiments, the results show that, from the visual evaluation, the low noise image is obtained by PSO-ICA de-noising method, and its noise decreased significantly. In order to evaluate the de-noising effect of night vision image more objectively, taking the natural light image as reference, the concept of relative peak signal-to-noise ratio (RPSNR) is proposed. From the RPSNR evaluation, compared with

  12. A Survey of the Relationship Between Noised Pollution, Honey and Vitamin E and Plasma Level of Blood Sexual Hormones in Noise-Exposed Rats

    Directory of Open Access Journals (Sweden)

    Kenani

    2015-02-01

    Full Text Available Background This study was conducted to examine the efficacy of honey and vitamin E on fertilization capacity of noise-exposed rats by assessing whether the plasma sexual hormones levels i.e. follicle stimulating hormone (FSH, luteinizing hormone (LH and testosterone are altered in relation with noise stress. Objectives Therefore, this study aimed to evaluate the effects of honey and vitamin E on the levels of sex hormones and male fertilization capacity of noise-exposed rats. Materials and Methods This study targeted 24 male rats that were randomly divided into four equal groups including the control group that were not exposed to noise and experimental groups 1, 2 and 3 that were the untreated, honey treated and vitamin E treated groups, respectively; all of which were exposed to noise for 50 days. Next, in order to measure serum sexual hormones, blood samples of experimental and control groups were taken and analyzed. Also in order to investigate the fertility capacity of rats, the male rats of all groups were coupled with female rats. Results The results showed that in the male rats exposed to the noise stress, the levels of FSH and LH rose and the testosterone secretion fell sharply compared to not exposed rats. Additionally, the continuing effects of noise stress injury could reduce the weight of the fetus and the number of live fetuses and survival rate of the fetus. However, honey and vitamin E improved serum testosterone concentration, while declined plasma FSH and LH secretion in noise-exposed rats and enhanced fertility rate by increasing the rate of healthy alive fetuses. Conclusions It seems that noise pollution has harmful effects on the fertility of males. Also these findings may suggest the use of a natural curative approach rather than pharmaceutical drugs to optimize both neuroendocrine gonadal axis and testicular integrity induced by pathogenesis stress, and enhance fertility capacity in men.

  13. Retinal Fundus Image Enhancement Using the Normalized Convolution and Noise Removing

    OpenAIRE

    Peishan Dai; Hanwei Sheng; Jianmei Zhang; Ling Li; Jing Wu; Min Fan

    2016-01-01

    Retinal fundus image plays an important role in the diagnosis of retinal related diseases. The detailed information of the retinal fundus image such as small vessels, microaneurysms, and exudates may be in low contrast, and retinal image enhancement usually gives help to analyze diseases related to retinal fundus image. Current image enhancement methods may lead to artificial boundaries, abrupt changes in color levels, and the loss of image detail. In order to avoid these side effects, a new ...

  14. Spatial resolution, signal-to-noise and information capacity of linear imaging systems

    CERN Document Server

    Gureyev, Timur

    2015-01-01

    A simple model for image formation in linear shift-invariant systems is considered, in which both the detected signal and the noise variance are almost constant over distances comparable with the width of the point-spread function of the system. It is shown that within the constraints of this model, the square of the signal-to-noise ratio is always proportional to the "volume" of the spatial resolution unit. The ratio of these two quantities divided by the incident density of the imaging particles (e.g. photons) represents a dimensionless invariant of the imaging system, which was previously termed the intrinsic imaging quality. This invariant is related to the notion of information capacity of imaging and communication systems as previously considered by Shannon, Gabor and others. It is demonstrated that the information capacity expressed in bits cannot exceed the total number of imaging particles utilised in the system. These results are then applied to a simple generic model of quantitative imaging and ana...

  15. Noise reduction in computed tomography using a multiplicative continuous-time image reconstruction method

    Science.gov (United States)

    Yamaguchi, Yusaku; Kojima, Takeshi; Yoshinaga, Tetsuya

    2016-03-01

    In clinical X-ray computed tomography (CT), filtered back-projection as a transform method and iterative reconstruction such as the maximum-likelihood expectation-maximization (ML-EM) method are known methods to reconstruct tomographic images. As the other reconstruction method, we have presented a continuous-time image reconstruction (CIR) system described by a nonlinear dynamical system, based on the idea of continuous methods for solving tomographic inverse problems. Recently, we have also proposed a multiplicative CIR system described by differential equations based on the minimization of a weighted Kullback-Leibler divergence. We prove theoretically that the divergence measure decreases along the solution to the CIR system, for consistent inverse problems. In consideration of the noisy nature of projections in clinical CT, the inverse problem belongs to the category of ill-posed problems. The performance of a noise-reduction scheme for a new (previously developed) CIR system was investigated by means of numerical experiments using a circular phantom image. Compared to the conventional CIR and the ML-EM methods, the proposed CIR method has an advantage on noisy projection with lower signal-to-noise ratios in terms of the divergence measure on the actual image under the same common measure observed via the projection data. The results lead to the conclusion that the multiplicative CIR method is more effective and robust for noise reduction in CT compared to the ML-EM as well as conventional CIR methods.

  16. Through-wall imaging and characterization of human activity using ultrawideband (UWB) random noise radar

    Science.gov (United States)

    Lai, Chieh-Ping; Narayanan, Ram M.

    2005-05-01

    Recent terrorist activities and law-enforcement situations involving hostage situations underscore the need for effective through-wall imaging. Current building interior imaging systems are based on short-pulse waveforms, which require specially designed antennas to subdue unwanted ringing. In addition, periodically transmitted pulses of energy are easily recognizable by the intelligent adversary who may employ appropriate countermeasures to confound detection. A coherent polarimetric random noise radar architecture is being developed based on UWB technology and software defined radio, which has great promise in its ability to covertly image obscured targets. The main advantages of the random noise radar lie in two aspects: first, random noise waveform has an ideal "thumbtack" ambiguity function, i.e., its down range and cross range resolution can be separately controlled, thus providing unambiguous high resolution imaging at any distance; second, random noise waveform is inherently low probability of intercept (LPI) and low probability of detection (LPD), i.e., it is immune from detection, jamming, and interference. Thus, it is an ideal candidate sensor for covert imaging of obscured regions in hostile environments. The coherency in the system can be exploited to field a fully-polarimetric system that can take advantage of polarization features in target recognition. Moving personnel can also be detected using Doppler processing. Simulation studies are used to analyze backscattered signals from the walls, and humans and other targets behind the walls. Real-time data processing shows human activity behind the wall and human target tracking. The high resolution provides excellent multipath and clutter rejection.

  17. Do outdoor environmental noise and atmospheric NO2 levels spatially overlap in urban areas?

    Science.gov (United States)

    Tenailleau, Quentin M; Bernard, Nadine; Pujol, Sophie; Parmentier, Anne-Laure; Boilleaut, Mathieu; Houot, Hélène; Joly, Daniel; Mauny, Frédéric

    2016-07-01

    The urban environment holds numerous emission sources for air and noise pollution, creating optimum conditions for environmental multi-exposure situations. Evaluation of the joint-exposure levels is the main obstacle for multi-exposure studies and one of the biggest challenges of the next decade. The present study aims to describe the noise/NO2 multi-exposure situations in the urban environment by exploring the possible discordant and concordant situations of both exposures. Fine-scale diffusion models were developed in the European medium-sized city of Besançon (France), and a classification method was used to evaluate the multi-exposure situations in the façade perimeter of 10,825 buildings. Although correlated (Pearson's r = 0.64, p noise and NO2 around buildings do not overlap, and 30% of the buildings were considered to be discordant in terms of the noise and NO2 exposure levels. This discrepancy is spatially structured and associated with variables describing the building's environment. Our results support the presence of several co-existing, multi-exposure situations across the city impacted by both the urban morphology and the emission and diffusion/propagation phases of each pollutant. Identifying the mechanisms of discrepancy and convergence of multi-exposure situations could help improve the health risk assessment and public health.

  18. Effects of image noise, respiratory motion, and motion compensation on 3D activity quantification in count-limited PET images

    Science.gov (United States)

    Siman, W.; Mawlawi, O. R.; Mikell, J. K.; Mourtada, F.; Kappadath, S. C.

    2017-01-01

    The aims of this study were to evaluate the effects of noise, motion blur, and motion compensation using quiescent-period gating (QPG) on the activity concentration (AC) distribution—quantified using the cumulative AC volume histogram (ACVH)—in count-limited studies such as 90Y-PET/CT. An International Electrotechnical Commission phantom filled with low 18F activity was used to simulate clinical 90Y-PET images. PET data were acquired using a GE-D690 when the phantom was static and subject to 1-4 cm periodic 1D motion. The static data were down-sampled into shorter durations to determine the effect of noise on ACVH. Motion-degraded PET data were sorted into multiple gates to assess the effect of motion and QPG on ACVH. Errors in ACVH at AC90 (minimum AC that covers 90% of the volume of interest (VOI)), AC80, and ACmean (average AC in the VOI) were characterized as a function of noise and amplitude before and after QPG. Scan-time reduction increased the apparent non-uniformity of sphere doses and the dispersion of ACVH. These effects were more pronounced in smaller spheres. Noise-related errors in ACVH at AC20 to AC70 were smaller (15%). The accuracy of ACmean was largely independent of the total count. Motion decreased the observed AC and skewed the ACVH toward lower values; the severity of this effect depended on motion amplitude and tumor diameter. The errors in AC20 to AC80 for the 17 mm sphere were  -25% and  -55% for motion amplitudes of 2 cm and 4 cm, respectively. With QPG, the errors in AC20 to AC80 of the 17 mm sphere were reduced to  -15% for motion amplitudes  0.5, QPG was effective at reducing errors in ACVH despite increases in image non-uniformity due to increased noise. ACVH is believed to be more relevant than mean or maximum AC to calculate tumor control and normal tissue complication probability. However, caution needs to be exercised when using ACVH in post-therapy 90Y imaging because of its susceptibility to image

  19. Design method of automotive powertrain mounting system based on vibration and noise limitations of vehicle level

    Science.gov (United States)

    Shangguan, Wen-Bin; Liu, Xiao-Ang; Lv, Zhao-Ping; Rakheja, Subhash

    2016-08-01

    The design logic and calculation method for determining mount stiffness and damping for a Powertrain Mounting System (PMS) based on reductions of vehicle vibration and noise contributed by mounts is proposed in this paper. Firstly, the design target for a PMS with regard to vibration and noise limitations of vehicle level contributed form mounts is described. Then a vehicle model with 13 Degree of Freedoms (DOFs) is proposed, which includes 6DOFs for the powertrain, 3 DOFs for the car body and 4DOFs for the four unsprung mass, and the dynamic equation for the model is derived. Some widely used models, such as the 6 DOFs model of the powertrain for the design calculation of a PMS, the 7 DOFs model (Body's 3 DOFs; unsprung mass's 4 DOFs) and the 9 DOFs model (powertrain's 6 DOFs; Body's 3 DOFs) for ride analysis of a vehicle, are the specific cases of the presented model of 13 DOF. Thirdly, the calculation method for obtaining the vibration of seat track and evaluation point and the noise at driver right ear is presented based on the mount forces and the vibration and noise transfer functions. An optimization process is proposed to get the mount stiffness and damping based on minimization of vehicle vibration and noise, and the optimized stiffness is validated by comparing the calculated vibration and noise and limitations. In the end of this paper, the natural frequencies and mode energies for the powertrain, the body and the unsprung mass are calculated using different models and the results are compared and analyzed.

  20. Critical assessment of day time traffic noise level at curbside open-air microenvironment of Kolkata City, India.

    Science.gov (United States)

    Kundu Chowdhury, Anirban; Debsarkar, Anupam; Chakrabarty, Shibnath

    2015-01-01

    The objective of the research work is to assess day time traffic noise level at curbside open-air microenvironment of Kolkata city, India under heterogeneous environmental conditions. Prevailing traffic noise level in terms of A-weighted equivalent noise level (Leq) at the microenvironment was in excess of 12.6 ± 2.1 dB(A) from the day time standard of 65 dB(A) for commercial area recommended by the Central Pollution Control Board (CPCB) of India. Noise Climate and Traffic Noise Index of the microenvironment were accounted for 13 ± 1.8 dB(A) and 88.8 ± 6.1 dB(A) respectively. A correlation analysis explored that prevailing traffic noise level of the microenvironment had weak negative (-0.21; p microenvironment of Kolkata City was higher than the standard recommended by CPCB of India. It was highly annoying also. Air temperature and relative humidity had little influence and the peak noise component had the most significant influence on the prevailing traffic noise level at curbside open-air microenvironment. Therefore, traffic noise level at the microenvironment of the city can be reduced with careful honking and driving.

  1. In-Flight Evaluation of Noise Levels and Assessment of Active Noise Reduction Systems in the Seahawk S-70B-2 Helicopter

    Science.gov (United States)

    1992-11-01

    Library Qantas Airways Limited Civil Aviation Authority Gas & Fuel Corporation of Vic., Manager Scientific Services Ampol Petroleum (Vic) Pty Ltd...Aircraft 3 2.3 Recording and Measurement System 5 2.4 Analysis Equipment 5 2.5 Test Procedure 5 3. RESULTS 7 3.1 Ambient Noise Levels in the S-70B-2 7...using spectral analysis techniques to determine the acoustic characteristics of this noise, b) measuring at-ear SPLs under the ALPHA helmet and

  2. An Interactive Procedure to Preserve the Desired Edges during the Image Processing of Noise Reduction

    Directory of Open Access Journals (Sweden)

    Huang Hsuan-Yu

    2010-01-01

    Full Text Available The paper propose a new procedure including four stages in order to preserve the desired edges during the image processing of noise reduction. A denoised image can be obtained from a noisy image at the first stage of the procedure. At the second stage, an edge map can be obtained by the Canny edge detector to find the edges of the object contours. Manual modification of an edge map at the third stage is optional to capture all the desired edges of the object contours. At the final stage, a new method called Edge Preserved Inhomogeneous Diffusion Equation (EPIDE is used to smooth the noisy images or the previously denoised image at the first stage for achieving the edge preservation. The Optical Character Recognition (OCR results in the experiments show that the proposed procedure has the best recognition result because of the capability of edge preservation.

  3. Non-Uniform Contrast and Noise Correction for Coded Source Neutron Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Santos-Villalobos, Hector J [ORNL; Bingham, Philip R [ORNL

    2012-01-01

    Since the first application of neutron radiography in the 1930s, the field of neutron radiography has matured enough to develop several applications. However, advances in the technology are far from concluded. In general, the resolution of scintillator-based detection systems is limited to the $10\\mu m$ range, and the relatively low neutron count rate of neutron sources compared to other illumination sources restricts time resolved measurement. One path toward improved resolution is the use of magnification; however, to date neutron optics are inefficient, expensive, and difficult to develop. There is a clear demand for cost-effective scintillator-based neutron imaging systems that achieve resolutions of $1 \\mu m$ or less. Such imaging system would dramatically extend the application of neutron imaging. For such purposes a coded source imaging system is under development. The current challenge is to reduce artifacts in the reconstructed coded source images. Artifacts are generated by non-uniform illumination of the source, gamma rays, dark current at the imaging sensor, and system noise from the reconstruction kernel. In this paper, we describe how to pre-process the coded signal to reduce noise and non-uniform illumination, and how to reconstruct the coded signal with three reconstruction methods correlation, maximum likelihood estimation, and algebraic reconstruction technique. We illustrates our results with experimental examples.

  4. PERFORMANCE ANALYSIS OF A MODIFIED DECOMPOSITION FILTER FOR NON IDENTICAL NOISES

    Directory of Open Access Journals (Sweden)

    K. Vasanth

    2010-11-01

    Full Text Available The proposed work aims in the restoration of images corrupted by Gaussian noise, impulse noise. The new algorithm significantly removes different noises and produce better image quality than standard median filter (SMF, Centre weighted median filter (CWF and threshold decomposition filter (TDF.The proposed algorithm (PA is tested on different images corrupted by all two noises and is found to produce better results in terms of the qualitative and quantitative measures of the image for noise densities up to 30% noise level for impulse noise, mean zero and 0.9% variance of Gaussian noise. The filter works well for speckle noise up to 0.8% variance.

  5. Particle image velocimetry correlation signal-to-noise ratio metrics and measurement uncertainty quantification

    CERN Document Server

    Xue, Zhenyu; Vlachos, Pavlos P

    2014-01-01

    In particle image velocimetry (PIV) the measurement signal is contained in the recorded intensity of the particle image pattern superimposed on a variety of noise sources. The signal-to-noise-ratio (SNR) strength governs the resulting PIV cross correlation and ultimately the accuracy and uncertainty of the resulting PIV measurement. Hence we posit that correlation SNR metrics calculated from the correlation plane can be used to quantify the quality of the correlation and the resulting uncertainty of an individual measurement. In this paper we present a framework for evaluating the correlation SNR using a set of different metrics, which in turn are used to develop models for uncertainty estimation. The SNR metrics and corresponding models presented herein are expanded to be applicable to both standard and filtered correlations. In addition, the notion of a valid measurement is redefined with respect to the correlation peak width in order to be consistent with uncertainty quantification principles and distinct ...

  6. Hand Depth Image Denoising and Superresolution via Noise-Aware Dictionaries

    Directory of Open Access Journals (Sweden)

    Huayang Li

    2016-01-01

    Full Text Available This paper proposes a two-stage method for hand depth image denoising and superresolution, using bilateral filters and learned dictionaries via noise-aware orthogonal matching pursuit (NAOMP based K-SVD. The bilateral filtering phase recovers singular points and removes artifacts on silhouettes by averaging depth data using neighborhood pixels on which both depth difference and RGB similarity restrictions are imposed. The dictionary learning phase uses NAOMP for training dictionaries which separates faithful depth from noisy data. Compared with traditional OMP, NAOMP adds a residual reduction step which effectively weakens the noise term within the residual during the residual decomposition in terms of atoms. Experimental results demonstrate that the bilateral phase and the NAOMP-based learning dictionaries phase corporately denoise both virtual and real depth images effectively.

  7. Measures for the reduction of the noise and vibration level of apartment house elevators. [changes in construction and insulation measures

    Science.gov (United States)

    Enescu, N.; Munteanu, M.; Stan, A.

    1974-01-01

    The reduction of the level of elevator noise and vibrations in apartment buildings was studied. By improving the mounting and gearing conditions of the winch and soundproofing the winch chamber, as well as by covering the elevator's control panel, the noise and vibration level was appreciably reduced.

  8. A novel breast ultrasound image segmentation algorithm based on neutrosophic similarity score and level set.

    Science.gov (United States)

    Guo, Yanhui; Şengür, Abdulkadir; Tian, Jia-Wei

    2016-01-01

    Breast ultrasound (BUS) image segmentation is a challenging task due to the speckle noise, poor quality of the ultrasound images and size and location of the breast lesions. In this paper, we propose a new BUS image segmentation algorithm based on neutrosophic similarity score (NSS) and level set algorithm. At first, the input BUS image is transferred to the NS domain via three membership subsets T, I and F, and then, a similarity score NSS is defined and employed to measure the belonging degree to the true tumor region. Finally, the level set method is used to segment the tumor from the background tissue region in the NSS image. Experiments have been conducted on a variety of clinical BUS images. Several measurements are used to evaluate and compare the proposed method's performance. The experimental results demonstrate that the proposed method is able to segment the BUS images effectively and accurately. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  9. Multi-spectral image enhancement algorithm based on keeping original gray level

    Science.gov (United States)

    Wang, Tian; Xu, Linli; Yang, Weiping

    2016-11-01

    Characteristics of multi-spectral imaging system and the image enhancement algorithm are introduced.Because histogram equalization and some other image enhancement will change the original gray level,a new image enhancement algorithm is proposed to maintain the gray level.For this paper, we have chosen 6 narrow-bands multi-spectral images to compare,the experimental results show that the proposed method is better than those histogram equalization and other algorithm to multi-spectral images.It also insures that histogram information contained in original features is preserved and guarantees to make use of data class information.What's more,on the combination of subjective and objective sharpness evaluation,details of the images are enhanced and noise is weaken.

  10. Conversion of mammographic images to appear with the noise and sharpness characteristics of a different detector and x-ray system

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, Alistair; Dance, David R.; Workman, Adam; Yip, Mary; Wells, Kevin; Young, Kenneth C. [National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Northern Ireland Regional Medical Physics Service, Forster Green Hospital, Belfast, BT8 4HD (United Kingdom); Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom); Centre for Vision, Speech and Signal Processing, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, GU2 7XH (United Kingdom); National Coordinating Centre for the Physics of Mammography, Royal Surrey County Hospital, Guildford, GU2 7XX, United Kingdom and Department of Physics, University of Surrey, Guildford, GU2 7XH (United Kingdom)

    2012-05-15

    validated by acquiring images of a CDMAM contrast detail test object (Artinis, The Netherlands) at five different doses for the three systems. The ASE CDMAM images were then converted to appear with the imaging characteristics of target CR and CSI detectors. Results: The measured threshold gold thicknesses of the simulated and target CDMAM images were closely matched at normal dose level and the average differences across the range of detail diameters were -4% and 0% for the CR and CSI systems, respectively. The conversion was successful for images acquired over a wide dose range. The average difference between simulated and target images for a given dose was a maximum of 11%. Conclusions: The validation shows that the image quality of a digital mammography image obtained with a particular system can be degraded, in terms of noise magnitude and color, sharpness, and contrast to account for differences in the detector and antiscatter grid. Potentially, this is a powerful tool for observer studies, as a range of image qualities can be examined by modifying an image set obtained at a single (better) image quality thus removing the patient variability when comparing systems.

  11. Estimation of background noise level on seismic station using statistical analysis for improved analysis accuracy

    Science.gov (United States)

    Han, S. M.; Hahm, I.

    2015-12-01

    We evaluated the background noise level of seismic stations in order to collect the observation data of high quality and produce accurate seismic information. Determining of the background noise level was used PSD (Power Spectral Density) method by McNamara and Buland (2004) in this study. This method that used long-term data is influenced by not only innate electronic noise of sensor and a pulse wave resulting from stabilizing but also missing data and controlled by the specified frequency which is affected by the irregular signals without site characteristics. It is hard and inefficient to implement process that filters out the abnormal signal within the automated system. To solve these problems, we devised a method for extracting the data which normally distributed with 90 to 99% confidence intervals at each period. The availability of the method was verified using 62-seismic stations with broadband and short-period sensors operated by the KMA (Korea Meteorological Administration). Evaluation standards were NHNM (New High Noise Model) and NLNM (New Low Noise Model) published by the USGS (United States Geological Survey). It was designed based on the western United States. However, Korean Peninsula surrounded by the ocean on three sides has a complicated geological structure and a high population density. So, we re-designed an appropriate model in Korean peninsula by statistically combined result. The important feature is that secondary-microseism peak appeared at a higher frequency band. Acknowledgements: This research was carried out as a part of "Research for the Meteorological and Earthquake Observation Technology and Its Application" supported by the 2015 National Institute of Meteorological Research (NIMR) in the Korea Meteorological Administration.

  12. Reflection seismic imaging of a hydraulically conductive fracture zone in a high noise area, Forsmark, Sweden

    Science.gov (United States)

    Juhlin, C.; Stephens, M. B.; Cosma, C.

    2007-05-01

    High resolution reflection seismic methods have proven to be useful tools for locating fracture zones in crystalline rock. Siting of potential high-level nuclear waste repositories is a particularly important application of these methods. By using small explosive sources (15-75 grams), high resolution images of the sub-surface have been obtained in the depth range 100 m to 2 km in Sweden, Canada and elsewhere. Although ambient noise conditions in areas such as the Fennoscandian and Canadian shields are generally low, industrial noise can be high in some areas, particularly at potential sites suitable for repositories, since these are often close to existing infrastructure. In addition, the presence of this infrastructure limits the choice of sources available to the geophysicist. Forsmark, located about 140 km north of Stockholm, is one such potential site where reflection seismics have been carried out. Existing infrastructure includes nuclear reactors for power generation and a low- level waste repository. In the vicinity of the reactors, it was not possible to use an explosive source due to permitting restrictions. Instead, a VIBSIST system consisting of a tractor mounted hydraulic hammer was used in the vicinity of the reactors. By repeatedly hitting the pavement, without breaking it, at predefined sweeps and then stacking the signals, shot records comparable to explosive data could be generated. These shot records were then processed using standard methods to produce stacked sections along 3 profiles within the reactor area. Clear reflections are seen in the uppermost 600 m along 3 of these profiles. Correlation of crossing profiles shows that the strongest reflection (B8) is generated by a gently east-southeast dipping interface. Prior to construction of the reactors, several boreholes were drilled to investigate the bedrock in the area. One of these boreholes was located close to where two of the profiles cross. Projection of the B8 reflection into the

  13. Background noise levels and correlation with ship traffic in the Gulf of Catania

    Science.gov (United States)

    Viola, Salvatore; Buscaino, Giuseppa; Caruso, Francesco; Chierici, Francesco; Embriaco, Davide; Favali, Paolo; Giovanetti, Gabriele; Grammauta, Roasario; Larosa, Giuseppina; Pavan, Gianni; Pellegrino, Carmelo; Pulvirenti, Sara; Riccobene, Giorgio; Sciacca, Virginia; Simeone, Francesco; Beranzoli, Laura; Marinaro, Giuditta

    2015-04-01

    In the last decades the growing interest in the evaluation of the underwater acoustic noise for studies in the fields of geology, biology and high-energy physics is driving the scientific community to collaborate towards a multidisciplinary approach to the topic. In June 2012 in the framework of the European project EMSO, a multidisciplinary underwater observatory, named NEMO-SN1, was installed 25 km off-shore the port of Catania, at a depth of 2100 m and operated until May 2013 by INFN (Istituto Nazionale di Fisica Nucleare) and INGV (Istituto Nazionale di Geofisica e Vulcanologia). NEMO-SN1 hosted aboard geophysical, oceanographic and acoustic sensors: among these a seismic hydrophone model SMID DT-405D(V). In this work, conducted within the activity of the SMO project, the results on the evaluation of the underwater acoustic pollution in the Gulf of Catania through SMID DT-405D(V) recordings are presented. The seismic hydrophone provided a data set of about 11 months of continuous (24/7) recordings. Underwater sounds have been continuously digitized at a sampling frequency of 2 kHz and the acquired data have been stored in 10min long files for off-line analysis. To describe one-year background noise levels, the mean integrated acoustic noise was measured every second (sampling frequency 2000, NFFT 2048) in the 1/3 octave bands with centre frequency 63 Hz and for each 10 minutes-long file the 5th, the 50th and the 98th percentiles were calculated. Measured noise was correlated with the shipping traffic in the area, thanks to the data provided by an AIS receiver installed at the INFN-Laboratori Nazionali del Sud. An acoustic noise increment was measured in coincidence with the passing of crafts in the area and it was possible to identify the characteristic spectrum of each ship. A simple model for the estimation of the acoustic noise induced by the ships passing through the area was developed. The model was applied by using AIS data acquired during the operation

  14. Classification of Partial Discharge Measured under Different Levels of Noise Contamination.

    Science.gov (United States)

    Jee Keen Raymond, Wong; Illias, Hazlee Azil; Abu Bakar, Ab Halim

    2017-01-01

    Cable joint insulation breakdown may cause a huge loss to power companies. Therefore, it is vital to diagnose the insulation quality to detect early signs of insulation failure. It is well known that there is a correlation between Partial discharge (PD) and the insulation quality. Although many works have been done on PD pattern recognition, it is usually performed in a noise free environment. Also, works on PD pattern recognition in actual cable joint are less likely to be found in literature. Therefore, in this work, classifications of actual cable joint defect types from partial discharge data contaminated by noise were performed. Five cross-linked polyethylene (XLPE) cable joints with artificially created defects were prepared based on the defects commonly encountered on site. Three different types of input feature were extracted from the PD pattern under artificially created noisy environment. These include statistical features, fractal features and principal component analysis (PCA) features. These input features were used to train the classifiers to classify each PD defect types. Classifications were performed using three different artificial intelligence classifiers, which include Artificial Neural Networks (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS) and Support Vector Machine (SVM). It was found that the classification accuracy decreases with higher noise level but PCA features used in SVM and ANN showed the strongest tolerance against noise contamination.

  15. Computer-assisted scan protocol and reconstruction (CASPAR)-reduction of image noise and patient dose.

    Science.gov (United States)

    Sperl, Jonathan; Beque, Dirk; Claus, Bernhard; De Man, Bruno; Senzig, Bob; Brokate, Martin

    2010-03-01

    X-ray computed tomography is a powerful medical imaging device. It allows high-resolution 3-D visualization of the human body. However, one drawback is the health risk associated with ionizing radiation. Simply downscaling the radiation intensities over the entire scan results in increased quantum noise. This paper proposes the concept of computer-assisted scan protocol and reconstruction. More specifically, we propose a method to compute patient and task-specific intensity profiles that achieve an optimal tradeoff between radiation dose and image quality. Therefore, reasonable image variance and dose metrics are derived. Conventional third-generation systems as well as inverted geometry concepts are considered. Two dose/noise minimization problems are formulated and solved by an efficient algorithm providing optimized milliampere (mA)-profiles. Thorax phantom simulations demonstrate the promising advantage of this technique: in this particular example, the dose is reduced by 53% for third-generation systems and by 86% for an inverted geometry in comparison to a sinusoidal mA-profile at a constant upper noise limit.

  16. Chronic exposure to low frequency noise at moderate levels causes impaired balance in mice.

    Directory of Open Access Journals (Sweden)

    Haruka Tamura

    Full Text Available We are routinely exposed to low frequency noise (LFN; below 0.5 kHz at moderate levels of 60-70 dB sound pressure level (SPL generated from various sources in occupational and daily environments. LFN has been reported to affect balance in humans. However, there is limited information about the influence of chronic exposure to LFN at moderate levels for balance. In this study, we investigated whether chronic exposure to LFN at a moderate level of 70 dB SPL affects the vestibule, which is one of the organs responsible for balance in mice. Wild-type ICR mice were exposed for 1 month to LFN (0.1 kHz and high frequency noise (HFN; 16 kHz at 70 dB SPL at a distance of approximately 10-20 cm. Behavior analyses including rotarod, beam-crossing and footprint analyses showed impairments of balance in LFN-exposed mice but not in non-exposed mice or HFN-exposed mice. Immunohistochemical analysis showed a decreased number of vestibular hair cells and increased levels of oxidative stress in LFN-exposed mice compared to those in non-exposed mice. Our results suggest that chronic exposure to LFN at moderate levels causes impaired balance involving morphological impairments of the vestibule with enhanced levels of oxidative stress. Thus, the results of this study indicate the importance of considering the risk of chronic exposure to LFN at a moderate level for imbalance.

  17. A New Algorithm for Detecting the Transition Region on Noise Image

    Institute of Scientific and Technical Information of China (English)

    Wang Hui; Luo Jianping

    2003-01-01

    An algorithm of ramp width reduction based on the gray information of neighborhood pixels is proposed, which can sharpen the ramp edge effectively Then, a new gray-weighted gradient operator and the automatic method to determine its parameter are introduced when detecting the transition region of images. Gray-weighted gradient operator can not only make the correlation of gradient and gray information as big as possible, but also resist the noise in the images. Some experiments show that the algorithm in this paper can extract the transition regaon more effectively.

  18. [The image noise effect on the results of Gamma knife dosimetry parameters test].

    Science.gov (United States)

    Cheng, Xiaojun; Zhang, Conghua; Hu, Chuanpeng; Dai, Fuyou; Wei, Kunjie; Chu, Caifang

    2012-12-01

    In order to analyze the image noise effect on the results of Gamma knife dosimetry parameter test, we tested the dosimetry parameters of the Gamma knives according to GBZ 168-2005. Radiological protection standards of X (gamma)-ray stereotactic radiosurgery for head treatment. Dose analysis software was applied to examine the testing film before and after image denoising, and SPSS 11.0 software was used for statistical analysis. The results showed that there was a significant difference in the results of the maximum deviation between radiation field size and its nominal value (t = 7.600, P Gamma knife dosimetry parameters, so as to cause deviations.

  19. Phase noise from aircraft motion: Compensation and effect on synthetic aperture radar images

    Science.gov (United States)

    Gabriel, Andrew K.; Goldstein, Richard M.

    1986-01-01

    Image degradation of airborne SAR imagery caused by phase errors introduced in the received signal by aircraft motion is discussed. Mechanical motion has a small bandwidth and does not affect the range signal, where the total echo time is typically 60 microsec. However, since the aperture length can be several seconds, the synthesized azimuth signal can have significant errors of which phase noise is the most important. An inertial navigation system can be used to compensate for these errors when processing the images. Calculations to evaluate how much improvement results from compensation are outlined.

  20. Images crossing borders: image and workflow sharing on multiple levels.

    Science.gov (United States)

    Ross, Peeter; Pohjonen, Hanna

    2011-04-01

    Digitalisation of medical data makes it possible to share images and workflows between related parties. In addition to linear data flow where healthcare professionals or patients are the information carriers, a new type of matrix of many-to-many connections is emerging. Implementation of shared workflow brings challenges of interoperability and legal clarity. Sharing images or workflows can be implemented on different levels with different challenges: inside the organisation, between organisations, across country borders, or between healthcare institutions and citizens. Interoperability issues vary according to the level of sharing and are either technical or semantic, including language. Legal uncertainty increases when crossing national borders. Teleradiology is regulated by multiple European Union (EU) directives and legal documents, which makes interpretation of the legal system complex. To achieve wider use of eHealth and teleradiology several strategic documents were published recently by the EU. Despite EU activities, responsibility for organising, providing and funding healthcare systems remains with the Member States. Therefore, the implementation of new solutions requires strong co-operation between radiologists, societies of radiology, healthcare administrators, politicians and relevant EU authorities. The aim of this article is to describe different dimensions of image and workflow sharing and to analyse legal acts concerning teleradiology in the EU.

  1. Fundamental Noise-Limited Optical Phase Locking at Femtowatt Light Levels

    Science.gov (United States)

    Dick, John; Tu, Meirong; Birnbaum, Kevin; Strekalov, Dmitry; Yu, Nan

    2008-01-01

    We describe an optical phase lock loop (PLL) designed to recover an optical carrier at powers below one picowatt in a Deep Space optical transponder. Previous low power optical phase lock has been reported with powers down to about 1 pW. We report the demonstration and characterization of the optical phase locking at femtowatt levels. We achieved a phase slip rate below one cycle-slip/second at powers down to 60 femtowatts. This phase slip rate corresponds to a frequency stability of 1 10(exp -14) at 1 s, a value better than any frequency standard available today for measuring times equal to a typical two-way delay between Earth and Mars. The PLL shows very robust stability at these power levels. We developed simulation software to optimize parameters of the second order PLL loop in the presence of laser flicker frequency noise and white phase (photon) noise, and verified the software with a white phase noise model by Viterbi. We also demonstrated precise Doppler tracking at femtowatt levels.

  2. Noise suppression algorithm of short-wave infrared star image for daytime star sensor

    Science.gov (United States)

    Wang, Wenjie; Wei, Xinguo; Li, Jian; Wang, Gangyi

    2017-09-01

    As an important development trend of star sensor technology, research on daytime star sensor technology can expand the applications of star sensor from spacecrafts to airborne vehicles. The biggest problem for daytime star sensor is the detection of dim stars from strong atmospheric background radiation. The use of short-wave infrared (SWIR) technology has been proven to be an effective approach to solve this problem. However, the SWIR star images inevitably contain stripe nonuniformity noise and defective pixels, which degrade the quality of the acquired images and affect the subsequent star spot extraction and star centroiding accuracy seriously. Because the characteristics of stripe nonuniformity and defective pixels in the SWIR star images change with time during a long term continuous operation, the method of one-time off-line calibration is not applicable. To solve this problem, an algorithm of noise suppression for SWIR star image is proposed. It firstly extracts non-background pixels by one-dimensional mean filtering. Then through one-dimensional feature point descriptor, which is used to distinguish the bright star spots pixels from defective pixels, various types of defective pixels are accurately detected. Finally, the method of moment matching is adopted to remove the stripe nonuniformity and the defective pixels are compensated effectively. The simulation experiments results indicates that the proposed algorithm can adaptively and effectively suppress the influence of stripe nonuniformity and defective pixels in SWIR star images and it is beneficial to obtain higher star centroiding accuracy.

  3. The effects of digital image processing for