WorldWideScience

Sample records for active noise reduction

  1. Active Noise Control for Vehicle Exhaust Noise Reduction

    Institute of Scientific and Technical Information of China (English)

    李克强; 杨殿阁; 郑四发; 连小珉; 田中丈晴

    2003-01-01

    An active noise control (ANC) method was developed for exhaust noise reduction for medium-duty diesel trucks. A modified variable step size least mean squares (LMS) algorithm was used for the controller in a variable environment that considered the vehicle's acceleration characteristics. The variable step size time-based synchronized filtered-x LMS method (SFX-TB) used an adaptive algorithm that was more efficient than the conventional filtered-x LMS algorithm. The simulation and the experimental tests show that the control trackability and stability provided by the algorithm during acceleration enable the ANC system to effectively reduce the vehicle exhaust noise.

  2. Digitally controlled active noise reduction with integrated speech communication

    NARCIS (Netherlands)

    Steeneken, H.J.M.; Verhave, J.A.

    2004-01-01

    Active noise reduction is a successful addition to passive ear-defenders for improvement of the sound attenuation at low frequencies. Design and assessment methods are discussed, focused on subjective and objective attenuation measurements, stability, and high noise level applications. Active noise

  3. Digitally controlled active noise reduction with integrated speech communication

    NARCIS (Netherlands)

    Steeneken, H.J.M.; Verhave, J.A.

    2004-01-01

    Active noise reduction is a successful addition to passive ear-defenders for improvement of the sound attenuation at low frequencies. Design and assessment methods are discussed, focused on subjective and objective attenuation measurements, stability, and high noise level applications. Active noise

  4. Binaural Integrated Active Noise Control and Noise Reduction in Hearing Aids

    DEFF Research Database (Denmark)

    Serizel, Romain; Moonen, Marc; Wouters, Jan;

    2013-01-01

    This paper presents a binaural approach to integrated active noise control and noise reduction in hearing aids and aims at demonstrating that a binaural setup indeed provides significant advantages in terms of the number of noise sources that can be compensated for and in terms of the causality...

  5. Foundations of Active Control - Active Noise Reduction Helmets

    DEFF Research Database (Denmark)

    Elmkjær, Torsten Haaber Leth

    2008-01-01

    This Ph.D. thesis includes fundamental considerations about topologies, algorithms, implementations, methods etc., that can enter in the next generation of active control (AC) systems. Specifically, a new variant of feedforward control referred to as confined feedforward active control (CFFAC......-output (MIMO) system that facilitates both feedforward and feedback control. The general system is then referred to as hybrid MIMO confined-feedforward feedback (HMIMOCFFFB) active noise reduction (ANR) system. The investigation of a multi-channel ANR system with hybrid feedforward and feedback topologies...... be computational intensive takes place at an even slower sampling rate hereby relaxing the requirements on a high bandwidth. It is demonstrated that computational savings as high as 40% can be achieved in a 192, 24, 3 kHz triple-rate system as compared with a 24 kHz single-rate system without sacrificing the ANR...

  6. Multichannel active noise control systems and algorithms for reduction on broadband noise

    NARCIS (Netherlands)

    Berkhoff, A.P.; Wesselink, J.M.

    2007-01-01

    Active noise contral systems for braadband noise reduction require substantial computing power, especially for multichannel systems and adaptive controllers. Furthermore, speed of convergence can be an issue as weil. In this paper, methods and techniques are described that are able to reduce the com

  7. Active-passive gradient shielding for MRI acoustic noise reduction.

    Science.gov (United States)

    Edelstein, William A; Kidane, Tesfaye K; Taracila, Victor; Baig, Tanvir N; Eagan, Timothy P; Cheng, Yu-Chung N; Brown, Robert W; Mallick, John A

    2005-05-01

    An important source of MRI acoustic noise-magnet cryostat warm-bore vibrations caused by eddy-current-induced forces-can be mitigated by a passive metal shield mounted on the outside of a vibration-isolated, vacuum-enclosed shielded gradient set. Finite-element (FE) calculations for a z-gradient indicate that a 2-mm-thick Cu layer wrapped on the gradient assembly can decrease mechanical power deposition in the warm bore and reduce warm-bore acoustic noise production by about 25 dB. Eliminating the conducting warm bore and other magnet parts as significant acoustic noise sources could lead to the development of truly quiet, fully functioning MRI systems with noise levels below 70 dB.

  8. Optimal periodic disturbance reduction for active noise cancelation

    Science.gov (United States)

    Kinney, C. E.; de Callafon, R. A.; Dunens, E.; Bargerhuff, R.; Bash, C. E.

    2007-08-01

    The design of an optimal internal model-based (IMB) controller by extending standard discrete time optimal control theory for IMB controllers is described. The optimal observer and state feedback gains of the IMB controller are given via the solution of discrete time algebraic Riccati equations. The design method is applied to an acoustic system that is subjected to disturbances from a server fan. Periodic disturbances from the server fan appear as harmonics of the fundamental frequency of the fan. Parametric models for the plant and non-periodic part of the disturbance are identified from experimental data. An internal model is designed in discrete time and the internal model principle is used to design a feedback controller that rejects periodic disturbances in the acoustic system. The controller is implemented in real-time and successfully attenuates the first four harmonics of the fan noise.

  9. Improving the Effectiveness of Communication Headsets with Active Noise Reduction: Influence of Control Structure

    Science.gov (United States)

    2005-04-01

    for two circumaural communication headsets with similar passive, and active, noise reductions, one with an analog feedback control system and the...the feedback control system to maintain stability of the feedback loop, as well as the presence of communication sounds sensed by the control

  10. Fundamental study of noise reduction by active noise control. Active soon seigyo ni yoru soon taisaku no kiso kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, T.; Naganawa, A. (Chubu Electric Power Co. Inc., Nagoya (Japan))

    1994-05-01

    Fundamental experiments were conducted on active noise control as sound insulation fence. This control method generates a sound source with the same amplitude and opposite phase as noise, and reduces noise through the interference of acoustic wave from the source. However, this method has too many problems with the three-dimensional sound field to be actually exploited in this environment. The following experiments were conducted to apply the active noise control to the sound insulation fence: one method of installing a geometric path along the inner side of the sound insulation fence used the acoustic delay process generated on the source side to attenuate the sound pressure level on top of the fence through interference of routing difference sound. The other method used an additional sound source attached to the bottom of the geometric path above to obtain a higher attenuation than using the simple sound insulation fence. At the second step, the active control duct model was used for the test. Then, the three-dimensional model test was conducted for active control of the sound insulation fence. The results of these fundamental experiments have indicated that each method can reduce the relative sound pressure level and the active noise control system using the acoustic phase difference can effectively reduce noise with dominant components in a low frequency band. There are still several problems with the three-dimensional mock-up model. 4 refs., 18 figs., 2 tabs.

  11. Jet Engine Noise Reduction

    Science.gov (United States)

    2009-04-01

    Technology Solutions, Lockheed Martin Robert S. Carnes , M.D. NRAC Member, Battelle Memorial Institute MajGen Paul A. Fratarangelo, USMC (Ret) NRAC...Development, Acquisition) (VADM Architzel). The Naval Research Advisory Committee members (Bowes, Bowler, Carnes and Fratarangelo) have broad...Lockheed Martin ADP Boeing: Jet Engine Noise Reduction for Tactical Fighter Aircraft Mr. Tom Kaemming, K. Viswanathan, Ph . D. Tactical Jet Noise

  12. A Computational Study of BVI Noise Reduction Using Active Twist Control

    Science.gov (United States)

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.

    2010-01-01

    The results of a computational study examining the effects of active-twist control on blade-vortex interaction (BVI) noise using the Apache Active Twist Rotor are presented. The primary goal of this activity is to reduce BVI noise during a low-speed descent flight condition using active-twist control. Rotor aeroelastic behavior was modeled using the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics code and the rotor noise was predicted using the acoustics code PSU-WOPWOP. The accuracy of the analysis was validated through comparisons with experimental acoustic data for the first generation Active Twist Rotor at an advance ratio of mu=0.14. The application of active-twist to the main rotor blade system consisted of harmonic actuation frequencies ranging from 2P to 5P, control phase angles from 0' to 360 , and tip-twist amplitudes ranging from 0.5 to 4.0 . The acoustic analysis was conducted for a single low-speed flight condition of advance ratio =0.14 and shaft angle-of-attack, c^=+6 , with BVI noise levels predicted on a flat plane of observers located 1.1 rotor diameters beneath the rotor. The results indicated reductions of up to 11dB in BVI noise using 1.25 tip-twist amplitude with negligible effects on 4P vertical hub shear.

  13. The use of active vibration control for the reduction of ICE interior noise

    Energy Technology Data Exchange (ETDEWEB)

    Schirmacher, R. [Mueller-BBM GmbH - Beratende Ingenieure fuer Akustik, Planegg (Germany)

    2001-07-01

    First generation ICE high speed trains show a disturbing low frequency noise of about 100 Hz audible inside the coaches. It is excited by unround wheels, propagates via the bogie to the body of the coach and is finally radiated as airborne sound. A mixed concept of active suspension at the bogie in connection with adaptive residual noise minimisation inside the passenger compartment is successfully applied to the problem. A prototype system utilizing piezo ceramic actuators was installed and tested on the rolling rig of Deutsche Bahn in Munich. The noise level reductions at single harmonics were more than 12 dB averaged over the whole compartment and more than 20 dB at single seats. Measurement results and practical experiences with the system are reported. (orig.)

  14. Reduction of turbomachinery noise

    Science.gov (United States)

    Waitz, Ian A. (Inventor); Brookfield, John M. (Inventor); Sell, Julian (Inventor); Hayden, Belva J. (Inventor); Ingard, K. Uno (Inventor)

    1999-01-01

    In the invention, propagating broad band and tonal acoustic components of noise characteristic of interaction of a turbomachine blade wake, produced by a turbomachine blade as the blade rotates, with a turbomachine component downstream of the rotating blade, are reduced. This is accomplished by injection of fluid into the blade wake through a port in the rotor blade. The mass flow rate of the fluid injected into the blade wake is selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake. With this fluid injection, reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved. In a further noise reduction technique, boundary layer fluid is suctioned into the turbomachine blade through a suction port on the side of the blade that is characterized as the relatively low-pressure blade side. As with the fluid injection technique, the mass flow rate of the fluid suctioned into the blade is here selected to reduce the momentum deficit of the wake to correspondingly increase the time-mean velocity of the wake and decrease the turbulent velocity fluctuations of the wake; reduction of both propagating broad band and tonal acoustic components of noise produced by interaction of the blade wake with a turbomachine component downstream of the rotating blade is achieved with this suction technique. Blowing and suction techniques are also provided in the invention for reducing noise associated with the wake produced by fluid flow around a stationary blade upstream of a rotating turbomachine.

  15. Experimental Study of Active Techniques for Blade/Vortex Interaction Noise Reduction

    Science.gov (United States)

    Kobiki, Noboru; Murashige, Atsushi; Tsuchihashi, Akihiko; Yamakawa, Eiichi

    This paper presents the experimental results of the effect of Higher Harmonic Control (HHC) and Active Flap on the Blade/Vortex Interaction (BVI) noise. Wind tunnel tests were performed with a 1-bladed rotor system to evaluate the simplified BVI phenomenon avoiding the complicated aerodynamic interference which is characteristically and inevitably caused by a multi-bladed rotor. Another merit to use this 1-bladed rotor system is that the several objective active techniques can be evaluated under the same condition installed in the same rotor system. The effects of the active techniques on the BVI noise reduction were evaluated comprehensively by the sound pressure, the blade/vortex miss distance obtained by Laser light Sheet (LLS), the blade surface pressure distribution and the tip vortex structure by Particle Image Velocimetry (PIV). The correlation among these quantities to describe the effect of the active techniques on the BVI conditions is well obtained. The experiments show that the blade/vortex miss distance is more dominant for BVI noise than the other two BVI governing factors, such as blade lift and vortex strength at the moment of BVI.

  16. Active Vibration Control for Helicopter Interior Noise Reduction Using Power Minimization

    Science.gov (United States)

    Mendoza, J.; Chevva, K.; Sun, F.; Blanc, A.; Kim, S. B.

    2014-01-01

    This report describes work performed by United Technologies Research Center (UTRC) for NASA Langley Research Center (LaRC) under Contract NNL11AA06C. The objective of this program is to develop technology to reduce helicopter interior noise resulting from multiple gear meshing frequencies. A novel active vibration control approach called Minimum Actuation Power (MAP) is developed. MAP is an optimal control strategy that minimizes the total input power into a structure by monitoring and varying the input power of controlling sources. MAP control was implemented without explicit knowledge of the phasing and magnitude of the excitation sources by driving the real part of the input power from the controlling sources to zero. It is shown that this occurs when the total mechanical input power from the excitation and controlling sources is a minimum. MAP theory is developed for multiple excitation sources with arbitrary relative phasing for single or multiple discrete frequencies and controlled by a single or multiple controlling sources. Simulations and experimental results demonstrate the feasibility of MAP for structural vibration reduction of a realistic rotorcraft interior structure. MAP control resulted in significant average global vibration reduction of a single frequency and multiple frequency excitations with one controlling actuator. Simulations also demonstrate the potential effectiveness of the observed vibration reductions on interior radiated noise.

  17. Adaptive Noise Reduction System

    Directory of Open Access Journals (Sweden)

    Ivana Ropuš

    2013-01-01

    Full Text Available Noise is an all-present environment pollutant, considered to be one of the greatest contemporary pollutants. World-wide, co-ordinated actions are conducted in order to develop systems which minimise the noise influence onto society.In this article we argue that novel approach to suppression of influence of noise is useful. Furthermore, we argue that the efficient approach is formulation of the efficient, broadly applicable, ubiquituous, adaptive noise-protection system. The approach combines the natural noise-protection form based on plants with the artificially formed coatings.Elements of the system are discussed, its formation and maintenance analysed and perspectives conjectured.

  18. Control strategies for aircraft airframe noise reduction

    Institute of Scientific and Technical Information of China (English)

    Li Yong; Wang Xunnian; Zhang Dejiu

    2013-01-01

    With the development of low-noise aircraft engine,airframe noise now represents a major noise source during the commercial aircraft's approach to landing phase.Noise control efforts have therefore been extensively focused on the airframe noise problems in order to further reduce aircraft overall noise.In this review,various control methods explored in the last decades for noise reduction on airframe components including high-lift devices and landing gears are summarized.We introduce recent major achievements in airframe noise reduction with passive control methods such as fairings,deceleration plates,splitter plates,acoustic liners,slat cove cover and side-edge replacements,and then discuss the potential and control mechanism of some promising active flow control strategies for airframe noise reduction,such as plasma technique and air blowing/suction devices.Based on the knowledge gained throughout the extensively noise control testing,a few design concepts on the landing gear,high-lift devices and whole aircraft are provided for advanced aircraft low-noise design.Finally,discussions and suggestions are given for future research on airframe noise reduction.

  19. Active Noise Control for Dishwasher noise

    Science.gov (United States)

    Lee, Nokhaeng; Park, Youngjin

    2016-09-01

    The dishwasher is a useful home appliance and continually used for automatically washing dishes. It's commonly placed in the kitchen with built-in style for practicality and better use of space. In this environment, people are easily exposed to dishwasher noise, so it is an important issue for the consumers, especially for the people living in open and narrow space. Recently, the sound power levels of the noise are about 40 - 50 dBA. It could be achieved by removal of noise sources and passive means of insulating acoustical path. For more reduction, such a quiet mode with the lower speed of cycle has been introduced, but this deteriorates the washing capacity. Under this background, we propose active noise control for dishwasher noise. It is observed that the noise is propagating mainly from the lower part of the front side. Control speakers are placed in the part for the collocation. Observation part of estimating sound field distribution and control part of generating the anti-noise are designed for active noise control. Simulation result shows proposed active noise control scheme could have a potential application for dishwasher noise reduction.

  20. Experiments on reduction of propeller induced interior noise by active control of cylinder vibration

    Science.gov (United States)

    Fuller, C. R.; Jones, J. D.

    1987-01-01

    The feasibility of reducing interior noise caused by advanced turbo propellers by controlling the vibration of aircraft fuselages was investigated by performing experiments in an anechoic chamber with an aircraft model test rig and apparatus. It was found that active vibration control provides reasonable global attenuation of interior noise levels for the cases of resonant (at 576 Hz) and forced (at 708 Hz) system response. The controlling mechanism behind the effect is structural-acoustic coupling between the shell and the contained field, termed interface modal filtering.

  1. Active noise control primer

    CERN Document Server

    Snyder, Scott D

    2000-01-01

    Active noise control - the reduction of noise by generating an acoustic signal that actively interferes with the noise - has become an active area of basic research and engineering applications. The aim of this book is to present all of the basic knowledge one needs for assessing how useful active noise control will be for a given problem and then to provide some guidance for designing, setting up, and tuning an active noise-control system. Written for students who have no prior knowledge of acoustics, signal processing, or noise control but who do have a reasonable grasp of basic physics and mathematics, the book is short and descriptive. It leaves for more advanced texts or research monographs all mathematical details and proofs concerning vibrations, signal processing and the like. The book can thus be used in independent study, in a classroom with laboratories, or in conjunction with a kit for experiment or demonstration. Topics covered include: basic acoustics; human perception and sound; sound intensity...

  2. Study on the active noise control method and the effect of noise reduction due to the multi-connected branch dusts. Gyakuiso no fukaon ni yoru soon seigyoho no kento to tarengata bunkikan ni yoru soon keigen koka

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Kiyoatsu.

    1989-04-01

    This paper reports the results of experimental studies on the utility of the active noise control method, and the effects of the multi-connected branch pipes silencer, concerning the reduction of noise. In the experiments of active noise control by using ducts, when the canceling sound was produced by the speaker set at the end of the short-length pipe corresponding to the one forth wave-length, the sound pressure of canceling noise was less one sixth as compared with setting the speaker at the wall of pipe. The noise reduction quantity to the random noise by the active noise control method was about as much as 15db. This method is not adaptable for noise with wide ranges of frequency. A branch pipe silencers, when it was used as multi-connected branch pipe, could extend the bounds of noise frequency which was able to be reduced and could increase the noise reduction quality. This silencer can deal with the fluctuation of frequency od noise and has higher practicability. 10 refs., 21 figs.

  3. A High Performance Approach to Local Active Noise Reduction in Noisy Cabins Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Spacecraft cabin is noisy and uncomfortable. Sometimes, the noise level can exceed 80 dBA. There are 2 challenges to meet the above needs. One is to generate an...

  4. Noise reduction of spiral ducts.

    Science.gov (United States)

    Lapka, Wojciech; Cempel, Czesław

    2007-01-01

    The paper presents noise reduction (NR) of spiral ducts as a result of computational modeling of acoustic wave propagation. Three-dimensional models were created with the finite element method in COMSOL Multiphysics version 3.3. Nine models of spiral ducts with 1-9 spiral leads were considered. Time-harmonic analysis was used to predict NR, which was shown in spectral and interval frequency bands. Spiral duct performance can be seen as a comparison of NR before and after a change from a circular to a spiral duct.

  5. Noise environment reduction foam spheres in space

    Science.gov (United States)

    Scharton, Terry; Kern, Dennis; Badilla, Gloria

    1989-01-01

    The advent of lightweight fairings for new spacecraft and the increased thrust of new launch vehicles have intensified the need for better techniques for predicting and for reducing the low frequency noise environment of spacecraft at liftoff. This paper presents a VAPEPS (VibroAcoustic Payload Environment Prediction System) parametrical analysis of the noise reduction of spacecraft fairings and explores a novel technique for increasing the low frequency noise reduction of lightweight fairing by approximately 10 dB.

  6. Supersonic Jet Noise Reduction Using Microjets

    Science.gov (United States)

    Gutmark, Ephraim; Cuppoletti, Dan; Malla, Bhupatindra

    2013-11-01

    Fluidic injection for jet noise reduction involves injecting secondary jets into a primary jet to alter the noise characteristics of the primary jet. A major challenge has been determining what mechanisms are responsible for noise reduction due to varying injector designs, injection parameters, and primary jets. The current study provides conclusive results on the effect of injector angle and momentum ux ratio on the acoustics and shock structure of a supersonic Md = 1.56 jet. It is shown that the turbulent mixing noise scales primarily with the injector momentum flux ratio. Increasing the injector momentum flux ratio increases streamwise vorticity generation and reduces peak turbulence levels. It is found that the shock-related noise components are most affected by the interaction of the shocks from the injectors with the primary shock structure of the jet. Increasing momentum flux ratio causes shock noise reduction until a limit where shock noise increases again. It is shown that the shock noise components and mixing noise components are reduced through fundamentally different mechanisms and maximum overall noise reduction is achieved by balancing the reduction of both components.

  7. Noise Reduction in Car Speech

    OpenAIRE

    V. Bolom

    2009-01-01

    This paper presents properties of chosen multichannel algorithms for speech enhancement in a noisy environment. These methods are suitable for hands-free communication in a car cabin. Criteria for evaluation of these systems are also presented. The criteria consider both the level of noise suppression and the level of speech distortion. The performance of multichannel algorithms is investigated for a mixed model of speech signals and car noise and for real signals recorded in a car. 

  8. Noise Reduction in Car Speech

    Directory of Open Access Journals (Sweden)

    V. Bolom

    2009-01-01

    Full Text Available This paper presents properties of chosen multichannel algorithms for speech enhancement in a noisy environment. These methods are suitable for hands-free communication in a car cabin. Criteria for evaluation of these systems are also presented. The criteria consider both the level of noise suppression and the level of speech distortion. The performance of multichannel algorithms is investigated for a mixed model of speech signals and car noise and for real signals recorded in a car. 

  9. Noise reduction in supersonic jets by nozzle fluidic inserts

    Science.gov (United States)

    Morris, Philip J.; McLaughlin, Dennis K.; Kuo, Ching-Wen

    2013-08-01

    Professor Philip Doak spent a very productive time as a consultant to the Lockheed-Georgia Company in the early 1970s. The focus of the overall research project was the prediction and reduction of noise from supersonic jets. Now, 40 years on, the present paper describes an innovative methodology and device for the reduction of supersonic jet noise. The goal is the development of a practical active noise reduction technique for low bypass ratio turbofan engines. This method introduces fluidic inserts installed in the divergent wall of a CD nozzle to replace hard-wall corrugation seals, which have been demonstrated to be effective by Seiner (2005) [1]. By altering the configuration and operating conditions of the fluidic inserts, active noise reduction for both mixing and shock noise has been obtained. Substantial noise reductions have been achieved for mixing noise in the maximum noise emission direction and in the forward arc for broadband shock-associated noise. To achieve these reductions (on the order of greater than 4 and 2 dB for the two main components respectively), practically achievable levels of injection mass flow rates have been used. The total injected mass flow rates are less than 4% of the core mass flow rate and the effective operating injection pressure ratio has been maintained at or below the same level as the nozzle pressure ratio of the core flow.

  10. A conceptual framework for noise reduction

    CERN Document Server

    Benesty, Jacob

    2015-01-01

    Though noise reduction and speech enhancement problems have been studied for at least five decades, advances in our understanding and the development of reliable algorithms are more important than ever, as they support the design of tailored solutions for clearly defined applications. In this work, the authors propose a conceptual framework that can be applied to the many different aspects of noise reduction, offering a uniform approach to monaural and binaural noise reduction problems, in the time domain and in the frequency domain, and involving a single or multiple microphones. Moreover, the derivation of optimal filters is simplified, as are the performance measures used for their evaluation.

  11. Active Noise Control of Radiated Noise from Jets Originating NASA

    Science.gov (United States)

    Doty, Michael J.; Fuller, Christopher R.; Schiller, Noah H.; Turner, Travis L.

    2013-01-01

    The reduction of jet noise using a closed-loop active noise control system with highbandwidth active chevrons was investigated. The high frequency energy introduced by piezoelectrically-driven chevrons was demonstrated to achieve a broadband reduction of jet noise, presumably due to the suppression of large-scale turbulence. For a nozzle with one active chevron, benefits of up to 0.8 dB overall sound pressure level (OASPL) were observed compared to a static chevron nozzle near the maximum noise emission angle, and benefits of up to 1.9 dB OASPL were observed compared to a baseline nozzle with no chevrons. The closed-loop actuation system was able to effectively reduce noise at select frequencies by 1-3 dB. However, integrated OASPL did not indicate further reduction beyond the open-loop benefits, most likely due to the preliminary controller design, which was focused on narrowband performance.

  12. Active linear mass absorber technology for the reduction of noise and vibration at a cylinder deactivation vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Rottner, T.; Eckel, H.G. [Vibracoustic GmbH und Co. KG (Germany); Kim, J.H. [Hyundai Motor Company (Korea); Klatt, C. [Freudenberg New Technologies, Weinheim (Germany)

    2007-07-01

    Cylinder deactivation is a suitable strategy for reducing the fuel consumption of a vehicle. In this particular case, a V6 engine runs under partial load conditions in a restricted engine speed range as an inline three cylinder engine by deactivating an entire bank. As a side effect, noise and vibrations in the deactivated condition deteriorate significantly. For comfort reasons, however, a similar noise and vibration level for both - full and deactivated engine running condition - is desired. To achieve this, active technology is used. In the cylinder deactivation mode, two active linear mass aborbers installed at the engine mounts cancel out the main disturbing engine excitation orders of the engine mount forces. As a result, the noise and vibration in the passenger compartment is significantly reduced. (orig.)

  13. Noise Reduction in the SSNPA

    Science.gov (United States)

    Gomez, M.; Roquemore, L.; Darrow, D.; Liu, D.

    2004-11-01

    A solid-state neutral particle analyzer (SSNPA) is being used to detect the escape of neutral particles on the National Spherical Torus Experiment (NSTX). The SSNPA has four channels, which view the horizontal midplane of NSTX. The output amplitude of the SSNPA is proportional to radiation energy. Neutral particles with energies up to 100 keV will be observed. The SSNPA is used to link changes in neutral particle flux with plasma events. The noise level associated with standard NIM electronics prevents this. Two solutions are proposed to fix this problem: 1) Increase the signal to noise ratio (S/N) in the system or 2) Ultra-fast digitization (UFD) of the signal. New electronics are being tested to increase the S/N. A close-coupled preamp/amplifier increase the gain by ˜1000, which increases the signal before noise is introduced. Ground loop problems are also being addressed. This system is presently being tested on NSTX. With UFD, the preamplifier will be connected to the digitizer and post-shot analysis will separate the signal from the noise using of PHA software. The above solutions will be discussed.

  14. 多通道有源噪声控制系统设计%Reduction of Noise in Chinese Y-7 Aircraft Using Active Noise Control (ANC)

    Institute of Scientific and Technical Information of China (English)

    吴亚锋; 黎中伟; 任辉; 李江红

    2001-01-01

    Active noise control, as applied to engineering projects, began around 1990. We designed a multi-channel active noise control (ANC) system for reducing the noise in front cabin in Chinese Y-7 propeller driven aircraft. In ANC applications, in order to reduce effectively the noise level in a large space, we have to match at any time the generated secondary sound field with the original primary sound field, so that a percentage of the entire primary noise field is effectively cancelled out by the entire secondary noise field. Via analyzing ANC time sequences, we developed a multi-channel adaptive control system that can simultaneously detect multiple error inputs and produce multiple canceling outputs. Our system consists of PC as main controller, TMS320-C30 DSP chip as slave processor, 16 A/D input channels and 8 D/A output channels. Applying our system to Chinese Y-7 aircraft appears to be successful; test results show that noise level of Y-7′s blade pass frequency (BPF) and its secondary harmonic frequency (2BPF) are attenuated by 13.4 dB and 5.5 dB respectively. Work remains to be done before our system becomes a part of Y-7 aircraft in actual flights.%基于实时数字信号处理系统理论,讨论有源噪声控制系统的电子设计方法。通过对控制时序的分析,设计了一实时多通道自适应控制系统,该系统以PC为主控机,以DSP TMS320-C30为从处理机,具有多路传感器同时输入和扬声器同时输出通道。该系统被应用于国产某型螺桨飞机的舱内噪声控制,取得了满意的降噪效果。

  15. Power Gating Based Ground Bounce Noise Reduction

    Directory of Open Access Journals (Sweden)

    M. Uma Maheswari

    2014-08-01

    Full Text Available As low power circuits are most popular the decrease in supply voltage leads to increase in leakage power with respect to the technology scaling. So for removing this kind of leakages and to provide a better power efficiency many power gating techniques are used. But the leakage due to ground connection to the active part of the circuit is very high rather than all other leakages. As it is mainly due to the back EMF of the ground connection it was called it as ground bounce noise. To reduce this noise different methodologies are designed. In this paper the design of such an efficient technique related to ground bounce noise reduction using power gating circuits and comparing the results using DSCH and Microwind low power tools. In this paper the analysis of adders such as full adders using different types of power gated circuits using low power VLSI design techniques and to present the comparison results between different power gating methods.

  16. Assessment Methods for Personal Active Noise Reduction Validated in an International Round Robin (Methodes d’evaluation des protecteurs auditifs a attenuation active du bruit)

    Science.gov (United States)

    2004-08-01

    d’évaluation des casques et des serre -tête équipés d’un dispositif d’atténuation active du bruit (ANR, Active Noise Reduction) sont différentes de celles...utilisées pour les protecteurs passifs. Les dispositifs ANR peuvent en effet produire des bruits parasites dûs au bruit de fond électronique. Ils...HECB USA. Les atténuations passives et actives du bruit de cinq serre -tête équipés d’un dispositif ANR et d’un système de communication ont été

  17. Flap Edge Noise Reduction Fins

    Science.gov (United States)

    Khorrami, Mehdi R. (Inventor); Choudhan, Meelan M. (Inventor)

    2015-01-01

    A flap of the type that is movably connected to an aircraft wing to provide control of an aircraft in flight includes opposite ends, wherein at least a first opposite end includes a plurality of substantially rigid, laterally extending protrusions that are spaced apart to form a plurality of fluidly interconnected passageways. The passageways have openings adjacent to upper and lower sides of the flap, and the passageways include a plurality of bends such that high pressure fluid flows from a high pressure region to a low pressure region to provide a boundary condition that inhibits noise resulting from airflow around the end of the flap.

  18. Simple noise-reduction method based on nonlinear forecasting

    Science.gov (United States)

    Tan, James P. L.

    2017-03-01

    Nonparametric detrending or noise reduction methods are often employed to separate trends from noisy time series when no satisfactory models exist to fit the data. However, conventional noise reduction methods depend on subjective choices of smoothing parameters. Here we present a simple multivariate noise reduction method based on available nonlinear forecasting techniques. These are in turn based on state-space reconstruction for which a strong theoretical justification exists for their use in nonparametric forecasting. The noise reduction method presented here is conceptually similar to Schreiber's noise reduction method using state-space reconstruction. However, we show that Schreiber's method has a minor flaw that can be overcome with forecasting. Furthermore, our method contains a simple but nontrivial extension to multivariate time series. We apply the method to multivariate time series generated from the Van der Pol oscillator, the Lorenz equations, the Hindmarsh-Rose model of neuronal spiking activity, and to two other univariate real-world data sets. It is demonstrated that noise reduction heuristics can be objectively optimized with in-sample forecasting errors that correlate well with actual noise reduction errors.

  19. Advanced digital signal processing and noise reduction

    CERN Document Server

    Vaseghi, Saeed V

    2008-01-01

    Digital signal processing plays a central role in the development of modern communication and information processing systems. The theory and application of signal processing is concerned with the identification, modelling and utilisation of patterns and structures in a signal process. The observation signals are often distorted, incomplete and noisy and therefore noise reduction, the removal of channel distortion, and replacement of lost samples are important parts of a signal processing system. The fourth edition of Advanced Digital Signal Processing and Noise Reduction updates an

  20. Knowledge Network Approach to Noise Reduction

    CERN Document Server

    Berrones, A

    2006-01-01

    Previous preliminary results on the application of knowledge networks to noise reduction in stationary harmonic and weakly chaotic signals are extended to more general cases. The formalism gives a novel algorithm from which statistical tests for the identification of deterministic behavior in noisy stationary time series can be constructed.

  1. Ground Bounce Noise Reduction in Vlsi Circuits

    Directory of Open Access Journals (Sweden)

    Vipin Kumar Sharma

    2015-12-01

    Full Text Available : Scaling of devices in CMOS technology leads to increase in parameter like Ground bounce noise, Leakage current, average power dissipation and short channel effect. FinFET are the promising substitute to replace CMOS. Ground bounce noise is produced when power gating circuit goes from SLEEP to ACTIVE mode transition. FinFET based designs are compared with MOSFET based designs on basis of different parameter like Ground bounce noise, leakage current and average power dissipation. HSPICE is the software tool used for simulation and circuit design.

  2. Adaptive Noise Reduction Scheme for Salt and Pepper

    CERN Document Server

    Gebreyohannes, Tina

    2012-01-01

    In this paper, a new adaptive noise reduction scheme for images corrupted by impulse noise is presented. The proposed scheme efficiently identifies and reduces salt and pepper noise. MAG (Mean Absolute Gradient) is used to identify pixels which are most likely corrupted by salt and pepper noise that are candidates for further median based noise reduction processing. Directional filtering is then applied after noise reduction to achieve a good tradeoff between detail preservation and noise removal. The proposed scheme can remove salt and pepper noise with noise density as high as 90% and produce better result in terms of qualitative and quantitative measures of images.

  3. 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

  4. High-Temperature Liners for Broadband Noise Reduction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Core noise will become a larger component of engine noise overall, as more efficient design trends of fan and jet noise reduction technologies are implemented. The...

  5. NASA/AHS rotorcraft noise reduction program - NASA Langley Acoustics Division contributions

    Science.gov (United States)

    Martin, Ruth M.

    1989-01-01

    An account is given of the contributions made by NASA-Langley's rotorcraft noise research programs over the last five years. Attention has been given to the broadband and blade-vortex interaction noise sources; both analytical and empirical noise-prediction codes have been developed and validated for several rotor noise sources, and the 'Rotonet' comprehensive system-noise prediction capability has been instituted. Among the technologies explored for helicopter noise reduction have been higher harmonic control and active vibration-suppression.

  6. An assessment of psychological noise reduction by landscape plants.

    Science.gov (United States)

    Yang, Fan; Bao, Zhi Yi; Zhu, Zhu Jun

    2011-04-01

    The emphasis in the term 'Green Transportation' is on the word 'green'. Green transportation focuses on the construction of a slow transport system with a visually pleasing, easy and secure trip environment composed of urban parks, green roadside spaces and some other space that is full of landscape plants. This trip environment encourages residents to make trip choices that reduce fuel consumption and pollution and is one of the most important ways of popularizing green transportation. To study the psychological benefits provided by urban parks and other landscape environments, we combined a subjective approach (a questionnaire) with an objective quantitative approach (emotional tests using an electroencephalogram; EEG). Using a questionnaire survey, we found that 90% of the subjects believed that landscape plants contribute to noise reduction and that 55% overrated the plants' actual ability to attenuate noise. Two videos (showing a traffic scene and a plant scene) were shown to 40 participants on video glasses. We detected and recorded EEG values with a portable electroencephalograph, and a comparison between the results of the two groups revealed that there was a highly significant asymmetry between the EEG activity of the vegetation scene and traffic scene groups. The results suggest that the emotions aroused by noise and visual stimuli are manifested in the synchronization of beta frequency band and the desynchronization of alpha frequency band, indicating that landscape plants can moderate or buffer the effects of noise. These findings indicate that landscape plants provide excess noise attenuating effects through subjects' emotional processing, which we term 'psychological noise reduction'.

  7. Noise and dust emissions from mining activities : a software for a first approach to the measurement management and selection of suitable reduction techniques

    Energy Technology Data Exchange (ETDEWEB)

    Cigna, C.; Lovera, E.; Patrucco, M. [Politecnico di Torino, Turin (Italy)

    2005-07-01

    Mining activities are often a matter of concern to local communities due to the potential impacts on the environment and landscape. As such, an effective balance is needed between socio-economic development and environmental protection. Mining activities in populated areas must be carefully planned and managed in order to avoid annoying local populations and to minimize health risks. This study was based on the criteria of the European Communities Commission to promote resource extraction and production methods that encourage eco-efficiency by developing best practice programs. In particular, this study defined and evaluated measurement, analysis and control criteria for the emission of chemical and physical pollutants from non-metal mining industries with particular reference to the reduction of noise and airborne particulates to the surrounding environment. The main focus of the study included on-site measuring campaigns in Italy's Lombardia mining region to collect data on mining techniques and technologies as well as pollutant emissions and propagation. The objective was to test the applicability of a newly proposed simplified monitoring systems and to evaluate the effective results of adopted pollution reduction strategies. A software-based database was also developed to manage detailed information on mining activities and to store the measured emissions data for future evaluation. 3 refs., 7 figs.

  8. Evaluation of the Advanced Subsonic Technology Program Noise Reduction Benefits

    Science.gov (United States)

    Golub, Robert A.; Rawls, John W., Jr.; Russell, James W.

    2005-01-01

    This report presents a detailed evaluation of the aircraft noise reduction technology concepts developed during the course of the NASA/FAA Advanced Subsonic Technology (AST) Noise Reduction Program. In 1992, NASA and the FAA initiated a cosponsored, multi-year program with the U.S. aircraft industry focused on achieving significant advances in aircraft noise reduction. The program achieved success through a systematic development and validation of noise reduction technology. Using the NASA Aircraft Noise Prediction Program, the noise reduction benefit of the technologies that reached a NASA technology readiness level of 5 or 6 were applied to each of four classes of aircraft which included a large four engine aircraft, a large twin engine aircraft, a small twin engine aircraft and a business jet. Total aircraft noise reductions resulting from the implementation of the appropriate technologies for each class of aircraft are presented and compared to the AST program goals.

  9. Noise Reduction Potential of Cellular Metals

    Directory of Open Access Journals (Sweden)

    Björn Hinze

    2012-06-01

    Full Text Available Rising numbers of flights and aircrafts cause increasing aircraft noise, resulting in the development of various approaches to change this trend. One approach is the application of metallic liners in the hot gas path of aero-engines. At temperatures of up to 600 °C only metallic or ceramic structures can be used. Due to fatigue loading and the notch effect of the pores, mechanical properties of porous metals are superior to the ones of ceramic structures. Consequently, cellular metals like metallic foams, sintered metals, or sintered metal felts are most promising materials. However, acoustic absorption depends highly on pore morphology and porosity. Therefore, both parameters must be characterized precisely to analyze the correlation between morphology and noise reduction performance. The objective of this study is to analyze the relationship between pore morphology and acoustic absorption performance. The absorber materials are characterized using image processing based on two dimensional microscopy images. The sound absorption properties are measured using an impedance tube. Finally, the correlation of acoustic behavior, pore morphology, and porosity is outlined.

  10. Identification and Reduction of Turbomachinery Noise Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Communities near airports are often exposed to high noise levels due to low flying aircraft in the takeoff and landing phases of flight. Propulsion source noise is...

  11. Noise Reduction with Microphone Arrays for Speaker Identification

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, Z

    2011-12-22

    Reducing acoustic noise in audio recordings is an ongoing problem that plagues many applications. This noise is hard to reduce because of interfering sources and non-stationary behavior of the overall background noise. Many single channel noise reduction algorithms exist but are limited in that the more the noise is reduced; the more the signal of interest is distorted due to the fact that the signal and noise overlap in frequency. Specifically acoustic background noise causes problems in the area of speaker identification. Recording a speaker in the presence of acoustic noise ultimately limits the performance and confidence of speaker identification algorithms. In situations where it is impossible to control the environment where the speech sample is taken, noise reduction filtering algorithms need to be developed to clean the recorded speech of background noise. Because single channel noise reduction algorithms would distort the speech signal, the overall challenge of this project was to see if spatial information provided by microphone arrays could be exploited to aid in speaker identification. The goals are: (1) Test the feasibility of using microphone arrays to reduce background noise in speech recordings; (2) Characterize and compare different multichannel noise reduction algorithms; (3) Provide recommendations for using these multichannel algorithms; and (4) Ultimately answer the question - Can the use of microphone arrays aid in speaker identification?

  12. Noise Reduction in an Undergraduate Library.

    Science.gov (United States)

    Bird, Charles P.; Puglisi, Dawn D.

    1984-01-01

    Reports on program initiated to reduce noise in undergraduate library through combination of space reallocation, rule changes, and staff monitoring of noise. Objective and subjective measures of noise (sound-level readings, preintervention and postintervention questionnaires) and results of intervention program are discussed. Memo distributed on…

  13. Applications of the Piezoelectric Active Control to the Reduction of Vibration and Noise%压电主动控制在减振和降噪中的应用

    Institute of Scientific and Technical Information of China (English)

    吴昱廷; 黄华林; 徐俊; 史翔; 魏晓勇

    2011-01-01

    The piezoelectric active control has broad prospects for the reduction of vibration and noise. Three solutions of the vibration reduction of the simply-supported beam, the noise reduction of the aluminum plate and the vibration reduction of the base plate have been designed in this paper. The experimental results showed that the reductions of the vibration and noise for the single signal frequency were all up to about 90% , and it proved that the reduction of the vibration and noise for the single frequency by using the piezoelectric active control was feasible and the performance was significant.%利用压电主动控制进行减振和降噪实验具有广阔的发展前景.该文设计了3个相关的方案:简支梁的减振、铝板的降噪和基座的减振.实验结果显示,对于单频信号减振和降噪的效果均可达90%,证明了通过压电主动控制来实现单频的减振和降噪的可行性和显著性.

  14. Circular cylinders with soft porous cover for flow noise reduction

    Science.gov (United States)

    Geyer, Thomas F.; Sarradj, Ennes

    2016-03-01

    The use of porous materials is one of several approaches to passively control or minimize the generation of flow noise. In order to investigate the possible reduction of noise from struts and other protruding parts (for example components of the landing gear or pantographs), acoustic measurements were taken in a small aeroacoustic wind tunnel on a set of circular cylinders with a soft porous cover. The aim of this study was to identify those materials that result in the best noise reduction, which refers to both tonal noise and broadband noise. The porous covers were characterized by their air flow resistivity, a parameter describing the permeability of an open-porous material. The results show that materials with low air flow resistivities lead to a noticeable flow noise reduction. Thereby, the main effect of the porous cylinder covers is that the spectral peak of the aeolian tone due to vortex shedding appears much narrower, but is not suppressed completely. Based on the measurement results, a basic model for the estimation of the total peak level of the aeolian tone was derived. In addition to the minimization of the vortex shedding noise, a reduction of broadband noise can be observed, especially at higher Reynolds numbers. The noise reduction increases with decreasing air flow resistivity of the porous covers, which means that materials that are highly permeable to air result in the best noise reduction.

  15. Complex diffusion process for noise reduction

    DEFF Research Database (Denmark)

    Nadernejad, Ehsan; Barari, A.

    2014-01-01

    Signal de-noising and restoration is an essential step for many signal processing algorithms and applications. One of the most common problems is the removal of some interesting structures in the signal during the restoration process. The capability of methods based on partial differential...... equations (PDEs) in image restoration and de-noising prompted many researchers to search for an improvement in the technique. In this paper, a new method is presented for signal de-noising, based on PDEs and Schrodinger equations, named as complex diffusion process (CDP). This method assumes that variations...... for signal de-noising. To evaluate the performance of the proposed method, a number of experiments have been performed using Sinusoid, multi-component and FM signals cluttered with noise. The results indicate that the proposed method outperforms the approaches for signal de-noising known in prior art....

  16. Phase Noise Reduction of Laser Diode

    Science.gov (United States)

    Zhang, T. C.; Poizat, J.-Ph.; Grelu, P.; Roch, J.-F.; Grangier, P.; Marin, F.; Bramati, A.; Jost, V.; Levenson, M. D.; Giacobino, E.

    1996-01-01

    Phase noise of single mode laser diodes, either free-running or using line narrowing technique at room temperature, namely injection-locking, has been investigated. It is shown that free-running diodes exhibit very large excess phase noise, typically more than 80 dB above shot-noise at 10 MHz, which can be significantly reduced by the above-mentioned technique.

  17. Identification and Reduction of Turbomachinery Noise Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Noise has become a primary consideration in the design and development of many products, particulary in aerospace, automotive and consumer product industries....

  18. A dual-cable noise reduction method for Langmuir probes

    Science.gov (United States)

    Yang, T. F.; Zu, Q. X.; Liu, Ping

    1995-07-01

    To obtain fast time response plasma properties, electron density and electron temperature, with a Langmuir probe, the applied probe voltage has to be swept at high frequency. Due to the RC characteristics of coaxial cables, an induced noise of a square-wave form will appear when a sawtooth voltage is applied to the probe. Such a noise is very annoying and difficult to remove, particularly when the probe signal is weak. This paper discusses a noise reduction method using a dual-cable circuit. One of the cables is active and the other is a dummy. Both of them are of equal length and are laid parallel to each other. The active cable carries the applied probe voltage and the probe current signal. The dummy one is not connected to the probe. After being carefully tuned, the induced noises from both cables are nearly identical and therefore can be effectively eliminated with the use of a differential amplifier. A clean I-V characteristic curve can thus be obtained. This greatly improves the accuracy and the time resolution of the values of ne and Te.

  19. Perceptually optimized gain function for cochlear implant signal-to-noise ratio based noise reduction.

    Science.gov (United States)

    Mauger, Stefan J; Dawson, Pam W; Hersbach, Adam A

    2012-01-01

    Noise reduction in cochlear implants has achieved significant speech perception improvements through spectral subtraction and signal-to-noise ratio based noise reduction techniques. Current methods use gain functions derived through mathematical optimization or motivated by normal listening psychoacoustic experiments. Although these gain functions have been able to improve speech perception, recent studies have indicated that they are not optimal for cochlear implant noise reduction. This study systematically investigates cochlear implant recipients' speech perception and listening preference of noise reduction with a range of gain functions. Results suggest an advantageous gain function and show that gain functions currently used for noise reduction are not optimal for cochlear implant recipients. Using the cochlear implant optimised gain function, a 27% improvement over the current advanced combination encoder (ACE) stimulation strategy in speech weighted noise and a 7% improvement over current noise reduction strategies were observed in babble noise conditions. The optimized gain function was also most preferred by cochlear implant recipients. The CI specific gain function derived from this study can be easily incorporated into existing noise reduction strategies, to further improve listening performance for CI recipients in challenging environments.

  20. An Assessment of Psychological Noise Reduction by Landscape Plants

    Directory of Open Access Journals (Sweden)

    Fan Yang

    2011-04-01

    Full Text Available The emphasis in the term ‘Green Transportation’ is on the word ‘green’. Green transportation focuses on the construction of a slow transport system with a visually pleasing, easy and secure trip environment composed of urban parks, green roadside spaces and some other space that is full of landscape plants. This trip environment encourages residents to make trip choices that reduce fuel consumption and pollution and is one of the most important ways of popularizing green transportation. To study the psychological benefits provided by urban parks and other landscape environments, we combined a subjective approach (a questionnaire with an objective quantitative approach (emotional tests using an electroencephalogram; EEG. Using a questionnaire survey, we found that 90% of the subjects believed that landscape plants contribute to noise reduction and that 55% overrated the plants’ actual ability to attenuate noise. Two videos (showing a traffic scene and a plant scene were shown to 40 participants on video glasses. We detected and recorded EEG values with a portable electroencephalograph, and a comparison between the results of the two groups revealed that there was a highly significant asymmetry between the EEG activity of the vegetation scene and traffic scene groups. The results suggest that the emotions aroused by noise and visual stimuli are manifested in the synchronization of beta frequency band and the desynchronization of alpha frequency band, indicating that landscape plants can moderate or buffer the effects of noise. These findings indicate that landscape plants provide excess noise attenuating effects through subjects’ emotional processing, which we term ‘psychological noise reduction’.

  1. Reduction of Bumblebee Noise Generated by GSM

    Directory of Open Access Journals (Sweden)

    Han Su Kyi

    2014-09-01

    Full Text Available This research work presents a method for reducing a bumblebee noise generated by a GSM system. Global smart phone penetration has been very swift and 2nd generation, 3rd generation and 4th generation communication technology are commercially used in the world. GSM technology uses a channel access method that combines frequency division multiple access (FDMA and time division multiple access (TDMA. There are four commercial frequency bands. GSM technology has a burst structure by a TDMA method. And hence, the GSM technology has a disadvantage; radiation noise is generated from an antenna propagation signal of the smart phone, and consequently, the voice quality of the smart phone is degraded. This noise is commonly known as bumblebee noise, buzz noise or TDMA noise. There have been several studies to reduce the noise since a release of GSM technology in a commercial market. Those studies mainly focused on designing infinite impulse response (IIR notch filters by the signal processing technology or on data burst transmission schemes.

  2. The application of active noise control technology to reduce noise from air pollution control equipment

    Energy Technology Data Exchange (ETDEWEB)

    Depies, C. R.; Kapsos, D. W.

    1996-08-01

    The basic concept of active noise control, i. e. to create a noise field in a space in order to destructively interfere with an existing noise, and in the process create a quieter space, was explained. The manner in which noise control technology can be used in air pollution control equipment was described and guidelines for application were provided. A number of case studies were used to illustrate the suitability of active noise control for low frequency noise problems, especially in the area of air pollution control equipment. Impressive reduction of low frequency noise, energy efficiency, ability to retrofit into an existing duct system, and the hardware`s insensitivity to dirty exhaust environments were cited as the principal reasons for the success of active noise control technology over more traditional in-line passive silencers. 1 ref., 8 figs.

  3. An assessment of propeller aircraft noise reduction technology

    Science.gov (United States)

    Metzger, F. Bruce

    1995-01-01

    This report is a review of the literature regarding propeller airplane far-field noise reduction. Near-field and cabin noise reduction are not specifically addressed. However, some of the approaches used to reduce far-field noise produce beneficial effects in the near-field and in the cabin. The emphasis is on propeller noise reduction but engine exhaust noise reduction by muffling is also addressed since the engine noise becomes a significant part of the aircraft noise signature when propeller noise is reduced. It is concluded that there is a substantial body of information available that can be used as the basis to reduce propeller airplane noise. The reason that this information is not often used in airplane design is the associated weight, cost, and performance penalties. It is recommended that the highest priority be given to research for reducing the penalties associated with lower operating RPM and propeller diameter while increasing the number of blades. Research to reduce engine noise and explore innovative propeller concepts is also recommended.

  4. Engine Validation of Noise and Emission Reduction Technology Phase I

    Science.gov (United States)

    Weir, Don (Editor)

    2008-01-01

    This final report has been prepared by Honeywell Aerospace, Phoenix, Arizona, a unit of Honeywell International, Inc., documenting work performed during the period December 2004 through August 2007 for the NASA Glenn Research Center, Cleveland, Ohio, under the Revolutionary Aero-Space Engine Research (RASER) Program, Contract No. NAS3-01136, Task Order 8, Engine Validation of Noise and Emission Reduction Technology Phase I. The NASA Task Manager was Dr. Joe Grady of the NASA Glenn Research Center. The NASA Contract Officer was Mr. Albert Spence of the NASA Glenn Research Center. This report is for a test program in which NASA funded engine validations of integrated technologies that reduce aircraft engine noise. These technologies address the reduction of engine fan and jet noise, and noise associated with propulsion/airframe integration. The results of these tests will be used by NASA to identify the engineering tradeoffs associated with the technologies that are needed to enable advanced engine systems to meet stringent goals for the reduction of noise. The objectives of this program are to (1) conduct system engineering and integration efforts to define the engine test-bed configuration; (2) develop selected noise reduction technologies to a technical maturity sufficient to enable engine testing and validation of those technologies in the FY06-07 time frame; (3) conduct engine tests designed to gain insight into the sources, mechanisms and characteristics of noise in the engines; and (4) establish baseline engine noise measurements for subsequent use in the evaluation of noise reduction.

  5. Nordic Standards for measurement of aircraft noise immission in residential areas and noise reduction of dwellings

    Science.gov (United States)

    Svane, Christian; Plovsing, Birger

    Quantification by measurement of aircraft noise in residential areas and air traffic noise reduction of dwellings suffer from sensibility to the measurement technique used. Around the Copenhagen Airport (200.000 opr./year) 3.500 families have been granted from 50% to 90% of sound insulation costs by the Danish Government. Based on experience from evaluation measurements carried out by the Danish Acoustical Institute, the authors have proposed standardized measurement methods for the outdoor aircraft noise in residential areas and for the noise reduction of dwellings. In 1989 both noise measurement methods were accepted as Nordic Standards (NORDTEST ACOU 074 and 075) by Denmark, Finland, Iceland, Norway and Sweden.

  6. Seismic exploration noise reduction in the Marginal Ice Zone.

    Science.gov (United States)

    Tollefsen, Dag; Sagen, Hanne

    2014-07-01

    A sonobuoy field was deployed in the Marginal Ice Zone of the Fram Strait in June 2011 to study the spatial variability of ambient noise. High noise levels observed at 10-200 Hz are attributed to distant (1400 km range) seismic exploration. The noise levels decreased with range into the ice cover; the reduction is fitted by a spreading loss model with a frequency-dependent attenuation factor less than for under-ice interior Arctic propagation. Numerical modeling predicts transmission loss of the same order as the observed noise level reduction and indicates a significant loss contribution from under-ice interaction.

  7. Wind Noise Reduction using Non-negative Sparse Coding

    DEFF Research Database (Denmark)

    Schmidt, Mikkel N.; Larsen, Jan; Hsiao, Fu-Tien

    2007-01-01

    We introduce a new speaker independent method for reducing wind noise in single-channel recordings of noisy speech. The method is based on non-negative sparse coding and relies on a wind noise dictionary which is estimated from an isolated noise recording. We estimate the parameters of the model...... and discuss their sensitivity. We then compare the algorithm with the classical spectral subtraction method and the Qualcomm-ICSI-OGI noise reduction method. We optimize the sound quality in terms of signal-to-noise ratio and provide results on a noisy speech recognition task....

  8. 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.

  9. Wind fence enclosures for infrasonic wind noise reduction.

    Science.gov (United States)

    Abbott, JohnPaul; Raspet, Richard; Webster, Jeremy

    2015-03-01

    A large porous wind fence enclosure has been built and tested to optimize wind noise reduction at infrasonic frequencies between 0.01 and 10 Hz to develop a technology that is simple and cost effective and improves upon the limitations of spatial filter arrays for detecting nuclear explosions, wind turbine infrasound, and other sources of infrasound. Wind noise is reduced by minimizing the sum of the wind noise generated by the turbulence and velocity gradients inside the fence and by the area-averaging the decorrelated pressure fluctuations generated at the surface of the fence. The effects of varying the enclosure porosity, top condition, bottom gap, height, and diameter and adding a secondary windscreen were investigated. The wind fence enclosure achieved best reductions when the surface porosity was between 40% and 55% and was supplemented by a secondary windscreen. The most effective wind fence enclosure tested in this study achieved wind noise reductions of 20-27 dB over the 2-4 Hz frequency band, a minimum of 5 dB noise reduction for frequencies from 0.1 to 20 Hz, constant 3-6 dB noise reduction for frequencies with turbulence wavelengths larger than the fence, and sufficient wind noise reduction at high wind speeds (3-6 m/s) to detect microbaroms.

  10. Supersonic Jet Noise: Main Sources and Reduction Methodologies

    Directory of Open Access Journals (Sweden)

    Mohammadreza Azimi

    2014-07-01

    Full Text Available The large velocity ratio and the presence of Shocks in the exhaust plume from low bypass engines or supersonic jetliners cause jet noise to be dominant component of overall aircraft noise, and therefore is an important issue in design of the next generation of civil supersonic transport. Jet noise reduction technology also has application in the design of highperformance tactical aircraft. Jet noise is of particular concern on aircraft carriers where it is necessary for deck crew to be in relatively close proximity to the aircraft at takeoff and landing. In this paper, a brief discussion about supersonic jet noise sources and a review of the main passive technologies employed for the reduction of supersonic jet noise are presented.

  11. External Acoustic Liners for Multi-Functional Aircraft Noise Reduction

    Science.gov (United States)

    Jones, Michael G. (Inventor); Thomas, Russell H. (Inventor); Nark, Douglas M. (Inventor); Howerton, Brian M. (Inventor); Czech, Michael J. (Inventor)

    2017-01-01

    Acoustic liners for aircraft noise reduction include one or more chambers that are configured to provide a pressure-release surface such that the engine noise generation process is inhibited and/or absorb sound by converting the sound into heat energy. The size and shape of the chambers can be selected to inhibit the noise generation process and/or absorb sound at selected frequencies.

  12. Noise Reduction Methods for Weighing Lysimeters

    Science.gov (United States)

    Mechanical vibration of the grass and crop weighing lysimeters, located at the University of California West Side Field Research and Extension Station at Five Points, CA generated noise in lysimeter mass measurements and reduced the quality of evapotranspiration (ET) data. Two filtering methods for ...

  13. Noise reduction method based on weighted manifold decomposition

    Institute of Scientific and Technical Information of China (English)

    Gan Jian-Chao; Xiao Xian-Ci

    2004-01-01

    A noise reduction method based on weighted manifold decomposition is proposed in this paper, which does not need knowledge of the chaotic dynamics and choosing number of eigenvalues. The simulation indicates that the performance of this method can increase the signal-to-noise ratio of noisy chaotic time series.

  14. Noise Reduction in the Time Domain using Joint Diagonalization

    DEFF Research Database (Denmark)

    Nørholm, Sidsel Marie; Benesty, Jacob; Jensen, Jesper Rindom

    2014-01-01

    , an estimate of the desired signal is found by subtraction of the noise estimate from the observed signal. The filter can be designed to obtain a desired trade-off between noise reduction and signal distortion, depending on the number of eigenvectors included in the filter design. This is explored through...

  15. Noise Reduction with Optimal Variable Span Linear Filters

    DEFF Research Database (Denmark)

    Jensen, Jesper Rindom; Benesty, Jacob; Christensen, Mads Græsbøll

    2016-01-01

    of eigenvectors stemming from a joint diagonalization of the covariance matrices of the signal of interest and the noise. The resulting filters are flexible in that it is possible to trade off distortion of the desired signal for improved noise reduction. This tradeoff is controlled by the number of eigenvectors...

  16. Prewhitening for Rank-Deficient Noise in Subspace Methods for Noise Reduction

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jensen, Søren Holdt

    2005-01-01

    A fundamental issue in connection with subspace methods for noise reduction is that the covariance matrix for the noise is required to have full rank, in order for the prewhitening step to be defined. However, there are important cases where this requirement is not fulfilled, e.g., when the noise...... also for rank deficient noise. We also demonstrate how to formulate this algorithm by means of a quotient ULV decomposition, which allows for faster computation and updating. Finally we apply our algorithm to a problem involving a speech signal contaminated by narrow-band noise....

  17. Single and multiple microphone noise reduction strategies in cochlear implants.

    Science.gov (United States)

    Kokkinakis, Kostas; Azimi, Behnam; Hu, Yi; Friedland, David R

    2012-06-01

    To restore hearing sensation, cochlear implants deliver electrical pulses to the auditory nerve by relying on sophisticated signal processing algorithms that convert acoustic inputs to electrical stimuli. Although individuals fitted with cochlear implants perform well in quiet, in the presence of background noise, the speech intelligibility of cochlear implant listeners is more susceptible to background noise than that of normal hearing listeners. Traditionally, to increase performance in noise, single-microphone noise reduction strategies have been used. More recently, a number of approaches have suggested that speech intelligibility in noise can be improved further by making use of two or more microphones, instead. Processing strategies based on multiple microphones can better exploit the spatial diversity of speech and noise because such strategies rely mostly on spatial information about the relative position of competing sound sources. In this article, we identify and elucidate the most significant theoretical aspects that underpin single- and multi-microphone noise reduction strategies for cochlear implants. More analytically, we focus on strategies of both types that have been shown to be promising for use in current-generation implant devices. We present data from past and more recent studies, and furthermore we outline the direction that future research in the area of noise reduction for cochlear implants could follow.

  18. A beamformer post-filter for cochlear implant noise reduction.

    Science.gov (United States)

    Hersbach, Adam A; Grayden, David B; Fallon, James B; McDermott, Hugh J

    2013-04-01

    Cochlear implant users have limited ability to understand speech in noisy conditions. Signal processing methods to address this issue that use multiple microphones typically use beamforming to perform noise reduction. However, the effectiveness of the beamformer is diminished as the number of interfering noises increases and the acoustic environment becomes more diffuse. A multi-microphone noise reduction algorithm that aims to address this issue is presented in this study. The algorithm uses spatial filtering to estimate the signal-to-noise ratio (SNR) and attenuates time-frequency elements that have poor SNR. The algorithm was evaluated by measuring intelligibility of speech embedded in 4-talker babble where the interfering talkers were spatially separated and changed location during the test. Twelve cochlear implant users took part in the evaluation, which demonstrated a significant mean improvement of 4.6 dB (standard error 0.4, P noise is spatially separated from the target speech.

  19. Mechanisms of active control for noise inside a vibrating cylinder

    Science.gov (United States)

    Lester, Harold C.; Fuller, Chris R.

    1987-01-01

    The active control of propeller-induced noise fields inside a flexible cylinder is studied with attention given to the noise reduction mechanisms inherent in the present coupled acoustic shell model. The active noise control model consists of an infinitely long aluminum cylinder with a radius of 0.4 m and a thickness of 0.001 m. Pressure maps are shown when the two external sources are driven in-phase at a frequency corresponding to Omega = 0.22.

  20. 主动噪声控制技术在工业换风扇降噪中的应用%Application of Active Noise Control Technique in Noise Reduction System of Industrial Exhaust Fan

    Institute of Scientific and Technical Information of China (English)

    吴亚锋; 姜节胜; 张森社

    2001-01-01

    The noise of exhaust fan is mainly consisted of pass frequency & low second harmonic frequency when blade is rotating. Noises on discrete frequency can be efficiently controled by using active noise control technique. A self control system which has 4 error input & 2 counteracting output is designed by the author. The satisfied result is obtained by using it on noise control system of exhaust fan.%指出了换风扇噪声主要是由风叶旋转时的通频及其低次谐频成分构成,应用主动噪声控制技术能够有效地抑制这些离散频率上的声音。笔者设计了一具有4个误差输入和两个抵消输出的自适应控制系统,并应用于换风扇噪声控制上,获得了满意的实验结果。

  1. Azimuthally Varying Noise Reduction Techniques Applied to Supersonic Jets

    Science.gov (United States)

    Heeb, Nicholas S.

    An experimental investigation into the effect of azimuthal variance of chevrons and fluidically enhanced chevrons applied to supersonic jets is presented. Flow field measurements of streamwise and cross-stream particle imaging velocimetry were employed to determine the causes of noise reduction, which was demonstrated through acoustic measurements. Results were obtained in the over- and under- expanded regimes, and at the design condition, though emphasis was placed on the overexpanded regime due to practical application. Surveys of chevron geometry, number, and arrangement were undertaken in an effort to reduce noise and/or incurred performance penalties. Penetration was found to be positively correlated with noise reduction in the overexpanded regime, and negatively correlated in underexpanded operation due to increased effective penetration and high frequency penalty, respectively. The effect of arrangement indicated the beveled configuration achieved optimal abatement in the ideally and underexpanded regimes due to superior BSAN reduction. The symmetric configuration achieved optimal overexpanded noise reduction due to LSS suppression from improved vortex persistence. Increases in chevron number generally improved reduction of all noise components for lower penetration configurations. Higher penetration configurations reached levels of saturation in the four chevron range, with the potential to introduce secondary shock structures and generate additional noise with higher number. Alternation of penetration generated limited benefit, with slight reduction of the high frequency penalty caused by increased shock spacing. The combination of alternating penetration with beveled and clustered configurations achieved comparable noise reduction to the standard counterparts. Analysis of the entire data set indicated initial improvements with projected area that saturated after a given level and either plateaued or degraded with additional increases. Optimal reductions

  2. Reduction of Wake-Stator Interaction Noise Using Passive Porosity

    Science.gov (United States)

    Tinetti, Ana F.; Kelly, Jeffrey J.; Thomas, Russell H.; Bauer, Steven X. S.

    2002-01-01

    The present study was conducted to assess the potential of Passive Porosity Technology as a mechanism to reduce interaction noise in turbomachinery by reducing the fluctuating forces acting on the vane surfaces. To do so, a typical fan stator airfoil was subjected to the effects of a transversely moving wake; time histories of the primitive aerodynamic variables, obtained from Computational Fluid Dynamics (CFD) solutions, were then input into an acoustic prediction code. This procedure was performed on the solid airfoil to obtain a baseline, and on a series of porous configurations in order to isolate those that yield maximum noise reductions without compromising the aerodynamic performance of the stator. It was found that communication between regions of high pressure differential - made possible by the use of passive porosity - is necessary to significantly alter the noise radiation pattern of the stator airfoil. In general, noise reductions were obtained for those configurations incorporating passive porosity in the region between x/c is approximately 0.15 on the suction side of the airfoil and x/c is approximately 0.20 on the pressure side. Reductions in overall radiated noise of approximately 1.0 dB were obtained. The noise benefit increased to about 2.5 dB when the effects of loading noise alone were considered.

  3. Noise reduction algorithm for glueball correlators

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Pushan, E-mail: tppm@iacs.res.in [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Kolkata (India); Mathur, Nilmani, E-mail: nilmani@theory.tifr.res.in [Department of Theoretical Physics, Tata Institute of Fundamental Research, Mumbai (India); Mondal, Sourav, E-mail: tpsm5@iacs.res.in [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Kolkata (India)

    2014-09-07

    We present an error reduction method for obtaining glueball correlators from Monte Carlo simulations of SU(3) lattice gauge theory. We explore the scalar and tensor channels at three different lattice spacings. Using this method we can follow glueball correlators to temporal separations even up to 1 fermi. We estimate the improvement over the naive method and compare our results with existing computations.

  4. Development of Active Noise Control System for Quieting Transformer Noise

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bok Kyu; Song, Seik Young; Choi, Huo Yul [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Yun, Dae Hea; Lee, Hyuk Jae [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

    1997-12-31

    The passive noise control technique made use of sound-absorbing or soundproofing materials, so it required a large area and high cost for installation and had a drawback of poor performance at low frequency. Compared to this, the Active Noise Control attenuates noise sound pressure by using secondary source which has same performance ay low-frequency. Furthermore, it is able to save space and expenses. - research on adaptive algorithms - evaluation of global attenuation of the control - computer simulation - real-time Active Noise Control System Hardware Implementation - ANC system setting in the noisy area.

  5. Development of Active Noise Control System for Quieting Transformer Noise

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Bok Kyu; Song, Seik Young; Choi, Huo Yul [Korea Electric Power Research Institute, Taejon (Korea, Republic of); Yun, Dae Hea; Lee, Hyuk Jae [Korea Electrotechnology Research Institute, Changwon (Korea, Republic of)

    1997-12-31

    The passive noise control technique made use of sound-absorbing or soundproofing materials, so it required a large area and high cost for installation and had a drawback of poor performance at low frequency. Compared to this, the Active Noise Control attenuates noise sound pressure by using secondary source which has same performance ay low-frequency. Furthermore, it is able to save space and expenses. - research on adaptive algorithms - evaluation of global attenuation of the control - computer simulation - real-time Active Noise Control System Hardware Implementation - ANC system setting in the noisy area.

  6. Research on Aerodynamic Noise Reduction for High-Speed Trains

    Directory of Open Access Journals (Sweden)

    Yadong Zhang

    2016-01-01

    Full Text Available A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD/Ffowcs Williams-Hawkings (FW-H acoustic analogy. An analysis of noise reduction methods based on the main noise sources was performed. An aerodynamic noise model for a full-scale high-speed train, including three coaches with six bogies, two inter-coach spacings, two windscreen wipers, and two pantographs, was established. Several low-noise design improvements for the high-speed train were identified, based primarily on the main noise sources; these improvements included the choice of the knuckle-downstream or knuckle-upstream pantograph orientation as well as different pantograph fairing structures, pantograph fairing installation positions, pantograph lifting configurations, inter-coach spacings, and bogie skirt boards. Based on the analysis, we designed a low-noise structure for a full-scale high-speed train with an average sound pressure level (SPL 3.2 dB(A lower than that of the original train. Thus, the noise reduction design goal was achieved. In addition, the accuracy of the aerodynamic noise calculation method was demonstrated via experimental wind tunnel tests.

  7. Prewhitening for Narrow-Band Noise in Subspace Methods for Noise Reduction

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jensen, Søren Holdt

    2004-01-01

    A fundamental issue in connection with subspace methods for noise reduction is that the covariance matrix for the noise is required to have full rank, in order for the prewhitening step to be defined. However, there are important cases where this requirement is not fulfilled, typically when...... that works also for rank deficient noise. We also demonstrate how to formulate this algorithm by means of a quotient ULV decomposition, which allows for faster computation and updating. Finally we apply our algorithm to a problem involving a speech signal contaminated by narrow-band noise....

  8. Noise reduction algorithm for glueball correlators

    Directory of Open Access Journals (Sweden)

    Pushan Majumdar

    2014-09-01

    Full Text Available We present an error reduction method for obtaining glueball correlators from Monte Carlo simulations of SU(3 lattice gauge theory. We explore the scalar and tensor channels at three different lattice spacings. Using this method we can follow glueball correlators to temporal separations even up to 1 fermi. We estimate the improvement over the naive method and compare our results with existing computations.

  9. REDUCTION OF NOISE OF ENVIRONMENTAL POLLUTION BY INSTALLING SILENCERS

    Directory of Open Access Journals (Sweden)

    Gorin V. A.

    2016-05-01

    Full Text Available The article describes the sources of noise Yeisk thermal power plant (TPP in excess of the permissible sound pressure levels in homes on the street. Gorky, 25. Eisk TPP is located near the residential area, where the permissible noise level standards adopted much more stringent than in the power plants. Prolonged exposure to noise leads to human disease noise disease. The scheme of movement of exhaust gases from the thermal power plant generating units Yeisk. Analysis of measurements of noise characteristics of main and auxiliary equipment showed that one of the main sources are sectioned estuaries double-barrel pipe height of 27 m and slices estuaries pipes emergency explosive valves flues installed on the roof at a height of 17 m. The previous Noise reduction nozzles that emit noise uniformly in all directions are replaced by advanced, whose index changed direction estuaries sections double-barrel tubes. This will change the level of radiated noise in residential development. If you change the angle of orientation of 135°-180°, the noise level in residential construction decreased by 7-10 dB. Shows a photograph of thermal power plants, residential buildings, the old and improved silencers

  10. Low-frequency noise reduction of lightweight airframe structures

    Science.gov (United States)

    Getline, G. L.

    1976-01-01

    The results of an experimental study to determine the noise attenuation characteristics of aircraft type fuselage structural panels were presented. Of particular interest was noise attenuation at low frequencies, below the fundamental resonances of the panels. All panels were flightweight structures for transport type aircraft in the 34,050 to 45,400 kg (75,000 to 100,000 pounds) gross weight range. Test data include the results of vibration and acoustic transmission loss tests on seven types of isotropic and orthotropically stiffened, flat and curved panels. The results show that stiffness controlled acoustically integrated structures can provide very high noise reductions at low frequencies without significantly affecting their high frequency noise reduction capabilities.

  11. Reduction of internal noise in auditory perceptual learning.

    Science.gov (United States)

    Jones, Pete R; Moore, David R; Amitay, Sygal; Shub, Daniel E

    2013-02-01

    This paper examines what mechanisms underlie auditory perceptual learning. Fifteen normal hearing adults performed two-alternative, forced choice, pure tone frequency discrimination for four sessions. External variability was introduced by adding a zero-mean Gaussian random variable to the frequency of each tone. Measures of internal noise, encoding efficiency, bias, and inattentiveness were derived using four methods (model fit, classification boundary, psychometric function, and double-pass consistency). The four methods gave convergent estimates of internal noise, which was found to decrease from 4.52 to 2.93 Hz with practice. No group-mean changes in encoding efficiency, bias, or inattentiveness were observed. It is concluded that learned improvements in frequency discrimination primarily reflect a reduction in internal noise. Data from highly experienced listeners and neural networks performing the same task are also reported. These results also indicated that auditory learning represents internal noise reduction, potentially through the re-weighting of frequency-specific channels.

  12. The relation between psychoacoustical factors and annoyance under different noise reduction conditions for railway noise.

    Science.gov (United States)

    Kasess, Christian H; Maly, Thomas; Majdak, Piotr; Waubke, Holger

    2017-05-01

    The A-weighted sound pressure level (SPL) is commonly used to assess the effect of noise reduction measures on noise-induced annoyance. While for road traffic noise loudness seems to be a better descriptor of annoyance, for railway noise a systematic investigation seems to be lacking. Thus, in this study, the relation between annoyance and perceptually motivated descriptors was investigated for various conditions of binaural recordings of pass-bys of cargo and passenger trains. The conditions included free field and spectral mitigations caused by a 4 m high noise barrier, a 1 m high noise barrier close to the track, and rail dampers. Forty listeners performed a free magnitude estimation of annoyance for different presentation levels and the ratings were fit to various models. Further, level changes required to evoke a noticeable change in annoyance (annoyance thresholds) were acquired. The models based on the A-weighted SPL explained the ratings and thresholds better when the reduction measure was explicitly provided as a parameter. However, the optimal models were loudness-level-based models, which were able to better describe the annoyance, even independently of the reduction measure. Both experiments underline the effectiveness of loudness when describing the annoyance in the area of railway noise reduction.

  13. Arrhythmia ECG Noise Reduction by Ensemble Empirical Mode Decomposition

    Directory of Open Access Journals (Sweden)

    Kang-Ming Chang

    2010-06-01

    Full Text Available A novel noise filtering algorithm based on ensemble empirical mode decomposition (EEMD is proposed to remove artifacts in electrocardiogram (ECG traces. Three noise patterns with different power—50 Hz, EMG, and base line wander – were embedded into simulated and real ECG signals. Traditional IIR filter, Wiener filter, empirical mode decomposition (EMD and EEMD were used to compare filtering performance. Mean square error between clean and filtered ECGs was used as filtering performance indexes. Results showed that high noise reduction is the major advantage of the EEMD based filter, especially on arrhythmia ECGs.

  14. Amplitude Noise Reduction of Ion Lasers with Optical Feedback

    Science.gov (United States)

    Herring, Gregory C.

    2011-01-01

    A reduction in amplitude noise on the output of a multi-mode continuous-wave Ar-ion laser was previously demonstrated when a fraction of the output power was retroreflected back into the laser cavity. This result was reproduced in the present work and a Fabry-Perot etalon was used to monitor the longitudinal mode structure of the laser. A decrease in the number of operating longitudinal cavity modes was observed simultaneously with the introduction of the optical feedback and the onset of the amplitude noise reduction. The noise reduction is a result of a reduced number of lasing modes, resulting in less mode beating and amplitude fluctuations of the laser output power.

  15. 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.

  16. Michelson Interferometer characterisation of noise reduction in DFB fibre lasers

    Science.gov (United States)

    Canagasabey, Albert; Jones, David; Mann, David; Canning, John; Fleming, Simon; Holdsworth, John

    2012-02-01

    A comparison is made between unpackaged and packaged distributed feedback (DFB) fibre lasers using the Michelson interferometer configuration for delayed self-heterodyne interferometery (MIDSHI) to ascertain the improvements to the external environmental noise, quantified by reductions in the Gaussian linewidth. Voigt fitting is used to extract and separate out the Lorentzian and Gaussian linewidth contributions and therefore the associated sources of noise. Significant improvements in the Gaussian linewidth were achieved as a result of significant reductions in the sensitivity of the DFB laser to external perturbations using packaging. However, a broadening of the laser Lorentzian linewidth was observed.

  17. Active vibrations and noise control for turboprop application research program activities

    Science.gov (United States)

    Paonessa, A.; Concilio, A.; Lecce, Leonardo V.

    1992-01-01

    The objectives of this work include the following: (1) development of active noise control techniques to alleviate inefficiencies and drawbacks of passive noise control approach especially at low frequencies; (2) reduction of structurally radiated noise applying external forces to the vibrating structure by means of force actuators made of piezoelectric material; and (3) reduction of fuselage vibration levels in propeller driven aircraft by means of distributed piezoelectric actuators that are actively controlled.

  18. Sound quality measures for speech in noise through a commercial hearing aid implementing digital noise reduction.

    Science.gov (United States)

    Ricketts, Todd A; Hornsby, Benjamin W Y

    2005-05-01

    This brief report discusses the affect of digital noise reduction (DNR) processing on aided speech recognition and sound quality measures in 14 adults fitted with a commercial hearing aid. Measures of speech recognition and sound quality were obtained in two different speech-in-noise conditions (71 dBA speech, +6 dB SNR and 75 dBA speech, +1 dB SNR). The results revealed that the presence or absence of DNR processing did not impact speech recognition in noise (either positively or negatively). Paired comparisons of sound quality for the same speech in noise signals, however, revealed a strong preference for DNR processing. These data suggest that at least one implementation of DNR processing is capable of providing improved sound quality, for speech in noise, in the absence of improved speech recognition.

  19. Content-dependent block noise reduction for mobile displays

    Science.gov (United States)

    Kim, Ga-Hee; Lee, Yoon-Gyoo; Kim, Han-Eol; Kim, Choon-Woo

    2012-01-01

    Number of pixels on mobile displays is rapidly increasing. Recently, mobile displays with more than one million pixels have been introduced into markets. However, most of multimedia contents to be displayed on mobile displays have much smaller pixel counts. For example, number of pixels for a T-DMB(terrestrial digital multimedia broadcasting) sequence is 320x240. When enlargement is applied to input sequence, perceived image quality would be degraded. Increase in visibility of block noise is one of the major reasons for image quality degradation on mobile displays. This paper presents a simple and computationally efficient method to reduce visibility of block noise on enlarged multimedia sequences. In proposed method, a simple low pass filtering is selectively applied to the pixels of block noises for reduction of block noise visibility as well as faithful reproduction of image details.

  20. The technology on noise reduction of the APD detection circuit

    Science.gov (United States)

    Wu, Xue-ying; Zheng, Yong-chao; Cui, Jian-yong

    2013-09-01

    The laser pulse detection is widely used in the field of laser range finders, laser communications, laser radar, laser Identification Friend or Foe, et al, for the laser pulse detection has the advantage of high accuracy, high sensitivity and strong anti-interference. The avalanche photodiodes (APD) has the advantage of high quantum efficiency, high response speed and huge gain. The APD is particularly suitable for weak signal detection. The technology that APD acts as the photodetector for weak signal reception and amplification is widely used in laser pulse detection. The APD will convert the laser signal to weak electrical signal. The weak signal is amplified, processed and exported by the circuit. In the circuit design, the optimal signal detection is one key point in photoelectric detection system. The issue discusses how to reduce the noise of the photoelectric signal detection circuit and how to improve the signal-to-noise ratio, related analysis and practice included. The essay analyzes the mathematical model of the signal-to-noise ratio for photoelectric conversion and the noise of the APD photoelectric detection system. By analysis the bandwidth of the detection system is determined, and the circuit devices are selected that match the APD. In the circuit design separated devices with low noise are combined with integrated operational amplifier for the purpose of noise reduction. The methods can effectively suppress the noise, and improve the detection sensitivity.

  1. 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%.

  2. Active Control of Fan Noise

    Institute of Scientific and Technical Information of China (English)

    Nobuhiko YAMASAKI; Hirotoshi TAJIMA

    2008-01-01

    In the wake-rotor interaction fan noise, a number of the interacting modes at the blade passing frequency (BPF)and its harmonics are generated which are prescribed by the number of stator and rotor blades etc. In the present study, the dominant mode is tried to be suppressed by the secondary sound from the loudspeaker actuators. One of the novel features of the present system is the adoption of the control board with the Field Programmable Gate Array (FPGA) hardware and the LabVIEW software to synchronize the circumferentially installed loudspeaker actuators with the relative location of rotational blades under arbitrary fan rotational speeds. The experiments were conducted under the conditions of three rotational speeds of 2004, 3150, and 4002 [rpm]. The reduction in the sound pressure level (SPL) was observed for all three rotational speeds. The sound pressure level at the BPF was reduced approximately 13 [dB] for 2004 [rpm] case, but not so large reduction was attained for other cases probably due to the inefficiency of the loudspeaker actuators at high frequencies

  3. Developing active noise control systems for noise attenuation in ducts

    Science.gov (United States)

    Campos, Rosely V.; Ivo, Rodrigo C.; Medeiros, Eduardo B.

    2002-11-01

    The present work describes some of the research effort on Active Noise Control (ANC) being jointly developed by the Catholic University of Minas Gerais (PUC-MINAS) and the Federal University of Minas Gerais (UFMG). Considerations about the implementation of Digital Signal Processing for noise control in ducts has been presented. The objective is to establish a study on Active Noise Control in ducts combining geometry and acoustic parameters modification together with adaptive digital filtering implementation. Both algorithm and digital signal processing details are also discussed. The main results for a typical application where real attenuation has been obtained are presented and considered according to their use in developing real applications. The authors also believe that the present text should provide an interesting overview for both designers and students concerned about Active Noise Control in ducts. (To be presented in Portuguese.)

  4. Novel active noise-reducing headset using earshell vibration control.

    Science.gov (United States)

    Rafaely, Boaz; Carrilho, Joao; Gardonio, Paolo

    2002-10-01

    Active noise-reducing (ANR) headsets are available commercially in applications varying from aviation communication to consumer audio. Current ANR systems use passive attenuation at high frequencies and loudspeaker-based active noise control at low frequencies to achieve broadband noise reduction. This paper presents a novel ANR headset in which the external noise transmitted to the user's ear via earshell vibration is reduced by controlling the vibration of the earshell using force actuators acting against an inertial mass or the earshell headband. Model-based theoretical analysis using velocity feedback control showed that current piezoelectric actuators provide sufficient force but require lower stiffness for improved low-frequency performance. Control simulations based on experimental data from a laboratory headset showed that good performance can potentially be achieved in practice by a robust feedback controller, while a single-frequency real-time control experiment verified that noise reduction can be achieved using earshell vibration control.

  5. Active noise control and application; Active soon seigyo gijutsu to sono tekiyorei

    Energy Technology Data Exchange (ETDEWEB)

    Muto, M.; Hayashi, M.; Kawai, T.; Sato, F.; Kanbe, K. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan); Inoue, Y.; Takada, K.

    1995-11-01

    The recent rapid progress of electronic devices and signal processing techniques has allowed the practical application of active noise control(ANC) for reduction of noise. The principle of ANC is to cancel a noise by an anti-noise which has the same amplitude of the noise but the inverse phase. For noise reduction in gas ducts, the one dimensional ANC theory can be applied. However, there are still several technical issues particulars to individual plants to be studied and solved. This paper describes the ANC system using the hydraulically actuated speaker which has been developed at IHI, and applications to reduction of low frequency sound emitted at the exit of a stack from a large induction fan. Another application for tractor cabin is also described, indicating successful noise reduction. 6 refs., 12 figs.

  6. Market Analysis of Soundproof and Noise Reduction Plate

    Directory of Open Access Journals (Sweden)

    Chang Heyu

    2017-01-01

    Full Text Available Since the reform and opening up, China has a booming economy development, transportation industry as an important part of the economic processes has made a considerable progress, and continue to promote the rapid economic development. At the end of 2012, China's highway mileage has reached 4.238 million km and highway mileage ranks first in the world. Transportation in promoting rapid economic development, but also brings the traffic noise which has a tremendous influence on residents’ daily life, and this influence has gradually deepening and widening, in this situation the production of noise reduction panel gradually emerged. In this paper, a noise barriers manufacturer’ business model in Beijing Daxing District and analyze existing data will be analyzed, it will give much guidance and reference for a new noise reduction factory. The study has shown that plant will target all levels of government departments in charge of roads and the property of management department of residence as our customer groups, increasing technological innovation and improving product quality to establish a more extensive business relationships, and gradually formed noise barriers market competitiveness.

  7. Aeroacoustic Evaluation of Flap and Landing Gear Noise Reduction Concepts

    Science.gov (United States)

    Khorrami, Mehdi R.; Humphreys, William M., Jr.; Lockard, David P.; Ravetta, Patricio A.

    2014-01-01

    Aeroacoustic measurements for a semi-span, 18% scale, high-fidelity Gulfstream aircraft model are presented. The model was used as a test bed to conduct detailed studies of flap and main landing gear noise sources and to determine the effectiveness of numerous noise mitigation concepts. Using a traversing microphone array in the flyover direction, an extensive set of acoustic data was obtained in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the information was acquired with the model in a landing configuration with the flap deflected 39 deg and the main landing gear alternately installed and removed. Data were obtained at Mach numbers of 0.16, 0.20, and 0.24 over directivity angles between 56 deg and 116 deg, with 90 deg representing the overhead direction. Measured acoustic spectra showed that several of the tested flap noise reduction concepts decrease the sound pressure levels by 2 - 4 dB over the entire frequency range at all directivity angles. Slightly lower levels of noise reduction from the main landing gear were obtained through the simultaneous application of various gear devices. Measured aerodynamic forces indicated that the tested gear/flap noise abatement technologies have a negligible impact on the aerodynamic performance of the aircraft model.

  8. Low frequency noise reduction using stiff light composite panels

    Institute of Scientific and Technical Information of China (English)

    DENG Yongchang; LIN Weizheng

    2003-01-01

    The experiment presented in this paper is to investigate and analyze the noise reduction at low frequency using stiff light composite panels. Since these composite panels are made of lightweight and stiff materials, this actuation strategy will enable the creation of composite panels for duct noise control without using traditional heavy structural mass. The results suggest that the mass-spring resonance absorption in the case of a comparatively stiff thick panel with a thin flexible plate is more efficient with minimum weight, when subjected to low-frequency (<500 Hz). The efficiency of the panel absorber depends on the mass of the thin flexible plate and the stiffness of the panel.

  9. 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.

  10. Noise reduction facilitated by dosage compensation in gene networks

    Science.gov (United States)

    Peng, Weilin; Song, Ruijie; Acar, Murat

    2016-01-01

    Genetic noise together with genome duplication and volume changes during cell cycle are significant contributors to cell-to-cell heterogeneity. How can cells buffer the effects of these unavoidable epigenetic and genetic variations on phenotypes that are sensitive to such variations? Here we show that a simple network motif that is essential for network-dosage compensation can reduce the effects of extrinsic noise on the network output. Using natural and synthetic gene networks with and without the network motif, we measure gene network activity in single yeast cells and find that the activity of the compensated network is significantly lower in noise compared with the non-compensated network. A mathematical analysis provides intuitive insights into these results and a novel stochastic model tracking cell-volume and cell-cycle predicts the experimental results. Our work implies that noise is a selectable trait tunable by evolution. PMID:27694830

  11. Impact of Noise and Noise Reduction on Processing Effort: A Pupillometry Study

    DEFF Research Database (Denmark)

    Wendt, Dorothea; Hietkamp, Renskje K; Lunner, Thomas

    2017-01-01

    Speech perception in adverse listening situations can be exhausting. Hearing loss particularly affects processing demands, as it requires increased effort for successful speech perception in background noise. Signal processing in hearing aids and noise reduction (NR) schemes aim to counteract...... the effect of noise and reduce the effort required for speech recognition in adverse listening situations. The present study examined the benefit of NR schemes, applying a combination of a digital NR and directional microphones, for reducing the processing effort during speech recognition. The effect...... of noise (intelligibility level) and different NR schemes on effort were evaluated by measuring the pupil dilation of listeners. In 2 different experiments, performance accuracy and peak pupil dilation (PPD) were measured in 24 listeners with hearing impairment while they performed a speech recognition...

  12. An improved video median noise reduction algorithm for ambulance vehicle terminal monitoring system

    Science.gov (United States)

    Ma, Xian-Min; Zhang, Hang

    2012-04-01

    An improved video median noise reduction algorithm is presented for 120 vehicle terminal monitoring system in this paper. The noise causes of the video images in many 120 ambulance vehicle video terminal monitor equipments are analyzed, and the space rigid body model of self-adaptive median noise reduction filter is established to decrease the noises of the video image transmission process. The noise reduction experiment of video images shows that the proposed video median noise reduction algorithm is superior to the traditional adaptive filtering method, because the new method has the superiority of space-time joint noise reduction.

  13. Joint models for noise annoyance and willingness to pay for road noise reduction

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Bue Bjørner, Thomas

    2006-01-01

    Recent contingent valuation (CV) studies of the willingness to pay (WTP) for road noise reduction have used stated annoyance as an independent variable. We argue that this may be inappropriate due to potential endogeneity bias. Instead, an alternative model is proposed that treats both WTP...

  14. Objective Measures of Listening Effort: Effects of Background Noise and Noise Reduction

    Science.gov (United States)

    Sarampalis, Anastasios; Kalluri, Sridhar; Edwards, Brent; Hafter, Ervin

    2009-01-01

    Purpose: This work is aimed at addressing a seeming contradiction related to the use of noise-reduction (NR) algorithms in hearing aids. The problem is that although some listeners claim a subjective improvement from NR, it has not been shown to improve speech intelligibility, often even making it worse. Method: To address this, the hypothesis…

  15. Objective Measures of Listening Effort: Effects of Background Noise and Noise Reduction

    Science.gov (United States)

    Sarampalis, Anastasios; Kalluri, Sridhar; Edwards, Brent; Hafter, Ervin

    2009-01-01

    Purpose: This work is aimed at addressing a seeming contradiction related to the use of noise-reduction (NR) algorithms in hearing aids. The problem is that although some listeners claim a subjective improvement from NR, it has not been shown to improve speech intelligibility, often even making it worse. Method: To address this, the hypothesis…

  16. Noise pollution of air compressor and its noise reduction procedures by using an enclosure

    Directory of Open Access Journals (Sweden)

    Farhad Forouharmajd

    2012-01-01

    Conclusions: An overall noise reduction by 25 dB with the use of mineral wool as an extra liner on the inside of the enclosure, suggests that the effectiveness of the enclosure can be increased by using such absorber materials.

  17. The NIRS Analysis Package: noise reduction and statistical inference.

    Science.gov (United States)

    Fekete, Tomer; Rubin, Denis; Carlson, Joshua M; Mujica-Parodi, Lilianne R

    2011-01-01

    Near infrared spectroscopy (NIRS) is a non-invasive optical imaging technique that can be used to measure cortical hemodynamic responses to specific stimuli or tasks. While analyses of NIRS data are normally adapted from established fMRI techniques, there are nevertheless substantial differences between the two modalities. Here, we investigate the impact of NIRS-specific noise; e.g., systemic (physiological), motion-related artifacts, and serial autocorrelations, upon the validity of statistical inference within the framework of the general linear model. We present a comprehensive framework for noise reduction and statistical inference, which is custom-tailored to the noise characteristics of NIRS. These methods have been implemented in a public domain Matlab toolbox, the NIRS Analysis Package (NAP). Finally, we validate NAP using both simulated and actual data, showing marked improvement in the detection power and reliability of NIRS.

  18. Portable Low-Frequency Noise Reduction Device for Both Small Open and Closed Spaces

    Directory of Open Access Journals (Sweden)

    Chao Wang

    2016-01-01

    Full Text Available Noise pollution has been given more attention due to its negative impacts on human health and disease. The portable low-frequency noise reduction device we developed in this research can provide an effective way for solving low-frequency noise pollution problem in the small space. This work describes the design principle and the prototype structures for two versions of V1.5 and V2.0 and builds the noise test systems for small spaces, respectively. These devices, installed on the outer surface of the small spaces, can automatically identify the noise spectrum and implement noise reduction by means of the active noise control (ANC technology. The testing results indicate that the noise can be reduced 12 dB in the range of 250 Hz~400 Hz for the small closed space while, for the small open space, the best effect of 5.88 dB occurs in the optimal frequency of 450 Hz. These effects will be weakened with the increasing distance away from the source and show the obvious axisymmetric distribution in the inverted cone space.

  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. Reduction of Altitude Diffuser Jet Noise Using Water Injection

    Science.gov (United States)

    Allgood, Daniel C.; Saunders, Grady P.; Langford, Lester A.

    2011-01-01

    A feasibility study on the effects of injecting water into the exhaust plume of an altitude rocket diffuser for the purpose of reducing the far-field acoustic noise has been performed. Water injection design parameters such as axial placement, angle of injection, diameter of injectors, and mass flow rate of water have been systematically varied during the operation of a subscale altitude test facility. The changes in acoustic far-field noise were measured with an array of free-field microphones in order to quantify the effects of the water injection on overall sound pressure level spectra and directivity. The results showed significant reductions in noise levels were possible with optimum conditions corresponding to water injection at or just upstream of the exit plane of the diffuser. Increasing the angle and mass flow rate of water injection also showed improvements in noise reduction. However, a limit on the maximum water flow rate existed as too large of flow rate could result in un-starting the supersonic diffuser.

  1. Gene regulation and noise reduction by coupling of stochastic processes

    Science.gov (United States)

    Ramos, Alexandre F.; Hornos, José Eduardo M.; Reinitz, John

    2015-02-01

    Here we characterize the low-noise regime of a stochastic model for a negative self-regulating binary gene. The model has two stochastic variables, the protein number and the state of the gene. Each state of the gene behaves as a protein source governed by a Poisson process. The coupling between the two gene states depends on protein number. This fact has a very important implication: There exist protein production regimes characterized by sub-Poissonian noise because of negative covariance between the two stochastic variables of the model. Hence the protein numbers obey a probability distribution that has a peak that is sharper than those of the two coupled Poisson processes that are combined to produce it. Biochemically, the noise reduction in protein number occurs when the switching of the genetic state is more rapid than protein synthesis or degradation. We consider the chemical reaction rates necessary for Poisson and sub-Poisson processes in prokaryotes and eucaryotes. Our results suggest that the coupling of multiple stochastic processes in a negative covariance regime might be a widespread mechanism for noise reduction.

  2. Reduction of Altitude Diffuser Jet Noise Using Water Injection

    Science.gov (United States)

    Allgood, Daniel C.; Saunders, Grady P.; Langford, Lester A.

    2014-01-01

    A feasibility study on the effects of injecting water into the exhaust plume of an altitude rocket diffuser for the purpose of reducing the far-field acoustic noise has been performed. Water injection design parameters such as axial placement, angle of injection, diameter of injectors, and mass flow rate of water have been systematically varied during the operation of a subscale altitude test facility. The changes in acoustic far-field noise were measured with an array of free-field microphones in order to quantify the effects of the water injection on overall sound pressure level spectra and directivity. The results showed significant reductions in noise levels were possible with optimum conditions corresponding to water injection at or just upstream of the exit plane of the diffuser. Increasing the angle and mass flow rate of water injection also showed improvements in noise reduction. However, a limit on the maximum water flow rate existed as too large of flow rate could result in un-starting the supersonic diffuser.

  3. A new noise reduction method for airborne gravity gradient data

    Science.gov (United States)

    Jirigalatu; Ebbing, Jörg; Sebera, Josef

    2016-09-01

    Airborne gravity gradient (AGG) measurements offer an increased resolution and accuracy compared to terrestrial measurements. But interpretation and processing of AGG data are often challenging as levelling errors and survey noise affect the data, and these effects are not easily recognised in the gradient components. We adopted the classic method of upward continuation in the noise reduction using the noise level estimates by the AGG system. By iteratively projecting the survey data to a lower level and upward continuing the data back to the survey height, parts of the high-frequency signal are suppressed. The filter, which is defined by this approach, is directly dependent on the noise level of the AGG data, the maximum number of iterations and the iterative step. We demonstrate the method by applying it to both synthetic data and real AGG data over Karasjok, Norway, and compare the results to the directional filtering method. The results show that the iterative filter can effectively reduce high-frequency noise in the data.

  4. Noise reduction of punch press mechanical clutch engagement

    Institute of Scientific and Technical Information of China (English)

    CHEN Wei; SUN Chang-qing; LI Yun-liang

    2005-01-01

    Among the noises of the punch press, blanking noise and engaging noise of the clutch should be paid most attention to. The latter is generated by the engagement impacts of the rotating key on the spline bush. In order to absorb the pressing energy and reduce the noise radiated, polyurethane cushions were added to the spline bush keyways and the clutch running noise reduction has reached 10.7 dB(A). Considering such factors as the running characteristics of the punch press clutch, the demand for cushioning performance and the demand of the clutch temperature field for damping materials, the temperature field of the rigid clutch spline bush was simulated to find out whether the temperature of polyurethane go beyond its critical application temperature, using the finite element method. According to the characteristic that the deforming memory alloy can restore the remembered shape with the temperature rising, the actual temperature of the spline bush was measured. Consequently, the theoretical temperature turned out to be close to the measured temperature.

  5. Innovative speckle noise reduction procedure in optical encryption

    Science.gov (United States)

    Vélez Zea, Alejandro; Fredy Barrera, John; Torroba, Roberto

    2017-05-01

    Encrypting techniques are currently of interest in the optical domain. A common issue when using coherent techniques is speckle noise which influences the final results. Most efforts to solve this issue were directed towards processing the output of the systems. Instead, we present an alternative approach where we seek to control the input to enhance the performance of these techniques. In particular, we analyze an encoding procedure with a joint transform correlator architecture as a case study. We first demonstrate the dependence of the output noise on the spatial distribution of the input, showing the existence of a neglected random correlation noise which contributes to the degradation of the output. We then propose a rearrangement of the input that results in a reduction of the noise level in the outcome. This rearrangement consists of separating the pixels of the input by introducing black pixels between them, keeping the usual remaining procedure unaltered. Our experimental approach opens up new possibilities for the applications of optical security techniques beyond the limitations imposed by noise.

  6. Noise Reduction for a MEMS-Gyroscope-Based Head Mouse.

    Science.gov (United States)

    Du, Jiaying; Gerdtman, Christer; Lindén, Maria

    2015-01-01

    In this paper, four different signal processing algorithms which can be applied to reduce the noise from a MEMS-gyroscope-based computer head mouse are presented. MEMS-gyroscopes are small, light, cheap and widely used in many electrical products. MultiPos, a MEMS-gyroscope-based computer head mouse system was designed for persons with movement disorders. Noise such as physiological tremor and electrical noise is a common problem for the MultiPos system. In this study four different signal processing algorithms were applied and evaluated by simulation in MATLAB and implementation in a dsPIC, with aim to minimize the noise in MultiPos. The algorithms were low-pass filter, Least Mean Square (LMS) algorithm, Kalman filter and Weighted Fourier Linear Combiner (WFLC) algorithm. Comparisons and system tests show that these signal processing algorithms can be used to improve the MultiPos system. The WFLC algorithm was found the best method for noise reduction in the application of a MEMS-gyroscope-based head mouse.

  7. Recruitment-of-loudness effects of attenuative noise reduction algorithms

    Science.gov (United States)

    Whitmal, Nathaniel; Vosoughi, Azadeh

    2002-05-01

    Hearing-impaired listeners have greater difficulty understanding speech in noise than normal-hearing listeners do. As a result, hearing aid users are often challenged by the inability of their hearing aids to improve intelligibility in noise. Several investigators have addressed this problem by using well-known signal processing methods (e.g., spectral subtraction, Wiener filtering) to enhance noise-corrupted speech. Unfortunately, these methods have failed to provide significant improvements in intelligibility. One possible explanation is the level-dependent nature of the attenuation that the algorithms impose on the speech. In the cases described above, this attenuation resembles the piecewise-linear input-output characteristic observed in certain recruitment-of-loudness simulators. The purpose of this study was to compare the intelligibility of processed speech with that expected for recruitment-of-loudness simulation. Trials of the CUNY Nonsense Syllable Test were conducted with 12 normal-hearing listeners, using syllables that were mixed with additive noise at SNRs of 6, 12, and 18 dB. Input-output characteristics for the signals were measured and used to determine the effective threshold shift imposed by the algorithms. Comparisons of measured intelligibility scores with articulation index-based intelligibility predictions indicate that the behavior of such noise reduction algorithms can be successfully modeled as a form of mild sensorineural hearing loss.

  8. Evaluation of Diesel Engine Noise Reduction Measures Based on Hierarchy Diagnosis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Effect of different noise reduction measures for diesel engines was evaluated based on hierarchy diagnosis. The hierarchy diagnosis chart and hierarchy judgment matrix were given.Through evaluation of noise reduction measures, the main strategies of noise reduction were found.The result shows that the noise reduction level of different frequency belts varies from measure to measure. The reduction capacity of different measures could not add simply, which relates to the problem of parameter matching.

  9. Aircraft noise reduction technology. [to show impact on individuals and communities, component noise sources, and operational procedures to reduce impact

    Science.gov (United States)

    1973-01-01

    Aircraft and airport noise reduction technology programs conducted by NASA are presented. The subjects discussed are: (1) effects of aircraft noise on individuals and communities, (2) status of aircraft source noise technology, (3) operational procedures to reduce the impact of aircraft noise, and (4) NASA relations with military services in aircraft noise problems. References to more detailed technical literature on the subjects discussed are included.

  10. 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...

  11. Propulsion Noise Reduction Research in the NASA Advanced Air Transport Technology Project

    Science.gov (United States)

    Van Zante, Dale; Nark, Douglas; Fernandez, Hamilton

    2017-01-01

    The Aircraft Noise Reduction (ANR) sub-project is focused on the generation, development, and testing of component noise reduction technologies progressing toward the NASA far term noise goals while providing associated near and mid-term benefits. The ANR sub-project has efforts in airframe noise reduction, propulsion (including fan and core) noise reduction, acoustic liner technology, and propulsion airframe aeroacoustics for candidate conventional and unconventional aircraft configurations. The current suite of propulsion specific noise research areas is reviewed along with emerging facility and measurement capabilities. In the longer term, the changes in engine and aircraft configuration will influence the suite of technologies necessary to reduce noise in next generation systems.

  12. Noise, Worker Perception, and Worker Concentration in Timber Harvesting Activity

    Directory of Open Access Journals (Sweden)

    Efi Yuliati Yovi

    2012-01-01

    Full Text Available Timber harvesting activities are unquestionably related with high risk of work accidents and health disorders.Such activities were not only burdened the workers with heavy physical workloads due to uneasy workingenvironment, and massive work materials and tools, but also physiopsychologically burdened workers as theywere imposed with both mechanical and acoustic vibrations (noise produced by the chainsaw. However,  it is acommon practice that most of the workers still ignored the importance of the use of noise reduction devices suchas earmuff or ear plug.  This study was aimed to reveal the factual effects of noise on work concentration of theworkers to provide a scientific basis in supporting efforts in improving workers’ attitude.  The results confirmedthat chainsaw might produce noise during operation.  Noise intensities received by both right and left ears werenot significantly different, indicating that left-handed and normal workers received similar degree of noise inboth side of ears. Further, results also showed that there was a significant difference on the perception and workconcentration of chainsaw operators versus sedentary people to the noise.  These findings proved that hearingability of chainsaw operators had declined due to frequent noise exposure.Keywords: timber harvesting, physio-psychological disorder, noise, chainsaw

  13. Tanlock loop noise reduction using an optimised phase detector

    Science.gov (United States)

    Al-kharji Al-Ali, Omar; Anani, Nader; Al-Qutayri, Mahmoud; Al-Araji, Saleh

    2013-06-01

    This article proposes a time-delay digital tanlock loop (TDTL), which uses a new phase detector (PD) design that is optimised for noise reduction making it amenable for applications that require wide lock range without sacrificing the level of noise immunity. The proposed system uses an improved phase detector design which uses two phase detectors; one PD is used to optimise the noise immunity whilst the other is used to control the acquisition time of the TDTL system. Using the modified phase detector it is possible to reduce the second- and higher-order harmonics by at least 50% compared with the conventional TDTL system. The proposed system was simulated and tested using MATLAB/Simulink using frequency step inputs and inputs corrupted with varying levels of harmonic distortion. A hardware prototype of the system was implemented using a field programmable gate array (FPGA). The practical and simulation results indicate considerable improvement in the noise performance of the proposed system over the conventional TDTL architecture.

  14. Supersonic Jet Noise Reduction Using Flapping Injection and Pulsed Injection

    Science.gov (United States)

    Hafsteinsson, Haukur; Eriksson, Lars-Erik; Cuppoletti, Daniel; Gutmark, Ephraim; Department of Applied Mechanics, Chalmers University of Technology Team; Department of Aerospace Engineering, University of Cincinatti Team; Swedish Defence Material Administration, Sweden Team

    2013-11-01

    Aircraft are in general noisy and there is a high demand for reducing their noise levels. The jet exhaust is in most cases the main noise source of the aircraft, especially for low bypass ratio jet engines. Fluidic injection affecting the shear layer close to the nozzle exit is a promising noise reduction technique as it can be turned of while not needed and thus the negative effect on the engine performance will be minimized. In the presented work, LES is used to compare steady-state mass flow injection with steady-state mass flow flapping jet injection. The work is a direct continuation of a previous LES study on pulsed injection which showed that the pulsed injection induced pressure pulses in the jet which caused increased tonal noise in the downstream directions. The injection system considered in the presented work consists of eight evenly distributed injectors at the nozzle exit plane with a 90° injection angle relative to the flow direction. Flapping jet injection is believed to minimize the creation of these pressure pulses since it provides steady-state mass flow. This work is funded by Swedish Defense Material Administration (FMV).

  15. Serration Design Methodology for Wind Turbine Noise Reduction

    Science.gov (United States)

    Mathew, J.; Singh, A.; Madsen, J.; Arce León, C.

    2016-09-01

    Trailing edge serrations are today an established method to reduce the aeroacoustic noise from wind turbine blades. In this paper, a brief introduction to the aerodynamic and acoustic design procedure used at LM Wind Power is given. Early field tests on serrations, retrofitted to the turbine blades, gave preliminary indication of their noise reduction potential. However, a multitude of challenges stand in the way of any proof of concept and a viable commercial product. LM undertook a methodical test and validation procedure to understand the impact of design parameters on serration performance, and quantify the uncertainties associated with the proposed designs. Aerodynamic and acoustic validation tests were carried out in number of wind tunnel facilities. Models were written to predict the aerodynamic, acoustic and structural performance of the serrations. LM serration designs have evolved over the period of time to address constraints imposed by aero performance, structural reliability, manufacturing and installation. The latest LM serration offering was tested in the field on three different wind turbines. A consistent noise reduction in excess of 1.5 dB was achieved in the field for all three turbines.

  16. Reduction of randomness in seismic noise as a short-term precursor to a volcanic eruption

    Science.gov (United States)

    Glynn, C. C.; Konstantinou, K. I.

    2016-11-01

    Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a clear short-term precursor to volcanic activity. The eruption was preceded on 29 September 1996 by a Mw ~5.6 earthquake that occurred in the caldera rim of the Bárdarbunga volcano. A significant reduction of randomness started occurring 8 days before the earthquake and 10 days before the onset of the eruption. This reduction was observed even at stations more than 100 km away from the eruption site. Randomness increased to its previous levels 160 minutes after the Bárdarbunga earthquake, during which time aftershocks migrated from the Bárdarbunga caldera to a site near the Gjálp eruption fissure. We attribute this precursory reduction of randomness to the lack of higher frequencies (>1 Hz) in the noise wavefield caused by high absorption losses as hot magma ascended in the upper crust.

  17. Noise reduction techniques for the restoration of musical recordings

    Science.gov (United States)

    Cappe, Olivier

    The evaluation of short time spectral attenuation techniques using a simplified model of standard noise suppression rules and with elementary test signals is assessed. Signal distortions induced by the restoration process are evaluated analytically, and their audibility is addressed by use of classic psychoacoustics results. Phenomena observed experimentally in previous studies, such as the modification of timbre, the appearance of modulations, and the spreading of transients, are brought to light. Drawing from these results, a noise reduction technique intended for enhancing musical signals is described. In the first step, the noisy signal is analyzed by use of a medium frequency resolution short time transform. The restoration then takes place in each subband in two different ways according to the nature of the subband signal: the processing is carried out block by block when steady signal components are detected, or locally otherwise. This approach was successfully applied to several musical recordings yielding promising results.

  18. A Family of Maximum SNR Filters for Noise Reduction

    DEFF Research Database (Denmark)

    Huang, Gongping; Benesty, Jacob; Long, Tao;

    2014-01-01

    This paper is devoted to the study and analysis of the maximum signal-to-noise ratio (SNR) filters for noise reduction both in the time and short-time Fourier transform (STFT) domains with one single microphone and multiple microphones. In the time domain, we show that the maximum SNR filters can...... significantly increase the SNR but at the expense of tremendous speech distortion. As a consequence, the speech quality improvement, measured by the perceptual evaluation of speech quality (PESQ) algorithm, is marginal if any, regardless of the number of microphones used. In the STFT domain, the maximum SNR....... This demonstrates that the maximum SNR filters, particularly the multichannel ones, in the STFT domain may be of great practical value....

  19. Environmental noise alters gastric myoelectrical activity: Effect of age

    Institute of Scientific and Technical Information of China (English)

    James S Castle; Jin-Hong Xing; Mark R Warner; Mark A Korsten

    2007-01-01

    AIM: To evaluate the effect of age and acoustic stress on gastric myoelectrical activity (GMA) and autonomic nervous system function,METHODS: Twenty-one male subjects (age range 22-71years, mean 44 years) were recruited and exposed, in random order, to three auditory stimuli (Hospital noise,conversation babble and traffic noise) after a 20-min baseline. All periods lasted 20 min and were interspersed with a 10 min of recovery. GMA was obtained using a Synectics Microdigitrapper. Autonomic nerve function was assessed by monitoring blood pressure and heart rate using an automatic recording device.RESULTS: Dominant power tended to decrease with increase of age (P<0.05). The overall percentage of three cycle per minute (CPM) activity decreased during exposure to hospital noise (12.0%, P < 0.05), traffic noise (13.9%, P < 0.05), and conversation babble(7.1%). The subjects in the younger group (< 50 years)showed a consistent reduction in the percentage of 3CPM activity during hospital noise (22.9%, P < 0.05),traffic noise (19.0%, P < 0.05), and conversation babble(15.5%). These observations were accompanied by a significant increase in bradygastria: hospital noise (P< 0.05) and traffic noise (P < 0.05). In contrast, the subjects over 50 years of age did not exhibit a significant decrease in 3 CPM activity. Regardless of age, noise did not alter blood pressure or heart rate.CONCLUSION: GMA changes with age. Loud noise can alter GMA, especially in younger individuals. Our data indicate that even short-term exposure to noise may alter the contractility of the stomach.

  20. Feasibility of noise reduction by a modification in ICU environment.

    Science.gov (United States)

    Luetz, A; Weiss, B; Penzel, T; Fietze, I; Glos, M; Wernecke, K D; Bluemke, B; Dehn, A M; Willemeit, T; Finke, A; Spies, C

    2016-07-01

    Noise is a proven cause of wakefulness and qualitative sleep disturbance in critically ill patients. A sound pressure level reduction can improve sleep quality, but there are no studies showing the feasibility of such a noise reduction in the intensive care unit (ICU) setting. Considering all available evidence, we redesigned two ICU rooms with the aim of investigating the physiological and clinical impact of a healing environment, including a noise reduction and day-night variations of sound level. Within an experimental design, we recorded 96 h of sound-pressure levels in standard ICU rooms and the modified ICU rooms. In addition, we performed a sound source observation by human observers. Our results show that we reduced A-weighted equivalent sound pressure levels and maximum sound pressure levels with our architectural interventions. During night-time, the modification led to a significant decrease in 50 dB threshold overruns from 65.5% to 39.9% (door side) and from 50% to 10.5% (window side). Sound peaks of more than 60 decibels were significantly reduced from 62.0% to 26.7% (door side) and 59.3% to 30.3% (window side). Time-series analysis of linear trends revealed a significantly more distinct day-night pattern in the modified rooms with lower sound levels during night-times. Observed sound sources during night revealed four times as many talking events in the standard room compared to the modified room. In summary, we show that it is feasible to reduce sound pressure levels using architectural modifications.

  1. Edge Preserved Speckle Noise Reduction Using Integrated Fuzzy Filters.

    Science.gov (United States)

    Biradar, Nagashettappa; Dewal, M L; Rohit, Manoj Kumar

    2014-01-01

    Echocardiographic images are inherent with speckle noise which makes visual reading and analysis quite difficult. The multiplicative speckle noise masks finer details, necessary for diagnosis of abnormalities. A novel speckle reduction technique based on integration of geometric, wiener, and fuzzy filters is proposed and analyzed in this paper. The denoising applications of fuzzy filters are studied and analyzed along with 26 denoising techniques. It is observed that geometric filter retains noise and, to address this issue, wiener filter is embedded into the geometric filter during iteration process. The performance of geometric-wiener filter is further enhanced using fuzzy filters and the proposed despeckling techniques are called integrated fuzzy filters. Fuzzy filters based on moving average and median value are employed in the integrated fuzzy filters. The performances of integrated fuzzy filters are tested on echocardiographic images and synthetic images in terms of image quality metrics. It is observed that the performance parameters are highest in case of integrated fuzzy filters in comparison to fuzzy and geometric-fuzzy filters. The clinical validation reveals that the output images obtained using geometric-wiener, integrated fuzzy, nonlocal means, and details preserving anisotropic diffusion filters are acceptable. The necessary finer details are retained in the denoised echocardiographic images.

  2. Application of variational mode decomposition to seismic random noise reduction

    Science.gov (United States)

    Liu, Wei; Cao, Siyuan; Wang, Zhiming

    2017-08-01

    We have proposed a new denoising method for the simultaneous noise reduction and preservation of seismic signals based on variational mode decomposition (VMD). VMD is a recently developed adaptive signal decomposition method and an advance in non-stationary signal analysis. It solves the mode-mixing and non-optimal reconstruction performance problems of empirical mode decomposition that have existed for a long time. By using VMD, a multi-component signal can be non-recursively decomposed into a series of quasi-orthogonal intrinsic mode functions (IMFs), each of which has a relatively local frequency range. Meanwhile, the signal will focus on a smaller number of obtained IMFs after decomposition, and thus the denoised result is able to be obtained by reconstructing these signal-dominant IMFs. Synthetic examples are given to demonstrate the effectiveness of the proposed approach and comparison is made with the complete ensemble empirical mode decomposition, which demonstrates that the VMD algorithm has lower computational cost and better random noise elimination performance. The application of on field seismic data further illustrates the superior performance of our method in both random noise attenuation and the recovery of seismic events.

  3. Filter for speckle noise reduction based on compressive sensing

    Science.gov (United States)

    Leportier, Thibault; Park, Min-Chul

    2016-12-01

    In holographic reconstruction, speckle noise is a serious factor that may degrade the image quality greatly. Several methods have been proposed, so far, to filter speckle from hologram reconstruction. The first approach is based on averaging several speckle patterns. The second solution is to apply a filter on the reconstructed image. In the first case, several holograms should be acquired, while compromise between speckle reduction and edge preservation is usually a challenge in the case of digital filtering. We propose a method to filter speckle noise based on compressive sensing (CS). CS is a method that has been demonstrated recently to reconstruct images with a sampling inferior to the Nyquist rate. By applying several times the CS algorithm on the hologram reconstruction with different initial downsampling, several versions of the same images can be reconstructed with slightly different speckle patterns. Then, speckle noise can be greatly decreased while preserving sharpness of the image. We demonstrate the effectiveness of our proposed method with simulations as well as with holograms acquired by phase-shifting method.

  4. The cost of applying current helicopter external noise reduction methods while maintaining realistic vehicle performance

    Science.gov (United States)

    Bowes, M. A.

    1978-01-01

    Analytical methods were developed and/or adopted for calculating helicopter component noise, and these methods were incorporated into a unified total vehicle noise calculation model. Analytical methods were also developed for calculating the effects of noise reduction methodology on helicopter design, performance, and cost. These methods were used to calculate changes in noise, design, performance, and cost due to the incorporation of engine and main rotor noise reduction methods. All noise reduction techniques were evaluated in the context of an established mission performance criterion which included consideration of hovering ceiling, forward flight range/speed/payload, and rotor stall margin. The results indicate that small, but meaningful, reductions in helicopter noise can be obtained by treating the turbine engine exhaust duct. Furthermore, these reductions do not result in excessive life cycle cost penalties. Currently available main rotor noise reduction methodology, however, is shown to be inadequate and excessively costly.

  5. Active vibration and noise control by hybrid active acoustic panels

    Energy Technology Data Exchange (ETDEWEB)

    Stoebener, U.; Gaul, L. [Stuttgart Univ. (Germany). Inst. A fuer Mechanik

    2001-07-01

    In the present paper a hybrid passive and active treatment for vibration and noise reduction of plate type structures is proposed. The treatment is manufactured as sandwich structure and is called hybrid active acoustic panel. The passive component is used to reduce the vibration and sound radiation for high frequencies whereas the active part of the system is designed for the low frequency range. By selecting the thickness of the passive damping layer a certain frequency limit is defined, which divides the high and low frequency range. The actuator and sensor layout of the active component is evaluated by using the mode shapes of the low frequency range. According to the evaluated layout a hybrid active acoustic panel is manufactured and experimentally tested. The experimental results validate the proposed concept. (orig.)

  6. Effects of noise reduction on AM and FM perception.

    Science.gov (United States)

    Ives, D Timothy; Calcus, Axelle; Kalluri, Sridhar; Strelcyk, Olaf; Sheft, Stanley; Lorenzi, Christian

    2013-02-01

    The goal of noise reduction (NR) algorithms in digital hearing aid devices is to reduce background noise whilst preserving as much of the original signal as possible. These algorithms may increase the signal-to-noise ratio (SNR) in an ideal case, but they generally fail to improve speech intelligibility. However, due to the complex nature of speech, it is difficult to disentangle the numerous low- and high-level effects of NR that may underlie the lack of speech perception benefits. The goal of this study was to better understand why NR algorithms do not improve speech intelligibility by investigating the effects of NR on the ability to discriminate two basic acoustic features, namely amplitude modulation (AM) and frequency modulation (FM) cues, known to be crucial for speech identification in quiet and in noise. Here, discrimination of complex, non-linguistic AM and FM patterns was measured for normal hearing listeners using a same/different task. The stimuli were generated by modulating 1-kHz pure tones by either a two-component AM or FM modulator with patterns changed by manipulating component phases. Modulation rates were centered on 3 Hz. Discrimination of AM and FM patterns was measured in quiet and in the presence of a white noise that had been passed through a gammatone filter centered on 1 kHz. The noise was presented at SNRs ranging from -6 to +12 dB. Stimuli were left as such or processed via an NR algorithm based on the spectral subtraction method. NR was found to yield small but systematic improvements in discrimination for the AM conditions at favorable SNRs but had little effect, if any, on FM discrimination. A computational model of early auditory processing was developed to quantify the fidelity of AM and FM transmission. The model captured the improvement in discrimination performance for AM stimuli at high SNRs with NR. However, the model also predicted a relatively small detrimental effect of NR for FM stimuli in contrast with the average

  7. Bio-inspired canopies for the reduction of roughness noise

    Science.gov (United States)

    Clark, Ian A.; Daly, Conor A.; Devenport, William; Alexander, W. Nathan; Peake, Nigel; Jaworski, Justin W.; Glegg, Stewart

    2016-12-01

    This work takes inspiration from the structure of the down covering the flight feathers of larger species of owls, which contributes to their ability to fly almost silently at frequencies above 1.6 kHz. Microscope photographs of the down show that it consists of hairs that form a structure similar to that of a forest. The hairs initially rise almost perpendicular to the feather surface but then bend over in the flow direction to form a canopy with an open area ratio of about 70 percent. Experiments have been performed to examine the noise radiated by a large open area ratio canopy suspended above a surface. The canopy is found to dramatically reduce pressure fluctuations on the underlying surface. While the canopy can produce its own sound, particularly at high frequencies, the reduction in surface pressure fluctuations can reduce the noise scattered from an underlying rough surface at lower frequencies. A theoretical model is developed which characterizes the mechanism of surface pressure reduction as a result of the mixing layer instability of flow over forest canopies.

  8. Research on the application of active sound barriers for the transformer noise abatement

    Directory of Open Access Journals (Sweden)

    Hu Sheng

    2016-01-01

    Full Text Available Sound barriers are a type of measure most commonly used in the noise abatement of transformers. In the noise abatement project of substations, the design of sound barriers is restrained by the portal frames which are used to hold up outgoing lines from the main transformers, which impacts the noise reduction effect. If active sound barriers are utilized in these places, the noise diffraction of sound barriers can be effectively reduced. At a 110kV Substation, an experiment using a 15-channel active sound barrier has been carried out. The result of the experiment shows that the mean noise reduction value (MNRV of the noise measuring points at the substation boundary are 1.5 dB (A. The effect of the active noise control system is impacted by the layout of the active noise control system, the acoustic environment on site and the spectral characteristic of the target area.

  9. Noise and vibration reduction of diesel engine vehicle making use of the active control engine mount (ACM) system; Active control engine mount (ACM) wo mochiitaa diesel engine tosaisha no seishukusei kojo

    Energy Technology Data Exchange (ETDEWEB)

    MShikata, T.; Aihara, T.; Hyodo, Y.; Aoki, K.; Hirade, T.; Kawazoe, H.; Sato, S.; Kimuraa, T.; Yonekura, K. [Nissan Motor Co. Ltd., Tokyo (Japan)

    1999-02-01

    The active control engine mount (ACM), adopted on `Presage` matched the newly developed direct-injection diesel engine called `NEO-Di YD25DDTi`, can reduce transmitted force to a body structure to almost zero in a wide variety of driving conditions by making use of an adaptive control method with synchronizes the filtered-X algorithm. The ACM system made great improvements in noise and vibration performance, so that fuel consumption, and quietness thanks to the ACM system. (author)

  10. Development of an acoustic actuator for launch vehicle noise reduction.

    Science.gov (United States)

    Henderson, Benjamin K; Lane, Steven A; Gussy, Joel; Griffin, Steve; Farinholt, Kevin M

    2002-01-01

    In many active noise control applications, it is necessary that acoustic actuators be mounted in small enclosures due to volume constraints and in order to remain unobtrusive. However, the air spring of the enclosure is detrimental to the low-frequency performance of the actuator. For launch vehicle noise control applications, mass and volume constraints are very limiting, but the low-frequency performance of the actuator is critical. This work presents a novel approach that uses a nonlinear buckling suspension system and partial evacuation of the air within the enclosure to yield a compact, sealed acoustic driver that exhibits a very low natural frequency. Linear models of the device are presented and numerical simulations are given to illustrate the advantages of this design concept. An experimental prototype was built and measurements indicate that this design can significantly improve the low-frequency response of compact acoustic actuators.

  11. Non-Causal Time-Domain Filters for Single-Channel Noise Reduction

    DEFF Research Database (Denmark)

    Jensen, Jesper Rindom; Benesty, Jacob; Christensen, Mads Græsbøll

    2012-01-01

    In many existing time-domain filtering methods for noise reduction in, e.g., speech processing, the filters are causal. Such causal filters can be implemented directly in practice. However, it is possible to improve the performance of such noise reduction filtering methods in terms of both noise ...

  12. A rapid prototyping system for broadband multichannel active noise and vibration control

    NARCIS (Netherlands)

    Wesselink, J.M.

    2009-01-01

    In recent years the need for active and passive noise reduction methods has increased. This is due to an increase in the ambient noise caused by industrialization and the extended use of power tools. The effects of noise on a person can be quite severe and can cause illness and in severe cased lead

  13. Noise reduction by magnetostatic coupling in geomagnetic-field sensors

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chong-Jun; Li, Min; Li, Jian-Wei [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Teng, Jiao, E-mail: cjzhao.ustb@gmail.com [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Guang-Hua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2014-11-15

    A new magnetoresistive (MR) thin film with a structure of “antiferromagnetic layer/pinned soft magnetic layer/non-magnetic MgO spacer layer/sensitive NiFe layer” was designed. The barber-pole MR elements with a Wheatstone bridge circuit were fabricated using photolithographic methods. The testing results show that, in comparison to the element with a typical structure of Ta/NiFe/Ta, the fabricated MR element shows significant reduction in the Barkhausen noise and the 1/f noise and good magnetic stability while maintaining high magnetic field sensitivity. This element with improved signals can be attributed to the magnetostatic coupling between the pinned soft magnetic layer and the sensitive NiFe layer, which can act as a small stabilizing field, leading to the coherent rotation of magnetic moment in the sensitive NiFe layer. - Highlights: • A new MR film with the structure of “IrMn/NiFe/MgO/NiFe” was designed. • The elements with a Wheatstone bridge circuit were fabricated using photolithography. • A reduced noisy and good magnetic stable signal was achieved. • The magnetostatic coupling can act as a small stabilizing field. • Coherent rotation of the magnetic moment happened in the sensing NiFe layer.

  14. Wake Management Strategies for Reduction of Turbomachinery Fan Noise

    Science.gov (United States)

    Waitz, Ian A.

    1998-01-01

    The primary objective of our work was to evaluate and test several wake management schemes for the reduction of turbomachinery fan noise. Throughout the course of this work we relied on several tools. These include 1) Two-dimensional steady boundary-layer and wake analyses using MISES (a thin-shear layer Navier-Stokes code), 2) Two-dimensional unsteady wake-stator interaction simulations using UNSFLO, 3) Three-dimensional, steady Navier-Stokes rotor simulations using NEWT, 4) Internal blade passage design using quasi-one-dimensional passage flow models developed at MIT, 5) Acoustic modeling using LINSUB, 6) Acoustic modeling using VO72, 7) Experiments in a low-speed cascade wind-tunnel, and 8) ADP fan rig tests in the MIT Blowdown Compressor.

  15. Tenfold reduction of Brownian noise in optical interferometry

    CERN Document Server

    Cole, Garrett D; Martin, Michael J; Ye, Jun; Aspelmeyer, Markus

    2013-01-01

    Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the preceding decade, the mechanical loss of these amorphous multilayer reflectors has at best been reduced by a factor of two. Here we demonstrate a new paradigm in optical coating technology based on direct-bonded monocrystalline multilayers, which exhibit both intrinsically low mechanical loss and high optical quality. Employing these "crystalline coatings" as end mirrors in a Fabry-P\\'erot cavity, we obtain a finesse of 150,000. More importantly, at room temperature, we observe a thermally-limited noise floor consistent with a tenfold reduction in mechanical damping when compared with the best dielectric multilayers. These results pave the way for the next generation of ultra-sensitive interferometers, as well as for new levels ...

  16. Noise and vibration reduction of diesel engine vehicle making use of the active control engine mount (ACM) system; Active control engine mount (ACM) wo mochiita diesel engine tosaisha no seishukusei kojo

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, K.; Hirade, T.; Hyodo, Y.; Aihara, T.; Shikata, T. [Nissan Motor Co. Ltd., Tokyo (Japan)

    1998-05-01

    An active control engine mount (ACM) system is described, which aims at reducing noise and vibration of diesel engine vehicles. ACM systems are arranged on the front and rear mounts, and reduce the noise by lowering the spring constant. The main body of an ACM system is a hydraulic mount, and is provided with a hydraulic pressure amplifier that makes use of liquid resonance, an electromagnetic actuator that converts hydraulic pressure into force, and a load sensor that detects the force that is transmitted to the vehicle body. The controller of an ACM control system feeds electric currents as needed to an actuator so as to keep the transmission of force to the minimum so that load sensor signals will be zero. The actuator employed in this report can augment the force generated there. All the parameters for the calculation model are optimized so that controllable input amplitude will increase. In the diesel engine vehicle into which ACM systems are incorporated, vibration during the idling operation is damped by approximately 10dB, the resultant vibration level as low as that of a gasoline engine vehicle. Harmonic components are also lowered in addition the second-order component. The same is true for the booming noise that is generated by a vehicle that is running, which is again damped by approximately 10dB. 2 refs., 14 figs.

  17. Active control of propeller induced noise fields inside a flexible cylinder

    Science.gov (United States)

    Lester, H. C.; Fuller, C. R.

    1986-01-01

    An active noise control model has been evaluated for reducing aircraft interior noise. The structural noise transmission properties of an aircraft fuselage were modelled as a flexible cylinder excited by external acoustic dipoles simulating the noise produced by twin propellers. The amplitudes of an internal distribution of monopole control sources were determined such that the area-weighted mean square acoustic pressure was minimized in the propeller plane. The noise control model was evaluated at low frequencies corresponding to the blade passage frequency and first few harmonics of a typical turbo-prop aircraft. Interior noise reductions of 20 25 dB were achieved, over a substantial region of the cylindrical cross-section, with just a few monopole control sources. The most favorable interior noise reductions were achieved when the active noise control model was used in combination with propeller source phasing.

  18. NOISE REDUCTION SCHEDULING METHOD IN A SHOP FLOOR AND ITS CASE STUDY

    Institute of Scientific and Technical Information of China (English)

    Liu Fei; Cao Huajun; Zhang Hua; Yuan Chuanping

    2003-01-01

    Noise reduction in a shop floor is one of the important parts of green manufacturing. In a shop floor, machine tools are the main noise sources in a shop floor. A new approach is discovered by investigation that the noise can be obviously reduced in a shop floor by optimizing the scheduling between work pieces and machine tools. Based on the discovery, a new method of noise reduction is proposed. A noise reduction scheduling model in a shop floor is established, and the application of the model is also discussed. A case is studied, which shows that the method and model are practical.

  19. 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).

  20. 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.

  1. Experimental investigation of the noise reduction of supersonic exhaust jets with fluidic inserts

    Science.gov (United States)

    Powers, Russell William Walter

    The noise produced by the supersonic, high temperature jets that exhaust from military aircraft is becoming a hazard to naval personnel and a disturbance to communities near military bases. Methods to reduce the noise produced from these jets in a practical full-scale environment are difficult. The development and analysis of distributed nozzle blowing for the reduction of radiated noise from supersonic jets is described. Model scale experiments of jets that simulate the exhaust jets from typical low-bypass ratio military jet aircraft engines during takeoff are performed. Fluidic inserts are created that use distributed blowing in the divergent section of the nozzle to simulate mechanical, hardwall corrugations, while having the advantage of being an active control method. This research focuses on model scale experiments to better understand the fluidic insert noise reduction method. Distributed blowing within the divergent section of the military-style convergent divergent nozzle alters the shock structure of the jet in addition to creating streamwise vorticity for the reduction of mixing noise. Enhancements to the fluidic insert design have been performed along with experiments over a large number of injection parameters and core jet conditions. Primarily military-style round nozzles have been used, with preliminary measurements of hardwall corrugations and fluidic inserts in rectangular nozzle geometries also performed. It has been shown that the noise reduction of the fluidic inserts is most heavily dependent upon the momentum flux ratio between the injector and core jet. Maximum reductions of approximately 5.5 dB OASPL have been observed with practical mass flow rates and injection pressures. The first measurements with fluidic inserts in the presence of a forward flight stream have been performed. Optimal noise reduction occurs at similar injector parameters in the presence of forward flight. Fluidic inserts in the presence of a forward flight stream were

  2. 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...

  3. Active control of aerodynamic noise; Active control ni yoru furyoku soon no seigyo

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, M. [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan)

    1996-10-01

    This paper introduces summary and examples of active noise control (ANC) and active flow control (AFC) as the aerodynamic noise control techniques. The ANC is a technique to generate noise of a reverse phase which cancels the original noise. Noise reduced especially effectively by the ANC is noise from fans and ducts used for engine air supply and exhaust. The ANC is effective in low frequencies, and when used with a passive method, a compact exhaust silencer can be realized, which has high noise reducing performance over the whole frequency band and has low pressure loss. Signal processing in active noise reduction system is always so adjusted that noise is discharged from a secondary noise source in which signals detected by a detection microphone is given a digital filter treatment, and output from an error microphone is minimized. The AFC has been incapable of realizing a reverse phase over a wide frequency band when depended on analog treatment. However, the authors have developed an adaptive type feedback control system, and verified that the system can be applied to any frequency variation and control it in a stable manner. 15 refs., 9 figs., 1 tab.

  4. Aero-Acoustics of Modern Transonic Fans—Fan Noise Reduction from Its Sources

    Institute of Scientific and Technical Information of China (English)

    L. Xu; J.D. Denton

    2003-01-01

    The noise of aerodynamics nature from modern transonic fan is examined from its sources with the perspective of noise reduction through aero-acoustics design using advanced Computational Fluid Dynamics (CFD) tools.In particular the problems associated with the forward propagating noise in the front is addressed. It is identified that the shock wave spillage from the leading edge near the fan tip is the main source of the tone noise. Two different approaches have been studied to reduce the forward arc tone noise and two state-of-art transonic fans are designed using the strategies developed. The following rig tests show that while the fans exhibit other noise problems,the primary goals of noise reduction have been achieved through both fans and the novel noise reduction concept vindicated.

  5. Noise reduction combining time-frequency epsilon-filter and M-transform.

    Science.gov (United States)

    Abe, Tomomi; Matsumoto, Mitsuharu; Hashimoto, Shuji

    2008-08-01

    This paper introduces noise reduction combining time-frequency epsilon-filter (TF epsilon-filter) and time-frequency M-transform (TF M-transform). Musical noise is an offensive noise generated due to noise reduction in the time-frequency domain such as spectral subtraction and TF epsilon-filter. It has a deleterious effect on speech recognition. To solve the problem, M-transform is introduced. M-transform is a linear transform based on M-sequence. The method combining the time-domain epsilon-filter (TD epsilon-filter) and time-domain M-transform (TD M-transform) can reduce not only white noise but also impulse noise. Musical noise is isolated in the time-frequency domain, which is similar to impulse noise in the time domain. On these prospects, this paper aims to reduce musical noise by improving M-transform for the time-frequency domain. Noise reduction by using TD M-transform and the TD epsilon-filter is first explained to clarify its features. Then, an improved method applying M-transform to the time-frequency domain, namely TF M-transform, is described. Noise reduction combining the TF epsilon-filter and TF M-transform is also proposed. The proposed method can reduce not only high-level nonstationary noise but also musical noise. Experimental results are also given to demonstrate the performance of the proposed method.

  6. SU-C-207B-02: Maximal Noise Reduction Filter with Anatomical Structures Preservation

    Energy Technology Data Exchange (ETDEWEB)

    Maitree, R; Guzman, G; Chundury, A; Roach, M; Yang, D [Washington University School of Medicine, St Louis, MO (United States)

    2016-06-15

    Purpose: All medical images contain noise, which can result in an undesirable appearance and can reduce the visibility of anatomical details. There are varieties of techniques utilized to reduce noise such as increasing the image acquisition time and using post-processing noise reduction algorithms. However, these techniques are increasing the imaging time and cost or reducing tissue contrast and effective spatial resolution which are useful diagnosis information. The three main focuses in this study are: 1) to develop a novel approach that can adaptively and maximally reduce noise while preserving valuable details of anatomical structures, 2) to evaluate the effectiveness of available noise reduction algorithms in comparison to the proposed algorithm, and 3) to demonstrate that the proposed noise reduction approach can be used clinically. Methods: To achieve a maximal noise reduction without destroying the anatomical details, the proposed approach automatically estimated the local image noise strength levels and detected the anatomical structures, i.e. tissue boundaries. Such information was used to adaptively adjust strength of the noise reduction filter. The proposed algorithm was tested on 34 repeating swine head datasets and 54 patients MRI and CT images. The performance was quantitatively evaluated by image quality metrics and manually validated for clinical usages by two radiation oncologists and one radiologist. Results: Qualitative measurements on repeated swine head images demonstrated that the proposed algorithm efficiently removed noise while preserving the structures and tissues boundaries. In comparisons, the proposed algorithm obtained competitive noise reduction performance and outperformed other filters in preserving anatomical structures. Assessments from the manual validation indicate that the proposed noise reduction algorithm is quite adequate for some clinical usages. Conclusion: According to both clinical evaluation (human expert ranking) and

  7. WAVELET TRANSFORM THRESHOLD NOISE REDUCTION METHODS IN THE OIL PIPELINE LEAKAGE MONITORING AND POSITIONING SYSTEM

    Institute of Scientific and Technical Information of China (English)

    Gao Chao; Zhou Shanxue

    2010-01-01

    This letter investigates the wavelet transform,as well as the principle and the method of the noise reduction based on wavelet transform,it chooses the threshold noise reduction,and discusses in detail the principles,features and design steps of the threshold method. Rigrsure,heursure,sqtwolog and minimization four kinds of threshold selection method are compared qualitatively,and quantitatively. The wavelet analysis toolbox of MATLAB helps to realize the computer simulation of the signal noise reduction. The graphics and calculated standard deviation of the various threshold noise reductions show that,when dealing with the actual pressure signal of the oil pipeline leakage,sqtwolog threshold selection method can effectively remove the noise. Aiming to the pressure signal of the oil pipeline leakage,the best choice is the wavelet threshold noise reduction with sqtwolog threshold. The leakage point is close to the actual position,with the relative error of less than 1%.

  8. Concurrent mechatronic design approach for active control of cavity noise

    Science.gov (United States)

    de Oliveira, L. P. R.; da Silva, M. M.; Sas, P.; Van Brussel, H.; Desmet, W.

    2008-07-01

    Active control is a potential solution to many noise and vibration problems for improving the low-frequency performance. Cavity noise reduction as encountered for instance in aircraft cabins and vehicle interiors is a typical example. However, the conventional design of these active solutions may lead to suboptimal products, since the interaction between the vibro-acoustic plant dynamics and control dynamics is usually not considered. A proper way to design such active systems would be considering control and plant parameters concurrently. To cope with this approach, a methodology to derive a fully coupled mechatronic model that deals with both the vibro-acoustic plant dynamics as well as the control parameters is proposed. The inclusion of sensor and actuator models is investigated, since it contributes to the model accuracy as it can confer frequency, phase or amplitude limitations to the control performance. The proposed methodology provides a reduced state-space model derived from a fully coupled vibro-acoustic finite element model. Experimental data on a vibro-acoustic vehicle cabin mock-up are used to validate the model reduction procedure. Regarding noise reduction, optimization results are presented considering both vibro-acoustic plant features, such as thicknesses, and control parameters, such as sensor and actuator placement and control gains. A collocated sensor/actuator pair is considered in a velocity feedback control strategy. The benefits of a concurrent mechatronic design when dealing with active structural-acoustic control solutions are addressed, illustrated and experimentally validated.

  9. Experimental Study on Noise Reduction of Punch Press

    Institute of Scientific and Technical Information of China (English)

    CHEN Wei; MA Xiang-ping; SUN Chang-qing

    2005-01-01

    To reduce the noise of punch press during the punching process, the polyurethane elastomer is used as the damping material. The experiments of reducing noise were made by means of adding the polyurethane elastomer at different positions of 100 kN and 1 000 kN punch press. The better effect of reducing the noise was obtained. With the research and analysis of a large number of test data, the "equivalent damping hypothesis" is put forward. The hypothesis makes the experiment of reducing noise be more simple and cost effective. This method would be exploited in area of vibration control and reducing noise.

  10. Simulation Study on Active Noise Control for a 4 Tesla MRI Scanner

    Science.gov (United States)

    Li, Mingfeng; Lim, Teik C.; Lee, Jing-Huei

    2008-01-01

    The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for MRI acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20 dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction. PMID:18060719

  11. Simulation study on active noise control for a 4-T MRI scanner.

    Science.gov (United States)

    Li, Mingfeng; Lim, Teik C; Lee, Jing-Huei

    2008-04-01

    The purpose of this work is to study computationally the possibility of the application of a hybrid active noise control technique for magnetic resonance imaging (MRI) acoustic noise reduction. A hybrid control system combined with both feedforward and feedback loops embedded is proposed for potential application on active MRI noise reduction. A set of computational simulation studies were performed. Sets of MRI acoustic noise emissions measured at the patient's left ear location were recorded and used in the simulation study. By comparing three different control systems, namely, the feedback, the feedforward and the hybrid control, our results revealed that the hybrid control system is the most effective. The hybrid control system achieved approximately a 20-dB reduction at the principal frequency component. We concluded that the proposed hybrid active control scheme could have a potential application for MRI scanner noise reduction.

  12. Active control of road booming noise in automotive interiors.

    Science.gov (United States)

    Oh, Shi-Hwan; Kim, Hyoun-suk; Park, Youngjin

    2002-01-01

    An active feedforward control system has been developed to reduce the road booming noise that has strong nonlinear characteristics. Four acceleration transducers were attached to the suspension system to detect reference vibration and two loudspeakers were used to attenuate the noise near the headrests of two front seats. A leaky constraint multiple filtered-X LMS algorithm with an IIR-based filter that has fast convergence speed and frequency selective controllability was proposed to increase the control efficiency in computing power and memory usage. During the test drive on the rough asphalt and turtle-back road at a constant speed of 60 km/h, we were able to achieve a reduction of around 6 dB of A-weighted sound pressure level in the road booming noise range with the proposed algorithm, which could not be obtained with the conventional multiple filtered-X LMS algorithm.

  13. Arecoline cannot alter testicular dysfunction and pineal activation caused by noise in wistar rat.

    Science.gov (United States)

    Saha, Indraneel; Chatterjee, Aniruddha; Chatterji, Urmi; Maiti, B R

    2017-07-13

    Millions of people consume betel nut for increased capacity to work and for stress reduction. The nut contains arecoline, which has multiple side effects on endocrine functions. Objective of the work is to investigate pineal-testicular responses to noise and after arecoline treatment in noise in rats. Noise exposure (100 dB, 6 h daily, 10 days) caused pineal stimulation ultrastructurally and at indoleamines level. Leydig cell dysfunction with fall of testosterone level and suppression of sex accessories were noticed. In contrast, pineal activity was inhibited and reproductive functions were stimulated after arecoline administration, confirmed from reversed changes to those of noise. Arecoline treatment in noise exposure showed same results as in noise both in pineal and in reproductive functions. It is concluded that noise causes testicular dysfunction probably by gonadotropin suppression induced by pineal melatonin in noise. Furthermore, arecoline cannot prevent it in noise in rats.

  14. 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...

  15. Reduction of noise and bias in randomly sampled power spectra

    DEFF Research Database (Denmark)

    Buchhave, Preben; Velte, Clara Marika

    2015-01-01

    We consider the origin of noise and distortion in power spectral estimates of randomly sampled data, specifically velocity data measured with a burst-mode laser Doppler anemometer. The analysis guides us to new ways of reducing noise and removing spectral bias, e.g., distortions caused by modific......We consider the origin of noise and distortion in power spectral estimates of randomly sampled data, specifically velocity data measured with a burst-mode laser Doppler anemometer. The analysis guides us to new ways of reducing noise and removing spectral bias, e.g., distortions caused...

  16. Noise reduction of high-power supercontinuum sources by back seeding

    DEFF Research Database (Denmark)

    Moselund, Peter Morten; Frosz, Michael Henoch; Thomsen, Carsten L.

    2009-01-01

    We investigate noise reduction in seeded supercontinuum generation at powers above the supercontinuum generation threshold and show that seeding of supercontinuum is also beneficial at high pump powers.......We investigate noise reduction in seeded supercontinuum generation at powers above the supercontinuum generation threshold and show that seeding of supercontinuum is also beneficial at high pump powers....

  17. Acoustical and Perceptual Comparison of Noise Reduction and Compression in Hearing Aids

    Science.gov (United States)

    Brons, Inge; Houben, Rolph; Dreschler, Wouter A.

    2015-01-01

    Purpose: Noise reduction and dynamic-range compression are generally applied together in hearing aids but may have opposite effects on amplification. This study evaluated the acoustical and perceptual effects of separate and combined processing of noise reduction and compression. Design: Recordings of the output of 4 hearing aids for speech in…

  18. Acoustical and Perceptual Comparison of Noise Reduction and Compression in Hearing Aids

    Science.gov (United States)

    Brons, Inge; Houben, Rolph; Dreschler, Wouter A.

    2015-01-01

    Purpose: Noise reduction and dynamic-range compression are generally applied together in hearing aids but may have opposite effects on amplification. This study evaluated the acoustical and perceptual effects of separate and combined processing of noise reduction and compression. Design: Recordings of the output of 4 hearing aids for speech in…

  19. 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

  20. Intrinsic 1/f device noise reduction and its effect on phase noise in CMOS ring oscillators

    NARCIS (Netherlands)

    Gierkink, Sander L.J.; Klumperink, Eric A.M.; Wel, van der Arnoud P.; Hoogzaad, Gian; Tuijl, van Ed (A.J.M.); Nauta, Bram

    1999-01-01

    This paper gives experimental proof of an intriguing physical effect: periodic on-off switching of MOS transistors in a CMOS ring oscillator reduces their intrinsic 1/f noise and hence the oscillator's close-in phase noise. More specifically, it is shown that the 1/f3 phase noise is dependent on the

  1. Comparative intelligibility investigation of single-channel noise-reduction algorithms for Chinese, Japanese, and English.

    Science.gov (United States)

    Li, Junfeng; Yang, Lin; Zhang, Jianping; Yan, Yonghong; Hu, Yi; Akagi, Masato; Loizou, Philipos C

    2011-05-01

    A large number of single-channel noise-reduction algorithms have been proposed based largely on mathematical principles. Most of these algorithms, however, have been evaluated with English speech. Given the different perceptual cues used by native listeners of different languages including tonal languages, it is of interest to examine whether there are any language effects when the same noise-reduction algorithm is used to process noisy speech in different languages. A comparative evaluation and investigation is taken in this study of various single-channel noise-reduction algorithms applied to noisy speech taken from three languages: Chinese, Japanese, and English. Clean speech signals (Chinese words and Japanese words) were first corrupted by three types of noise at two signal-to-noise ratios and then processed by five single-channel noise-reduction algorithms. The processed signals were finally presented to normal-hearing listeners for recognition. Intelligibility evaluation showed that the majority of noise-reduction algorithms did not improve speech intelligibility. Consistent with a previous study with the English language, the Wiener filtering algorithm produced small, but statistically significant, improvements in intelligibility for car and white noise conditions. Significant differences between the performances of noise-reduction algorithms across the three languages were observed.

  2. High-Temperature Smart Structures for Engine Noise Reduction and Performance Enhancement

    Science.gov (United States)

    Quackenbush, Todd R.; McKillip, Robert M., Jr.

    2011-01-01

    One of key NASA goals is to develop and integrate noise reduction technology to enable unrestricted air transportation service to all communities. One of the technical priorities of this activity has been to account for and reduce noise via propulsion/airframe interactions, identifying advanced concepts to be integrated with the airframe to mitigate these noise-producing mechanisms. An adaptive geometry chevron using embedded smart structures technology offers the possibility of maximizing engine performance while retaining and possibly enhancing the favorable noise characteristics of current designs. New high-temperature shape memory alloy (HTSMA) materials technology enables the devices to operate in both low-temperature (fan) and high-temperature (core) exhaust flows. Chevron-equipped engines have demonstrated reduced noise in testing and operational use. It is desirable to have the noise benefits of chevrons in takeoff/landing conditions, but have them deployed into a minimum drag position for cruise flight. The central feature of the innovation was building on rapidly maturing HTSMA technology to implement a next-generation aircraft noise mitigation system centered on adaptive chevron flow control surfaces. In general, SMA-actuated devices have the potential to enhance the demonstrated noise reduction effectiveness of chevron systems while eliminating the associated performance penalty. The use of structurally integrated smart devices will minimize the mechanical and subsystem complexity of this implementation. The central innovations of the effort entail the modification of prior chevron designs to include a small cut that relaxes structural stiffness without compromising the desired flow characteristics over the surface; the reorientation of SMA actuation devices to apply forces to deflect the chevron tip, exploiting this relaxed stiffness; and the use of high-temperature SMA (HTSMA) materials to enable operation in the demanding core chevron environment

  3. The Effects of Noise Reduction on Social Behaviors.

    Science.gov (United States)

    Carbone, Vincent J.; Duncan, Phillip K.

    1986-01-01

    The study found no relationship between improved social behavior in a group of juveniles residing at a county shelter care facility and decreased frequency and duration of disruptions above 85 decibels. Subjects did reduce noise levels when stereo listening was made contingent on reduced noise. (Author/DB)

  4. Perceptual evaluation of noise reduction in hearing aids

    NARCIS (Netherlands)

    Brons, I.

    2013-01-01

    Difficulty to understand speech in noisy situations is the number-one complaint of hearing aid users. Hearing aid manufacturers take measures against the problem of speech in noise by implementing signal-processing algorithms that should reduce background noise. The most widely applied measure again

  5. Methods for clinical evaluation of noise reduction techniques in abdominopelvic CT.

    Science.gov (United States)

    Ehman, Eric C; Yu, Lifeng; Manduca, Armando; Hara, Amy K; Shiung, Maria M; Jondal, Dayna; Lake, David S; Paden, Robert G; Blezek, Daniel J; Bruesewitz, Michael R; McCollough, Cynthia H; Hough, David M; Fletcher, Joel G

    2014-01-01

    Most noise reduction methods involve nonlinear processes, and objective evaluation of image quality can be challenging, since image noise cannot be fully characterized on the sole basis of the noise level at computed tomography (CT). Noise spatial correlation (or noise texture) is closely related to the detection and characterization of low-contrast objects and may be quantified by analyzing the noise power spectrum. High-contrast spatial resolution can be measured using the modulation transfer function and section sensitivity profile and is generally unaffected by noise reduction. Detectability of low-contrast lesions can be evaluated subjectively at varying dose levels using phantoms containing low-contrast objects. Clinical applications with inherent high-contrast abnormalities (eg, CT for renal calculi, CT enterography) permit larger dose reductions with denoising techniques. In low-contrast tasks such as detection of metastases in solid organs, dose reduction is substantially more limited by loss of lesion conspicuity due to loss of low-contrast spatial resolution and coarsening of noise texture. Existing noise reduction strategies for dose reduction have a substantial impact on lowering the radiation dose at CT. To preserve the diagnostic benefit of CT examination, thoughtful utilization of these strategies must be based on the inherent lesion-to-background contrast and the anatomy of interest. The authors provide an overview of existing noise reduction strategies for low-dose abdominopelvic CT, including analytic reconstruction, image and projection space denoising, and iterative reconstruction; review qualitative and quantitative tools for evaluating these strategies; and discuss the strengths and limitations of individual noise reduction methods.

  6. Speech recognition in noise using bilateral open-fit hearing aids: the limited benefit of directional microphones and noise reduction.

    Science.gov (United States)

    Magnusson, Lennart; Claesson, Ann; Persson, Maria; Tengstrand, Tomas

    2013-01-01

    To investigate speech recognition performance in noise with bilateral open-fit hearing aids and as reference also with closed earmolds, in omnidirectional mode, directional mode, and directional mode in conjunction with noise reduction. A within-subject design with repeated measures across conditions was used. Speech recognition thresholds in noise were obtained for the different conditions. Twenty adults without prior experience with hearing aids. All had symmetric sensorineural mild hearing loss in the lower frequencies and moderate to severe hearing loss in the higher frequencies. Speech recognition performance in noise was not significantly better with an omnidirectional microphone compared to unaided, whereas performance was significantly better with a directional microphone (1.6 dB with open fitting and 4.4 dB with closed earmold) compared to unaided. With open fitting, no significant additional advantage was obtained by combining the directional microphone with a noise reduction algorithm, but with closed earmolds a significant additional advantage of 0.8 dB was obtained. The significant, though limited, advantage of directional microphones and the absence of additional significant improvement by a noise reduction algorithm should be considered when fitting open-fit hearing aids.

  7. Active noise control of forced and induced draft fans in power generating plants

    Energy Technology Data Exchange (ETDEWEB)

    Eldada, M.V.

    1985-05-01

    A study was carried out into active noise reduction of forced draft fans in power generation plants. Active noise reduction involves detecting noise, inverting the phase and re-introducing the anti-phase signal into the duct to cancel the noise through destructive interference. Acoustic pressure transfer functions were meaured in-situ along a cross section of a 15 ft diameter fan inlet. A computer modal analysis program was written and used to analyze the field data. It was found that in frequencies between ca 5 Hz and 45 Hz the energy propagates mainly in the plane wave mode, while in higher frequencies the energy was carried mainly by higher order propagation modes. The project objective was to cancel noise up to a frequency of 130 Hz, but current technology restricted active cancellation to plane waves only. Three alternatives were considered: install a feed forward active noise control system to cancel noise at frequencies below 45 Hz; conduct research on active noise control of higher order propagation modes in ducts; or install a feed back active noise control system and a duct splitter in order to cancel noise between 30 and 130 Hz. It was recommended that the third option be selected as the next phase of the research project, which would comprise a 20 ft duct splitter and microphones, filters, amplifiers, loudspekers and cabinets. 6 refs., 12 figs.

  8. 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.

  9. Survey of techniques for reduction of wind turbine blade trailing edge noise.

    Energy Technology Data Exchange (ETDEWEB)

    Barone, Matthew Franklin

    2011-08-01

    Aerodynamic noise from wind turbine rotors leads to constraints in both rotor design and turbine siting. The primary source of aerodynamic noise on wind turbine rotors is the interaction of turbulent boundary layers on the blades with the blade trailing edges. This report surveys concepts that have been proposed for trailing edge noise reduction, with emphasis on concepts that have been tested at either sub-scale or full-scale. These concepts include trailing edge serrations, low-noise airfoil designs, trailing edge brushes, and porous trailing edges. The demonstrated noise reductions of these concepts are cited, along with their impacts on aerodynamic performance. An assessment is made of future research opportunities in trailing edge noise reduction for wind turbine rotors.

  10. A simulation study of harmonics regeneration in noise reduction for electric and acoustic stimulation.

    Science.gov (United States)

    Hu, Yi

    2010-05-01

    Recent research results show that combined electric and acoustic stimulation (EAS) significantly improves speech recognition in noise, and it is generally established that access to the improved F0 representation of target speech, along with the glimpse cues, provide the EAS benefits. Under noisy listening conditions, noise signals degrade these important cues by introducing undesired temporal-frequency components and corrupting harmonics structure. In this study, the potential of combining noise reduction and harmonics regeneration techniques was investigated to further improve speech intelligibility in noise by providing improved beneficial cues for EAS. Three hypotheses were tested: (1) noise reduction methods can improve speech intelligibility in noise for EAS; (2) harmonics regeneration after noise reduction can further improve speech intelligibility in noise for EAS; and (3) harmonics sideband constraints in frequency domain (or equivalently, amplitude modulation in temporal domain), even deterministic ones, can provide additional benefits. Test results demonstrate that combining noise reduction and harmonics regeneration can significantly improve speech recognition in noise for EAS, and it is also beneficial to preserve the harmonics sidebands under adverse listening conditions. This finding warrants further work into the development of algorithms that regenerate harmonics and the related sidebands for EAS processing under noisy conditions.

  11. 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.

  12. 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

  13. X-/Ka-band dichroic plate noise temperature reduction

    Science.gov (United States)

    Veruttipong, W.; Lee, P.

    1994-11-01

    The X-/Ka-band (8.4 GHz/32.0 GHz) dichroic plate installed as DSS 13 contributes an estimated 3 K to the system noise temperature at 32.0 GHz. Approximately 1 percent of the Ka-band incident field is reflected by the plate into the 300-K environment of the DSS-13 pedestal room. A low-cost, easily implemented method of reducing the noise temperature is presented. Using a curved reflector, the reflected field can be re-focused into an 80-K cold load, reducing the noise temperature contribution of the dichroic plate by about 2 K.

  14. Research on Aerodynamic Noise Reduction for High-Speed Trains

    OpenAIRE

    Yadong Zhang; Jiye Zhang; Tian Li; Liang Zhang; Weihua Zhang

    2016-01-01

    A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H)...

  15. Research on Aerodynamic Noise Reduction for High-Speed Trains

    OpenAIRE

    Yadong Zhang; Jiye Zhang; Tian Li; Liang Zhang; Weihua Zhang

    2016-01-01

    A broadband noise source model based on Lighthill’s acoustic theory was used to perform numerical simulations of the aerodynamic noise sources for a high-speed train. The near-field unsteady flow around a high-speed train was analysed based on a delayed detached-eddy simulation (DDES) using the finite volume method with high-order difference schemes. The far-field aerodynamic noise from a high-speed train was predicted using a computational fluid dynamics (CFD)/Ffowcs Williams-Hawkings (FW-H)...

  16. The effect of a hearing aid noise reduction algorithm on the acquisition of novel speech contrasts.

    Science.gov (United States)

    Marcoux, André M; Yathiraj, Asha; Côté, Isabelle; Logan, John

    2006-12-01

    Audiologists are reluctant to prescribe digital hearing aids with active digital noise reduction (DNR) to pre-verbal children due to their potential for an adverse effect on the acquisition of language. The present study investigated the relation between DNR and language acquisition by modeling pre-verbal language acquisition using adult listeners presented with a non-native speech contrast. Two groups of normal-hearing, monolingual Anglophone subjects were trained over four testing sessions to discriminate novel, difficult to discriminate, non-native Hindi speech contrasts in continuous noise, where one group listened to both speech items and noise processed with DNR, and where the other group listened to unprocessed speech in noise. Results did not reveal a significant difference in performance between groups across testing sessions. A significant learning effect was noted for both groups between the first and second testing sessions only. Overall, DNR does not appear to enhance or impair the acquisition of novel speech contrasts by adult listeners.

  17. Active noise cancellation in hearing devices

    DEFF Research Database (Denmark)

    2013-01-01

    Disclosed is a hearing device system comprising at least one hearing aid circuitry and at least one active noise cancellation unit, the at least one hearing aid circuitry comprises at least one input transducer adapted to convert a first audio signal to an electric audio signal; a signal processor...... to said generated sound pressure, wherein the hearing device system further comprises a combiner unit adapted to combine the processed electric audio signal with the active noise cancellation signal, to obtain a combined signal and to provide the combined signal to the output transducer....... connected to the at least one input transducer and adapted to process said electric audio signal by at least partially correcting for a hearing loss of a user; an output transducer adapted to generate from at least said processed electric audio signal a sound pressure in an ear canal of the user, whereby...

  18. Technical Possibilities of Noise Reduction in Material Cutting by Abrasive Water-jet

    OpenAIRE

    Radvanská, Agáta; Ergić, Todor; IVANDIĆ, Željko; Hloch, Sergej; Valiček, Jan; Mullerova, Jana

    2009-01-01

    The technical procedure of noise reduction in material cutting by abrasive water-jet is described in this paper. The paper is aimed at the implementation of technical possibilities of noise reduction in the cutting of material by abrasive water-jet technology. Both the theoretical and experimental investigations were performed to verify and specify the new findings in the reduction of acoustic sound pressure at abrasive water-jet machining of engineering materials. By means of identification,...

  19. A Noise Reduction Preprocessor for Mobile Voice Communication

    Directory of Open Access Journals (Sweden)

    Rainer Martin

    2004-07-01

    Full Text Available We describe a speech enhancement algorithm which leads to significant quality and intelligibility improvements when used as a preprocessor to a low bit rate speech coder. This algorithm was developed in conjunction with the mixed excitation linear prediction (MELP coder which, by itself, is highly susceptible to environmental noise. The paper presents novel as well as known speech and noise estimation techniques and combines them into a highly effective speech enhancement system. The algorithm is based on short-time spectral amplitude estimation, soft-decision gain modification, tracking of the a priori probability of speech absence, and minimum statistics noise power estimation. Special emphasis is placed on enhancing the performance of the preprocessor in nonstationary noise environments.

  20. Advanced Acoustic Blankets for Improved Aircraft Interior Noise Reduction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In this project advanced acoustic blankets for improved low frequency interior noise control in aircraft will be developed and demonstrated. The improved performance...

  1. Noise and its reduction in graphene based nanopore devices.

    Science.gov (United States)

    Kumar, Ashvani; Park, Kyeong-Beom; Kim, Hyun-Mi; Kim, Ki-Bum

    2013-12-13

    Ionic current fluctuations in graphene nanopore devices are a ubiquitous phenomenon and are responsible for degraded spatial and temporal resolution. Here, we descriptively investigate the impact of different substrate materials (Si and quartz) and membrane thicknesses on noise characteristics of graphene nanopore devices. To mitigate the membrane fluctuations and pin-hole defects, a SiNx membrane is transferred onto the substrate and a pore of approximately 70 nm in diameter is perforated prior to the graphene transfer. Comprehensive noise study reveals that the few layer graphene transferred onto the quartz substrate possesses low noise level and higher signal to noise ratio as compared to single layer graphene, without deteriorating the spatial resolution. The findings here point to improvement of graphene based nanopore devices for exciting opportunities in future single-molecule genomic screening devices.

  2. Acoustic noise reduction in a 4 T MRI scanner.

    Science.gov (United States)

    Mechefske, Chris K; Geris, Ryan; Gati, Joseph S; Rutt, Brian K

    2002-01-01

    High-field, high-speed magnetic resonance imaging (MRI) can generate high levels of noise. There is ongoing concern in the medical and imaging research communities regarding the detrimental effects of high acoustic levels on auditory function, patient anxiety, verbal communication between patients and health care workers and ultimately MR image quality. In order to effectively suppress the noise levels inside MRI scanners, the sound field needs to be accurately measured and characterized. This paper presents the results of measurements of the sound radiation from a gradient coil cylinder within a 4 T MRI scanner under a variety of conditions. These measurement results show: (1) that noise levels can be significantly reduced through the use of an appropriately designed passive acoustic liner; and (2) the true noise levels that are experienced by patients during echo planar imaging.

  3. Noise Reduction in High-Throughput Gene Perturbation Screens

    Science.gov (United States)

    Motivation: Accurate interpretation of perturbation screens is essential for a successful functional investigation. However, the screened phenotypes are often distorted by noise, and their analysis requires specialized statistical analysis tools. The number and scope of statistical methods available...

  4. Study on the application of digital signal processor (DSP) to adaptive control. 2. Active noise control to noise from a duct; DSP ni yoru tekio seigyo. 2. Duct kaikotan no soon eno active noise control

    Energy Technology Data Exchange (ETDEWEB)

    Kino, N.; Kitagawa, T.; Aoki, K. [Shizuoka Industrial Research Institute of Shizuoka prefecture, Shizuoka (Japan)

    1995-09-01

    Recent developments in signal processing technology, computer and LSI technology, especially DSP technology have made it possible to process sampled and quantized sound signals in real time. So sound field processing technology and sound field control technology have been made rapid progress. Active noise control technology is one of the sound field control technologies. And it can be applied to low frequency noise reduction problems that we couldn`t cope with in usual way. So we developed an experimental device of active noise control. We report how we developed this device and refer to the experimental results about a random frequency noise in this report. 5 refs., 18 figs., 1 tab.

  5. Noise reduction of a Libbrecht--Hall style current driver

    CERN Document Server

    Seck, Christopher M; Cook, Eryn C; Odom, Brian C; Steck, Daniel A

    2016-01-01

    The Libbrecht--Hall circuit is a well-known, low-noise current driver for narrow-linewidth diode lasers. An important feature of the circuit is a current limit to protect the laser diode. As the current approaches the maximum limit, however, the noise in the laser current increases dramatically. This paper documents this behavior and explores simple circuit modifications to alleviate this issue.

  6. Analysis of Beamformer Directed Single-Channel Noise Reduction System for Hearing Aid Applications

    DEFF Research Database (Denmark)

    Jensen, Jesper; Pedersen, Michael Syskind

    2015-01-01

    We study multi-microphone noise reduction systems consisting of a beamformer and a single-channel (SC) noise reduction stage. In particular, we present and analyse a maximum likelihood (ML) method for jointly estimating the target and noise power spectral densities (psd's) entering the SC filter....... We show that the estimators are minimum variance and unbiased, and provide closed-form expressions for their mean-square error (MSE). Furthermore, we show that the MSE of the noise psd estimator is particularly simple: it is independent of target signal characteristics, frequency, and microphone...

  7. Noise reduction for centrifugal fan with non-isometric forward-swept blade impeller

    Institute of Scientific and Technical Information of China (English)

    Jianfeng MA; Datong QI; Yijun MAO

    2008-01-01

    To reduce the noise of the T9-19No.4A centri-fugal fan, whose impeller has equidistant forward-swept blades, two new impellers with different blade spacing were designed and an experimental study was conducted. Both the fan's aerodynamic performance and noise were measured when the two redesigned impellers were com-pared with the original ones. The test results are discussed in detail and the effect of the noise reduction method for a centrifugal fan using impellers with non-isometric for-ward-swept blades was analyzed, which can serve as a reference for researches on reduction of fan noise.

  8. The Structure and Noise Reduction Capacity of Owl Down

    Science.gov (United States)

    Jaworski, Justin; Clark, Ian; Alexander, Nathan; Devenport, William; Daly, Conor; Peake, Nigel; Glegg, Stewart

    2014-11-01

    Many species of owl rely on specialized plumage to reduce their self-noise levels and enable hunting in acoustic stealth. In contrast to the leading-edge comb and compliant trailing-edge fringe attributes of owls, the aeroacoustic impact of the fluffy down material on the upper wing surface remains largely speculative as a means to eliminate aerodynamic noise across a broad range of frequencies. Photographic analysis of the owl down reveals a unique forest-like structure, whereby the down fibers rise straight up from the wing surface and then bend into the flow direction to form a porous canopy, with an open area fraction of approximately 70%. Experimental measurements demonstrate that the canopy feature reduces dramatically the turbulent pressure levels on the wing surface by up to 30dB, which affects the roughness noise characteristic of the down in a manner consistent with the theory of flows over and through vegetation. Mathematical models developed for the turbulence noise generation by the down fibers and for the mixing-layer instability above the porous canopy furnish a theoretical basis to understand the influence of the down geometric structure on its self-noise signature and noise suppression characteristics.

  9. Reduction of tire road noise by acoustic absorption: Numerical evaluation of the pass-by noise level reduction using the normal incidence acoustic absorption coefficient

    OpenAIRE

    Hamet, J. F.

    2004-01-01

    Convention GRD2/2000/30202; Rapport de recherche; Comments: This report is an INRETS-LTE edition of the SILVIA -INRETS-013-WP2 report "Estimation of the attenuation of rolling noise by acoustic absorption", dated 19/09/2004. Summary: Part of INRETS task in the SILVIA project is to study the influence of the pavement characteristics on the generation and the propagation of road traffic noise using existing models. This work addresses the reduction of tire-road noise by absorption effects. It a...

  10. Active noise control technology. Active soon seigyo gijutsu

    Energy Technology Data Exchange (ETDEWEB)

    Eguchi, M.; Kokubo, F.; Tanaka, S.; Yao, K. (Sharp Corp., Osaka (Japan))

    1994-05-10

    The signal processing method of the Active Noise Control (ANC) system was studied. The principle of ANC is to output secondary sound waves having opposite phase, identical amplitude from the control point of the sound wave of the primary sound source, and eliminate the noise by interference. As application fields, there are air conditioner ducts and compressors as one dimensional noise source, and automobile and axial fan as three dimensional noise source. In order to improve the stability of coefficient renewal algorithm of Adaptive Digital Filter (ADF), for generation of opposite phase noise, DC-LMS algorithm which can control the rise in gain of specified frequency zone was proposed. Furthermore, with the purpose of reducing the amount of operation, the introduction of lattice type AR filter was tested for the stability of the filter in IIR-ADF (Infinite Impulse Response Adaptive Digital Filter) and its application process. The applicability studies of these improved methods on the noise inside of ducts were actually measured, and the effect was verified. For the multi-channel control of 3 dimensional noise source, reference scanning method to reduce the filter operation was proposed. In the partial space noise eliminating experiment, it was made clear that it possesses equivalent effect to error scanning method. 11 refs., 14 figs., 1 tab.

  11. Active Control of Fan Noise: Feasibility Study. Volume 3; Active Fan Noise Cancellation in the NASA Lewis Active Noise Control Fan Facility

    Science.gov (United States)

    Pla, Frederic G.; Hu, Ziqiang; Sutliff, Daniel L.

    1996-01-01

    This report describes the Active Noise Cancellation (ANC) System designed by General Electric and tested in the NASA Lewis Research Center's (LERC) 48 inch Active Noise Control Fan (ANCF). The goal of this study is to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for global active noise cancellation of fan tones. The GE ANC system is based on a modal control approach. A known acoustic mode propagating in the fan duct is canceled using an array of flush-mounted compact sound sources. The canceling modal signal is generated by a modal controller. Inputs to the controller are signals from a shaft encoder and from a microphone array which senses the residual acoustic mode in the duct. The key results are that the (6,0) was completely eliminated at the 920 Hz design frequency and substantially reduced elsewhere. The total tone power was reduced 6.8 dB (out of a possible 9.8 dB). Farfield reductions of 15 dB (SPL) were obtained. The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB PWL decrease. The results indicate that global attenuation of PWL at the target frequency was obtained in the aft quadrant using an ANC actuator and sensor system totally contained within the duct. The quality of the results depended on precise mode generation. High spillover into spurious modes generated by the ANC actuator array caused less than optimum levels of PWL reduction. The variation in spillover is believed to be due to calibration procedure, but must be confirmed in subsequent tests.

  12. Minimizing noise in fiberglass aquaculture tanks: Noise reduction potential of various retrofits

    Science.gov (United States)

    Equipment used in intensive aquaculture systems, such as pumps and blowers can produce underwater sound levels and frequencies within the range of fish hearing. The impacts of underwater noise on fish are not well known, but limited research suggests that subjecting fish to noise could result in imp...

  13. SVD-based optimal filtering for noise reduction in dual microphone hearing aids: a real time implementation and perceptual evaluation.

    Science.gov (United States)

    Maj, Jean-Baptiste; Royackers, Liesbeth; Moonen, Marc; Wouters, Jan

    2005-09-01

    In this paper, the first real-time implementation and perceptual evaluation of a singular value decomposition (SVD)-based optimal filtering technique for noise reduction in a dual microphone behind-the-ear (BTE) hearing aid is presented. This evaluation was carried out for a speech weighted noise and multitalker babble, for single and multiple jammer sound source scenarios. Two basic microphone configurations in the hearing aid were used. The SVD-based optimal filtering technique was compared against an adaptive beamformer, which is known to give significant improvements in speech intelligibility in noisy environment. The optimal filtering technique works without assumptions about a speaker position, unlike the two-stage adaptive beamformer. However this strategy needs a robust voice activity detector (VAD). A method to improve the performance of the VAD was presented and evaluated physically. By connecting the VAD to the output of the noise reduction algorithms, a good discrimination between the speech-and-noise periods and the noise-only periods of the signals was obtained. The perceptual experiments demonstrated that the SVD-based optimal filtering technique could perform as well as the adaptive beamformer in a single noise source scenario, i.e., the ideal scenario for the latter technique, and could outperform the adaptive beamformer in multiple noise source scenarios.

  14. 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.

  15. Evaluation of a novel method of noise reduction using computer-simulated mammograms.

    Science.gov (United States)

    Tischenko, Oleg; Hoeschen, Christoph; Dance, David R; Hunt, Roger A; Maidment, Andrew D A; Bakic, Predrag R

    2005-01-01

    A novel method of noise reduction has been tested for mammography using computer-simulated images for which the truth is known exactly. This method is based on comparing two images. The images are compared at different scales, using a cross-correlation function as a measure of similarity to define the image modifications in the wavelet domain. The computer-simulated images were calculated for noise-free primary radiation using a quasi-realistic voxel phantom. Two images corresponding to slightly different geometry were produced. Gaussian noise was added with certain properties to simulate quantum noise. The added noise could be reduced by >70% using the proposed method without any noticeable corruption of the structures. It is possible to save 50% dose in mammography by producing two images (each 25% of the dose for a standard mammogram). Additionally, a reduction of the anatomical noise and, therefore, better detection rates of breast cancer in mammography are possible.

  16. Noise Reduction Analysis on Inverter Driven Two-Cylinder Rotary Compressor

    Science.gov (United States)

    Nonaka, Ryutaro; Suda, Akihiro; Matumoto, Kenzou

    Two-cylinder rotary compressor is dynamically balanced well because two rollers in each cylinder chamber are located in opposite sides. Thus, it helps to reduce the circumferential vibration based on the tracking torque ripple for gas compression. This concept has been recently applied to room airconditioners (RACs) for the purpose of reducing vibration and noise of the unit. However, it consequently requires the compressor, which is one of the main noise factors, extremely low noise to reduce RAC noise. This paper describes generating mechanisms of the compressor noise established by analysis using signal processing and computer aided engineering. In addition, concrete countermeasures are presented for the noise reduction of the two-cylinder rotary compressor. In conclusion, Countermeasures for resonance in cavities were achieved by reducing 630Hz∼1KHz levels and the effect of muffler in the chamber contributed to the reduction of 3KHz∼6KHz levels.

  17. Experiments to Determine Neighborhood Reactions to Light Airplanes With and Without External Noise Reduction

    Science.gov (United States)

    Elwell, Fred S

    1953-01-01

    The work reported was part of a program of experimentation with external noise reduction on light airplanes. This particular study was in effect a byproduct survey conceived to utilize already available equipment and personnel to further the findings of the original research and to determine reactions in populated neighborhoods to light aircraft with and without noise-reduction equipment. The findings indicate that at the 10 sites within and about metropolitan Boston the degree of noise reduction previously found to be aerodynamically and structurally feasible did eliminate substantially all neighborhood objections to noise per se. The evidence clearly suggests that, when the noise nuisance is minimized to the extent found feasible, the number and severity of other objections also diminish -- evidently because the flight operations are noticed less when heard less.

  18. Noise reduction of a composite cylinder subjected to random acoustic excitation

    Science.gov (United States)

    Grosveld, Ferdinand W.; Beyer, T.

    1989-01-01

    Interior and exterior noise measurements were conducted on a stiffened composite floor-equipped cylinder, with and without an interior trim installed. Noise reduction was obtained for the case of random acoustic excitation in a diffuse field; the frequency range of interest was 100-800-Hz one-third octave bands. The measured data were compared with noise reduction predictions from the Propeller Aircraft Interior Noise (PAIN) program and from a statistical energy analysis. Structural model parameters were not predicted well by the PAIN program for the given input parameters; this resulted in incorrect noise reduction predictions for the lower one-third octave bands where the power flow into the interior of the cylinder was predicted on a mode-per-mode basis.

  19. A Two-Sensor Noise Reduction System: Applications for Hands-Free Car Kit

    Directory of Open Access Journals (Sweden)

    Régine Le Bouquin-Jeannès

    2003-10-01

    Full Text Available This paper presents a two-microphone speech enhancer designed to remove noise in hands-free car kits. The algorithm, based on the magnitude squared coherence, uses speech correlation and noise decorrelation to separate speech from noise. The remaining correlated noise is reduced using cross-spectral subtraction. Particular attention is focused on the estimation of the different spectral densities (noise and noisy signals power spectral densities which are critical for the quality of the algorithm. We also propose a continuous noise estimation, avoiding the need of vocal activity detector. Results on recorded signals are provided, showing the superiority of the two-sensor approach to single microphone techniques.

  20. Research on noise and vibration reduction at DB to improve the environmental friendliness of railway traffic

    Science.gov (United States)

    Schulte-Werning, B.; Beier, M.; Degen, K. G.; Stiebel, D.

    2006-06-01

    One of the most prominent keywords relating to the environmental friendliness of railway traffic is noise reduction. Thus, the research and development programme "Low Noise Railway" of Deutsche Bahn (DB) is under way to treat the noise of the vehicles and infrastructure. The noise reduction of the trains and the rail/wheel system are being tackled within several projects. The direct noise experienced by railway-lineside residents due to train movements on the track can be reduced by minimising the sound radiation directly at the source. This is the first-choice solution, as it proves to be the most effective countermeasure regarding a cost-benefit relation. The limit values for the noise emission as specified in the technical specification for interoperability are an essential criterion to be confirmed during the procurement process of railway vehicles. A recently developed acoustical quality management scheme establishes systematic noise management to complete the vehicle procurement process in the phases of concept, design, construction and manufacturing. In freight traffic quiet railway wheels for block brake operation will play an important role in the future to meet the goal of a low-noise railway system. A first attempt to realise successfully the low-noise potential of such optimised wheels was performed, even if with mixed results. To show ways of reducing the noise of the cooling ventilation in locomotives, DB is a partner in a development project led by Siemens. A notable 8 dB(A) noise reduction was measured. Concerning bridge noise, a project was started based on an effective and cost-efficient combination of experiments and simulations in order to develop specifications for the construction of generic low-noise bridges.

  1. Reduction of Impact Noise of Trams on a Major Bridge

    NARCIS (Netherlands)

    Dittrich, M.G.; Bosshaart, C.; Wessels, P.W.

    2015-01-01

    As part of a recent renovation of the Erasmus bridge in Rotterdam, improvements were made to reduce impact noise caused by trams passing a series of rai! joints. The bridge inciudes several different sections inciuding a bascule bridge and is in an inner city tocation with new adjacent apartment bui

  2. 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…

  3. Techniques for the reduction of low frequency noise in buildings

    NARCIS (Netherlands)

    Zuada Coelho, B.A.; Koopman, A.

    2012-01-01

    Vibration isolation of buildings is often achieved by introducing spring systems at the foundation level. This can be an effective measure, especially against vibrations induced by noise, but it is also very costly. Due to the current usage of the cities space, where buildings and infrastructures sh

  4. Reduction of HCCI combustion noise through piston crown design

    DEFF Research Database (Denmark)

    Pedersen, Troels Dyhr; Schramm, Jesper

    2010-01-01

    Seven shapes of piston crowns have been evaluated for their ability to reduce HCCI knock and transmission of combustion noise to the engine. The performance of each piston crown was evaluated with measurements of cylinder pressure, engine vibration and acoustic sound pressure measured one meter a...

  5. 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.

  6. Evaluation of the efficiency of the shields for reduction of airplane noise effects

    Directory of Open Access Journals (Sweden)

    В. Ф. Шило

    1999-09-01

    Full Text Available Acoustic shield is one of the most effective means for reduction of transport noise effect, avia­tion included. Noise shields are widely used in world practice. Acoustic efficiency of shields depends on many factors, therefore it is necessary to use, on the designing stage, complicated methodical and computer means for their substantiation

  7. Perceptual effects of noise reduction by time-frequency masking of noisy speech.

    Science.gov (United States)

    Brons, Inge; Houben, Rolph; Dreschler, Wouter A

    2012-10-01

    Time-frequency masking is a method for noise reduction that is based on the time-frequency representation of a speech in noise signal. Depending on the estimated signal-to-noise ratio (SNR), each time-frequency unit is either attenuated or not. A special type of a time-frequency mask is the ideal binary mask (IBM), which has access to the real SNR (ideal). The IBM either retains or removes each time-frequency unit (binary mask). The IBM provides large improvements in speech intelligibility and is a valuable tool for investigating how different factors influence intelligibility. This study extends the standard outcome measure (speech intelligibility) with additional perceptual measures relevant for noise reduction: listening effort, noise annoyance, speech naturalness, and overall preference. Four types of time-frequency masking were evaluated: the original IBM, a tempered version of the IBM (called ITM) which applies limited and non-binary attenuation, and non-ideal masking (also tempered) with two different types of noise-estimation algorithms. The results from ideal masking imply that there is a trade-off between intelligibility and sound quality, which depends on the attenuation strength. Additionally, the results for non-ideal masking suggest that subjective measures can show effects of noise reduction even if noise reduction does not lead to differences in intelligibility.

  8. Development of active control technique for engine noise. Engine soon no active seigyo gijutsu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, H.; Nakao, N.; Butsuen, T. (Mazda Motor Corp., Hiroshima (Japan))

    1994-03-31

    As a measure to reduce engine noise in a car, the active noise control (ANC) technique to eliminate noise by another noise of antiphase has been studied. The conventional filtered-x LMS control algorithm has been generally applied to the ANC, but a large quantity of arithmetic operation used for filtering is practically problematic. This paper proposes the new algorithm of which control effects and practicability have been improved by utilizing periodicity of engine noise and by introducing the idea of error scanning. This algorithm requires only 30-50% of the arithmetic operation of the above LMS method. Concerning the actual system structure, arrangement and the number of microphones have been examined based on the detailed measurement results of the spatial distribution of noise in a car. As a result, the suitable arrangement of only three microphones to reduce noise in the whole interior space of a car is found. Through the experiments, maximum noise reduction of 8dB (A scale) has been achieved at each seat position. 7 refs., 9 figs., 1 tab.

  9. 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.

  10. Noise Reduction Evaluation of Multi-Layered Viscoelastic Infinite Cylinder under Acoustical Wave Excitation

    OpenAIRE

    Mofakhami, M.R.; H. Hosseini Toudeshky; Sh. Hosseini Hashemi

    2008-01-01

    In this paper sound transmission through the multilayered viscoelastic air filled cylinders subjected to the incident acoustic wave is studied using the technique of separation of variables on the basis of linear three dimensional theory of elasticity. The effect of interior acoustic medium on the mode maps (frequency vs geometry) and noise reduction is investigated. The effects of internal absorption and external moving medium on noise reduction are also evaluated. The dynamic viscoelastic p...

  11. Automotive active noise control (ANC) system. Jidoshayo active noise control (ANC) system

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, S. (Nissan Motor Co. Ltd., Tokyo (Japan))

    1992-11-25

    This paper introduces a successful development of an active noise control (ANC) system that selects and controls noise in an automobile compartment. This is a system that Nissan has developed for practical use for the first time in the world by using an adaptive control theory and a digital signal processor (DSP) that uses ultra-high speed operating elements. The principle for noise silencing in the ANC system utilizes interference of cyclic amplitude of sound with opposite phase. Sounds in an automobile include informative sounds, agreeable sounds, and noise, and combinations of these sounds work complexly on people in a car, of which extent varies depending on individuals. The adaptive control minimizes sounds picked up by a microphone into controlled speaker sound via an multiple error filtered algorithm (MEF-[sub X]LMS) and an adaptive digital filter. Major components of the system include a microphone, a speaker, and a control unit (comprising the adaptive algorithm and the adaptive filter), all having been developed newly. A DSP that operates on ultra-high speed operating elements was used for speedy compliance with complex algorithms, so that the controlled sound combined of engine noise with compartment sound field can be calculated. The noise was reduced by more than 10 dB at maximum. 7 figs.

  12. Flavin reduction activates Drosophila cryptochrome.

    Science.gov (United States)

    Vaidya, Anand T; Top, Deniz; Manahan, Craig C; Tokuda, Joshua M; Zhang, Sheng; Pollack, Lois; Young, Michael W; Crane, Brian R

    2013-12-17

    Entrainment of circadian rhythms in higher organisms relies on light-sensing proteins that communicate to cellular oscillators composed of delayed transcriptional feedback loops. The principal photoreceptor of the fly circadian clock, Drosophila cryptochrome (dCRY), contains a C-terminal tail (CTT) helix that binds beside a FAD cofactor and is essential for light signaling. Light reduces the dCRY FAD to an anionic semiquinone (ASQ) radical and increases CTT proteolytic susceptibility but does not lead to CTT chemical modification. Additional changes in proteolytic sensitivity and small-angle X-ray scattering define a conformational response of the protein to light that centers at the CTT but also involves regions remote from the flavin center. Reduction of the flavin is kinetically coupled to CTT rearrangement. Chemical reduction to either the ASQ or the fully reduced hydroquinone state produces the same conformational response as does light. The oscillator protein Timeless (TIM) contains a sequence similar to the CTT; the corresponding peptide binds dCRY in light and protects the flavin from oxidation. However, TIM mutants therein still undergo dCRY-mediated degradation. Thus, photoreduction to the ASQ releases the dCRY CTT and promotes binding to at least one region of TIM. Flavin reduction by either light or cellular reductants may be a general mechanism of CRY activation.

  13. Improving word recognition in noise among hearing-impaired subjects with a single-channel cochlear noise-reduction algorithm.

    Science.gov (United States)

    Fink, Nir; Furst, Miriam; Muchnik, Chava

    2012-09-01

    A common complaint of the hearing impaired is the inability to understand speech in noisy environments even with their hearing assistive devices. Only a few single-channel algorithms have significantly improved speech intelligibility in noise for hearing-impaired listeners. The current study introduces a cochlear noise reduction algorithm. It is based on a cochlear representation of acoustic signals and real-time derivation of a binary speech mask. The contribution of the algorithm for enhancing word recognition in noise was evaluated on a group of 42 normal-hearing subjects, 35 hearing-aid users, 8 cochlear implant recipients, and 14 participants with bimodal devices. Recognition scores of Hebrew monosyllabic words embedded in Gaussian noise at several signal-to-noise ratios (SNRs) were obtained with processed and unprocessed signals. The algorithm was not effective among the normal-hearing participants. However, it yielded a significant improvement in some of the hearing-impaired subjects under different listening conditions. Its most impressive benefit appeared among cochlear implant recipients. More than 20% improvement in recognition score of noisy words was obtained by 12, 16, and 26 hearing-impaired at SNR of 30, 24, and 18 dB, respectively. The algorithm has a potential to improve speech intelligibility in background noise, yet further research is required to improve its performances.

  14. Adaptive Subband Filtering Method for MEMS Accelerometer Noise Reduction

    Directory of Open Access Journals (Sweden)

    Piotr PIETRZAK

    2008-12-01

    Full Text Available Silicon microaccelerometers can be considered as an alternative to high-priced piezoelectric sensors. Unfortunately, relatively high noise floor of commercially available MEMS (Micro-Electro-Mechanical Systems sensors limits the possibility of their usage in condition monitoring systems of rotating machines. The solution of this problem is the method of signal filtering described in the paper. It is based on adaptive subband filtering employing Adaptive Line Enhancer. For filter weights adaptation, two novel algorithms have been developed. They are based on the NLMS algorithm. Both of them significantly simplify its software and hardware implementation and accelerate the adaptation process. The paper also presents the software (Matlab and hardware (FPGA implementation of the proposed noise filter. In addition, the results of the performed tests are reported. They confirm high efficiency of the solution.

  15. Power Mapping and Noise Reduction for Financial Correlations

    Science.gov (United States)

    Andersson, P.-J.; Oeberg, A.; Guhr, T.

    2005-09-01

    The spectral properties of financial correlation matrices can show features known from completely random matrices. A major reason is noise originating from the finite lengths of the financial time series used to compute the correlation matrix elements. In recent years, various methods have been proposed to reduce this noise, i.e. to clean the correlation matrices. This is of direct practical relevance for risk management in portfolio optimization. In this contribution, we discuss in detail the power mapping, a new shrinkage method. We show that the relevant parameter is, to a certain extent, self-determined. Due to the ``chirality'' and the normalization of the correlation matrix, the optimal shrinkage parameter is fixed. We apply the power mapping and the well-known filtering method to market data and compare them by optimizing stock portfolios. We address the rôle of constraints by excluding short selling in the optimization.

  16. Landing Gear Door Liners for Airframe Noise Reduction

    Science.gov (United States)

    Jones, Michael G. (Inventor); Howerton, Brian M. (Inventor); Van De Ven, Thomas (Inventor)

    2014-01-01

    A landing gear door for retractable landing gear of aircraft includes an acoustic liner. The acoustic liner includes one or more internal cavities or chambers having one or more openings that inhibit the generation of sound at the surface and/or absorb sound generated during operation of the aircraft. The landing gear door may include a plurality of internal chambers having different geometries to thereby absorb broadband noise.

  17. Experimental Comparison of Signal Subspace Based Noise Reduction Methods

    DEFF Research Database (Denmark)

    Hansen, Peter Søren Kirk; Hansen, Per Christian; Hansen, Steffen Duus

    1999-01-01

    The signal subspace approach for non-parametric speech enhancement is considered. Several algorithms have been proposed in the literature but only partly analyzed. Here, the different algorithms are compared, and the emphasis is put onto the limiting factors and practical behavior of the estimato....... Experimental results show that the signal subspace approach may lead to a significant enhancement of the signal to noise ratio of the output signal....

  18. Experimental Comparison of Signal Subspace Based Noise Reduction Methods

    OpenAIRE

    Hansen, Peter Søren Kirk; Hansen, Per Christian; Hansen, Steffen Duus; Sørensen, John Aasted

    1999-01-01

    The signal subspace approach for non-parametric speech enhancement is considered. Several algorithms have been proposed in the literature but only partly analyzed. Here, the different algorithms are compared, and the emphasis is put onto the limiting factors and practical behavior of the estimators. Experimental results show that the signal subspace approach may lead to a significant enhancement of the signal to noise ratio of the output signal.

  19. 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.

  20. 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

  1. Active Control of Fan Noise: Feasibility Study. Volume 4; Flyover System Noise Studies

    Science.gov (United States)

    Kraft, R. E.; Janardan, B. A.; Gliebe, P. R.; Kontos, G. C.

    1996-01-01

    An extension of a prior study has been completed to examine the potential reduction of aircraft flyover noise by the method of active noise control (ANC). It is assumed that the ANC system will be designed such that it cancels discrete tones radiating from the engine fan inlet or fan exhaust duct, at least to the extent that they no longer protrude above the surrounding broadband noise levels. Thus, without considering the engineering details of the ANC system design, tone levels am arbitrarily removed from the engine component noise spectrum and the flyover noise EPNL levels are compared with and without the presence of tones. The study was conducted for a range of engine cycles, corresponding to fan pressure ratios of 1.3, 1.45, 1.6, and 1.75. This report is an extension of an effort reported previously. The major conclusions drawn from the prior study, which was restricted to fan pressure ratios of 1.45 and 1.75, are that, for a fan pressure ratio of 1.75, ANC of tones gives about the same suppression as acoustic treatment without ANC. For a fan pressure ratio of 1.45, ANC appears to offer less effectiveness from passive treatment. In the present study, the other two fan pressure ratios are included in a more detailed examination of the benefits of the ANC suppression levels. The key results of this extended study are the following observations: (1) The maximum overall benefit obtained from suppression of BPF alone was 2.5 EPNdB at high fan speeds. The suppression benefit increases with increase in fan pressure ratio (FPR), (2) The maximum overall benefit obtained from suppression of the first three harmonics was 3 EPNdB at high speeds. Suppression benefit increases with increase in FPR, (3) At low FPR, only about 1.0 EPNdB maximum reduction was obtained. Suppression is primarily from reduction of BPF at high FPR values and from the combination of tones at low FPR, (4) The benefit from ANC is about the same as the benefit from passive treatment at fan pressure

  2. [Noise in intensive care units. Noise reduction by modification of gas humidification].

    Science.gov (United States)

    Berg, P W; Stuttmann, R; Doehn, M

    1997-10-01

    Today, noise pollution is an evident and ubiquitous problem even in intensive care units. Noise can disturb the physiological and psychological balance in patients and staff. Especially intubated patients and those breathing spontaneously through a T-piece are exposed to the noise emitted by the nebuliser used to humidity the respiratory gas. This may make patients feel uncomfortable. To reduce noise pollution in the ICU a modified T-piece has been developed and investigated. In order to heat and humidity the respiratory gas a Conchaterm III unit (Kendall company) and a thermo flow cylinder (De Vilbiss company) is necessary. While respiratory gas is flowing, water is sucked out of the heated thermoflow cylinder and nebulised according to the Venturi-Bernoulli principle. To adjust the oxygen concentration of the respiratory gas a plastic ring must be turned to either close (98% oxygen) or open a valve allowing room air to mix (40% oxygen). Noise pollution of the unit varies with admixture of room air. With a new device--a special oxygen-air mixing chamber--the oxygen concentration of the respiratory gas can be adjusted outside the thermoflow cylinder, hardly producing any noise pollution. Therefore the principle of nebulisation could be changed to humidification. A thermoflow cylinder without the nebulisation unit allows the respiratory gas to flow through the thermoflow cylinder over heated and evaporating water, hardly causing any noise pollution. In both types of T-pieces the temperature of the respiratory gas is controlled and corrected by the Conchaterm unit. As the result of these modifications, noise pollution has been reduced from 70 dB(A) to 55 dB(A). In the modified T-piece, the quality of humidification has been evaluated with a fresh gas flow of 22 l/min and at a gas temperature of 37 degrees C, not only collecting condensed water but also lost water. The modified T-piece allows a physiological humidification of the respiratory gas. The modified T

  3. Noise Reduction Analysis of Radar Rainfall Using Chaotic Dynamics and Filtering Techniques

    Directory of Open Access Journals (Sweden)

    Soojun Kim

    2014-01-01

    Full Text Available The aim of this study is to evaluate the filtering techniques which can remove the noise involved in the time series. For this, Logistic series which is chaotic series and radar rainfall series are used for the evaluation of low-pass filter (LF and Kalman filter (KF. The noise is added to Logistic series by considering noise level and the noise added series is filtered by LF and KF for the noise reduction. The analysis for the evaluation of LF and KF techniques is performed by the correlation coefficient, standard error, the attractor, and the BDS statistic from chaos theory. The analysis result for Logistic series clearly showed that KF is better tool than LF for removing the noise. Also, we used the radar rainfall series for evaluating the noise reduction capabilities of LF and KF. In this case, it was difficult to distinguish which filtering technique is better way for noise reduction when the typical statistics such as correlation coefficient and standard error were used. However, when the attractor and the BDS statistic were used for evaluating LF and KF, we could clearly identify that KF is better than LF.

  4. Development of an active noise control system with minimized amount of calculation; Shoenzan ryogata active soon seigyo system no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, M. [Hitachi, Ltd., Tokyo (Japan); Sasaki, M.; Hori, Y. [Gifu University, Gifu (Japan); Fujisawa, F. [Hachinohe Institute of Technology, Aomori (Japan); Sumida, I. [Chubu University, Nagoya (Japan)

    1997-12-20

    This paper proposes an active noise control system with minimized amount of calculation for periodic noise. A modified algorithm based on the filtered-x adaptive notch filter is applied on the diesel engine noise generate d in the cabin of an all-terrain vehicle. Diesel engine noise is periodic and includes some harmonic components due to engine rotation. Numerical simulation results using measured data indicated that the proposed system could be controlled by using fewer calculations compared to the conventional system. The controller was made using an eight bit microcomputer without a digital signal processor and installed in the vehicle. Results of the driving tests achieved a large noise reduction for some harmonic components, second, fourth and sixth order components. This shows that the control system is effective for noise reduction. 5 refs., 8 figs., 6 tabs.

  5. 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.

  6. Advanced Acoustic Blankets for Improved Aircraft Interior Noise Reduction Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed Phase II research effort is to develop heterogeneous (HG) blankets for improved sound reduction in aircraft structures. Phase I...

  7. Active Aircraft Pylon Noise Control System

    Science.gov (United States)

    Thomas, Russell H. (Inventor); Czech, Michael J. (Inventor); Elmiligui, Alaa A. (Inventor)

    2017-01-01

    An active pylon noise control system for an aircraft includes a pylon structure connecting an engine system with an airframe surface of the aircraft and having at least one aperture to supply a gas or fluid therethrough, an intake portion attached to the pylon structure to intake a gas or fluid, a regulator connected with the intake portion via a plurality of pipes, to regulate a pressure of the gas or fluid, a plenum chamber formed within the pylon structure and connected with the regulator, and configured to receive the gas or fluid as regulated by the regulator, and a plurality of injectors in communication with the plenum chamber to actively inject the gas or fluid through the plurality of apertures of the pylon structure.

  8. [Noise-reduction function and its affecting factors of urban plant communities in Shanghai].

    Science.gov (United States)

    Zhang, Qing-Fei; Zheng, Si-Jun; Xia, Lei; Wu, Hai-Ping; Zhang, Ming-Li; Li, Ming-Sheng

    2007-10-01

    The factor analysis on the relationships between excess noise attenuation (decrement after noise propagating 30 m) and 8 structural characteristics of 19 urban plant communities in Shanghai showed that all the plant communities had notable effects on reducing noise, and the noise attenuation ability of the communities was significantly higher than that of lawn (P attenuation ability, i.e., those of > or = 10 dB(A), 6-10 dB(A), and attenuation ability of the communities were leaf area index, average bifurcate height, average height, coverage, and average canopy diameter, and their correlation coefficients with noise attenuation were 0.343, 0.318, 0.285, 0.226 and 0.193, respectively. These five factors had a cumulative contribution rate of 65.47%, suggesting that they should be considered in stress when designing urban greenbelt for noise reduction.

  9. 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.

  10. 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.

  11. Research and constructive solutions on the reduction of slosh noise

    Science.gov (United States)

    Manta (Balas, M.; Balas, R.; Doicin, C. V.

    2016-11-01

    The paper presents a product design making of, over a “delicate issue” in automotive industry as slosh noise phenomena. Even though the current market tendency shows great achievements over this occurrence, in this study, the main idea is to design concepts of slosh noise baffles adapted for serial life existing fuel tanks in the automotive industry. Moreover, starting with internal and external research, going further through reversed engineering and applying own baffle technical solutions from conceptual sketches to 3D design, the paper shows the technical solutions identified as an alternative to a new development of fuel tank. Based on personal and academic experience there were identified several problematics and the possible answers based on functional analysis, in order to avoid blocking points. The idea of developing baffles adapted to already existent fuel tanks leaded to equivalent solutions analyzed from functional point of view. Once this stage is finished, a methodology will be used so as to choose the optimum solution so as to get the functional design.

  12. On-line Monitoring and Active Control for Transformer Noise

    Science.gov (United States)

    Liang, Jiabi; Zhao, Tong; Tian, Chun; Wang, Xia; He, Zhenhua; Duan, Lunfeng

    This paper introduces the system for on-line monitoring and active noise control towards the transformer noise based on LabVIEW and the hardware equipment including the hardware and software. For the hardware part, it is mainly focused on the composition and the role of hardware devices, as well as the mounting location in the active noise control experiment. And the software part introduces the software flow chats, the measurement and analysis module for the sound pressure level including A, B, C weighting methods, the 1/n octave spectrum and the power spectrum, active noise control module and noise data access module.

  13. Active noise control: A tutorial for HVAC designers

    Energy Technology Data Exchange (ETDEWEB)

    Gelin, L.J.

    1997-08-01

    This article will identify the capabilities and limitations of ANC in its application to HVAC noise control. ANC can be used in ducted HVAC systems to cancel ductborne, low-frequency fan noise by injecting sound waves of equal amplitude and opposite phase into an air duct, as close as possible to the source of the unwanted noise. Destructive interference of the fan noise and injected noise results in sound cancellation. The noise problems that it solves are typically described as rumble, roar or throb, all of which are difficult to address using traditional noise control methods. This article will also contrast the use of active against passive noise control techniques. The main differences between the two noise control measures are acoustic performance, energy consumption, and design flexibility. The article will first present the fundamentals and basic physics of ANC. The application to real HVAC systems will follow.

  14. Active Noise Control of the Heavy Truck Interior Cab

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In order to control the noise of the heavy truck interior cab effectively, the active noise control methods are employed. First, an interior noise field test for the heavy truck is performed, and frequencies of interior noise of this vehicle are analyzed. According to the spectrum analysis of acquired noise signal, it is found out that the main frequencies of interior noise are less than 800Hz. Then the least squares lattice (LSL) algorithm is used as signal processing algorithm of the controller and a closed-loop control DSP system, based on TMS 320VC5416, is developed. The residual signal at driver's ear is used as feedback signal. Lastly, the developed ANC system is loaded into the heavy truck cab, and controlling the noise at driver's ear for that truck at different driving speeds is attempted. The noise control test results indicate that the cab interior noise is reduced averagely by 0.9 dBA at different driving speeds.

  15. Subspace-Based Noise Reduction for Speech Signals via Diagonal and Triangular Matrix Decompositions

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jensen, Søren Holdt

    2007-01-01

    We survey the definitions and use of rank-revealing matrix decompositions in single-channel noise reduction algorithms for speech signals. Our algorithms are based on the rank-reduction paradigm and, in particular, signal subspace techniques. The focus is on practical working algorithms, using bo...... with working Matlab code and applications in speech processing....

  16. Subspace-Based Noise Reduction for Speech Signals via Diagonal and Triangular Matrix Decompositions

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jensen, Søren Holdt

    We survey the definitions and use of rank-revealing matrix decompositions in single-channel noise reduction algorithms for speech signals. Our algorithms are based on the rank-reduction paradigm and, in particular, signal subspace techniques. The focus is on practical working algorithms, using bo...... with working Matlab code and applications in speech processing....

  17. A bulk-controlled ring-VCO with 1/f-noise reduction for frequency ΔΣ modulator

    DEFF Research Database (Denmark)

    Tuan Vu, CAO; Wisland, Dag T.; Lande, Tor Sverre

    The paper introduces a bulk-controlled ring-VCO with a tail transistor utilizing flicker-noise (1/f-noise) reduction techniques for a frequency-based DeltaSigma modulator (FDSM). This VCO converts an analog input voltage to phase information under various bias conditions ranging from sub......-threshold to saturation. By using the 1/f-noise reduction circuit which is based on the switched bias technique, the simulations indicate that less noise is transferred to the output when the 1/f-noise reduction circuit is used. The phase noise of the proposed VCO is improved by 7.6% while maintaining tuning...

  18. Lead-Lag Control for Helicopter Vibration and Noise Reduction

    Science.gov (United States)

    Gandhi, Farhan

    1995-01-01

    As a helicopter transitions from hover to forward flight, the main rotor blades experience an asymmetry in flow field around the azimuth, with the blade section tangential velocities increasing on the advancing side and decreasing on the retreating side. To compensate for the reduced dynamic pressure on the retreating side, the blade pitch angles over this part of the rotor disk are increased. Eventually, a high enough forward speed is attained to produce compressibility effects on the advancing side of the rotor disk and stall on the retreating side. The onset of these two phenomena drastically increases the rotor vibratory loads and power requirements, thereby effectively establishing a limit on the maximum achievable forward speed. The alleviation of compressibility and stall (and the associated decrease in vibratory loads and power) would potentially result in an increased maximum forward speed. In the past, several methods have been examined and implemented to reduce the vibratory hub loads. Some of these methods are aimed specifically at alleviating vibration at very high flight speeds and increasing the maximum flight speed, while others focus on vibration reduction within the conventional flight envelope. Among the later are several types passive as well as active schemes. Passive schemes include a variety of vibration absorbers such as mechanical springs, pendulums, and bifilar absorbers. These mechanism are easy to design and maintain, but incur significant weight and drag penalties. Among the popular active control schemes in consideration are Higher Harmonic Control (HHC) and Individual Blade Control (IBC). HHC uses a conventional swash plate to generate a multi-cyclic pitch input to the blade. This requires actuators capable of sufficiently high power and bandwidth, increasing the cost and weight of the aircraft. IBC places actuators in the rotating reference frame, requiring the use of slip rings capable of transferring enough power to the actuators

  19. Noise reduction in muon tomography for detecting high density objects

    CERN Document Server

    Benettoni, M; Bonomi, G; Calvagno, G; Calvini, P; Checchia, P; Cortelazzo, G; Cossutta, L; Donzella, A; Furlan, M; Gonella, F; Pegoraro, M; Garola, A Rigoni; Ronchese, P; Squarcia, S; Subieta, M; Vanini, S; Viesti, G; Zanuttigh, P; Zenoni, A; Zumerle, G

    2013-01-01

    The muon tomography technique, based on multiple Coulomb scattering of cosmic ray muons, has been proposed as a tool to detect the presence of high density objects inside closed volumes. A new and innovative method is presented in this paper to handle the density fluctuations (noise) of reconstructed images, that are a known problem of this technique. The effectiveness of our method is evaluated using experimental data obtained with a muon tomography prototype located at Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (INFN). The results reported in this paper, obtained with real cosmic ray data, show that with appropriate image filtering and muon momentum classification, the muon tomography technique can detect in short times high density materials, such as lead, when surrounded by light or medium density material. A comparison with algorithms published in literature is also presented.

  20. Noise reduction in muon tomography for detecting high density objects

    Science.gov (United States)

    Benettoni, M.; Bettella, G.; Bonomi, G.; Calvagno, G.; Calvini, P.; Checchia, P.; Cortelazzo, G.; Cossutta, L.; Donzella, A.; Furlan, M.; Gonella, F.; Pegoraro, M.; Rigoni Garola, A.; Ronchese, P.; Squarcia, S.; Subieta, M.; Vanini, S.; Viesti, G.; Zanuttigh, P.; Zenoni, A.; Zumerle, G.

    2013-12-01

    The muon tomography technique, based on multiple Coulomb scattering of cosmic ray muons, has been proposed as a tool to detect the presence of high density objects inside closed volumes. In this paper a new and innovative method is presented to handle the density fluctuations (noise) of reconstructed images, a well known problem of this technique. The effectiveness of our method is evaluated using experimental data obtained with a muon tomography prototype located at the Legnaro National Laboratories (LNL) of the Istituto Nazionale di Fisica Nucleare (INFN). The results reported in this paper, obtained with real cosmic ray data, show that with appropriate image filtering and muon momentum classification, the muon tomography technique can detect high density materials, such as lead, albeit surrounded by light or medium density material, in short times. A comparison with algorithms published in literature is also presented.

  1. 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.

  2. 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.

  3. IMPROVING VOICE ACTIVITY DETECTION VIA WEIGHTING LIKELIHOOD AND DIMENSION REDUCTION

    Institute of Scientific and Technical Information of China (English)

    Wang Huanliang; Han Jiqing; Li Haifeng; Zheng Tieran

    2008-01-01

    The performance of the traditional Voice Activity Detection (VAD) algorithms declines sharply in lower Signal-to-Noise Ratio (SNR) environments. In this paper, a feature weighting likelihood method is proposed for noise-robust VAD. The contribution of dynamic features to likelihood score can be increased via the method, which improves consequently the noise robustness of VAD.Divergence based dimension reduction method is proposed for saving computation, which reduces these feature dimensions with smaller divergence value at the cost of degrading the performance a little.Experimental results on Aurora Ⅱ database show that the detection performance in noise environments can remarkably be improved by the proposed method when the model trained in clean data is used to detect speech endpoints. Using weighting likelihood on the dimension-reduced features obtains comparable, even better, performance compared to original full-dimensional feature.

  4. Noise reduction by the application of an air-bubble curtain in offshore pile driving

    Science.gov (United States)

    Tsouvalas, A.; Metrikine, A. V.

    2016-06-01

    Underwater noise pollution is a by-product of marine industrial operations. In particular, the noise generated when a foundation pile is driven into the soil with an impact hammer is considered to be harmful for the aquatic species. In an attempt to reduce the ecological footprint, several noise mitigation techniques have been investigated. Among the various solutions proposed, the air-bubble curtain is often applied due to its efficacy in noise reduction. In this paper, a model is proposed for the investigation of the sound reduction during marine piling when an air-bubble curtain is placed around the pile. The model consists of the pile, the surrounding water and soil media, and the air-bubble curtain which is positioned at a certain distance from the pile surface. The solution approach is semi-analytical and is based on the dynamic sub-structuring technique and the modal decomposition method. Two main results of the paper can be distinguished. First, a new model is proposed that can be used for predictions of the noise levels in a computationally efficient manner. Second, an analysis is presented of the principal mechanisms that are responsible for the noise reduction due to the application of the air-bubble curtain in marine piling. The understanding of these mechanisms turns to be crucial for the exploitation of the maximum efficiency of the system. It is shown that the principal mechanism of noise reduction depends strongly on the frequency content of the radiated sound and the characteristics of the bubbly medium. For piles of large diameter which radiate most of the acoustic energy at relatively low frequencies, the noise reduction is mainly attributed to the mismatch of the acoustic impedances between the seawater and the bubbly layer. On the contrary, for smaller piles and when the radiated acoustic energy is concentrated at frequencies close to, or higher than, the resonance frequency of the air bubbles, the sound absorption within the bubbly layer

  5. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    Science.gov (United States)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  6. NOISE REDUCTION FOR FAST FADING CHANNEL BY RECURRENT LEAST SQUARES SUPPORT VECTOR MACHINES IN EMBEDDING PHASE SPACES

    Institute of Scientific and Technical Information of China (English)

    Xiang Zheng; Zhang Taiyi; Sun Jiancheng

    2006-01-01

    A new strategy for noise reduction of fast fading channel is presented. Firstly, more information is acquired utilizing the reconstructed embedding phase space. Then, based on the Recurrent Least Squares Support Vector Machines (RLS-SVM), noise reduction of the fast fading channel is realized. This filtering technique does not make use of the spectral contents of the signal. Based on the stability and the fractal of the chaotic attractor, the RLS-SVM algorithm is a better candidate for the nonlinear time series noise-reduction. The simulation results shows that better noise-reduction performance is acquired when the signal to noise ratio is 12dB.

  7. High Bypass Ratio Jet Noise Reduction and Installation Effects Including Shielding Effectiveness

    Science.gov (United States)

    Thomas, Russell H.; Czech, Michael J.; Doty, Michael J.

    2013-01-01

    An experimental investigation was performed to study the propulsion airframe aeroacoustic installation effects of a separate flow jet nozzle with a Hybrid Wing Body aircraft configuration where the engine is installed above the wing. Prior understanding of the jet noise shielding effectiveness was extended to a bypass ratio ten application as a function of nozzle configuration, chevron type, axial spacing, and installation effects from additional airframe components. Chevron types included fan chevrons that are uniform circumferentially around the fan nozzle and T-fan type chevrons that are asymmetrical circumferentially. In isolated testing without a pylon, uniform chevrons compared to T-fan chevrons showed slightly more low frequency reduction offset by more high frequency increase. Phased array localization shows that at this bypass ratio chevrons still move peak jet noise source locations upstream but not to nearly the extent, as a function of frequency, as for lower bypass ratio jets. For baseline nozzles without chevrons, the basic pylon effect has been greatly reduced compared to that seen for lower bypass ratio jets. Compared to Tfan chevrons without a pylon, the combination with a standard pylon results in more high frequency noise increase and an overall higher noise level. Shielded by an airframe surface 2.17 fan diameters from nozzle to airframe trailing edge, the T-fan chevron nozzle can produce reductions in jet noise of as much as 8 dB at high frequencies and upstream angles. Noise reduction from shielding decreases with decreasing frequency and with increasing angle from the jet inlet. Beyond an angle of 130 degrees there is almost no noise reduction from shielding. Increasing chevron immersion more than what is already an aggressive design is not advantageous for noise reduction. The addition of airframe control surfaces, including vertical stabilizers and elevon deflection, showed only a small overall impact. Based on the test results, the best

  8. Assessment of Soft Vane and Metal Foam Engine Noise Reduction Concepts

    Science.gov (United States)

    Jones, Michael G.; Parrott, Tony L.; Sutliff, Daniel L.; Hughes, Chris

    2009-01-01

    Two innovative fan-noise reduction concepts developed by NASA are presented - soft vanes and over-the-rotor metal foam liners. Design methodologies are described for each concept. Soft vanes are outlet guide vanes with internal, resonant chambers that communicate with the exterior aeroacoustic environment via a porous surface. They provide acoustic absorption via viscous losses generated by interaction of unsteady flows with the internal solid structure. Over-the-rotor metal foam liners installed at or near the fan rotor axial plane provide rotor noise absorption. Both concepts also provide pressure-release surfaces that potentially inhibit noise generation. Several configurations for both concepts are evaluated with a normal incidence tube, and the results are used to guide designs for implementation in two NASA fan rigs. For soft vanes, approximately 1 to 2 dB of broadband inlet and aft-radiated fan noise reduction is achieved. For over-the-rotor metal foam liners, up to 3 dB of fan noise reduction is measured in the low-speed fan rig, but minimal reduction is measured in the high-speed fan rig. These metal foam liner results are compared with a static engine test, in which inlet sound power level reductions up to 5 dB were measured. Brief plans for further development are also provided.

  9. Noise Reduction Evaluation of Multi-Layered Viscoelastic Infinite Cylinder under Acoustical Wave Excitation

    Directory of Open Access Journals (Sweden)

    M.R. Mofakhami

    2008-01-01

    Full Text Available In this paper sound transmission through the multilayered viscoelastic air filled cylinders subjected to the incident acoustic wave is studied using the technique of separation of variables on the basis of linear three dimensional theory of elasticity. The effect of interior acoustic medium on the mode maps (frequency vs geometry and noise reduction is investigated. The effects of internal absorption and external moving medium on noise reduction are also evaluated. The dynamic viscoelastic properties of the structure are rigorously taken into account with a power law technique that models the viscoelastic damping of the cylinder. A parametric study is also performed for the two layered infinite cylinders to obtain the effect of viscoelastic layer characteristics such as thickness, material type and frequency dependency of viscoelastic properties on the noise reduction. It is shown that using constant and frequency dependent viscoelastic material with high loss factor leads to the uniform noise reduction in the frequency domain. It is also shown that the noise reduction obtained for constant viscoelastic material property is subjected to some errors in the low frequency range with respect to those obtained for the frequency dependent viscoelastic material.

  10. Active Noise Feedback Control Using a Neural Network

    Directory of Open Access Journals (Sweden)

    Zhang Qizhi

    2001-01-01

    Full Text Available The active noise control (ANC is discussed. Many digital ANC systems often based on the filter-x algorithm for finite impulse response (FIR filter use adaptive filtering techniques. But if the primary noise path is nonlinear, the control system based on adaptive filter technology will be invalid. In this paper, an adaptive active nonlinear noise feedback control approach using a neural network is derived. The feedback control system drives a secondary signal to destructively interfere with the original noise to cut down the noise power. An on-line learning algorithm based on the error gradient descent method was proposed, and the local stability of closed loop system is proved using the discrete Lyapunov function. A nonlinear simulation example shows that the adaptive active noise feedback control method based on a neural network is very effective to the nonlinear noise control.

  11. Noise reduction in electronic speckle pattern interferometry fringes by fourth-order partial differential equations

    Science.gov (United States)

    Lv, Wei; Tang, Chen; Wang, Wenping

    2007-01-01

    Noise reduction is one of the largest problems and biggest difficulties involved in electronic speckle pattern interferometry (ESPI). Although the second-order PDEs denoising method is a useful tool of noise reduction for the ESPI fringe patterns, its main drawback is that the second-order PDE model does not remove impulse noise, a 3×3 mean window filter is generally needed to improve the fringes. For overcome this main drawback, in this paper we apply the fourth-order PDE denoising model to the computer-simulated and experimentally obtained ESPI fringe, respectively. In both tests, the fourth-order PDE denoising model clearly outperforms the second-order PDE denoising model. Experimental results have confirmed that the fourth-order PDE denoising model is capable of removing noise in ESPI fringe images effectively.

  12. Active control of periodic fan noise in laptops: spectral width requirements in delayed buffer implementation

    Directory of Open Access Journals (Sweden)

    H. A. Cordourier‐Maruri

    2009-08-01

    Full Text Available An active control system intended for the reduction of strictly periodic noise components in computer cooling fans is described,which is based on high‐performance digital sound device architectures found in some personal computers. The systemovercomes causality and synchronization constrains imposed by delayed buffering, as usually found in computer audioprocessing. Performance of the system is demonstrated and evaluated through measurements in a physical implementation ofactive noise control of synthetic tones combined with laptop fan noise, carried out under anechoic and slightly reverberantconditions. Tests on other types of tonal noise sources, like an electrical transformer, were also carried out. However, its widerapplicability to the cancellation of tonal noise has been proved compromised by weak periodicity issues found and reported inthis work. Also, a study of noise spectral width requirements for successful operation is presented.

  13. Noise Reduction of MEMS Gyroscope Based on Direct Modeling for an Angular Rate Signal

    OpenAIRE

    Liang Xue; Chengyu Jiang; Lixin Wang; Jieyu Liu; Weizheng Yuan

    2015-01-01

    In this paper, a novel approach for processing the outputs signal of the microelectromechanical systems (MEMS) gyroscopes was presented to reduce the bias drift and noise. The principle for the noise reduction was presented, and an optimal Kalman filter (KF) was designed by a steady-state filter gain obtained from the analysis of KF observability. In particular, the true angular rate signal was directly modeled to obtain an optimal estimate and make a self-compensation for the gyroscope witho...

  14. Numerical filtering techniques for the reduction of noise in digital telemetry data

    Science.gov (United States)

    Helfrich-Stone, Thomas M.

    Telemetry data noise is due to the marginal or complete loss of telemetry carrier signal, leading to errors in the PCM data received. Attention is presently given to several postflight numerical filtering techniques for the reduction and/or removal of noise in digital telemetry data, prior to use in automated computer data analysis. The techniques encompass manual filtering, upper/lower bound filtering, mean-plus/minus standard deviation filtering, rate-of-change filtering, multiple-measurement filtering, and multiple filters.

  15. Development of Novel Methods for the Reduction of Noise and Weight in Helicopter Transmissions

    Science.gov (United States)

    Dimofte, Florin; Keith, Theo G., Jr.

    2003-01-01

    Over the 70-year evolution of the helicopter, man's understanding of vibration control has greatly increased. However, in spite of the increased performance, the extent of helicopter vibration problems has not significantly diminished. Crew vibration and noise remains important factors in the design of all current helicopters. With more complex and critical demands being placed on aircrews, it is essential that vibration and noise not impair their performance. A major source of helicopter cabin noise (which has been measured at a sound pressure level of over 100 dB) is the gearbox. Reduction of this noise has been a goal of NASA and the U.S. Army. Gear mesh noise is typically in the frequency range of 1000 to 3000 Hz, a range important for speech. A requirement for U.S. Army/NASA Advanced Rotorcraft Transmission project has been a 10-dB reduction compared to current designs. A combined analytical/experimental effort has been underway, since the end of the 80's, to study effects of design parameters on noise production. The noise generated by the gear mesh can be transmitted to the surrounding media through the bearings that support the gear shaft. Therefore, the use of fluid film bearings instead of rolling element bearings could reduce the transmission noise by 10 dB. In addition, the fluid film bearings that support the gear shaft can change the dynamics of the gear assembly by providing damping to the system and by being softer than rolling element bearings. Wave bearings can attenuate, and filter, the noise generated by a machine component due to the dynamic stiffness and damping coefficients. The attenuation ratio could be as large as 35-40 dB. The noise components at higher frequencies than a synchronous frequency can be almost eliminated.

  16. 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

  17. Single-Channel Noise Reduction using Unified Joint Diagonalization and Optimal Filtering

    DEFF Research Database (Denmark)

    Nørholm, Sidsel Marie; Benesty, Jacob; Jensen, Jesper Rindom;

    2014-01-01

    In this paper, the important problem of single-channel noise reduction is treated from a new perspective. The problem is posed as a filtering problem based on joint diagonalization of the covariance matrices of the desired and noise signals. More specifically, the eigenvectors from the joint...... diagonalization corresponding to the least significant eigenvalues are used to form a filter, which effectively estimates the noise when applied to the observed signal. This estimate is then subtracted from the observed signal to form an estimate of the desired signal, i.e., the speech signal. In doing this, we...

  18. Noise and speckle reduction in synthetic aperture radar imagery by nonparametric Wiener filtering.

    Science.gov (United States)

    Caprari, R S; Goh, A S; Moffatt, E K

    2000-12-10

    We present a Wiener filter that is especially suitable for speckle and noise reduction in multilook synthetic aperture radar (SAR) imagery. The proposed filter is nonparametric, not being based on parametrized analytical models of signal statistics. Instead, the Wiener-Hopf equation is expressed entirely in terms of observed signal statistics, with no reference to the possibly unobservable pure signal and noise. This Wiener filter is simple in concept and implementation, exactly minimum mean-square error, and directly applicable to signal-dependent and multiplicative noise. We demonstrate the filtering of a genuine two-look SAR image and show how a nonnegatively constrained version of the filter substantially reduces ringing.

  19. Transient noise reduction in cochlear implant users: a multi-band approach

    Directory of Open Access Journals (Sweden)

    Karl-Heinz Dyballa

    2016-08-01

    Full Text Available A previously-tested transient noise reduction (TNR algorithm for cochlear implant (CI users was modified to detect and attenuate transients independently across multiple frequency-bands. Since speech and transient noise are often spectrally distinct, we hypothesized that benefits in speech intelligibility can be achieved over the earlier single- band design. Fifteen experienced CI users (49 to 72 years were tested unilaterally using pre-processed stimuli delivered directly to a speech processor. Speech intelligibility in transient and soft stationary noise, subjective sound quality and the recognition of warning signals was investigated in three processing conditions: no TNR (TNRoff, single- band TNR (TNRsgl and multi-band TNR (TNRmult. Notably, TNRmult improved speech reception thresholds (SRTs in cafeteria noise and office noise by up to 3 dB over both TNRoff and TNRsgl, and yielded higher comfort and clarity ratings in cafeteria noise. Our results indicate that multi-band transient noise reduction may be advantageous compared to a single-band approach, and reveal a substantial overall potential for TNR to improve speech perception and listening comfort in CI users.

  20. Use of a plane jet for flow-induced noise reduction of tandem rods

    Science.gov (United States)

    Zhao, Kun; Yang, Xi-xiang; Okolo, Patrick N.; Zhang, Wei-hua; Bennett, Gareth J.

    2016-06-01

    Unsteady wake from upstream components of landing gear impinging on downstream components could be a strong noise source. The use of a plane jet is proposed to reduce this flow-induced noise. Tandem rods with different gap widths were utilized as the test body. Both acoustic and aerodynamic tests were conducted in order to validate this technique. Acoustic test results proved that overall noise emission from tandem rods could be lowered and tonal noise could be removed with use of the plane jet. However, when the plane jet was turned on, in some frequency range it could be the subsequent main contributor instead of tandem rods to total noise emission whilst in some frequency range rods could still be the main contributor. Moreover, aerodynamic tests fundamentally studied explanations for the noise reduction. Specifically, not only impinging speed to rods but speed and turbulence level to the top edge of the rear rod could be diminished by the upstream plane jet. Consequently, the vortex shedding induced by the rear rod was reduced, which was confirmed by the speed, Reynolds stress as well as the velocity fluctuation spectral measured in its wake. This study confirmed the potential use of a plane jet towards landing gear noise reduction. Project partially supported by the European Union FP7 CleanSky Joint Technology Initiative “ALLEGRA” (Grant No. 308225).

  1. SVD-Based Optimal Filtering Technique for Noise Reduction in Hearing Aids Using Two Microphones

    Directory of Open Access Journals (Sweden)

    Moonen Marc

    2002-01-01

    Full Text Available We introduce a new SVD-based (Singular value decomposition strategy for noise reduction in hearing aids. This technique is evaluated for noise reduction in a behind-the-ear (BTE hearing aid where two omnidirectional microphones are mounted in an endfire configuration. The behaviour of the SVD-based technique is compared to a two-stage adaptive beamformer for hearing aids developed by Vanden Berghe and Wouters (1998. The evaluation and comparison is done with a performance metric based on the speech intelligibility index (SII. The speech and noise signals are recorded in reverberant conditions with a signal-to-noise ratio of and the spectrum of the noise signals is similar to the spectrum of the speech signal. The SVD-based technique works without initialization nor assumptions about a look direction, unlike the two-stage adaptive beamformer. Still, for different noise scenarios, the SVD-based technique performs as well as the two-stage adaptive beamformer, for a similar filter length and adaptation time for the filter coefficients. In a diffuse noise scenario, the SVD-based technique performs better than the two-stage adaptive beamformer and hence provides a more flexible and robust solution under speaker position variations and reverberant conditions.

  2. SVD-Based Optimal Filtering Technique for Noise Reduction in Hearing Aids Using Two Microphones

    Science.gov (United States)

    Maj, Jean-Baptiste; Moonen, Marc; Wouters, Jan

    2002-12-01

    We introduce a new SVD-based (Singular value decomposition) strategy for noise reduction in hearing aids. This technique is evaluated for noise reduction in a behind-the-ear (BTE) hearing aid where two omnidirectional microphones are mounted in an endfire configuration. The behaviour of the SVD-based technique is compared to a two-stage adaptive beamformer for hearing aids developed by Vanden Berghe and Wouters (1998). The evaluation and comparison is done with a performance metric based on the speech intelligibility index (SII). The speech and noise signals are recorded in reverberant conditions with a signal-to-noise ratio of [InlineEquation not available: see fulltext.] and the spectrum of the noise signals is similar to the spectrum of the speech signal. The SVD-based technique works without initialization nor assumptions about a look direction, unlike the two-stage adaptive beamformer. Still, for different noise scenarios, the SVD-based technique performs as well as the two-stage adaptive beamformer, for a similar filter length and adaptation time for the filter coefficients. In a diffuse noise scenario, the SVD-based technique performs better than the two-stage adaptive beamformer and hence provides a more flexible and robust solution under speaker position variations and reverberant conditions.

  3. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    Science.gov (United States)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  4. The ART of representation: Memory reduction and noise tolerance in a neural network vision system

    Science.gov (United States)

    Langley, Christopher S.

    The Feature Cerebellar Model Arithmetic Computer (FCMAC) is a multiple-input-single-output neural network that can provide three-degree-of-freedom (3-DOF) pose estimation for a robotic vision system. The FCMAC provides sufficient accuracy to enable a manipulator to grasp an object from an arbitrary pose within its workspace. The network learns an appearance-based representation of an object by storing coarsely quantized feature patterns. As all unique patterns are encoded, the network size grows uncontrollably. A new architecture is introduced herein, which combines the FCMAC with an Adaptive Resonance Theory (ART) network. The ART module categorizes patterns observed during training into a set of prototypes that are used to build the FCMAC. As a result, the network no longer grows without bound, but constrains itself to a user-specified size. Pose estimates remain accurate since the ART layer tends to discard the least relevant information first. The smaller network performs recall faster, and in some cases is better for generalization, resulting in a reduction of error at recall time. The ART-Under-Constraint (ART-C) algorithm is extended to include initial filling with randomly selected patterns (referred to as ART-F). In experiments using a real-world data set, the new network performed equally well using less than one tenth the number of coarse patterns as a regular FCMAC. The FCMAC is also extended to include real-valued input activations. As a result, the network can be tuned to reject a variety of types of noise in the image feature detection. A quantitative analysis of noise tolerance was performed using four synthetic noise algorithms, and a qualitative investigation was made using noisy real-world image data. In validation experiments, the FCMAC system outperformed Radial Basis Function (RBF) networks for the 3-DOF problem, and had accuracy comparable to that of Principal Component Analysis (PCA) and superior to that of Shape Context Matching (SCM), both

  5. 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.

  6. Resonant Activation Induced by Four-Value Noise

    Institute of Scientific and Technical Information of China (English)

    LIU Hui; HAN Yin-Xia; HOU De-Fu; LI Jing-Hui; LI Jia-Rong

    2008-01-01

    The phenomenon of the resonant activation (RA) of a particle over a fluctuating potential barrier with a four-value noise is investigated. It is shown that the mean first passage time (MFPT) displays six minima as the function of the transition rates γ1, γ2, γ3, γ4,γ5, and γ6 of the four-value noise, respectively. In addition, the effect of other parameters of the system, such as the noise strength D of the additive Gaussian white noise and the parameter value a,b, c, and d of the four-value noise, on the RAs is also investigated.

  7. Reduction of SEM noise and extended application to prediction of CD uniformity and its experimental validation

    Science.gov (United States)

    Kim, Hoyeon; Hwang, Chan; Oh, Seok-hwan; Yeo, Jeongho; Kim, Young hee

    2011-03-01

    As the design rule of Integrated Circuits(IC) becomes smaller, the precise measurement of Critical Dimension (CD) of features and minimization of deviation in CD measured becomes a vital issue. In this paper, a simple frequency analysis method to extract the noise from SEM images was used to evaluate the contribution of SEM noise in CD Uniformity. Multiple SEM images of simple Line and Space (L/S) patterns were analyzed and a model of frequency profile (Power Spectrum Density (PSD) model) was made using an offline analyzing tool based on Matlab®. From this profile, white noise and 1/f profile were separated. Noises are eliminated to generate a noise reduced PSD profile to make CD results. The contribution of white noise on CD measurement can be assessed using Line Width Roughness (LWR) measurement. Furthermore, CD uniformity can be also predicted from the model. This prediction is based on an assumption that CD uniformity is equal to LWR if the inspection area is extended to infinity and appropriate sampling method is applied. The results showed that the contribution of white noise on LWR can be up to around 70% (in power) without any noise reduction measures (sum line averaging) after imaging in photo resist image. For experimental validation, CD uniformity is predicted from the model for different measurement conditions and compared with real measurement. For a result, CD uniformity prediction (3sigma) from the model shows within 20% in accuracy with real CD uniformity value measured from the photo resist image.

  8. Noise Reduction with Lobed Mixers: Nozzle-Length and Free-Jet Speed Effects

    Science.gov (United States)

    Mengle, Vinod G.; Dalton, William N.; Bridges, James C.; Boyd, Kathy C.

    1997-01-01

    Acoustic test results are presented for 1/4th-scaled nozzles with internal lobed mixers used for reduction of subsonic jet noise of turbofan engines with bypass ratio above 5 and jet speeds up to 830 ft/s. One coaxial and three forced lobe mixers were tested with variations in lobe penetration, cut-outs in lobe-sidewall, lobe number and nozzle-length. Measured exit flow profiles and thrusts are used to assist the inferences from acoustic data. It is observed that lobed mixers reduce the low-frequency noise due to more uniformly mixed exit flow; but they may also increase the high-frequency noise at peak perceived noise (PNL) angle and angles upstream of it due to enhanced mixing inside the nozzle. Cut-outs and low lobe penetration reduce the annoying portion of the spectrum but lead to less uniform exit flow. Due to the dominance of internal duct noise in unscalloped, high-penetration mixers their noise is not reduced as much with increase in free-jet speed as that of coaxial or cut-out lobed mixers. The latter two mixers also show no change in PNL over the wide range of nozzle-lengths tested because most of their noise sources are outside the nozzle; whereas, the former show an increase in noise with decrease in nozzle-length.

  9. Simulation Model of the ANC System for Noise Reduction in the Real Ambient

    Directory of Open Access Journals (Sweden)

    STOJANOVIC, V. O.

    2013-08-01

    Full Text Available The simulation model of ANC system for noise reduction caused by rotating machines in a room was described in the first part of this paper. This simulation model was presented in an acoustic-electrical diagram. The detailed mathematical analysis of the adaptive algorithm was performed. The second part of the paper presents the simulation results of the application of the ANC system for the noise reduction of fans in a room intended for a classroom. Simulation was performed for sine and real aroused signal. The results are presented both numerically and graphically and the comparative analysis was also done.

  10. Active Noise Feedback Control Using a Neural Network

    OpenAIRE

    Zhang Qizhi; Jia Yongle

    2001-01-01

    The active noise control (ANC) is discussed. Many digital ANC systems often based on the filter-x algorithm for finite impulse response (FIR) filter use adaptive filtering techniques. But if the primary noise path is nonlinear, the control system based on adaptive filter technology will be invalid. In this paper, an adaptive active nonlinear noise feedback control approach using a neural network is derived. The feedback control system drives a secondary signal to destructively interfere with ...

  11. Wind-tunnel fan noise reduction including effects of turning vanes on noise propagation

    Science.gov (United States)

    Soderman, P. T.; Hoglund, L. E.

    1979-01-01

    Fan silencers with low-pressure drop have been designed and installed in the NASA Ames 7- by 10-Foot Wind Tunnel No. 1. The silencers are composed of an absorbent lining flush with the wind-tunnel walls upstream of the fan and an absorbent splitter in the duct downstream of the fan. An acoustical insertion loss of 4 to 12 dB was measured between 100 and 1000 Hz. High-frequency performance of the silencers was reduced by test-section noise and by corner vanes which turned the sound waves so they followed the duct axis. Sound below 1.2 kHz diffracted around the 305-mm-long vanes and impinged on acoustically absorbent corner walls. Wind-tunnel flow losses are discussed.

  12. Active noise control: a review of the field.

    Science.gov (United States)

    Gordon, R T; Vining, W D

    1992-11-01

    Active noise control (ANC) is the application of the principle of the superposition of waves to noise attenuation problems. Much progress has been made toward applying ANC to narrow-band, low-frequency noise in confined spaces. During this same period, the application of ANC to broad-band noise or noise in three-dimensional spaces has seen little progress because of the recent quantification of serious physical limitations, most importantly, noncausality, stability, spatial mismatch, and the infinite gain controller requirement. ANC employs superposition to induce destructive interference to affect the attenuation of noise. ANC was believed to utilize the mechanism of phase cancellation to achieve the desired attenuation. However, current literature points to other mechanisms that may be operating in ANC. Categories of ANC are one-dimensional field and duct noise, enclosed spaces and interior noise, noise in three-dimensional spaces, and personal hearing protection. Development of active noise control stems from potential advantages in cost, size, and effectiveness. There are two approaches to ANC. In the first, the original sound is processed and injected back into the sound field in antiphase. The second approach is to synthesize a cancelling waveform. ANC of turbulent flow in pipes and ducts is the largest area in the field. Much work into the actual mechanism involved and the causal versus noncausal aspects of system controllers has been done. Fan and propeller noise can be divided into two categories: noise generated directly as the blade passing tones and noise generated as a result of blade tip turbulence inducing vibration in structures. Three-dimensional spaces present a noise environment where physical limitations are magnified and the infinite gain controller requirement is confronted. Personal hearing protection has been shown to be best suited to the control of periodic, low-frequency noise.

  13. Optimization and Modeling of Noise Reduction for Turbulent Jets with Induced Asymmetry

    Science.gov (United States)

    Rostamimonjezi, Sara

    This project relates to the development of next-generation high-speed aircraft that are efficient and environmentally compliant. The emphasis of the research is on reducing noise from high-performance engines that will power these aircraft. A strong component of engine noise is jet mixing noise that comes from the turbulent mixing process between the high-speed exhaust flow of the engine and the atmosphere. The fan flow deflection method (FFD) suppresses jet noise by deflecting the fan stream downward, by a few degrees, with respect to the core stream. This reduces the convective Mach number of the primary shear layer and turbulent kinetic energy in the downward direction and therefore reduces the noise emitted towards the ground. The redistribution of the fan stream is achieved with inserting airfoil-shaped vanes inside the fan duct. Aerodynamic optimization of FFD has been done by Dr. Juntao Xiong using a computational fluid dynamics code to maximize reduction of noise perceived by the community while minimizing aerodynamic losses. The optimal vane airfoils are used in a parametric experimental study of 50 4-vane deflector configurations. The vane chord length, angle of attack, and azimuthal location are the parameters studied in acoustic optimization. The best vane configuration yields a reduction in cumulative (downward + sideline) effective perceived noise level (EPNL) of 5.3 dB. The optimization study underscores the sensitivity of FFD to deflector parameters and the need for careful design in the practical implementation of this noise reduction approach. An analytical model based on Reynolds Averaged Navier Stokes (RANS) and acoustic analogy is developed to predict the spectral changes from a known baseline in the direction of peak emission. A generalized form for space-time correlation is introduced that allows shapes beyond the traditional exponential forms. Azimuthal directivity based on the wavepacket model of jet noise is integrated with the acoustic

  14. Statistical CT noise reduction with multiscale decomposition and penalized weighted least squares in the projection domain

    Energy Technology Data Exchange (ETDEWEB)

    Tang Shaojie; Tang Xiangyang [Imaging and Medical Physics, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1701 Uppergate Dr., C-5018, Atlanta, Georgia 30322 (United States); School of Automation, Xi' an University of Posts and Telecommunications, Xi' an, Shaanxi 710121 (China); Imaging and Medical Physics, Department of Radiology and Imaging Sciences, Emory University School of Medicine, 1701 Uppergate Dr., C-5018, Atlanta, Georgia 30322 (United States)

    2012-09-15

    Purposes: The suppression of noise in x-ray computed tomography (CT) imaging is of clinical relevance for diagnostic image quality and the potential for radiation dose saving. Toward this purpose, statistical noise reduction methods in either the image or projection domain have been proposed, which employ a multiscale decomposition to enhance the performance of noise suppression while maintaining image sharpness. Recognizing the advantages of noise suppression in the projection domain, the authors propose a projection domain multiscale penalized weighted least squares (PWLS) method, in which the angular sampling rate is explicitly taken into consideration to account for the possible variation of interview sampling rate in advanced clinical or preclinical applications. Methods: The projection domain multiscale PWLS method is derived by converting an isotropic diffusion partial differential equation in the image domain into the projection domain, wherein a multiscale decomposition is carried out. With adoption of the Markov random field or soft thresholding objective function, the projection domain multiscale PWLS method deals with noise at each scale. To compensate for the degradation in image sharpness caused by the projection domain multiscale PWLS method, an edge enhancement is carried out following the noise reduction. The performance of the proposed method is experimentally evaluated and verified using the projection data simulated by computer and acquired by a CT scanner. Results: The preliminary results show that the proposed projection domain multiscale PWLS method outperforms the projection domain single-scale PWLS method and the image domain multiscale anisotropic diffusion method in noise reduction. In addition, the proposed method can preserve image sharpness very well while the occurrence of 'salt-and-pepper' noise and mosaic artifacts can be avoided. Conclusions: Since the interview sampling rate is taken into account in the projection domain

  15. Experimental and numerical analysis on noise reduction in a multi-blade centrifugal fan

    Science.gov (United States)

    Chen, X. J.; Y Cao, T.; Su, J.; Qin, G. L.

    2013-12-01

    In this work, analysis on noise source and reduction in a multi-blade centrifugal fan used for air-conditioners was carried out by experimental and numerical methods. Firstly, an experimental system using microphone mounted on volute surface for measuring surface pressure fluctuations of volute was designed and introduced, then surface pressure fluctuations of the whole volute for a multi-blade centrifugal fan were measured by this system, and the inlet noise for this fan was also obtained. And then, based on the experimental results, the aerodynamic noise source of the studied fan was analysed. The surface pressure fluctuations of the volute showed that there were largest surface pressure fluctuations near the volute tongue, and peaks appeared at the Blade Passing Frequency (BPF). The spectra of fan inlet noise showed that the peaks also appeared at BPF, and noise levels in a wide range of frequency were also larger. Secondly, the internal flow of the fan was simulated by commercial software under the same conditions with the experiment, and then the fluid flow and acoustic power field were obtained and discussed. The contours of acoustic power level showed that the larger noise was generated at the impeller area close to the outlet of scroll and at the volute tongue, which is same as that from experiment. Based on all of the results, we can find that the vortex noise is an important part of fan noise for the studied fan, and the rotation noise also cannot be neglected. Finally, several reduction methods that are thought to be effective based on experimental and numerical results were suggested.

  16. Comparison of various decentralised structural and cavity feedback control strategies for transmitted noise reduction through a double panel structure

    Science.gov (United States)

    Ho, Jen-Hsuan; Berkhoff, Arthur

    2014-03-01

    This paper compares various decentralised control strategies, including structural and acoustic actuator-sensor configuration designs, to reduce noise transmission through a double panel structure. The comparison is based on identical control stability indexes. The double panel structure consists of two panels with air in between and offers the advantages of low sound transmission at high frequencies, low heat transmission, and low weight. The double panel structure is widely used, such as in the aerospace and automotive industries. Nevertheless, the resonance of the cavity and the poor sound transmission loss at low frequencies limit the double panel's noise control performance. Applying active structural acoustic control to the panels or active noise control to the cavity has been discussed in many papers. In this paper, the resonances of the panels and the cavity are considered simultaneously to further reduce the transmitted noise through an existing double panel structure. A structural-acoustic coupled model is developed to investigate and compare various structural control and cavity control methods. Numerical analysis and real-time control results show that structural control should be applied to both panels. Three types of cavity control sources are presented and compared. The results indicate that the largest noise reduction is obtained with cavity control by loudspeakers modified to operate as incident pressure sources.

  17. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    Science.gov (United States)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  18. Evaluation of Neural Networks Performance in Active Cancellation of Acoustic Noise

    Directory of Open Access Journals (Sweden)

    Mehrshad Salmasi,

    2014-12-01

    Full Text Available Active Noise Control (ANC works on the principle of destructive interference between the primary disturbance field heard as undesired noise and the secondary field which is generated from control actuators. In the simplest system, the disturbance field can be a simple sine wave, and the secondary field is the same sine wave but 180 degrees out of phase. This research presents an investigation on the use of different types of neural networks in active noise control. Performance of the multilayer perceptron (MLP, Elman and generalized regression neural networks (GRNN in active cancellation of acoustic noise signals is investigated and compared in this paper. Acoustic noise signals are selected from a Signal Processing Information Base (SPIB database. In order to compare the networks appropriately, similar structures and similar training and test samples are deduced for neural networks. The simulation results show that MLP, GRNN, and Elman neural networks present proper performance in active cancellation of acoustic noise. It is concluded that Elman and MLP neural networks have better performance than GRNN in noise attenuation. It is demonstrated that designed ANC system achieve good noise reduction in low frequencies.

  19. 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.

  20. Study of active noise control in ducts. Kanrokei ni okeru nodoteki soon seigyo hoho no kento

    Energy Technology Data Exchange (ETDEWEB)

    Nakao, Yoshiatsu

    1988-08-01

    On an active control to reduce noise in ducts, the theoretical and experimental studies of the energies ratio of the noise and the cancelling sound which should be produced by a speaker, were carried out. In case the cancelling sound was produced by the speaker which was set in the branch duct, the energies ratio varied with the setting position, the length and the cross section of the branch duct and the frequency of the noise. As the non-dimensional length of the branch duct was drawing near 0.5, the energies ratio became small. But when the non-dimensional length was 0, the ratio did not become smaller than 1. The experimental test confirmed that it was possible to reduce the noise by the cancelling sound which energies ratio was as small as about one hundredth of the noise. In case the noise was the pure sound, and the wave-length was over one fourth of the duct diameter, it was possible to reduce the noise more than 40 dB. And in case the wave-length was one eighth the reduction quantity was about 20 dB. Therefore, in case the noise is the pure sound or close to the pure sound, it is possible to apply the active noise control. 5 references, 23 figures.

  1. Noise reduction in long‐period seismograms by way of array summing

    Science.gov (United States)

    Ringler, Adam; Wilson, David; Storm, Tyler; Marshall, Benjamin T.; Hutt, Charles R.; Holland, Austin

    2016-01-01

    Long‐period (>100  s period) seismic data can often be dominated by instrumental noise as well as local site noise. When multiple collocated sensors are installed at a single site, it is possible to improve the overall station noise levels by applying stacking methods to their traces. We look at the noise reduction in long‐period seismic data by applying the time–frequency phase‐weighted stacking method of Schimmel and Gallart (2007) as well as the phase‐weighted stacking (PWS) method of Schimmel and Paulssen (1997) to four collocated broadband sensors installed in the quiet Albuquerque Seismological Laboratory underground vault. We show that such stacking methods can improve vertical noise levels by as much as 10 dB over the mean background noise levels at 400 s period, suggesting that greater improvements could be achieved with an array involving multiple sensors. We also apply this method to reduce local incoherent noise on horizontal seismic records of the 2 March 2016 Mw 7.8 Sumatra earthquake, where the incoherent noise levels at very long periods are similar in amplitude to the earthquake signal. To maximize the coherency, we apply the PWS method to horizontal data where relative azimuths between collocated sensors are estimated and compared with a simpler linear stack with no azimuthal rotation. Such methods could help reduce noise levels at various seismic stations where multiple high‐quality sensors have been deployed. Such small arrays may also provide a solution to improving long‐period noise levels at Global Seismographic Network stations.

  2. Automotive Interior Noise Reduction in High Frequency Using Statistical Energy Analysis

    Institute of Scientific and Technical Information of China (English)

    CHEN Xin; WANG Deng-feng; ZHU Lei; MA Zheng-dong

    2009-01-01

    Statistical energy analysis (SEA) is an effective method for predicting high frequency vibro-acoustic performance of automobiles. A full vehicle SEA model is presented for interior noise reduction. It is composed of a number of subsystems based on a 3D model with all parameters for each subsystem. The excitation inputs are measured through road tests in different conditions, including inputs from the engine vibration and the sound pressure of the engine bay. The accuracy in high frequency of SEA model is validated, by comparing the analysis results with the testing pressure level data at driver's right ear. Noise contribution and sensitivity of key subsystems are analyzed. Finally, the effectiveness of noise reduction is verified. Based on the SEA model, an approach combining test and simulation is proposed for the noise vibration and harshness (NVH) design in vehicle development. It contains building the SEA model, testing for subsystem parameter identification, validating the simulation model, identifying subsystem power inputs, analyzing the design sensitivity. An example is given to demonstrate the interior noise reduction in high frequency.

  3. 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.

  4. Study on ventilation and noise reduction in the main transformer room in indoor substation

    Directory of Open Access Journals (Sweden)

    Hu Sheng

    2016-01-01

    Full Text Available The noise emission should be considered in the ventilation and cooling design for the main transformer room of indoor substation. In this study, based on Soundplan software, effects of four common ventilation and cooling schemes on the cooling and sound insulation were compared. The research showed that the region with low noise requirement, the ventilation could be set on the outer wall or on the door of the main transformer room, while the region with high noise requirement, air inlet muffler or ventilation through the cable interlayer under the main transformer room must be used. All of the four kinds of ventilation schemes, ventilation through the cable interlayer is the best in cooling and noise reduction.

  5. Noise reduction and estimation in multiple micro-electro-mechanical inertial systems

    Science.gov (United States)

    Waegli, Adrian; Skaloud, Jan; Guerrier, Stéphane; Eulàlia Parés, Maria; Colomina, Ismael

    2010-06-01

    This research studies the reduction and the estimation of the noise level within a redundant configuration of low-cost (MEMS-type) inertial measurement units (IMUs). Firstly, independent observations between units and sensors are assumed and the theoretical decrease in the system noise level is analyzed in an experiment with four MEMS-IMU triads. Then, more complex scenarios are presented in which the noise level can vary in time and for each sensor. A statistical method employed for studying the volatility of financial markets (GARCH) is adapted and tested for the usage with inertial data. This paper demonstrates experimentally and through simulations the benefit of direct noise estimation in redundant IMU setups.

  6. Numerical prediction of underwater noise reduction during offshore pile driving by a Small Bubble Curtain

    DEFF Research Database (Denmark)

    Göttsche, Klaus Marco; Juhl, Peter Møller; Steinhagen, Ulrich

    2013-01-01

    Small Bubble Curtains are an effective technique to reduce the underwater noise being emitted during offshore pile driving. In order to protect the marine fauna, noise reduction becomes even more important, since the increasing contribution of offshore wind energy leads to a rising number......, a method is presented in order to predict the rate of noise attenuation achieved by a Small Bubble Curtain. For this purpose, the bubble distribution is determined with Computational Fluid Dynamics. The noise radiation during pile driving is simulated by Finite Element Analysis and an Effective Medium...... Approach considers the acoustic effects within the Bubble Curtain. The pressure level at an arbitrary distance from the pile is determined by a Parabolic Equation method. Furthermore, comparisons between simulations and offshore measurements are presented. This combination of four methods provides...

  7. Numerical prediction of underwater noise reduction during offshore pile driving by a Small Bubble Curtain

    DEFF Research Database (Denmark)

    Göttsche, Klaus Marco; Juhl, Peter Møller; Steinhagen, Ulrich

    2013-01-01

    Small Bubble Curtains are an effective technique to reduce the underwater noise being emitted during offshore pile driving. In order to protect the marine fauna, noise reduction becomes even more important, since the increasing contribution of offshore wind energy leads to a rising number...... of offshore construction sites in order to cover the need for clean energy. Within the Bubble Curtain air bubbles are injected into the water surrounding the pile. When these are driven by the pressure wave being emitted from the pile, reflection, scattering and absorption effects occur. Within this paper......, a method is presented in order to predict the rate of noise attenuation achieved by a Small Bubble Curtain. For this purpose, the bubble distribution is determined with Computational Fluid Dynamics. The noise radiation during pile driving is simulated by Finite Element Analysis and an Effective Medium...

  8. Noise reduction in multiple-echo data sets using singular value decomposition.

    Science.gov (United States)

    Bydder, Mark; Du, Jiang

    2006-09-01

    A method is described for denoising multiple-echo data sets using singular value decomposition (SVD). Images are acquired using a multiple gradient- or spin-echo sequence, and the variation of the signal with echo time (TE) in all pixels is subjected to SVD analysis to determine the components of the signal variation. The least significant components are associated with small singular values and tend to characterize the noise variation. Applying a "minimum variance" filter to the singular values suppresses the noise components in a way that optimally approximates the underlying noise-free images. The result is a reduction in noise in the individual TE images with minimal degradation of the spatial resolution and contrast. Phantom and in vivo results are presented.

  9. Noise floor reduction of an Er:fiber laser-based photonic microwave generator

    CERN Document Server

    Jiang, Haifeng; Quinlan, Franklyn; Fortier, Tara; Diddams, Scott A

    2011-01-01

    The generation of microwaves from optical signals suffers from thermal and shot noise inherent in the photodetection process. This problem is more acute at lower pulse repetition rates where photodiode saturation limits the achievable signal-to-noise ratio. In this paper, we demonstrate a 10-15 dB reduction in the 10 GHz phase noise floor by multiplication of the pulse repetition rate. Starting with a 250 MHz fundamentally mode-locked erbium(Er):fiber laser, we compare two different approaches to repetition rate multiplication: Fabry-Perot cavity filtering and a cascaded, unbalanced Mach-Zehnder fiber-based interferometer. These techniques reduce the phase noise floor on the 10 GHz photodetected harmonic to -158 dBc/Hz and -162 dBc/Hz, respectively, for Fourier frequencies higher than 100 kHz.

  10. Reduction of the recorded speckle noise in holographic 3D printer.

    Science.gov (United States)

    Utsugi, Takeru; Yamaguchi, Masahiro

    2013-01-14

    A holographic 3D printer produces a high-quality 3D image reproduced by a full-color, full-parallax holographic stereogram with high-density light-ray recording. In order to produce a high-resolution holographic stereogram, we have to solve the problem of speckle noise in this system. For equalizing an intensity distribution inside the elementary hologram, the object beam is modulated by a diffuser. However the diffuser typically generates speckles, which is recorded in the holographic stereogram. It is localized behind the reconstructed image as a granularity noise. First we show the problems of some conventional ways for suppressing the granularity noise using a band-limited diffuser, and then we analyze an approach using a moving diffuser for the reduction of this noise. In the result, it is found that recording with a moving diffuser is effective for reducing the granularity noise at infinity of reconstructed image, although an alternative noise occurs. Moreover we propose a new method introducing multiple exposures to suppress the noise effectively.

  11. Intelligent background noise reduction technology in cable fault locator using the magneto-acoustic synchronous method

    Science.gov (United States)

    Mi, JianWei; Huang, JiFa; Fang, XiaoLi; Fan, LiBin

    2017-01-01

    The magneto-acoustic synchronous method has found wide application in accurate positioning of power cable fault due to its advantages of high accuracy and strong ability to reject interference. In the view of principle, the magneto-acoustic synchronous method needs to detect the discharge sound signal and electromagnetic signal emitted from the fault point, but the discharge sound signal is easy to be interfered by the ambient noise around and the magnetic sound synchronization. Therefore, it is challenging to quickly and accurately detect the fault location of cable especially in strong background noise environment. On the other hand, the spectral subtraction is a relatively traditional and effective method in many intelligent background noise reduction technologies, which is characterized by a relatively small computational cost and strong real-time performance. However, its application is limited because the algorithm displays poor performance in low Signal to Noise Ratio (SNR) environment. Aiming at the shortcoming of the spectral subtraction that de-noising effect is weak in low SNR environment, this paper proposes an improved spectral subtraction combining the magnetic sound synchronous principle and analyzing the properties of discharging sound. This method can accurately estimate noise in real time and optimize the performance of the basic spectral subtraction thus solving the problem that the magneto-acoustic synchronous method is unsatisfactory for positioning cable fault in the strong background noise environment.

  12. Gabor-based anisotropic diffusion for speckle noise reduction in medical ultrasonography.

    Science.gov (United States)

    Zhang, Qi; Han, Hong; Ji, Chunhong; Yu, Jinhua; Wang, Yuanyuan; Wang, Wenping

    2014-06-01

    In ultrasound (US), optical coherence tomography, synthetic aperture radar, and other coherent imaging systems, images are corrupted by multiplicative speckle noise that obscures image interpretation. An anisotropic diffusion (AD) method based on the Gabor transform, named Gabor-based anisotropic diffusion (GAD), is presented to suppress speckle in medical ultrasonography. First, an edge detector using the Gabor transform is proposed to capture directionality of tissue edges and discriminate edges from noise. Then the edge detector is embedded into the partial differential equation of AD to guide the diffusion process and iteratively denoise images. To enhance GAD's adaptability, parameters controlling diffusion are determined from a fully formed speckle region that is automatically detected. We evaluate the GAD on synthetic US images simulated with three models and clinical images acquired in vivo. Compared with seven existing speckle reduction methods, the GAD is superior to other methods in terms of noise reduction and detail preservation.

  13. Children's Performance in Complex Listening Conditions: Effects of Hearing Loss and Digital Noise Reduction

    Science.gov (United States)

    Pittman, Andrea

    2011-01-01

    Purpose: To determine the effect of hearing loss (HL) on children's performance for an auditory task under demanding listening conditions and to determine the effect of digital noise reduction (DNR) on that performance. Method: Fifty children with normal hearing (NH) and 30 children with HL (8-12 years of age) categorized words in the presence of…

  14. TEM Cell Testing of Cable Noise Reduction Techniques from 2 MHz to 200 MHz -- Part 2

    Science.gov (United States)

    Bradley, Arthur T.; Evans, William C.; Reed, Joshua L.; Shimp, Samuel K., III; Fitzpatrick, Fred D.

    2008-01-01

    This paper presents empirical results of cable noise reduction techniques as demonstrated in a TEM cell operating with radiated fields from 2 - 200 MHz. It is the second part of a two-paper series. The first paper discussed cable types and shield connections. In this second paper, the effects of load and source resistances and chassis connections are examined. For each topic, well established theories are compared to data from a real-world physical system. Finally, recommendations for minimizing cable susceptibility (and thus cable emissions) are presented. There are numerous papers and textbooks that present theoretical analyses of cable noise reduction techniques. However, empirical data is often targeted to low frequencies (e.g. 100 MHz). Additionally, a comprehensive study showing the relative effects of various noise reduction techniques is needed. These include the use of dedicated return wires, twisted wiring, cable shielding, shield connections, changing load or source impedances, and implementing load- or source-to-chassis isolation. We have created an experimental setup that emulates a real-world electrical system, while still allowing us to independently vary a host of parameters. The goal of the experiment was to determine the relative effectiveness of various noise reduction techniques when the cable is in the presence of radiated emissions from 2 MHz to 200 MHz.

  15. Study on the Noise Reduction of Vehicle Exhaust NOX Spectra Based on Adaptive EEMD Algorithm

    Directory of Open Access Journals (Sweden)

    Kai Zhang

    2017-01-01

    Full Text Available It becomes a key technology to measure the concentration of the vehicle exhaust components with the transmission spectra. But in the conventional methods for noise reduction and baseline correction, such as wavelet transform, derivative, interpolation, polynomial fitting, and so forth, the basic functions of these algorithms, the number of decomposition layers, and the way to reconstruct the signal have to be adjusted according to the characteristics of different components in the transmission spectra. The parameter settings of the algorithms above are not transcendental, so with them, it is difficult to achieve the best noise reduction effect for the vehicle exhaust spectra which are sharp and drastic in the waveform. In this paper, an adaptive ensemble empirical mode decomposition (EEMD denoising model based on a special normalized index optimization is proposed and used in the spectral noise reduction of vehicle exhaust NOX. It is shown with the experimental results that the method can effectively improve the accuracy of the spectral noise reduction and simplify the denoising process and its operation difficulty.

  16. Numerical evaluation of the performance of active noise control systems

    Science.gov (United States)

    Mollo, C. G.; Bernhard, R. J.

    1990-01-01

    This paper presents a generalized numerical technique for evaluating the optimal performance of active noise controllers. In this technique, the indirect BEM numerical procedures are used to derive the active noise controllers for optimal control of enclosed harmonic sound fields where the strength of the noise sources or the description of the enclosure boundary may not be known. The performance prediction for a single-input single-output system is presented, together with the analysis of the stability and observability of an active noise-control system employing detectors. The numerical procedures presented can be used for the design of both the physical configuration and the electronic components of the optimal active noise controller.

  17. Measured and calculated noise reduction of rail dampers and absorption plates on a high speed slab track

    NARCIS (Netherlands)

    Dittrich, M.G.; Graafland, F.; Eisses, A.R.; Nijhof, M.J.J.

    2015-01-01

    Rail dampers and sound absorbing plates have been tested on a high speed railway slab track in a walled cutting at a noise sensitive location. Their noise reduction has been determined from pass-by measurements during service and predicted using BEM calculations. The cutting depth, noise barrier hei

  18. A hybrid active/passive exhaust noise control system for locomotives

    Science.gov (United States)

    Remington, Paul J.; Knight, J. Scott; Hanna, Doug; Rowley, Craig

    2005-01-01

    A prototype hybrid system consisting of active and passive components for controlling far-field locomotive exhaust noise has been designed, assembled, and tested on a locomotive. The system consisted of a resistive passive silencer for controlling high-frequency broadband noise and a feedforward multiple-input, multiple-output active control system for suppressing low-frequency tonal noise. The active system used ten roof-mounted bandpass speaker enclosures with 2-12-in. speakers per enclosure as actuators, eight roof-mounted electret microphones as residual sensors, and an optical tachometer that sensed locomotive engine speed as a reference sensor. The system was installed on a passenger locomotive and tested in an operating rail yard. Details of the system are described and the near-field and far-field noise reductions are compared against the design goal. .

  19. Multichannel active control of random noise in a small reverberant room

    DEFF Research Database (Denmark)

    Laugesen, Søren; Elliott, Stephen J.

    1993-01-01

    An algorithm for multichannel adaptive IIR (infinite impulse response) filtering is presented and applied to the active control of broadband random noise in a small reverberant room. Assuming complete knowledge of the primary noise, the theoretically optimal reductions of acoustic energy...... multichannel FIR (finite impulse response) and IIR filters are then compared for a four-secondary-source, eight-error microphone active control system, and it is found that for the present application FIR filters are sufficient when the primary noise source is a loudspeaker. Some experiments are then presented...... with the primary noise field generated by a panel excited by a loudspeaker in an adjoining room. These results show that far better performances are provided by IIR and FIR filters when the primary source has a lightly damped dynamic behavior which the active controller must model...

  20. Effects of noise reduction on speech intelligibility, perceived listening effort, and personal preference in hearing-impaired listeners.

    Science.gov (United States)

    Brons, Inge; Houben, Rolph; Dreschler, Wouter A

    2014-10-13

    This study evaluates the perceptual effects of single-microphone noise reduction in hearing aids. Twenty subjects with moderate sensorineural hearing loss listened to speech in babble noise processed via noise reduction from three different linearly fitted hearing aids. Subjects performed (a) speech-intelligibility tests, (b) listening-effort ratings, and (c) paired-comparison ratings on noise annoyance, speech naturalness, and overall preference. The perceptual effects of noise reduction differ between hearing aids. The results agree well with those of normal-hearing listeners in a previous study. None of the noise-reduction algorithms improved speech intelligibility, but all reduced the annoyance of noise. The noise reduction that scored best with respect to noise annoyance and preference had the worst intelligibility scores. The trade-off between intelligibility and listening comfort shows that preference measurements might be useful in addition to intelligibility measurements in the selection of noise reduction. Additionally, this trade-off should be taken into consideration to create realistic expectations in hearing-aid users.

  1. EXPERIMENTAL INVESTIGATION OF PARAMETERS EFFECTING THE NOISE REDUCTION IN HERMITICALLY SEALED RECIPROCATING COMPRESSOR

    Directory of Open Access Journals (Sweden)

    G.Laxmaiah

    2011-07-01

    Full Text Available Hermetic reciprocating compressors are most commonly used in the refrigeration industry. The main source of noise in refrigerating and air conditioning machinery is the compressor. Reduction of noise in compressors is a complex criterion as many factors such as Shell Thickness, Shell Material, Suction Port Area and Discharge Port Area etc. contribute its effect on the noise and they also interact in a complex manner. In this work a screening test is carried out to find the relative effect of the parameters and their interaction, which can be used as an initial step for further investigations concentrating on the most influencing parameters and their interactions using Taguchi Technique. Here Shell Thickness (ST, Shell Material (SM, Suction Port Area (SPA and Discharge Port Area (DPA are chosen as input parameters and the noise is the output parameter. L8 orthogonal array is selected, the factors are assigned and experiments are carried out. Column effect method is used to find the most effective parameters for the noise reduction in the compressor.

  2. Perception Neural Networks for Active Noise Control Systems

    Directory of Open Access Journals (Sweden)

    Wang Xiaoli

    2012-11-01

    Full Text Available In a response to a growing demand for environments of 70dB or less noise levels, many industrial sectors have focused with some form of noise control system. Active noise control (ANC has proven to be the most effective technology. This paper mainly investigates application of neural network on self-adaptation system in active noise control (ANC. An active silencing control system is made which adopts a motional feedback loudspeaker as not a noise controlling source but a detecting sensor. The working fundamentals and the characteristics of the motional feedback loudspeaker are analyzed in detail. By analyzing each acoustical path, identification based adaptive linear neural network is built. This kind of identifying method can be achieved conveniently. The estimated result of each sound channel matches well with its real sound character, respectively.

  3. Active noise control: A panacea for noise pollution. AntiGeluid: Een panacee tegen geluidsoverlast

    Energy Technology Data Exchange (ETDEWEB)

    Van den Dool, T.C. (Afdeling AntiGeluid, TNO Technisch Physische Dienst, Eindhoven (Netherlands))

    1994-09-01

    Active noise control (ANC) has a number of advantages compared to passive silencers, although it is not suitable for large noise pollution sources or large spaces, because many microphones, loudspeakers and much processing power is needed in these cases. ANC products include head sets, exhaust silencers, HVAC systems and systems for narrow enclosures with tonal noise pollution like cars and aeroplanes. The price of dedicated electronic systems is still decreasing which will positively affect the cost of ANC. 5 figs., 2 ills., 3 refs.

  4. Detection threshold for sound distortion resulting from noise reduction in normal-hearing and hearing-impaired listeners.

    Science.gov (United States)

    Brons, Inge; Dreschler, Wouter A; Houben, Rolph

    2014-09-01

    Hearing-aid noise reduction should reduce background noise, but not disturb the target speech. This objective is difficult because noise reduction suffers from a trade-off between the amount of noise removed and signal distortion. It is unknown if this important trade-off differs between normal-hearing (NH) and hearing-impaired (HI) listeners. This study separated the negative effect of noise reduction (distortion) from the positive effect (reduction of noise) to allow the measurement of the detection threshold for noise-reduction (NR) distortion. Twelve NH subjects and 12 subjects with mild to moderate sensorineural hearing loss participated in this study. The detection thresholds for distortion were determined using an adaptive procedure with a three-interval, two-alternative forced-choice paradigm. Different levels of distortion were obtained by changing the maximum amount of noise reduction. Participants were also asked to indicate their preferred NR strength. The detection threshold for overall distortion was higher for HI subjects than for NH subjects, suggesting that stronger noise reduction can be applied for HI listeners without affecting the perceived sound quality. However, the preferred NR strength of HI listeners was closer to their individual detection threshold for distortion than in NH listeners. This implies that HI listeners tolerate fewer audible distortions than NH listeners.

  5. Development of a SMA-Based, Slat-Gap Filler for Airframe Noise Reduction

    Science.gov (United States)

    Turner, Travis L.; Long, David L.

    2015-01-01

    Noise produced by unsteady flow around aircraft structures, termed airframe noise, is an important source of aircraft noise during the approach and landing phases of flight. Conventional leading-edge-slat devices for high lift on typical transport aircraft are a prominent source of airframe noise. Many concepts for slat noise reduction have been investigated. Slat-cove fillers have emerged as an attractive solution, but they maintain the gap flow, leaving some noise production mechanisms unabated, and thus represent a nonoptimal solution. Drooped-leading-edge (DLE) concepts have been proposed as "optimal" because the gap flow is eliminated. The deployed leading edge device is not distinct and separate from the main wing in DLE concepts and the high-lift performance suffers at high angles of attack (alpha) as a consequence. Elusive high-alpha performance and excessive weight penalty have stymied DLE development. The fact that high-lift performance of DLE systems is only affected at high alpha suggests another concept that simultaneously achieves the high-lift of the baseline airfoil and the noise reduction of DLE concepts. The concept involves utilizing a conventional leading-edge slat device and a deformable structure that is deployed from the leading edge of the main wing and closes the gap between the slat and main wing, termed a slat-gap filler (SGF). The deployable structure consists of a portion of the skin of the main wing and it is driven in conjunction with the slat during deployment and retraction. Benchtop models have been developed to assess the feasibility and to study important parameters. Computational models have assisted in the bench-top model design and provided valuable insight in the parameter space as well as the feasibility.

  6. Evaluation of Airframe Noise Reduction Concepts via Simulations Using a Lattice Boltzmann Approach

    Science.gov (United States)

    Fares, Ehab; Casalino, Damiano; Khorrami, Mehdi R.

    2015-01-01

    Unsteady computations are presented for a high-fidelity, 18% scale, semi-span Gulfstream aircraft model in landing configuration, i.e. flap deflected at 39 degree and main landing gear deployed. The simulations employ the lattice Boltzmann solver PowerFLOW® to simultaneously capture the flow physics and acoustics in the near field. Sound propagation to the far field is obtained using a Ffowcs Williams and Hawkings acoustic analogy approach. In addition to the baseline geometry, which was presented previously, various noise reduction concepts for the flap and main landing gear are simulated. In particular, care is taken to fully resolve the complex geometrical details associated with these concepts in order to capture the resulting intricate local flow field thus enabling accurate prediction of their acoustic behavior. To determine aeroacoustic performance, the farfield noise predicted with the concepts applied is compared to high-fidelity simulations of the untreated baseline configurations. To assess the accuracy of the computed results, the aerodynamic and aeroacoustic impact of the noise reduction concepts is evaluated numerically and compared to experimental results for the same model. The trends and effectiveness of the simulated noise reduction concepts compare well with measured values and demonstrate that the computational approach is capable of capturing the primary effects of the acoustic treatment on a full aircraft model.

  7. 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.

  8. Improvements to local projective noise reduction through higher order and multiscale refinements

    Science.gov (United States)

    Moore, Jack Murdoch; Small, Michael; Karrech, Ali

    2015-06-01

    The broad spectrum characteristic of signals from nonlinear systems obstructs noise reduction techniques developed for linear systems. Local projection was developed to reduce noise while preserving nonlinear deterministic structures, and a second order refinement to local projection which was proposed ten years ago does so particularly effectively. It involves adjusting the origin of the projection subspace to better accommodate the geometry of the attractor. This paper describes an analytic motivation for the enhancement from which follows further higher order and multiple scale refinements. However, the established enhancement is frequently as or more effective than the new filters arising from solely geometric considerations. Investigation of the way that measurement errors reinforce or cancel throughout the refined local projection procedure explains the special efficacy of the existing enhancement, and leads to a new second order refinement offering widespread gains. Different local projective filters are found to be best suited to different noise levels. At low noise levels, the optimal order increases as noise increases. At intermediate levels second order tends to be optimal, while at high noise levels prototypical local projection is most effective. The new higher order filters perform better relative to established filters for longer signals or signals corresponding to higher dimensional attractors.

  9. Active noise control in fuselage design

    NARCIS (Netherlands)

    Krakers, L.A.; Tooren, M.J.L. van; Beukers, A.; Berkhof, A.P.; Goeje, M.P. de

    2003-01-01

    To achieve comfortable noise levels inside the passenger cabin, sound damping measures have to be taken to improve the sound insulation properties of the bare airframe. Usually the sound insulation requirements of a passenger cabin are met after the mechanical design of the fuselage structure is alr

  10. A reliable ground bounce noise reduction technique for nanoscale CMOS circuits

    Science.gov (United States)

    Sharma, Vijay Kumar; Pattanaik, Manisha

    2015-11-01

    Power gating is the most effective method to reduce the standby leakage power by adding header/footer high-VTH sleep transistors between actual and virtual power/ground rails. When a power gating circuit transitions from sleep mode to active mode, a large instantaneous charge current flows through the sleep transistors. Ground bounce noise (GBN) is the high voltage fluctuation on real ground rail during sleep mode to active mode transitions of power gating circuits. GBN disturbs the logic states of internal nodes of circuits. A novel and reliable power gating structure is proposed in this article to reduce the problem of GBN. The proposed structure contains low-VTH transistors in place of high-VTH footer. The proposed power gating structure not only reduces the GBN but also improves other performance metrics. A large mitigation of leakage power in both modes eliminates the need of high-VTH transistors. A comprehensive and comparative evaluation of proposed technique is presented in this article for a chain of 5-CMOS inverters. The simulation results are compared to other well-known GBN reduction circuit techniques at 22 nm predictive technology model (PTM) bulk CMOS model using HSPICE tool. Robustness against process, voltage and temperature (PVT) variations is estimated through Monte-Carlo simulations.

  11. Active noise control with fast array recursive least squares filters using a parallel implementation for numerical stability

    NARCIS (Netherlands)

    Berkhoff, A.P.; Ophem, S. van

    2015-01-01

    Noise reduction in feedforward active noise control systems with a rapidly changing primary path requires rapid convergence and fast tracking. This can be accomplished with a fast-array Kalman method which uses an efficient rotation matrix technique to calculate the filter parameters. However, finit

  12. Active noise control with fast array recursive least squares filters using a parallel implementation for numerical stability

    NARCIS (Netherlands)

    Berkhoff, Arthur P.; van Ophem, S.; Glorieux, C.

    2015-01-01

    Significant noise reduction in feedforward active noise control systems with a rapidly changing primary path requires rapid convergence and fast tracking performance. This can be accomplished with a fast-array Kalman method which uses an efficient rotation matrix technique to calculate the filter

  13. Active noise control with fast array recursive least squares filters using a parallel implementation for numerical stability

    NARCIS (Netherlands)

    Berkhoff, A.P.; Ophem, S. van

    2015-01-01

    Noise reduction in feedforward active noise control systems with a rapidly changing primary path requires rapid convergence and fast tracking. This can be accomplished with a fast-array Kalman method which uses an efficient rotation matrix technique to calculate the filter parameters. However,

  14. Assessment of an ICA-based noise reduction method for multi-channel auditory evoked potentials

    Science.gov (United States)

    Mirahmadizoghi, Siavash; Bell, Steven; Simpson, David

    2015-03-01

    In this work a new independent component analysis (ICA) based method for noise reduction in evoked potentials is evaluated on for auditory late responses (ALR) captured with a 63-channel electroencephalogram (EEG) from 10 normal-hearing subjects. The performance of the new method is compared with a single channel alternative in terms of signal to noise ratio (SNR), the number of channels with an SNR above an empirically derived statistical critical value and an estimate of hearing threshold. The results show that the multichannel signal processing method can significantly enhance the quality of the signal and also detected hearing thresholds significantly lower than with the single channel alternative.

  15. Phase noise reduction of a semiconductor laser in a composite optical phase-locked loop

    Science.gov (United States)

    Satyan, Naresh; Sendowski, Jacob; Vasilyev, Arseny; Rakuljic, George; Yariv, Amnon

    2010-12-01

    The bandwidth and residual phase noise of optical phase-locked loops (OPLLs) using semiconductor lasers are typically constrained by the nonuniform frequency modulation response of the laser, limiting their usefulness in a number of applications. It is shown in this work that additional feedback control using an optical phase modulator improves the coherence between the master and slave lasers in the OPLL by achieving bandwidths determined only by the propagation delay in the loop. A phase noise reduction by more than a factor of two is demonstrated in a proof-of-concept experiment using a commercial distributed feedback semiconductor laser.

  16. 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.

  17. Smart materials and active noise and vibration control in vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, M. van [TNO Institute of Applied Physics, Delft (Netherlands)

    2001-07-01

    Results are presented for the reduction of sound radiated from a structure using different control methodologies. Two approaches for active structural acoustic control are mentioned to reduce sound radiated by the structure: the acoustic approach or the vibro-acoustic approach. In both cases integrated actuators in structure materials are necessary to realise feasible products. Furthermore the development of an efficient shaker for Active Isolation techniques is described. The prototype of TNO TPD can produce a force of 400 N up to 250 Hz at a good performance-volume ratio. To enhance the robustness of the active control applications, the use of the subspace identification based control methods are developed. The robustness property of subspace identification methods forms the basis of an accurate model updating mechanism, using small size data batches. The performed simulations reveal excellent robustness performance under very general noise conditions or during operation of the control system. Furthermore the development of the techniques can be exploited to realise sound comfort requirements to enhance audible communications of vehicle related applications. To anticipate to these developments in the automotive industry, TNO has set up a Sound and Vibrations Research Centre with Twente University and a research program on Smart Panels with the Delft University. To investigate the potential markets and applications for sound comfort in the means of transportation, TNO-TPD and the Institute of Sound and Vibration Research in England (ISVR) have agreed on a cooperative venture to develop and realise 'active control of electroacoustics' (ACE). (orig.)

  18. Initial results of a model rotor higher harmonic control (HHC) wind tunnel experiment on BVI impulsive noise reduction

    Science.gov (United States)

    Splettstoesser, W. R.; Lehmann, G.; van der Wall, B.

    1989-09-01

    Initial acoustic results are presented from a higher harmonic control (HHC) wind tunnel pilot experiment on helicopter rotor blade-vortex interaction (BVI) impulsive noise reduction, making use of the DFVLR 40-percent-scaled BO-105 research rotor in the DNW 6m by 8m closed test section. Considerable noise reduction (of several decibels) has been measured for particular HHC control settings, however, at the cost of increased vibration levels and vice versa. The apparently adverse results for noise and vibration reduction by HHC are explained. At optimum pitch control settings for BVI noise reduction, rotor simulation results demonstrate that blade loading at the outer tip region is decreased, vortex strength and blade vortex miss-distance are increased, resulting altogether in reduced BVI noise generation. At optimum pitch control settings for vibration reduction adverse effects on blade loading, vortex strength and blade vortex miss-distance are found.

  19. Active Control of Automotive Intake Noise under Rapid Acceleration using the Co-FXLMS Algorithm

    Science.gov (United States)

    Lee, Hae-Jin; Lee, Gyeong-Tae; Oh, Jae-Eung

    The method of reducing automotive intake noise can be classified by passive and active control techniques. However, passive control has a limited effect of noise reduction at low frequency range (below 500 Hz) and is limited by the space of the engine room. However, active control can overcome these passive control limitations. The active control technique mostly uses the Least-Mean-Square (LMS) algorithm, because the LMS algorithm can easily obtain the complex transfer function in real-time, particularly when the Filtered-X LMS (FXLMS) algorithm is applied to an active noise control (ANC) system. However, the convergence performance of the LMS algorithm decreases significantly when the FXLMS algorithm is applied to the active control of intake noise under rapidly accelerating driving conditions. Therefore, in this study, the Co-FXLMS algorithm was proposed to improve the control performance of the FXLMS algorithm during rapid acceleration. The Co-FXLMS algorithm is realized by using an estimate of the cross correlation between the adaptation error and the filtered input signal to control the step size. The performance of the Co-FXLMS algorithm is presented in comparison with that of the FXLMS algorithm. Experimental results show that active noise control using Co-FXLMS is effective in reducing automotive intake noise during rapid acceleration.

  20. 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.

  1. Application of Feedforward Adaptive Active-Noise Control for Reducing Blade Passing Noise in Centrifugal Fans

    Science.gov (United States)

    WU, J.-D.; BAI, M. R.

    2001-02-01

    This paper describes two configurations of feedforward adaptive active-noise control (ANC) technique for reducing blade passing noise in centrifugal fans. In one configuration, the control speaker is installed at the cut-off region of the fan, while in the other configuration at the exit duct. The proposed ANC system is based on the filtered-x least-mean-squares (FXLMS) algorithm with multi-sine synthesized reference signal and frequency counting and is implemented by using a digital signal processor (DSP). Experiments are carried out to evaluate the proposed system for reducing the noise at the blade passing frequency (BPF) and its harmonics at various flow speeds. The results of the experiment indicated that the ANC technique is effective in reducing the blade passing noise for two configurations by using the feedforward adaptive control.

  2. 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 ...

  3. Dual-microphone and binaural noise reduction techniques for improved speech intelligibility by hearing aid users

    Science.gov (United States)

    Yousefian Jazi, Nima

    Spatial filtering and directional discrimination has been shown to be an effective pre-processing approach for noise reduction in microphone array systems. In dual-microphone hearing aids, fixed and adaptive beamforming techniques are the most common solutions for enhancing the desired speech and rejecting unwanted signals captured by the microphones. In fact, beamformers are widely utilized in systems where spatial properties of target source (usually in front of the listener) is assumed to be known. In this dissertation, some dual-microphone coherence-based speech enhancement techniques applicable to hearing aids are proposed. All proposed algorithms operate in the frequency domain and (like traditional beamforming techniques) are purely based on the spatial properties of the desired speech source and does not require any knowledge of noise statistics for calculating the noise reduction filter. This benefit gives our algorithms the ability to address adverse noise conditions, such as situations where interfering talker(s) speaks simultaneously with the target speaker. In such cases, the (adaptive) beamformers lose their effectiveness in suppressing interference, since the noise channel (reference) cannot be built and updated accordingly. This difference is the main advantage of the proposed techniques in the dissertation over traditional adaptive beamformers. Furthermore, since the suggested algorithms are independent of noise estimation, they offer significant improvement in scenarios that the power level of interfering sources are much more than that of target speech. The dissertation also shows the premise behind the proposed algorithms can be extended and employed to binaural hearing aids. The main purpose of the investigated techniques is to enhance the intelligibility level of speech, measured through subjective listening tests with normal hearing and cochlear implant listeners. However, the improvement in quality of the output speech achieved by the

  4. A Study on Bus Noise Reduction%大客车降噪的研究

    Institute of Scientific and Technical Information of China (English)

    吴诰珪; 吴伟先

    2001-01-01

    运用噪声分离、频谱分析等技术手段,找出了GZ6921型后置柴油机大客车噪声超过国家标准的原因,并对主要噪声源及其频谱分布进行了分析.对各主要噪声源--排气系统、冷却系统和发动机舱采取相应的降噪措施,如降低风扇转速,改善抗性消声器的降噪能力,修改冷却风进风道,平衡车两侧的噪声源,在发动机舱中粘贴吸音材料等.改进后GZ6921型大客车最大加速度时的车外噪声由91.5dB(A)降到86dB(A)以下,达到国标GB1495-75"机动车允许噪声"的规定.%In this Paper,noise separation and frequency spectrum analyzingtechniques are used to find out why the noise level of the bus of GZ6921 model with rear-placed diesel engine layout exceeds the limit set by the national standard,the nain noise sources and their frequency spectrum distribution are thus identified.Noise reduction measures which are aimed at the main noise sources such as the exhaust system,the cooling air-intake system and the engine cabin are applied,including slowing down the fan's rotation speed,enhancing noise reduction ability of the acoustic-reactive type muffler,modifying the shape of cooling air-intake path,balancing noise in both sides of the bus and adopting sound-absorber in the engine cabin.After these treatments,outside noise level of the bus with maximum acceleration declines from 91.5 dB(A) to lower than 86 dB(A),which meets the "permitted Noise Level of Motor Vehicle"defined by the “GB 1495-79”national standard.

  5. Reduction of the 1/f Noise Induced Phase Noise in a CMOS Ring Oscillator by Increasing the Amplitude of Oscillation

    NARCIS (Netherlands)

    Gierkink, S.L.J.; Wel, van der A.P.; Hoogzaad, G.; Klumperink, E.A.M.; Tuijl, van A.J.M.

    1998-01-01

    Spectrum measurement results of a CMOS ring oscillator are presented that show a 10 dB decrease in 1/f noise induced phase noise at a 2 dB increase in carrier power. Simple ring oscillator theory predicts that the 1/f noise induced phase noise is independent of carrier power. It is shown that an inc

  6. Application of chaotic noise reduction techniques to chaotic data trained by ANN

    Indian Academy of Sciences (India)

    C Chandra Shekara Bhat; M R Kaimal; T R Ramamohan

    2001-10-01

    We propose a novel method of combining artificial neural networks (ANNs) with chaotic noise reduction techniques that captures the metric and dynamic invariants of a chaotic time series, e.g. a time series obtained by iterating the logistic map in chaotic regimes. Our results indicate that while the feedforward neural network is capable of capturing the dynamical and metric invariants of chaotic time series within an error of about 25%, ANNs along with chaotic noise reduction techniques, such as Hammel’s method or the local projective method, can significantly improve these results. This further suggests that the effort on the ANN to train data corresponding to complex structures can be significantly reduced. This technique can be applied in areas like signal processing, data communication, image processing etc.

  7. Robust Distributed Noise Reduction in Hearing Aids with External Acoustic Sensor Nodes

    Directory of Open Access Journals (Sweden)

    Marc Moonen

    2009-01-01

    Full Text Available The benefit of using external acoustic sensor nodes for noise reduction in hearing aids is demonstrated in a simulated acoustic scenario with multiple sound sources. A distributed adaptive node-specific signal estimation (DANSE algorithm, that has a reduced communication bandwidth and computational load, is evaluated. Batch-mode simulations compare the noise reduction performance of a centralized multi-channel Wiener filter (MWF with DANSE. In the simulated scenario, DANSE is observed not to be able to achieve the same performance as its centralized MWF equivalent, although in theory both should generate the same set of filters. A modification to DANSE is proposed to increase its robustness, yielding smaller discrepancy between the performance of DANSE and the centralized MWF. Furthermore, the influence of several parameters such as the DFT size used for frequency domain processing and possible delays in the communication link between nodes is investigated.

  8. 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.

  9. TEM Cell Testing of Cable Noise Reduction Techniques From 2 MHz to 200 MHz - Part 1

    Science.gov (United States)

    Bradley, Arthur T.; Evans, William C.; Reed, Joshua L.; Shimp, Samuel K.; Fitzpatrick, Fred D.

    2008-01-01

    This paper presents empirical results of cable noise reduction techniques as demonstrated in a TEM cell operating with radiated fields from 2 - 200 MHz. It is the first part of a two-paper series. This first paper discusses cable types and shield connections. In the second paper, the effects of load and source resistances and chassis connections are examined. For each topic, well established theories are compared to data from a real-world physical system. Finally, recommendations for minimizing cable susceptibility (and thus cable emissions) are presented. There are numerous papers and textbooks that present theoretical analyses of cable noise reduction techniques. However, empirical data is often targeted to low frequencies (e.g. 100 MHz). Additionally, a comprehensive study showing the relative effects of various noise reduction techniques is needed. These include the use of dedicated return wires, twisted wiring, cable shielding, shield connections, changing load or source impedances, and implementing load- or source-to-chassis isolation. We have created an experimental setup that emulates a real-world electrical system, while still allowing us to independently vary a host of parameters. The goal of the experiment was to determine the relative effectiveness of various noise reduction techniques when the cable is in the presence of radiated emissions from 2 MHz to 200 MHz. The electronic system (Fig. 1) consisted of two Hammond shielded electrical enclosures, one containing the source resistance, and the other containing the load resistance. The boxes were mounted on a large aluminium plate acting as the chassis. Cables connecting the two boxes measured 81 cm in length and were attached to the boxes using standard D38999 military-style connectors. The test setup is shown in Fig. 2. Electromagnetic fields were created using an HP8657B signal generator, MiniCircuits ZHL-42W-SMA amplifier, and an EMCO 5103 TEM cell. Measurements were taken using an Agilent E4401B

  10. Development of a Voice Activity Controlled Noise Canceller

    Directory of Open Access Journals (Sweden)

    Aini Hussain

    2012-05-01

    Full Text Available In this paper, a variable threshold voice activity detector (VAD is developed to control the operation of a two-sensor adaptive noise canceller (ANC. The VAD prohibits the reference input of the ANC from containing some strength of actual speech signal during adaptation periods. The novelty of this approach resides in using the residual output from the noise canceller to control the decisions made by the VAD. Thresholds of full-band energy and zero-crossing features are adjusted according to the residual output of the adaptive filter. Performance evaluation of the proposed approach is quoted in terms of signal to noise ratio improvements as well mean square error (MSE convergence of the ANC. The new approach showed an improved noise cancellation performance when tested under several types of environmental noise. Furthermore, the computational power of the adaptive process is reduced since the output of the adaptive filter is efficiently calculated only during non-speech periods.

  11. Subspace-Based Noise Reduction for Speech Signals via Diagonal and Triangular Matrix Decompositions

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Jensen, Søren Holdt

    2007-01-01

    We survey the definitions and use of rank-revealing matrix decompositions in single-channel noise reduction algorithms for speech signals. Our algorithms are based on the rank-reduction paradigm and, in particular, signal subspace techniques. The focus is on practical working algorithms, using both...... diagonal (eigenvalue and singular value) decompositions and rank-revealing triangular decompositions (ULV, URV, VSV, ULLV and ULLIV). In addition we show how the subspace-based algorithms can be evaluated and compared by means of simple FIR filter interpretations. The algorithms are illustrated...... with working Matlab code and applications in speech processing....

  12. Evaluation of Variable-Depth Liner Configurations for Increased Broadband Noise Reduction

    Science.gov (United States)

    Jones, M. G.; Watson, W. R.; Nark, D. M.; Howerton, B. M.

    2015-01-01

    This paper explores the effects of variable-depth geometry on the amount of noise reduction that can be achieved with acoustic liners. Results for two variable-depth liners tested in the NASA Langley Grazing Flow Impedance Tube demonstrate significant broadband noise reduction. An impedance prediction model is combined with two propagation codes to predict corresponding sound pressure level profiles over the length of the Grazing Flow Impedance Tube. The comparison of measured and predicted sound pressure level profiles is sufficiently favorable to support use of these tools for investigation of a number of proposed variable-depth liner configurations. Predicted sound pressure level profiles for these proposed configurations reveal a number of interesting features. Liner orientation clearly affects the sound pressure level profile over the length of the liner, but the effect on the total attenuation is less pronounced. The axial extent of attenuation at an individual frequency continues well beyond the location where the liner depth is optimally tuned to the quarter-wavelength of that frequency. The sound pressure level profile is significantly affected by the way in which variable-depth segments are distributed over the length of the liner. Given the broadband noise reduction capability for these liner configurations, further development of impedance prediction models and propagation codes specifically tuned for this application is warranted.

  13. Improved Reproduction of Stops in Noise Reduction Systems with Adaptive Windows and Nonstationarity Detection

    Directory of Open Access Journals (Sweden)

    Dirk Mauler

    2009-01-01

    Full Text Available A new block-based noise reduction system is proposed which focuses on the preservation of transient sounds like stops or speech onsets. The power level of consonants has been shown to be important for speech intelligibility. In single-channel noise reduction systems, however, these sounds are frequently severely attenuated. The main reasons for this are an insufficient temporal resolution of transient sounds and a delayed tracking of important control parameters. The key idea of the proposed system is the detection of non-stationary input data. Depending on that decision, a pair of spectral analysis-synthesis windows is selected which either provides high temporal or high spectral resolution. Furthermore, the decision-directed approach for the estimation of the a priori SNR is modified so that speech onsets are tracked more quickly without sacrificing performance in stationary signal regions. The proposed solution shows significant improvements in the preservation of stops with an overall system delay (input-output, excluding group delay of noise reduction filter of only 10 milliseconds.

  14. Quelling Cabin Noise in Turboprop Aircraft via Active Control

    Science.gov (United States)

    Kincaid, Rex K.; Laba, Keith E.; Padula, Sharon L.

    1997-01-01

    Cabin noise in turboprop aircraft causes passenger discomfort, airframe fatigue, and employee scheduling constraints due to OSHA standards for exposure to high levels of noise. The noise levels in the cabins of turboprop aircraft are typically 10 to 30 decibels louder than commercial jet noise levels. However. unlike jet noise the turboprop noise spectrum is dominated by a few low frequency tones. Active structural acoustic control is a method in which the control inputs (used to reduce interior noise) are applied directly to a vibrating structural acoustic system. The control concept modeled in this work is the application of in-plane force inputs to piezoceramic patches bonded to the wall of a vibrating cylinder. The goal is to determine the force inputs and locations for the piezoceramic actuators so that: (1) the interior noise is effectively damped; (2) the level of vibration of the cylinder shell is not increased; and (3) the power requirements needed to drive the actuators are not excessive. Computational experiments for data taken from a computer generated model and from a laboratory test article at NASA Langley Research Center are provided.

  15. Active control of internal cabin noise in cars. Aktive Innengeraeuschreduzierung bei Kraftfahrzeugen

    Energy Technology Data Exchange (ETDEWEB)

    Felske, A.; Gawron, H.J.; Schaaf, K.

    1990-01-01

    It is an important research task to develop methods for active noise control. In addition to reviewing possible operational areas, we discuss the efficiency based on measurements of a broadband active head-set and present an experimental two-channel system for active noise control which was tested in a VW Passat with 4 cylinder engine. Having solved the problem of decoupling in multi-channel systems, a reduction of the interior noise level for 2nd order frequencies up to 20 dB could be achieved. Standard speaker systems were used. Diagrams of sound pressure levels show the efficiency of the active compensation as a function of motor speed for the co-driver's right ear, and as a function of location both in longitudinal and transversal direction within the car cabin at a fixed motor speed. (orig./HW).

  16. In Situ Active Control of Noise in a 4-Tesla MRI Scanner

    Science.gov (United States)

    Li, Mingfeng; Rudd, Brent; Lim, Teik C.; Lee, Jing-Huei

    2011-01-01

    Purpose To evaluate the effectiveness of the proposed active noise control (ANC) system for the reduction of the acoustic noise emission generated by a 4 T MRI scanner during operation and to assess the feasibility of developing an ANC device that can be deployed in situ. Materials and Methods Three typical scanning sequences, namely EPI (echo planar imaging), GEMS (gradient echo multi-slice) and MDEFT (Modified Driven Equilibrium Fourier Transform), were used for evaluating the performance of the ANC system, which was composed of a magnetic compatible headset and a multiple reference feedforward filtered-x least mean square controller. Results The greatest reduction, about 55 dB, was achieved at the harmonic at a frequency of 1.3 kHz in the GEMS case. Approximately 21 dB and 30 dBA overall reduction was achieved for GEMS noise across the entire audible frequency range. For the MDEFT sequence, the control system achieved 14 dB and 14 dBA overall reduction in the audible frequency range, while 13 dB and 14 dBA reduction was obtained for the EPI case. Conclusion The result is highly encouraging because it shows great potential for treating MRI noise with an ANC application during real time scanning. PMID:21751284

  17. Active structural acoustic control of helicopter interior multifrequency noise using input-output-based hybrid control

    Science.gov (United States)

    Ma, Xunjun; Lu, Yang; Wang, Fengjiao

    2017-09-01

    This paper presents the recent advances in reduction of multifrequency noise inside helicopter cabin using an active structural acoustic control system, which is based on active gearbox struts technical approach. To attenuate the multifrequency gearbox vibrations and resulting noise, a new scheme of discrete model predictive sliding mode control has been proposed based on controlled auto-regressive moving average model. Its implementation only needs input/output data, hence a broader frequency range of controlled system is modelled and the burden on the state observer design is released. Furthermore, a new iteration form of the algorithm is designed, improving the developing efficiency and run speed. To verify the algorithm's effectiveness and self-adaptability, experiments of real-time active control are performed on a newly developed helicopter model system. The helicopter model can generate gear meshing vibration/noise similar to a real helicopter with specially designed gearbox and active struts. The algorithm's control abilities are sufficiently checked by single-input single-output and multiple-input multiple-output experiments via different feedback strategies progressively: (1) control gear meshing noise through attenuating vibrations at the key points on the transmission path, (2) directly control the gear meshing noise in the cabin using the actuators. Results confirm that the active control system is practical for cancelling multifrequency helicopter interior noise, which also weakens the frequency-modulation of the tones. For many cases, the attenuations of the measured noise exceed the level of 15 dB, with maximum reduction reaching 31 dB. Also, the control process is demonstrated to be smoother and faster.

  18. A Modified Structure for Feed Forward Active Noise Control Systems With Improved Performa

    Directory of Open Access Journals (Sweden)

    P.Babu

    2010-09-01

    Full Text Available Several approaches have been introduced in literature for active noise control (ANC systems. SinceFxLMS algorithm appears to be the best choice as a controller filter, researchers tend to improveperformance of ANC systems by enhancing and modifying this algorithm. In this paper, the existingFxLMS algorithm is modified which provides a new structure for improving the noise reduction andconvergence rate. Here the proposed method uses two variable step sizes, one for control filter andanother for modelling filter. The control filter step size is varied based on the secondary path thresholdsignal l dˆ . The modelling filter step size is varied based on error signal f (n . It is shown that in theproposed method ANC system noise reduction rate and convergence rate are improved dynamically thanthe FxLMS variable step size methods. The computer simulations results indicate effectiveness of theproposed method.

  19. Aerodynamic Measurements of a Gulfstream Aircraft Model With and Without Noise Reduction Concepts

    Science.gov (United States)

    Neuhart, Dan H.; Hannon, Judith A.; Khorrami, Mehdi R.

    2014-01-01

    Steady and unsteady aerodynamic measurements of a high-fidelity, semi-span 18% scale Gulfstream aircraft model are presented. The aerodynamic data were collected concurrently with acoustic measurements as part of a larger aeroacoustic study targeting airframe noise associated with main landing gear/flap components, gear-flap interaction noise, and the viability of related noise mitigation technologies. The aeroacoustic tests were conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Wind Tunnel with the facility in the acoustically treated open-wall (jet) mode. Most of the measurements were obtained with the model in landing configuration with the flap deflected at 39º and the main landing gear on and off. Data were acquired at Mach numbers of 0.16, 0.20, and 0.24. Global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Comparison of the present results with those acquired during a previous test shows a significant reduction in the lift experienced by the model. The underlying cause was traced to the likely presence of a much thicker boundary layer on the tunnel floor, which was acoustically treated for the present test. The steady and unsteady pressure fields on the flap, particularly in the regions of predominant noise sources such as the inboard and outboard tips, remained unaffected. It is shown that the changes in lift and drag coefficients for model configurations fitted with gear/flap noise abatement technologies fall within the repeatability of the baseline configuration. Therefore, the noise abatement technologies evaluated in this experiment have no detrimental impact on the aerodynamic performance of the aircraft model.

  20. Towards Truly Quiet MRI: animal MRI magnetic field gradients as a test platform for acoustic noise reduction

    Science.gov (United States)

    Edelstein, William; El-Sharkawy, Abdel-Monem

    2013-03-01

    Clinical MRI acoustic noise, often substantially exceeding 100 dB, causes patient anxiety and discomfort and interferes with functional MRI (fMRI) and interventional MRI. MRI acoustic noise reduction is a long-standing and difficult technical challenge. The noise is basically caused by large Lorentz forces on gradient windings--surrounding the patient bore--situated in strong magnetic fields (1.5 T, 3 T or higher). Pulsed currents of 300 A or more are switched through the gradient windings in sub-milliseconds. Experimenting with hardware noise reduction on clinical scanners is difficult and expensive because of the large scale and weight of clinical scanner components (gradient windings ~ 1000 kg) that require special handling equipment in large engineering test facilities. Our approach is to produce a Truly Quiet (test platform for acoustic noise reduction measures that can be implemented in clinical scanners. We have so far decreased noise in an animal scale imager from 108 dB to 71 dB, a 37 dB reduction. Our noise reduction measures include: a gradient container that can be evacuated; inflatable antivibration mounts to prevent transmission of vibrations from gradient winding to gradient container; vibration damping of wires going from gradient to the outside world via the gradient container; and a copper passive shield to prevent the generation of eddy currents in the metal cryostat inner bore, which in turn can vibrate and produce noise.

  1. Hybrid Active Noise Control using Adjoint LMS Algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Hyun Do; Hong, Sik Ki [Dankook University (Korea, Republic of)

    1998-07-01

    A multi-channel hybrid active noise control(MCHANC) is derived by combining hybrid active noise control techniques and adjoint LMS algorithms, and this algorithm is applied to an active noise control system in a three dimensional enclosure. A MCHANC system uses feed forward and feedback filters simultaneously to cancel noises in an enclosure. The adjoint LMs algorithm, in which the error is filtered through an adjoint filter of the secondary channel, is also used to reduce the computational burden of adaptive filters. The overall attenuation performance and convergence characteristics of MCHANC algorithm is better than both multiple-channel feed forward algorithms and multiple-channel feedback algorithms. In a large enclosure, the acoustic reverberation can be very long, which means a very high order feed forward filter must be used to cancel the reverberation noises. Strong reverberation noises are generally narrow band and low frequency, which can be effectively predicted and canceled by a feedback adaptive filters. So lower order feed forward filter taps can be used in MCHANC algorithm which combines advantages of fast convergence and small excess mean square error. In this paper, computer simulations and real time implementations is carried out on a TMS320C31 processor to evaluate the performance of the MCHANC systems. (author). 11 refs., 11 figs., 1 tab.

  2. 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.

  3. A PIV Study of Slotted Air Injection for Jet Noise Reduction

    Science.gov (United States)

    Henderson, Brenda S.; Wernet, Mark P.

    2012-01-01

    Results from acoustic and Particle Image Velocimetry (PIV) measurements are presented for single and dual-stream jets with fluidic injection on the core stream. The fluidic injection nozzles delivered air to the jet through slots on the interior of the nozzle at the nozzle trailing edge. The investigations include subsonic and supersonic jet conditions. Reductions in broadband shock noise and low frequency mixing noise were obtained with the introduction of fluidic injection on single stream jets. Fluidic injection was found to eliminate shock cells, increase jet mixing, and reduce turbulent kinetic energy levels near the end of the potential core. For dual-stream subsonic jets, the introduction of fluidic injection reduced low frequency noise in the peak jet noise direction and enhanced jet mixing. For dual-stream jets with supersonic fan streams and subsonic core streams, the introduction of fluidic injection in the core stream impacted the jet shock cell structure but had little effect on mixing between the core and fan streams.

  4. Prediction and Reduction of Aerodynamic Noise of the Multiblade Centrifugal Fan

    Directory of Open Access Journals (Sweden)

    Shuiqing Zhou

    2014-08-01

    Full Text Available An aerodynamic and aeroacoustic investigation of the multiblade centrifugal fan is proposed in this paper, and a hybrid technique of combining flow field calculation and acoustic analysis is applied to solve the aeroacoustic problem of multiblade centrifugal fan. The unsteady flow field of the multiblade centrifugal fan is predicted by solving the incompressible Reynolds-averaged Navier-Stokes (RANS equations with conventional computing techniques for fluid dynamics. The principal noise source induced is extracted from the calculation of the flow field by using acoustic principles, and the modeled sources on inner and outer surfaces of the volute are calculated with multiregional boundary element method (BEM. Through qualitative analysis, the sound pressure amplitude distribution of the multiblade centrifugal fan in near field is given and the sound pressure level (SPL spectrum diagram of monitoring points in far field is obtained. Based on the analysis results, the volute tongue structure is adjusted and then a low-noise design for the centrifugal fan is proposed. The comparison of noise tests shows the noise reduction of improved fan model is more obvious, which is in good agreement with the prediction using the hybrid techniques.

  5. Numerical simulation of tandem-cylinder noise-reduction using plasma-based flow control

    Science.gov (United States)

    Wang, Meng; Eltaweel, Ahmed; Thomas, Flint; Kozlov, Alexey; Kim, Dongjoo

    2011-11-01

    The noise of low-Mach-number flow over tandem cylinders at ReD = 22 , 000 and its reduction using plasma actuators are simulated numerically to confirm and extend earlier experimental results. The numerical approach is based on large-eddy simulation for the turbulent flow field, a semi-empirical plasma actuation model, and Lighthill's theory for acoustic calculation. Excellent agreement between LES and experimental results is obtained for both the baseline flow and flow with plasma control in terms of wake velocity profiles, turbulence intensity, and frequency spectra of pressure fluctuations on the downstream cylinder. The validated flow-field results allow an accurate acoustic analysis based on Lighthill's equation, which is solved using a boundary-element method. The effectiveness of plasma actuators for reducing noise is demonstrated. In the baseline flow, the acoustic field is dominated by the interaction of the downstream cylinder with the upstream wake. With flow control the interaction noise is reduced drastically through suppression of vortex shedding from the upstream cylinder, and the vortex-shedding noise from the downstream cylinder becomes dominant. The peak sound pressure level is reduced by approximately 15 dB. Supported by NASA Cooperative Agreement NNX07AO09A.

  6. Improved Kalman Filter Method for Measurement Noise Reduction in Multi Sensor RFID Systems

    Directory of Open Access Journals (Sweden)

    Min Chul Kim

    2011-10-01

    Full Text Available Recently, the range of available Radio Frequency Identification (RFID tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various sensors. In the multi-sensing environment, some noisy signals are obtained because of the changing surroundings. We propose in this paper an improved Kalman filter method to reduce noise and obtain correct data. Performance of Kalman filter is determined by a measurement and system noise covariance which are usually called the R and Q variables in the Kalman filter algorithm. Choosing a correct R and Q variable is one of the most important design factors for better performance of the Kalman filter. For this reason, we proposed an improved Kalman filter to advance an ability of noise reduction of the Kalman filter. The measurement noise covariance was only considered because the system architecture is simple and can be adjusted by the neural network. With this method, more accurate data can be obtained with smart RFID tags. In a simulation the proposed improved Kalman filter has 40.1%, 60.4% and 87.5% less Mean Squared Error (MSE than the conventional Kalman filter method for a temperature sensor, humidity sensor and oxygen sensor, respectively. The performance of the proposed method was also verified with some experiments.

  7. Application of Vibrational Power Flow to a Passenger Car for Reduction of Interior Noise

    Directory of Open Access Journals (Sweden)

    S.K. Lee

    2000-01-01

    Full Text Available Reduction of structure-borne noise in the compartment of a car is an important task in automotive engineering. Transfer path analysis using the vibroacoustic reciprocity technique or multiple path decomposition method has generally been used for structure-borne noise path analysis. These methods are useful for solving a particular problem, but they do not quantify the effectiveness of vibration isolation of each isolator of a vehicle. To quantify the effectiveness of vibration isolation, vibrational power flow has been used for a simple isolation system or a laboratory-based isolation system. It is often difficult to apply the vibrational power flow technique to a complex isolation system like a car. In this paper, a simple equation is derived for calculation of the vibrational power flow of an isolation system with multiple isolators such as a car. It is successfully applied not only to quantifying the relative contributions of eighteen isolators, but also to reducing the structure-borne noise of a passenger car. According to the results, the main contributor of the eighteen isolators is the rear roll mount of an engine. The reduced structure-borne noise level is about 5dBA.

  8. Improved Kalman filter method for measurement noise reduction in multi sensor RFID systems.

    Science.gov (United States)

    Eom, Ki Hwan; Lee, Seung Joon; Kyung, Yeo Sun; Lee, Chang Won; Kim, Min Chul; Jung, Kyung Kwon

    2011-01-01

    Recently, the range of available radio frequency identification (RFID) tags has been widened to include smart RFID tags which can monitor their varying surroundings. One of the most important factors for better performance of smart RFID system is accurate measurement from various sensors. In the multi-sensing environment, some noisy signals are obtained because of the changing surroundings. We propose in this paper an improved Kalman filter method to reduce noise and obtain correct data. Performance of Kalman filter is determined by a measurement and system noise covariance which are usually called the R and Q variables in the Kalman filter algorithm. Choosing a correct R and Q variable is one of the most important design factors for better performance of the Kalman filter. For this reason, we proposed an improved Kalman filter to advance an ability of noise reduction of the Kalman filter. The measurement noise covariance was only considered because the system architecture is simple and can be adjusted by the neural network. With this method, more accurate data can be obtained with smart RFID tags. In a simulation the proposed improved Kalman filter has 40.1%, 60.4% and 87.5% less mean squared error (MSE) than the conventional Kalman filter method for a temperature sensor, humidity sensor and oxygen sensor, respectively. The performance of the proposed method was also verified with some experiments.

  9. 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.

  10. Vortex shedding noise reduction by single dielectric barrier discharge plasma actuators

    OpenAIRE

    Al-Sadawi, L; Chong, TP

    2016-01-01

    An experimental study of active control of vortex shedding narrow band tonal noise from both blunt and rounded trailing edge of a profiled body at zero incidences was performed using Single Dielectric Barrier plasma actuators (DBD). Acoustics and flow measurements were carried out in an open jet, aerocoustic wind tunnel at Reynolds numbers ranging from 7x104 to 4x105. The noise results were obtained using single microphone, while both PIV and hot-wire were used for flow measurement in order t...

  11. A bulk-controlled ring-VCO with 1/f-noise reduction for frequency ΔΣ modulator

    DEFF Research Database (Denmark)

    Tuan Vu, CAO; Wisland, Dag T.; Lande, Tor Sverre

    The paper introduces a bulk-controlled ring-VCO with a tail transistor utilizing flicker-noise (1/f-noise) reduction techniques for a frequency-based DeltaSigma modulator (FDSM). This VCO converts an analog input voltage to phase information under various bias conditions ranging from sub...

  12. 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.

  13. Noise reduction in acoustic measurements with a particle velocity sensor by means of a cross-correlation technique

    NARCIS (Netherlands)

    Honschoten, van J.W.; Druyvesteyn, W.F.; Kuipers, H.; Raangs, R.; Krijnen, G.J.M.

    2004-01-01

    In this paper a method is presented to reduce the noise level of a particle velocity sensor, a thermal two-wire sensor sensitive to acoustic particle velocities, which yields a reduction of the noise of 30 dB. The method is based on utilisation of cross- instead of auto-correlation spectra of two of

  14. Reward Pays the Cost of Noise Reduction in Motor and Cognitive Control

    Science.gov (United States)

    Manohar, Sanjay G.; Chong, Trevor T.-J.; Apps, Matthew A.J.; Batla, Amit; Stamelou, Maria; Jarman, Paul R.; Bhatia, Kailash P.; Husain, Masud

    2015-01-01

    Summary Speed-accuracy trade-off is an intensively studied law governing almost all behavioral tasks across species. Here we show that motivation by reward breaks this law, by simultaneously invigorating movement and improving response precision. We devised a model to explain this paradoxical effect of reward by considering a new factor: the cost of control. Exerting control to improve response precision might itself come at a cost—a cost to attenuate a proportion of intrinsic neural noise. Applying a noise-reduction cost to optimal motor control predicted that reward can increase both velocity and accuracy. Similarly, application to decision-making predicted that reward reduces reaction times and errors in cognitive control. We used a novel saccadic distraction task to quantify the speed and accuracy of both movements and decisions under varying reward. Both faster speeds and smaller errors were observed with higher incentives, with the results best fitted by a model including a precision cost. Recent theories consider dopamine to be a key neuromodulator in mediating motivational effects of reward. We therefore examined how Parkinson’s disease (PD), a condition associated with dopamine depletion, alters the effects of reward. Individuals with PD showed reduced reward sensitivity in their speed and accuracy, consistent in our model with higher noise-control costs. Including a cost of control over noise explains how reward may allow apparent performance limits to be surpassed. On this view, the pattern of reduced reward sensitivity in PD patients can specifically be accounted for by a higher cost for controlling noise. PMID:26096975

  15. Usefulness of acoustic noise reduction in brain MRI using Quiet-T{sub 2}-

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Se Jy [Dept. of Medical science Graduate school, Chonnam National University, Gwangju (Korea, Republic of); Kim, Young Keun [Dept. of Radiotechnology, Gwangju Health university, Gwangju (Korea, Republic of)

    2016-03-15

    Acoustic noise during magnetic resonance imaging (MRI) is the main source for patient discomfort. we report our preliminary experience with this technique in neuroimaging with regard to subjective and objective noise levels and image quality. 60 patients(29 males, 31 females, average age of 60.1) underwent routine brain MRI with 3.0 Tesla (MAGNETOM Tim Trio; Siemens, Germany) system and 12-channel head coil. Q-T{sub 2} and T{sub 2} sequence were performed. Measurement of sound pressure levels (SPL) and heart rate on Q-T{sub 2} and T{sub 2} was performed respectively. Quantitative analysis was carried out by measuring the SNR, CNR, and SIR values of Q-T{sub 2}, T{sub 2} and a statistical analysis was performed using independent sample T-test. Qualitative analysis was evaluated by the eyes for the overall quality image of Q-T{sub 2} and T{sub 2}. A 5-point evaluation scale was used, including excellent(5), good(4), fair(3), poor(2), and unacceptable(1). The average noise and peak noise decreased by 15dBA and 10dBA on T2 and Q-T2 test. Also, the average value of heartbeat rate was lower in Q-T2 for 120 seconds in each test, but there was no statistical significance. The quantitative analysis showed that there was no significant difference between CNR and SIR, and there was a significant difference (p<0.05) as SNR had a lower average value on Q-T{sub 2}. According to the qualitative analysis, the overall quality image of 59 case T{sub 2} and Q-T{sub 2} was evaluated as excellent at 5 points, and 1 case was evaluated as good at 4 points due to a motion artifact. Q-T{sub 2} is a promising technique for acoustic noise reduction and improved patient comfort.

  16. Reduction of air pollution levels downwind of a road with an upwind noise barrier

    Science.gov (United States)

    Enayati Ahangar, Faraz; Heist, David; Perry, Steven; Venkatram, Akula

    2017-04-01

    We propose a dispersion model to estimate the impact of a solid noise barrier upwind of a highway on air pollution concentrations downwind of the road. The model, based on data from wind tunnel experiments conducted by Heist et al. (2009), assumes that the upwind barrier has two main effects: 1) it creates a recirculation zone behind the barrier that sweeps the emissions from the highway back towards the wall, and 2) it enhances vertical dispersion and initial mixing. By combining the upwind barrier model with the mixed wake model for a downwind barrier described in Schulte et al. (2014), we are able to model dispersion of emissions from a highway with noise barriers on both sides. The model provides a good description of measurements made in the wind tunnel. The presence of an upwind barrier causes reductions in concentrations relative to those measured downwind of a road with no barriers. The reduction can be as large as that caused by a downwind barrier if the recirculation zone covers the width of the highway. Barriers on both sides of the highway result in larger reductions downwind of the barriers than those caused by a single barrier either upwind or downwind. As expected, barrier effects are small beyond 10 barrier heights downwind of the highway. We also propose a tentative model to estimate on-road concentrations within the recirculation zone induced by the upwind barrier.

  17. Study of performance of acoustic fixture for using in noise reduction rate tests of hearing protection devices

    Directory of Open Access Journals (Sweden)

    zam Biabani

    2016-06-01

    Full Text Available Introduction:One of the recommended methods for evaluation effectiveness of hearing protection is use the acoustic fixture accordance with standard ISO 4869-3. The aim of this study was evaluate the acoustic performance of fixture for using in noise reduction rate tests of hearing protection devices in the laboratory. Methods: In this cross-sectional study , noise reduction rates of five common ear muffs used in the Iran industries were investigated based on the ISO 11904 standard, microphone in real ear method, using noise dosimeter (SVANTEK , Model SV102 equipped with microphone SV25 model which can install inside the ear on 30 subjects under laboratory conditions. Also, noise reduction rate of earmuffs was determined using the fixture model AVASINA9402 accordance with standard procedures. Data were analyzed using the software SPSS21. Results: The results showed the real noise reduction rates of the earmuffs on the studied subjects are from 59% to 94% nominal reduction rates. That rates for the ear muffs on the studied fixture are from 64% to 92.The results showed that the noise reduction rates of the ear muffs on subjects compared with and noise reduction rates of the ear muffs on fixture were not statistically significant (p> 0.05. Conclusion: The results showed the accuracy of noise reduction rate of earmuffs using the fixture compared with real subjects is acceptable. Hence, the fixture is good choice for environments where there’s no possibility of acoustic evaluation on real subjects, also for quality control of productions in the earmuff manufacturers.

  18. Effect of compression, digital noise reduction and directionality on envelope difference index, log-likelihood ratio and perceived quality

    Directory of Open Access Journals (Sweden)

    Chinnaraj Geetha

    2014-03-01

    Full Text Available The aim of the present study was to evaluate the use of the envelope difference index (EDI and log-likelihood ratio (LLR to quantify the independent and interactive effects of wide dynamic range compression, digital noise reduction and directionality, and to carry out selfrated quality measures. A recorded sentence embedded in speech spectrum noise at +5 dB signal to noise ratio was presented to a four channel digital hearing aid and the output was recorded with different combinations of algorithms at 30, 45 and 70 dB HL levels of presentation through a 2 cc coupler. EDI and LLR were obtained in comparison with the original signal using MATLAB software. In addition, thirty participants with normal hearing sensitivity rated the output on the loudness and clarity parameters of quality. The results revealed that the temporal changes happening at the output is independent of the number of algorithms activated together in a hearing aid. However, at a higher level of presentation, temporal cues are better preserved if all of these algorithms are deactivated. The spectral components speech tend to get affected by the presentation level. The results also indicate the importance of quality rating as this helps in considering whether the spectral and/or temporal deviations created in the hearing aid are desirable or not.

  19. DFT-Domain Based Single-Microphone Noise Reduction for Speech Enhancement

    DEFF Research Database (Denmark)

    C. Hendriks, Richard; Gerkmann, Timo; Jensen, Jesper

    for speech enhancement comprises a history of more than 30 years of research. In this survey, we wish to demonstrate the significant advances that have been made during the last decade in the field of discrete Fourier transform domain-based single-channel noise reduction for speech enhancement.......Furthermore, our goal is to provide a concise description of a state-of-the-art speech enhancement system, and demonstrate the relative importance of the various building blocks of such a system. This allows the non-expert DSP practitioner to judge the relevance of each building block and to implement a close...

  20. Region-based active contour with noise and shape priors

    CERN Document Server

    Lecellier, François; Fadili, Jalal; Aubert, Gilles; Revenu, Marinette; Saloux, Eric

    2008-01-01

    In this paper, we propose to combine formally noise and shape priors in region-based active contours. On the one hand, we use the general framework of exponential family as a prior model for noise. On the other hand, translation and scale invariant Legendre moments are considered to incorporate the shape prior (e.g. fidelity to a reference shape). The combination of the two prior terms in the active contour functional yields the final evolution equation whose evolution speed is rigorously derived using shape derivative tools. Experimental results on both synthetic images and real life cardiac echography data clearly demonstrate the robustness to initialization and noise, flexibility and large potential applicability of our segmentation algorithm.

  1. Reduction of Helicopter BVI Noise, Vibration, and Power Consumption Through Individual Blade Control

    Science.gov (United States)

    Jacklin, Stephen A.; Blaas, Achim; Teves, Dietrich; Kube, Roland; Warmbrodt, William (Technical Monitor)

    1994-01-01

    A wind tunnel test was conducted with a full-scale BO 105 helicopter rotor to evaluate the potential of open-loop individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The wind tunnel test was an international collaborative effort between NASA/U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the German Aerospace Laboratory (DLR) and was conducted under the auspices of the U.S./German MOU on Rotorcraft Aeromechanics. In this test the normal blade pitch links of the rotor were replaced by servo-actuators so that the pitch of each blade could be controlled independently of the other blades. The specially designed servoactuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. The wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center. An extensive amount of measurement information was acquired for each IBC data point. These data include rotor performance, static and dynamic hub forces and moments, rotor loads, control loads, inboard and outboard blade pitch motion, and BVI noise data. The data indicated very significant (80 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic input at the critical descent (terminal approach) condition. The data also showed that performance improvements of up to 7 percent could be obtained using 2P input at high-speed forward flight conditions.

  2. Cogging Torque and Acoustic Noise Reduction in High Torque BLDC Motors by Teeth Pairings

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Min [Halla Climate Control Co. (Korea, Republic of); Hwang, Sang Moon [Pusan National University (Korea, Republic of)

    1999-03-01

    This paper investigates reduction of acoustic noise and cogging torque in a BLDC motor with larger stator slot open width. Using energy method, cogging torque is analytically determined with airgap MMF function and airgap permeance function and confirmed by FEM analysis. It show that the cogging torque is firstly governed by N{sub L} G{sub NL} B{sub NL} with the fundamental period of N{sub L}, where N{sub L} is the least common multiple of the number of slots and the number of poles, G{sub NL}, airgap permeance function and B{sub NL}, airgap MMF function. It also shows that there exist several tooth width which minimizes the cogging torque, for the motors that smaller slot open width or stator teeth notching is not available. And it proposes a teeth pairing with two different tooth width which can effectively eliminate the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1 dB. (author). 9 refs., 13 figs., 1 tab.

  3. Computational analysis of noise reduction devices in axial fans with stabilized finite element formulations

    Science.gov (United States)

    Corsini, A.; Rispoli, F.; Sheard, A. G.; Tezduyar, T. E.

    2012-12-01

    The paper illustrates how a computational fluid mechanic technique, based on stabilized finite element formulations, can be used in analysis of noise reduction devices in axial fans. Among the noise control alternatives, the study focuses on the use of end-plates fitted at the blade tips to control the leakage flow and the related aeroacoustic sources. The end-plate shape is configured to govern the momentum transfer to the swirling flow at the blade tip. This flow control mechanism has been found to have a positive link to the fan aeroacoustics. The complex physics of the swirling flow at the tip, developing under the influence of the end-plate, is governed by the rolling up of the jet-like leakage flow. The RANS modelling used in the computations is based on the streamline-upwind/Petrov-Galerkin and pressure-stabilizing/Petrov-Galerkin methods, supplemented with the DRDJ stabilization. Judicious determination of the stabilization parameters involved is also a part of our computational technique and is described for each component of the stabilized formulation. We describe the flow physics underlying the design of the noise control device and illustrate the aerodynamic performance. Then we investigate the numerical performance of the formulation by analysing the inner workings of the stabilization operators and of their interaction with the turbulence model.

  4. Reduction of Helicopter BVI Noise, Vibration, and Power Consumption Through Individual Blade Control

    Science.gov (United States)

    Jacklin, Stephen A.; Blaas, Achim; Teves, Dietrich; Kube, Roland; Warmbrodt, William (Technical Monitor)

    1994-01-01

    A wind tunnel test was conducted with a full-scale BO 105 helicopter rotor to evaluate the potential of open-loop individual blade control (IBC) to improve rotor performance, to reduce blade vortex interaction (BVI) noise, and to alleviate helicopter vibrations. The wind tunnel test was an international collaborative effort between NASA/U.S. Army AFDD, ZF Luftfahrttechnik, Eurocopter Deutschland, and the German Aerospace Laboratory (DLR) and was conducted under the auspices of the U.S./German MOU on Rotorcraft Aeromechanics. In this test the normal blade pitch links of the rotor were replaced by servo-actuators so that the pitch of each blade could be controlled independently of the other blades. The specially designed servoactuators and IBC control system were designed and manufactured by ZF Luftfahrttechnik, GmbH. The wind tunnel test was conducted in the 40- by 80-Foot Wind Tunnel at the NASA Ames Research Center. An extensive amount of measurement information was acquired for each IBC data point. These data include rotor performance, static and dynamic hub forces and moments, rotor loads, control loads, inboard and outboard blade pitch motion, and BVI noise data. The data indicated very significant (80 percent) simultaneous reductions in both BVI noise and hub vibrations could be obtained using multi-harmonic input at the critical descent (terminal approach) condition. The data also showed that performance improvements of up to 7 percent could be obtained using 2P input at high-speed forward flight conditions.

  5. Random resampling masks: a non-Bayesian one-shot strategy for noise reduction in digital holography.

    Science.gov (United States)

    Bianco, V; Paturzo, M; Memmolo, P; Finizio, A; Ferraro, P; Javidi, B

    2013-03-01

    Holographic imaging may become severely degraded by a mixture of speckle and incoherent additive noise. Bayesian approaches reduce the incoherent noise, but prior information is needed on the noise statistics. With no prior knowledge, one-shot reduction of noise is a highly desirable goal, as the recording process is simplified and made faster. Indeed, neither multiple acquisitions nor a complex setup are needed. So far, this result has been achieved at the cost of a deterministic resolution loss. Here we propose a fast non-Bayesian denoising method that avoids this trade-off by means of a numerical synthesis of a moving diffuser. In this way, only one single hologram is required as multiple uncorrelated reconstructions are provided by random complementary resampling masks. Experiments show a significant incoherent noise reduction, close to the theoretical improvement bound, resulting in image-contrast improvement. At the same time, we preserve the resolution of the unprocessed image.

  6. Reduction of Static Power with Minimized Ground Bounce Noise Using Sleep Signal Slew Rate Modulation In 45nm Technology

    Directory of Open Access Journals (Sweden)

    M. Naga Pramod Reddy

    2014-06-01

    Full Text Available In MTCMOS Integrated Circuit design there exists a significant trade-off between static power consumption and technology scaling. In Modern circuits increase in power dissipation is significant due to combination of higher clock speeds, greater functional integration and smaller process geometries resulting in dominant static power consumption component. This is a big challenge for the circuit designer. However, the designers do have few methods like sleep transistor approach, sleepy stack approach to reduce this static power consumption. However all of these methods do have their own drawbacks. In order to achieve lower static power consumptions one has to sacrifice area and circuit performance metrics. In this paper we propose a new enhancement to available static power reduction techniques by modulating the sleep signal slew rate. We have designed the basic CMOS circuits in MTCMOS to achieve significant reduction in Static power consumption. For Sleep signal slew rate modulation we have proposed a modulator called triple phase sleep signal slew rate modulator. By using this Triple Phase Sleep signal modulator(TPS we can control the noise at ground distribution network (ground bounce noise produced during sleep to active state transition. By using TPS we can decrease the reactivation time to a recognizable extent, along with reduced power (static and dynamic dissipation.

  7. First Test of Fan Active Noise Control (ANC) Completed

    Science.gov (United States)

    2005-01-01

    With the advent of ultrahigh-bypass engines, the space available for passive acoustic treatment is becoming more limited, whereas noise regulations are becoming more stringent. Active noise control (ANC) holds promise as a solution to this problem. It uses secondary (added) noise sources to reduce or eliminate the offending noise radiation. The first active noise control test on the low-speed fan test bed was a General Electric Company system designed to control either the exhaust or inlet fan tone. This system consists of a "ring source," an induct array of error microphones, and a control computer. Fan tone noise propagates in a duct in the form of spinning waves. These waves are detected by the microphone array, and the computer identifies their spinning structure. The computer then controls the "ring source" to generate waves that have the same spinning structure and amplitude, but 180 out of phase with the fan noise. This computer generated tone cancels the fan tone before it radiates from the duct and is heard in the far field. The "ring source" used in these tests is a cylindrical array of 16 flat-plate acoustic radiators that are driven by thin piezoceramic sheets bonded to their back surfaces. The resulting source can produce spinning waves up to mode 7 at levels high enough to cancel the fan tone. The control software is flexible enough to work on spinning mode orders from -6 to 6. In this test, the fan was configured to produce a tone of order 6. The complete modal (spinning and radial) structure of the tones was measured with two builtin sets of rotating microphone rakes. These rakes provide a measurement of the system performance independent from the control system error microphones. In addition, the far-field noise was measured with a semicircular array of 28 microphones. This test represents the first in a series of tests that demonstrate different active noise control concepts, each on a progressively more complicated modal structure. The tests are

  8. Prediction and reduction of internal blade-passing frequency noise of the centrifugal fan in a refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seungyub; Heo, Seung; Cheong, Cheolung [School of Mechanical Engineering, Pusan National University, 30, Jangjeon-dong, Geumjeong-gu, Pusan 609-735 (Korea)

    2010-09-15

    The internal blade-passing frequency (BPF) noise of a centrifugal fan in a household refrigerator is computed using a hybrid method. The unsteady flow field of the centrifugal fan in a duct is predicted by solving the incompressible Reynolds-averaged Navier-Stokes equations with conventional computational fluid dynamics techniques. The principal sources of noise are then extracted from the predicted flow field through the acoustic analogy. Finally, the internal BPF noise is predicted using the modeled sources in combination with the boundary element method. A parametric study using this hybrid technique shows that the BPF noise levels predicted for various non-dimensional cutoff distances closely follow the experimental data. Based on this result, a low-noise design for the centrifugal fan is proposed. A BPF noise reduction of approximately 3 dB is achieved in comparison with the original model, which is in good agreement with the prediction using the hybrid techniques. (author)

  9. Investigating Differences in Preferred Noise Reduction Strength Among Hearing Aid Users

    Directory of Open Access Journals (Sweden)

    Tobias Neher

    2016-06-01

    Full Text Available Even though hearing aid (HA users can respond very differently to noise reduction (NR processing, knowledge about possible drivers of this variability (and thus ways of addressing it in HA fittings is sparse. The current study investigated differences in preferred NR strength among HA users. Participants were groups of experienced users with clear preferences (“NR lovers”; N = 14 or dislikes (“NR haters”; N = 13 for strong NR processing, as determined in two earlier studies. Maximally acceptable background noise levels, detection thresholds for speech distortions caused by NR processing, and self-reported “sound personality” traits were considered as candidate measures for explaining group membership. Participants also adjusted the strength of the (binaural coherence-based NR algorithm to their preferred level. Consistent with previous findings, NR lovers favored stronger processing than NR haters, although there also was some overlap. While maximally acceptable noise levels and detection thresholds for speech distortions tended to be higher for NR lovers than for NR haters, group differences were only marginally significant. No clear group differences were observed in the self-report data. Taken together, these results indicate that preferred NR strength is an individual trait that is fairly stable across time and that is not easily captured by psychoacoustic, audiological, or self-report measures aimed at indexing susceptibility to background noise and processing artifacts. To achieve more personalized NR processing, an effective approach may be to let HA users determine the optimal setting themselves during the fitting process.

  10. Investigating Differences in Preferred Noise Reduction Strength Among Hearing Aid Users

    Science.gov (United States)

    Wagener, Kirsten C.

    2016-01-01

    Even though hearing aid (HA) users can respond very differently to noise reduction (NR) processing, knowledge about possible drivers of this variability (and thus ways of addressing it in HA fittings) is sparse. The current study investigated differences in preferred NR strength among HA users. Participants were groups of experienced users with clear preferences (“NR lovers”; N = 14) or dislikes (“NR haters”; N = 13) for strong NR processing, as determined in two earlier studies. Maximally acceptable background noise levels, detection thresholds for speech distortions caused by NR processing, and self-reported “sound personality” traits were considered as candidate measures for explaining group membership. Participants also adjusted the strength of the (binaural coherence-based) NR algorithm to their preferred level. Consistent with previous findings, NR lovers favored stronger processing than NR haters, although there also was some overlap. While maximally acceptable noise levels and detection thresholds for speech distortions tended to be higher for NR lovers than for NR haters, group differences were only marginally significant. No clear group differences were observed in the self-report data. Taken together, these results indicate that preferred NR strength is an individual trait that is fairly stable across time and that is not easily captured by psychoacoustic, audiological, or self-report measures aimed at indexing susceptibility to background noise and processing artifacts. To achieve more personalized NR processing, an effective approach may be to let HA users determine the optimal setting themselves during the fitting process. PMID:27604781

  11. Thermal Noise Reduction and Absorption Optimisation via Multi-Material Coatings

    CERN Document Server

    Steinlechner, Jessica; Hough, Jim; Krueger, Christoph; Rowan, Sheila; Schnabel, Roman

    2014-01-01

    Future gravitational wave detectors (GWDs) such as Advanced LIGO upgrades and the Einstein Telescope are planned to operate at cryogenic temperatures using crystalline silicon (cSi) test-mass mirrors at an operation wavelength of 1550 nm. The reduction in temperature in principle provides a direct reduction in coating thermal noise, but the presently used coating stacks which are composed of silica (SiO2) and tantala (Ta2O5) show cryogenic loss peaks which results in less thermal noise improvement than might be expected. Due to low mechanical loss at low temperature amorphous silicon (aSi) is a very promising candidate material for dielectric mirror coatings and could replace Ta2O5. Unfortunately, such a aSi/SiO2 coating is not suitable for use in GWDs due to high optical absorption in aSi coatings. We explore the use of a three material based coating stack. In this multi-material design the low absorbing Ta2O5 in the outermost coating layers significantly reduces the incident light power, while aSi is used o...

  12. Boeing's variable geometry chevron: morphing aerospace structures for jet noise reduction

    Science.gov (United States)

    Calkins, Frederick T.; Mabe, James H.; Butler, George W.

    2006-03-01

    Boeing is applying cutting edge smart material actuators to the next generation morphing technologies for aircraft. This effort has led to the Variable Geometry Chevrons (VGC), which utilize compact, light weight, and robust shape memory alloy (SMA) actuators. These actuators morph the shape of chevrons on the trailing edge of a jet engine in order to optimize acoustic and performance objectives at multiple flight conditions. We have demonstrated a technical readiness level of 7 by successfully flight testing the VGCs on a Boeing 777-300ER with GE-115B engines. In this paper we describe the VGC design, development and performance during flight test. Autonomous operation of the VGCs, which did not require a control system or aircraft power, was demonstrated. A parametric study was conducted showing the influence of VGC configurations on shockcell generated cabin noise reduction during cruise. The VGC system provided a robust test vehicle to explore chevron configurations for community and shockcell noise reduction. Most importantly, the VGC concept demonstrated an exciting capability to optimize jet nozzle performance at multiple flight conditions.

  13. The correlation study of parallel feature extractor and noise reduction approaches

    Energy Technology Data Exchange (ETDEWEB)

    Dewi, Deshinta Arrova; Sundararajan, Elankovan; Prabuwono, Anton Satria [Industrial Computing Research Group, Centre for Artificial Intelligence Technology, Universiti Kebangsaan Malaysia, 43600 Bangi (Malaysia)

    2015-05-15

    This paper presents literature reviews that show variety of techniques to develop parallel feature extractor and finding its correlation with noise reduction approaches for low light intensity images. Low light intensity images are normally displayed as darker images and low contrast. Without proper handling techniques, those images regularly become evidences of misperception of objects and textures, the incapability to section them. The visual illusions regularly clues to disorientation, user fatigue, poor detection and classification performance of humans and computer algorithms. Noise reduction approaches (NR) therefore is an essential step for other image processing steps such as edge detection, image segmentation, image compression, etc. Parallel Feature Extractor (PFE) meant to capture visual contents of images involves partitioning images into segments, detecting image overlaps if any, and controlling distributed and redistributed segments to extract the features. Working on low light intensity images make the PFE face challenges and closely depend on the quality of its pre-processing steps. Some papers have suggested many well established NR as well as PFE strategies however only few resources have suggested or mentioned the correlation between them. This paper reviews best approaches of the NR and the PFE with detailed explanation on the suggested correlation. This finding may suggest relevant strategies of the PFE development. With the help of knowledge based reasoning, computational approaches and algorithms, we present the correlation study between the NR and the PFE that can be useful for the development and enhancement of other existing PFE.

  14. Active control of vibrations and noise by electrorheological fluids and piezoelectric materials

    Science.gov (United States)

    Amorosi, Joseph J.

    The combination of electrorheological (ER) fluids and piezoelectric actuators into one actively controlled intelligent sandwich plate structure for either noise or vibration control is investigated in this study. The simply supported sandwich plate consists of a core of four cavities filled with ER fluid, two elastic outer face plates, bottom plate cross stiffeners and symmetrically bonded surface piezoceramic (PZT) actuator patches. Analytical and computational simulations are performed to obtain the resultant structural response to random inputs, noise transmission into a rectangular enclosure, and sound radiation into a semi-infinite acoustic half space. An equivalent, homogeneous plate model is used in the modal decomposition of the derived governing equations of motion. This equivalency is obtained by taking the modal frequencies and mode shapes, calculated by the finite element method, to be that of the sandwich plate. The effect of actively controlling the ER fluid's stiffness material properties is incorporated into the modal frequencies and mode shapes by altering the sandwich plate's core shear and elastic moduli whereas ER fluid controllable damping is directly incorporated into the governing equations of motion as equivalent modal damping. The effect of the PZT actuators is incorporated into the governing equations of motion through direct velocity feedback utilizing collocated control. A two part control strategy is developed. First, the appropriate ER fluid voltage potential and then the PZT actuator gains are selected. Numerical results obtained in this study indicate that using ER and PZT active control up to 50 dB of noise reduction is possible at certain frequency ranges. In addition, about 15 dB reduction of the overall radiated sound pressure level can be obtained. However, for the available ER and PZT materials, the reduction of overall sound pressure to random input is shown to be on the order of 5 to 8 decibels. To improve on noise

  15. 变电站噪声特性及降噪控制措施%Control Measures on Substation Noise Characteristics and Noise Reduction Technology

    Institute of Scientific and Technical Information of China (English)

    邵宇鹰; 张思平

    2014-01-01

    目前变电站噪声对周边环境的影响愈发明显,并已成为亟待解决的环境问题。通过对厦门站噪声特性的测试分析,确定了噪声的主要传播途径,通过针对性降噪措施的实施,利用开发的声全息技术可以快速准确地识别配电站、变配电设备的噪声源。通过对噪声源及传播路径的改善,可有效降低变配电设备的噪声量级。%Current transformer noise influences on surrounding environment more and more obvious,and has become a pressing environmental problems.Determined by the test and analysis the characteristics of the xia-men station noise,noise is the main route of transmission,and introduces a series of corresponding noise re-duction measures.Noise sources can be quickly and accurately identified to the distribution station and power distribution equipments.using acoustic holography technology.The improvement of noise source and propaga-tion path can effectively reduce the noise level variable power distribution equipment.

  16. Effect of Two Advanced Noise Reduction Technologies on the Aerodynamic Performance of an Ultra High Bypass Ratio Fan

    Science.gov (United States)

    Hughes, Christoper E.; Gazzaniga, John A.

    2013-01-01

    A wind tunnel experiment was conducted in the NASA Glenn Research Center anechoic 9- by 15-Foot Low-Speed Wind Tunnel to investigate two new advanced noise reduction technologies in support of the NASA Fundamental Aeronautics Program Subsonic Fixed Wing Project. The goal of the experiment was to demonstrate the noise reduction potential and effect on fan model performance of the two noise reduction technologies in a scale model Ultra-High Bypass turbofan at simulated takeoff and approach aircraft flight speeds. The two novel noise reduction technologies are called Over-the-Rotor acoustic treatment and Soft Vanes. Both technologies were aimed at modifying the local noise source mechanisms of the fan tip vortex/fan case interaction and the rotor wake-stator interaction. For the Over-the-Rotor acoustic treatment, two noise reduction configurations were investigated. The results showed that the two noise reduction technologies, Over-the-Rotor and Soft Vanes, were able to reduce the noise level of the fan model, but the Over-the-Rotor configurations had a significant negative impact on the fan aerodynamic performance; the loss in fan aerodynamic efficiency was between 2.75 to 8.75 percent, depending on configuration, compared to the conventional solid baseline fan case rubstrip also tested. Performance results with the Soft Vanes showed that there was no measurable change in the corrected fan thrust and a 1.8 percent loss in corrected stator vane thrust, which resulted in a total net thrust loss of approximately 0.5 percent compared with the baseline reference stator vane set.

  17. Speech quality evaluation of a sparse coding shrinkage noise reduction algorithm with normal hearing and hearing impaired listeners.

    Science.gov (United States)

    Sang, Jinqiu; Hu, Hongmei; Zheng, Chengshi; Li, Guoping; Lutman, Mark E; Bleeck, Stefan

    2015-09-01

    Although there are numerous papers describing single-channel noise reduction strategies to improve speech perception in a noisy environment, few studies have comprehensively evaluated the effects of noise reduction algorithms on speech quality for hearing impaired (HI). A model-based sparse coding shrinkage (SCS) algorithm has been developed, and has shown previously (Sang et al., 2014) that it is as competitive as a state-of-the-art Wiener filter approach in speech intelligibility. Here, the analysis is extended to include subjective quality ratings and a method called Interpolated Paired Comparison Rating (IPCR) is adopted to quantitatively link the benefit of speech intelligibility and speech quality. The subjective quality tests are performed through IPCR to efficiently quantify noise reduction effects on speech quality. Objective measures including frequency-weighted segmental signal-to-noise ratio (fwsegSNR), perceptual evaluation of speech quality (PESQ) and hearing aid speech quality index (HASQI) are adopted to predict the noise reduction effects. Results show little difference in speech quality between the SCS and the Wiener filter algorithm but a difference in quality rating between the HI and NH listeners. HI listeners generally gave better quality ratings of noise reduction algorithms than NH listeners. However, SCS reduced the noise more efficiently at the cost of higher distortions that were detected by NH but not by the HI. SCS is a promising candidate for noise reduction algorithms for HI. In general, care needs to be taken when adopting algorithms that were originally developed for NH participants into hearing aid applications. An algorithm that is evaluated negatively with NH might still bring benefits for HI participants.

  18. Wideband CMOS low noise amplifier including an active balun

    NARCIS (Netherlands)

    Blaakmeer, S.C.; Klumperink, Eric A.M.; Leenaerts, D.M.W.; Nauta, Bram

    2007-01-01

    An inductorless LNA with active balun is proposed for multi-standard radio applications between 100MHz and 6GHz [1]. It exploits a combination of a common-gate (CG) stage and an common-source (CS) stage with replica biasing to maximize balanced operation, while simultaneously canceling the noise and

  19. A Review of Virtual Sensing Algorithms for Active Noise Control

    Directory of Open Access Journals (Sweden)

    Danielle Moreau

    2008-11-01

    Full Text Available Traditional local active noise control systems minimise the measured acoustic pressure to generate a zone of quiet at the physical error sensor location. The resulting zone of quiet is generally limited in size and this requires the physical error sensor be placed at the desired location of attenuation, which is often inconvenient. To overcome this, a number of virtual sensing algorithms have been developed for active noise control. Using the physical error signal, the control signal and knowledge of the system, these virtual sensing algorithms estimate the error signal at a location that is remote from the physical error sensor, referred to as the virtual location. Instead of minimising the physical error signal, the estimated error signal is minimised with the active noise control system to generate a zone of quiet at the virtual location. This paper will review a number of virtual sensing algorithms developed for active noise control. Additionally, the performance of these virtual sensing algorithms in numerical simulations and in experiments is discussed and compared.

  20. Applications of active adaptive noise control to jet engines

    Science.gov (United States)

    Shoureshi, Rahmat; Brackney, Larry

    1993-01-01

    During phase 2 research on the application of active noise control to jet engines, the development of multiple-input/multiple-output (MIMO) active adaptive noise control algorithms and acoustic/controls models for turbofan engines were considered. Specific goals for this research phase included: (1) implementation of a MIMO adaptive minimum variance active noise controller; and (2) turbofan engine model development. A minimum variance control law for adaptive active noise control has been developed, simulated, and implemented for single-input/single-output (SISO) systems. Since acoustic systems tend to be distributed, multiple sensors, and actuators are more appropriate. As such, the SISO minimum variance controller was extended to the MIMO case. Simulation and experimental results are presented. A state-space model of a simplified gas turbine engine is developed using the bond graph technique. The model retains important system behavior, yet is of low enough order to be useful for controller design. Expansion of the model to include multiple stages and spools is also discussed.

  1. Multi-channel Kalman filters for active noise control

    NARCIS (Netherlands)

    Ophem, S. van; Berkhoff, A.P.

    2013-01-01

    By formulating the feed-forward broadband active noise control problem as a state estimation problem it is possible to achieve a faster rate of convergence than the filtered reference least mean squares algorithm and possibly also a better tracking performance. A multiple input/multiple output

  2. Multi-channel Kalman filters for active noise control

    NARCIS (Netherlands)

    van Ophem, S.; Berkhoff, Arthur P.

    By formulating the feed-forward broadband active noise control problem as a state estimation problem it is possible to achieve a faster rate of convergence than the filtered reference least mean squares algorithm and possibly also a better tracking performance. A multiple input/multiple output

  3. Case of electro-magnetic shielding building. Pt. 2. Reduction method of magnetic noise due to microtremor in magnetically shielded room; Kenchiku setsubi ni okeru denji shield no jitsurei. 2. Shield room no bishindo ni kiinsuru jiki noise taisaku

    Energy Technology Data Exchange (ETDEWEB)

    Yamazaki, K.; Abe, T.; Kamei, Y. [Takenaka Corp., Osaka (Japan)

    2000-01-05

    Magnetic sensitivity can be limited by microtremor of magnetically shielded room (MSR) used for the measurements of extremely magnetic fields such as biomagnetic measurements as well as environmental magnetic noise at low frequencies caused by trains, motorcars traffics and elevators but each of which can be reduced by MSR. The relation between the vibration of MSR and magnetic noise, and the reduction method of the magnetic noise due to microtremor of MSR are discussed experimentally. The correlations were high between acceleration in horizontal direction of ceiling panel and magnetic signal in horizontal and vertical directions. The magnetic noises were almost proportional to the displacement on the ceiling panel of MSR. Further an active isolation system was installed as a base of MSR to reduce the microtremor of the MSR. We also measured reduction effect of vibration and magnetic noise in an MSR actually mounted on TACMI by experiment when artificial vibrations were applied to the MSR by means of heal impacts and by a truck which run over a wood panel (height is 50 mm) on the road nearby at a speed of 20km per hour. (author)

  4. Method and system to perform energy-extraction based active noise control

    Science.gov (United States)

    Kelkar, Atul (Inventor); Joshi, Suresh M. (Inventor)

    2009-01-01

    A method to provide active noise control to reduce noise and vibration in reverberant acoustic enclosures such as aircraft, vehicles, appliances, instruments, industrial equipment and the like is presented. A continuous-time multi-input multi-output (MIMO) state space mathematical model of the plant is obtained via analytical modeling and system identification. Compensation is designed to render the mathematical model passive in the sense of mathematical system theory. The compensated system is checked to ensure robustness of the passive property of the plant. The check ensures that the passivity is preserved if the mathematical model parameters are perturbed from nominal values. A passivity-based controller is designed and verified using numerical simulations and then tested. The controller is designed so that the resulting closed-loop response shows the desired noise reduction.

  5. Noise reduction by sparse representation in learned dictionaries for application to blind tip reconstruction problem

    Science.gov (United States)

    Jóźwiak, Grzegorz

    2017-03-01

    Scanning probe microscopy (SPM) is a well known tool used for the investigation of phenomena in objects in the nanometer size range. However, quantitative results are limited by the size and the shape of the nanoprobe used in experiments. Blind tip reconstruction (BTR) is a very popular method used to reconstruct the upper boundary on the shape of the probe. This method is known to be very sensitive to all kinds of interference in the atomic force microscopy (AFM) image. Due to mathematical morphology calculus, the interference makes the BTR results biased rather than randomly disrupted. For this reason, the careful choice of methods used for image enhancement and denoising, as well as the shape of a calibration sample are very important. In the paper, the results of thorough investigations on the shape of a calibration standard are shown. A novel shape is proposed and a tool for the simulation of AFM images of this calibration standard was designed. It was shown that careful choice of the initial tip allows us to use images of hole structures to blindly reconstruct the shape of a probe. The simulator was used to test the impact of modern filtration algorithms on the BTR process. These techniques are based on sparse approximation with function dictionaries learned on the basis of an image itself. Various learning algorithms and parameters were tested to determine the optimal combination for sparse representation. It was observed that the strong reduction of noise does not guarantee strong reduction in reconstruction errors. It seems that further improvements will be possible by the combination of BTR and a noise reduction procedure.

  6. SU-E-I-77: A Noise Reduction Technique for Energy-Resolved Photon-Counting Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Lam Ng, A; Ding, H; Cho, H; Molloi, S [University of California, Irvine, CA (United States)

    2014-06-01

    Purpose: Finding the optimal energy threshold setting for an energy-resolved photon-counting detector has an important impact on the maximization of contrast-to-noise-ratio (CNR). We introduce a noise reduction method to enhance CNR by reducing the noise in each energy bin without altering the average gray levels in the projection and image domains. Methods: We simulated a four bin energy-resolved photon-counting detector based on Si with a 10 mm depth of interaction. TASMIP algorithm was used to simulate a spectrum of 65 kVp with 2.7 mm Al filter. A 13 mm PMMA phantom with hydroxyapatite and iodine at different concentrations (100, 200 and 300 mg/ml for HA, and 2, 4, and 8 mg/ml for Iodine) was used. Projection-based and Image-based energy weighting methods were used to generate weighted images. A reference low noise image was used for noise reduction purposes. A Gaussian-like weighting function which computes the similarity between pixels of interest was calculated from the reference image and implemented on a pixel by pixel basis for the noisy images. Results: CNR improvement compared to different methods (Charge-Integrated, Photon-Counting and Energy-Weighting) and after noise reduction was highly task-dependent. The CNR improvement with respect to the Charge-Integrated CNR for hydroxyapatite and iodine were 1.8 and 1.5, respectively. In each of the energy bins, the noise was reduced by approximately factor of two without altering their respective average gray levels. Conclusion: The proposed noise reduction technique for energy-resolved photon-counting detectors can significantly reduce image noise. This technique can be used as a compliment to the current energy-weighting methods in CNR optimization.

  7. Diffusion of Active Particles Subject both to Additive and Multiplicative Noises

    Institute of Scientific and Technical Information of China (English)

    WANG Shao-Hua; YANG Ming; WU Da-Jin

    2011-01-01

    We consider a Langevin equation of active Brownian motion which contains a multiplicative as well as an additive noise term.We study the dependences of the effective diffusion coefficient Deff on both the additive and multiplicative noises.It is found that for fixed small additive noise intensity Deff varies non-monotonously with multiplicative noise intensity, with a minimum at a moderate value of multiplicative noise, and Deff increases monotonously, however, with the multiplicative noise intensity for relatively strong additive noise; for fixed multiplicative noise intensity Deff decreases with growing additive noise intensity until it approaches a constant.An explanation is also given of the different behavior of Deff as additive and multiplicative noises approach infinity,respectively.%@@ We consider a Langevin equation of active Brownian motion which contains a multiplicative as well as an additive noise term.We study the dependences of the effective diffusion coefficient Deff on both the additive and multiplicative noises.It is found that for fixed small additive noise intensity Deff varies non-monotonously with multiplicative noise intensity, with a minimum at a moderate value of multiplicative noise, and Deff increases monotonously, however, with the multiplicative noise intensity for relatively strong additive noise; for fixed multiplicative noise intensity Deff decreases with growing additive noise intensity until it approaches a constant.An explanation is also given of the different behavior of Deff as additive and multiplicative noises approach infinity, respectively.

  8. The Development And Implementation Of A Concept To Permanent Reduction Of Noise Pollution In Production Taking Into Account The Legal And Economic Framework Conditions

    Science.gov (United States)

    Zaušková, Lucia; Czán, Andrej; Babík, Ondrej; Piešová, Marianna

    2015-12-01

    Article deals with the issue of reducing noise impact in real conditions of industrial production. The solution includes measurements and calculations of noise level the person is exposed to and developing proposals for effective reduction of noise levels at the specific workplace. When assessing noise levels and design to reduce it to an acceptable level we will consider the legal, safety and economic conditions.

  9. Noise, Worker Perception, and Worker Concentration in Timber Harvesting Activity

    OpenAIRE

    Efi Yuliati Yovi; Suryaningsih Suryaningsih

    2012-01-01

    Timber harvesting activities are unquestionably related with high risk of work accidents and health disorders.Such activities were not only burdened the workers with heavy physical workloads due to uneasy workingenvironment, and massive work materials and tools, but also physiopsychologically burdened workers as theywere imposed with both mechanical and acoustic vibrations (noise) produced by the chainsaw. However,  it is acommon practice that most of the workers still ignored the importance ...

  10. Noise reduction method for nonlinear signal based on maximum variance unfolding and its application to fault diagnosis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A new noise reduction method for nonlinear signal based on maximum variance unfolding(MVU)is proposed.The noisy sig- nal is firstly embedded into a high-dimensional phase space based on phase space reconstruction theory,and then the manifold learning algorithm MVU is used to perform nonlinear dimensionality reduction on the data of phase space in order to separate low-dimensional manifold representing the attractor from noise subspace.Finally,the noise-reduced signal is obtained through reconstructing the low-dimensional manifold.The simulation results of Lorenz system show that the proposed MVU-based noise reduction method outperforms the KPCA-based method and has the advantages of simple parameter estimation and low parameter sensitivity.The proposed method is applied to fault detection of a vibration signal from rotor-stator of aero engine with slight rubbing fault.The denoised results show that the slight rubbing features overwhelmed by noise can be effectively extracted by the proposed noise reduction method.

  11. Comparisons of SCR and Active-set Methods for PAPR Reduction in OFDM Systems

    Directory of Open Access Journals (Sweden)

    Qihui Liang

    2010-04-01

    Full Text Available signal to clipping noise ratio (SCR and active-set methods are two existing methods for peak-to-average power ratio (PAPR reduction based on tone reservation. In this paper, the computational complexities of these two methods are analyzed and simulation is done for comparing their PAPR-reducing performance. The simulation results show that active-set method requires less computational complexity than that of SCR method while they achieve similar PAPR reduction performance. 

  12. The effect of human activity noise on the acoustic quality in open plan office

    DEFF Research Database (Denmark)

    Dehlbæk, Tania Stenholt; Jeong, Cheol-Ho; Brunskog, Jonas

    2016-01-01

    A disadvantage of open plan offices is the noise annoyance. Noise problems in open plan offices have been dealt with in several studies, and standards have been set up. Still, what has not been taken into account is the effect of human activity noise on acoustic conditions. In this study, measure...... D2,S have an impact on the variation in the activity noise. At 1 kHz, the technical background noise influences human activity noise positively. In both octave bands, the human activity noise level varies significantly with the office type, from a call center to a lawyer’s office....

  13. Nonlinear complex diffusion approaches based on a novel noise estimation for noise reduction in phase-resolved optical coherence tomography (Conference Presentation)

    Science.gov (United States)

    Xia, Shaoyan; Huang, Yong; Tan, Xiaodi

    2016-03-01

    Partial differential equation (PDE)-based nonlinear diffusion processes have been widely used for image denoising. In the traditional nonlinear anisotropic diffusion denoising techniques, behavior of the diffusion depends highly on the gradient of image. However, it is difficult to get a good effect if we use these methods to reduce noise in optical coherence tomography images. Because background has the gradient that is very similar to regions of interest, so background noise will be mistaken for edge information and cannot be reduced. Therefore, nonlinear complex diffusion approaches using texture feature(NCDTF) for noise reduction in phase-resolved optical coherence tomography is proposed here, which uses texture feature in OCT images and structural OCT images to remove noise in phase-resolved OCT. Taking into account the fact that texture between background and signal region is different, which can be linked with diffusion coefficient of nonlinear complex diffusion model, we use NCDTF method to reduce noises of structure and phase images first. Then, we utilize OCT structure images to filter phase image in OCT. Finally, to validate our method, parameters such as image SNR, contrast-to-noise ratio (CNR), equivalent number of looks (ENL), and edge preservation were compared between our approach and median filter, Gaussian filter, wavelet filter, nonlinear complex diffusion filter (NCDF). Preliminary results demonstrate that NCDTF method is more effective than others in keeping edges and denoising for phase-resolved OCT.

  14. Noise Reduction of MEMS Gyroscope Based on Direct Modeling for an Angular Rate Signal

    Directory of Open Access Journals (Sweden)

    Liang Xue

    2015-02-01

    Full Text Available In this paper, a novel approach for processing the outputs signal of the microelectromechanical systems (MEMS gyroscopes was presented to reduce the bias drift and noise. The principle for the noise reduction was presented, and an optimal Kalman filter (KF was designed by a steady-state filter gain obtained from the analysis of KF observability. In particular, the true angular rate signal was directly modeled to obtain an optimal estimate and make a self-compensation for the gyroscope without needing other sensor’s information, whether in static or dynamic condition. A linear fit equation that describes the relationship between the KF bandwidth and modeling parameter of true angular rate was derived from the analysis of KF frequency response. The test results indicated that the MEMS gyroscope having an ARW noise of 4.87°/h0.5 and a bias instability of 44.41°/h were reduced to 0.4°/h0.5 and 4.13°/h by the KF under a given bandwidth (10 Hz, respectively. The 1σ estimated error was reduced from 1.9°/s to 0.14°/s and 1.7°/s to 0.5°/s in the constant rate test and swing rate test, respectively. It also showed that the filtered angular rate signal could well reflect the dynamic characteristic of the input rate signal in dynamic conditions. The presented algorithm is proved to be effective at improving the measurement precision of the MEMS gyroscope.

  15. A novel coupling of noise reduction algorithms for particle flow simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zimoń, M.J., E-mail: malgorzata.zimon@stfc.ac.uk [School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL (United Kingdom); James Weir Fluids Lab, Mechanical and Aerospace Engineering Department, The University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Reese, J.M. [School of Engineering, The University of Edinburgh, Edinburgh EH9 3JL (United Kingdom); Emerson, D.R. [Scientific Computing Department, STFC Daresbury Laboratory, Warrington WA4 4AD (United Kingdom)

    2016-09-15

    Proper orthogonal decomposition (POD) and its extension based on time-windows have been shown to greatly improve the effectiveness of recovering smooth ensemble solutions from noisy particle data. However, to successfully de-noise any molecular system, a large number of measurements still need to be provided. In order to achieve a better efficiency in processing time-dependent fields, we have combined POD with a well-established signal processing technique, wavelet-based thresholding. In this novel hybrid procedure, the wavelet filtering is applied within the POD domain and referred to as WAVinPOD. The algorithm exhibits promising results when applied to both synthetically generated signals and particle data. In this work, the simulations compare the performance of our new approach with standard POD or wavelet analysis in extracting smooth profiles from noisy velocity and density fields. Numerical examples include molecular dynamics and dissipative particle dynamics simulations of unsteady force- and shear-driven liquid flows, as well as phase separation phenomenon. Simulation results confirm that WAVinPOD preserves the dimensionality reduction obtained using POD, while improving its filtering properties through the sparse representation of data in wavelet basis. This paper shows that WAVinPOD outperforms the other estimators for both synthetically generated signals and particle-based measurements, achieving a higher signal-to-noise ratio from a smaller number of samples. The new filtering methodology offers significant computational savings, particularly for multi-scale applications seeking to couple continuum informations with atomistic models. It is the first time that a rigorous analysis has compared de-noising techniques for particle-based fluid simulations.

  16. A novel coupling of noise reduction algorithms for particle flow simulations

    Science.gov (United States)

    Zimoń, M. J.; Reese, J. M.; Emerson, D. R.

    2016-09-01

    Proper orthogonal decomposition (POD) and its extension based on time-windows have been shown to greatly improve the effectiveness of recovering smooth ensemble solutions from noisy particle data. However, to successfully de-noise any molecular system, a large number of measurements still need to be provided. In order to achieve a better efficiency in processing time-dependent fields, we have combined POD with a well-established signal processing technique, wavelet-based thresholding. In this novel hybrid procedure, the wavelet filtering is applied within the POD domain and referred to as WAVinPOD. The algorithm exhibits promising results when applied to both synthetically generated signals and particle data. In this work, the simulations compare the performance of our new approach with standard POD or wavelet analysis in extracting smooth profiles from noisy velocity and density fields. Numerical examples include molecular dynamics and dissipative particle dynamics simulations of unsteady force- and shear-driven liquid flows, as well as phase separation phenomenon. Simulation results confirm that WAVinPOD preserves the dimensionality reduction obtained using POD, while improving its filtering properties through the sparse representation of data in wavelet basis. This paper shows that WAVinPOD outperforms the other estimators for both synthetically generated signals and particle-based measurements, achieving a higher signal-to-noise ratio from a smaller number of samples. The new filtering methodology offers significant computational savings, particularly for multi-scale applications seeking to couple continuum informations with atomistic models. It is the first time that a rigorous analysis has compared de-noising techniques for particle-based fluid simulations.

  17. Noise Reduction in Brainwaves by Using Both EEG Signals and Frontal Viewing Camera Images

    Directory of Open Access Journals (Sweden)

    Kang Ryoung Park

    2013-05-01

    Full Text Available Electroencephalogram (EEG-based brain-computer interfaces (BCIs have been used in various applications, including human–computer interfaces, diagnosis of brain diseases, and measurement of cognitive status. However, EEG signals can be contaminated with noise caused by user’s head movements. Therefore, we propose a new method that combines an EEG acquisition device and a frontal viewing camera to isolate and exclude the sections of EEG data containing these noises. This method is novel in the following three ways. First, we compare the accuracies of detecting head movements based on the features of EEG signals in the frequency and time domains and on the motion features of images captured by the frontal viewing camera. Second, the features of EEG signals in the frequency domain and the motion features captured by the frontal viewing camera are selected as optimal ones. The dimension reduction of the features and feature selection are performed using linear discriminant analysis. Third, the combined features are used as inputs to support vector machine (SVM, which improves the accuracy in detecting head movements. The experimental results show that the proposed method can detect head movements with an average error rate of approximately 3.22%, which is smaller than that of other methods.

  18. Environmentally Responsible Aviation: Propulsion Research to Enable Fuel Burn, Noise and Emissions Reduction

    Science.gov (United States)

    Van Zante, Dale; Suder, Kenneth

    2015-01-01

    The NASA Environmentally Responsible Aviation (ERA) program is maturing technologies to enable simultaneous reduction of fuel burn, noise and emissions from an aircraft engine system. Three engine related Integrated Technology Demonstrations (ITDs) have been completed at Glenn Research Center in collaboration with Pratt Whitney, General Electric and the Federal Aviation Administration. The engine technologies being matured are: a low NOx, fuel flexible combustor in partnership with Pratt Whitney; an ultra-high bypass, ducted propulsor system in partnership with Pratt Whitney and FAA; and high pressure ratio, front-stage core compressor technology in partnership with General Electric. The technical rationale, test configurations and overall results from the test series in each ITD are described. ERA is using system analysis to project the benefits of the ITD technologies on potential aircraft systems in the 2025 timeframe. Data from the ITD experiments were used to guide the system analysis assumptions. Results from the current assessments for fuel burn, noise and oxides of nitrogen emissions are presented.

  19. Noise Reduction Properties of an Experimental Bituminous Slurry with Crumb Rubber Incorporated by the Dry Process

    Directory of Open Access Journals (Sweden)

    Moisés Bueno

    2014-08-01

    Full Text Available Nowadays, cold technology for asphalt pavement in the field of road construction is considered as an alternative solution to conventional procedures from both an economic and environmental point of view. Among these techniques, bituminous slurry surfacing is obtaining an important role due to the properties of the obtained wearing course. The functional performance of this type of surfaces is directly related to its rough texture. Nevertheless, this parameter has a significant influence on the tire/road noise generation. To reduce this undesirable effect on the sound performance, new designs of elastic bituminous slurries have been developed. Within the FENIX project, this work presents the acoustical characterization of an experimental bituminous slurry with crumb rubber from wasted automobile tires incorporated by the dry process. The obtained results show that, under controlled operational parameters, the close proximity sound levels associated to the experimental slurry are considerably lower than those emitted by a conventional slurry wearing course. However, after one year of supporting traffic loads and different weather conditions, the evaluated bituminous slurry, although it conserves the original noise reduction properties in relation to the conventional one, noticeably increases the generated sound emission. Therefore, it is required to continue improving the design of experimental surfaces in order to enhance its long-term performance.

  20. Global-mode based linear feedback control of a supersonic jet for noise reduction

    Science.gov (United States)

    Natarajan, Mahesh; Freund, Jonathan; Bodony, Daniel

    2016-11-01

    The loudest source of high-speed jet noise appears to be describable by unsteady wavepackets that resemble instabilities. We seek to reduce their acoustic impact with a control strategy that uses global modes to model their dynamics and structural sensitivity of the linearized compressible Navier-Stokes operator to identify an effective linear feedback control. For a case with co-located actuators and sensors adjacent the nozzle, we demonstrate the method on an axisymmetric Mach 1.5 jet. Direct numerical simulations using this control show significant noise reduction. Eigenanalysis of the controlled mean flows reveal fundamental changes in the spectrum at frequencies lower than that used by the control, with the quieter flows having unstable eigenvalues that correspond to eigenfunctions without significant support in the acoustic field. A specific trend is observed in the mean flow quantities as the flow becomes quieter, with changes in the mean flow becoming significant only further downstream of the nozzle exit. The quieter flows also have a stable shock-cell structure that extends further downstream. A phase plot of the POD coefficients for the flows show that the quieter flows are more regular in time. Funded by the Office of Naval Research.

  1. Proper orthogonal decomposition and wavelet methods for noise reduction in particle-based transport calculations

    Science.gov (United States)

    Nguyen van Ye, Romain; Del-Castillo-Negrete, Diego; Spong, D.; Hirshman, S.; Farge, M.

    2008-11-01

    A limitation of particle-based transport calculations is the noise due to limited statistical sampling. Thus, a key element for the success of these calculations is the development of efficient denoising methods. Here we discuss denoising techniques based on Proper Orthogonal Decomposition (POD) and Wavelet Decomposition (WD). The goal is the reconstruction of smooth (denoised) particle distribution functions from discrete particle data obtained from Monte Carlo simulations. In 2-D, the POD method is based on low rank truncations of the singular value decomposition of the data. For 3-D we propose the use of a generalized low rank approximation of matrices technique. The WD denoising is based on the thresholding of empirical wavelet coefficients [Donoho et al., 1996]. The methods are illustrated and tested with Monte-Carlo particle simulation data of plasma collisional relaxation including pitch angle and energy scattering. As an application we consider guiding-center transport with collisions in a magnetically confined plasma in toroidal geometry. The proposed noise reduction methods allow to achieve high levels of smoothness in the particle distribution function using significantly less particles in the computations.

  2. Chemical Noise Reduction via Mass Spectrometry and Ion/Ion Charge Inversion: Amino Acids

    Science.gov (United States)

    Hassell, Kerry M.; LeBlanc, Yves C.; McLuckey, Scott A.

    2011-01-01

    Charge inversion ion/ion reactions can provide a significant reduction in chemical noise associated with mass spectra derived from complex mixtures for species comprised of both acidic and basic sites, provided the ions derived from the matrix largely undergo neutralization. Amino acids constitute an important class of amphoteric compounds that undergo relatively efficient charge inversion. Precipitated plasma constitutes a relatively complex biological matrix that yields detectable signals at essentially every mass-to-charge value over a wide range. This chemical noise can be dramatically reduced by using multiply-charged reagent ions that can invert the charge of species amenable to the transfer of multiple charges upon a single interaction and by detecting product ions of opposite polarity. The principle is illustrated here with amino acids present in precipitated plasma subjected to ionization in the positive mode, reaction with anions derived from negative nano-electrospray ionization of poly (amido amine) dendrimer generation 3.5, and mass analysis in the negative ion mode. PMID:21456599

  3. A “Salt and Pepper” Noise Reduction Scheme for Digital Images Based on Support Vector Machines Classification and Regression

    Directory of Open Access Journals (Sweden)

    Hilario Gómez-Moreno

    2014-01-01

    Full Text Available We present a new impulse noise removal technique based on Support Vector Machines (SVM. Both classification and regression were used to reduce the “salt and pepper” noise found in digital images. Classification enables identification of noisy pixels, while regression provides a means to determine reconstruction values. The training vectors necessary for the SVM were generated synthetically in order to maintain control over quality and complexity. A modified median filter based on a previous noise detection stage and a regression-based filter are presented and compared to other well-known state-of-the-art noise reduction algorithms. The results show that the filters proposed achieved good results, outperforming other state-of-the-art algorithms for low and medium noise ratios, and were comparable for very highly corrupted images.

  4. Noise Reduction in Breath Sound Files Using Wavelet Transform Based Filter

    Science.gov (United States)

    Syahputra, M. F.; Situmeang, S. I. G.; Rahmat, R. F.; Budiarto, R.

    2017-04-01

    The development of science and technology in the field of healthcare increasingly provides convenience in diagnosing respiratory system problem. Recording the breath sounds is one example of these developments. Breath sounds are recorded using a digital stethoscope, and then stored in a file with sound format. This breath sounds will be analyzed by health practitioners to diagnose the symptoms of disease or illness. However, the breath sounds is not free from interference signals. Therefore, noise filter or signal interference reduction system is required so that breath sounds component which contains information signal can be clarified. In this study, we designed a filter called a wavelet transform based filter. The filter that is designed in this study is using Daubechies wavelet with four wavelet transform coefficients. Based on the testing of the ten types of breath sounds data, the data is obtained in the largest SNRdB bronchial for 74.3685 decibels.

  5. Linear adaptive noise-reduction filters for tomographic imaging: Optimizing for minimum mean square error

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Winston Y. [Univ. of California, Berkeley, CA (United States)

    1993-04-01

    This thesis solves the problem of finding the optimal linear noise-reduction filter for linear tomographic image reconstruction. The optimization is data dependent and results in minimizing the mean-square error of the reconstructed image. The error is defined as the difference between the result and the best possible reconstruction. Applications for the optimal filter include reconstructions of positron emission tomographic (PET), X-ray computed tomographic, single-photon emission tomographic, and nuclear magnetic resonance imaging. Using high resolution PET as an example, the optimal filter is derived and presented for the convolution backprojection, Moore-Penrose pseudoinverse, and the natural-pixel basis set reconstruction methods. Simulations and experimental results are presented for the convolution backprojection method.

  6. Motion detection, noise reduction, texture suppression, and contour enhancement by spatiotemporal Gabor filters with surround inhibition.

    Science.gov (United States)

    Petkov, Nicolai; Subramanian, Easwar

    2007-12-01

    We study the orientation and speed tuning properties of spatiotemporal three-dimensional (3D) Gabor and motion energy filters as models of time-dependent receptive fields of simple and complex cells in the primary visual cortex (V1). We augment the motion energy operator with surround suppression to model the inhibitory effect of stimuli outside the classical receptive field. We show that spatiotemporal integration and surround suppression lead to substantial noise reduction. We propose an effective and straightforward motion detection computation that uses the population code of a set of motion energy filters tuned to different velocities. We also show that surround inhibition leads to suppression of texture and thus improves the visibility of object contours and facilitates figure/ground segregation and the detection and recognition of objects.

  7. 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.

  8. Age-Related Benefits of Digital Noise Reduction for Short-Term Word Learning in Children with Hearing Loss

    Science.gov (United States)

    Pittman, Andrea

    2011-01-01

    Purpose: To determine the rate of word learning for children with hearing loss (HL) in quiet and in noise compared to normal-hearing (NH) peers. The effects of digital noise reduction (DNR) were examined for children with HL. Method: Forty-one children with NH and 26 children with HL were grouped by age (8-9 years and 11-12 years). The children…

  9. 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.)

  10. Robust active noise control in the loadmaster area of a military transport aircraft.

    Science.gov (United States)

    Kochan, Kay; Sachau, Delf; Breitbach, Harald

    2011-05-01

    The active noise control (ANC) method is based on the superposition of a disturbance noise field with a second anti-noise field using loudspeakers and error microphones. This method can be used to reduce the noise level inside the cabin of a propeller aircraft. However, during the design process of the ANC system, extensive measurements of transfer functions are necessary to optimize the loudspeaker and microphone positions. Sometimes, the transducer positions have to be tailored according to the optimization results to achieve a sufficient noise reduction. The purpose of this paper is to introduce a controller design method for such narrow band ANC systems. The method can be seen as an extension of common transducer placement optimization procedures. In the presented method, individual weighting parameters for the loudspeakers and microphones are used. With this procedure, the tailoring of the transducer positions is replaced by adjustment of controller parameters. Moreover, the ANC system will be robust because of the fact that the uncertainties are considered during the optimization of the controller parameters. The paper describes the necessary theoretic background for the method and demonstrates the efficiency in an acoustical mock-up of a military transport aircraft.

  11. Hybrid Active/Passive Jet Engine Noise Suppression System

    Science.gov (United States)

    Parente, C. A.; Arcas, N.; Walker, B. E.; Hersh, A. S.; Rice, E. J.

    1999-01-01

    A novel adaptive segmented liner concept has been developed that employs active control elements to modify the in-duct sound field to enhance the tone-suppressing performance of passive liner elements. This could potentially allow engine designs that inherently produce more tone noise but less broadband noise, or could allow passive liner designs to more optimally address high frequency broadband noise. A proof-of-concept validation program was undertaken, consisting of the development of an adaptive segmented liner that would maximize attenuation of two radial modes in a circular or annular duct. The liner consisted of a leading active segment with dual annuli of axially spaced active Helmholtz resonators, followed by an optimized passive liner and then an array of sensing microphones. Three successively complex versions of the adaptive liner were constructed and their performances tested relative to the performance of optimized uniform passive and segmented passive liners. The salient results of the tests were: The adaptive segmented liner performed well in a high flow speed model fan inlet environment, was successfully scaled to a high sound frequency and successfully attenuated three radial modes using sensor and active resonator arrays that were designed for a two mode, lower frequency environment.

  12. Noise Reduction of Steel Cord Conveyor Belt Defect Electromagnetic Signal by Combined Use of Improved Wavelet and EMD

    Directory of Open Access Journals (Sweden)

    Hong-Wei Ma

    2016-09-01

    Full Text Available In order to reduce the noise of a defect electromagnetic signal of the steel cord conveyor belt used in coal mines, a new signal noise reduction method by combined use of the improved threshold wavelet and Empirical Mode Decomposition (EMD is proposed. Firstly, the denoising method based on the improved threshold wavelet is applied to reduce the noise of a defect electromagnetic signal obtained by an electromagnetic testing system. Then, the EMD is used to decompose the denoised signal and then the effective Intrinsic Mode Function (IMF is extracted by the dominant eigenvalue strategy. Finally, the signal reconstruction is carried out by utilizing the obtained IMF. In order to verify the proposed noise reduction method, the experiments are carried out in two cases including the defective joint and steel wire rope break. The experimental results show that the proposed method in this paper obtains the higher Signal to Noise Ratio (SNR for the defect electromagnetic signal noise reduction of steel cord conveyor belts.

  13. Design and optimization of a noise reduction system for infrasonic measurements using elements with low acoustic impedance.

    Science.gov (United States)

    Alcoverro, Benoit; Le Pichon, Alexis

    2005-04-01

    The implementation of the infrasound network of the International Monitoring System (IMS) for the enforcement of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) increases the effort in the design of suitable noise reducer systems. In this paper we present a new design consisting of low impedance elements. The dimensioning and the optimization of this discrete mechanical system are based on numerical simulations, including a complete electroacoustical modeling and a realistic wind-noise model. The frequency response and the noise reduction obtained for a given wind speed are compared to statistical noise measurements in the [0.02-4] Hz frequency band. The effects of the constructive parameters-the length of the pipes, inner diameters, summing volume, and number of air inlets-are investigated through a parametric study. The studied system consists of 32 air inlets distributed along an overall diameter of 16 m. Its frequency response is flat up to 4 Hz. For a 2 m/s wind speed, the maximal noise reduction obtained is 15 dB between 0.5 and 4 Hz. At lower frequencies, the noise reduction is improved by the use of a system of larger diameter. The main drawback is the high-frequency limitation introduced by acoustical resonances inside the pipes.

  14. Gain-induced speech distortions and the absence of intelligibility benefit with existing noise-reduction algorithms.

    Science.gov (United States)

    Kim, Gibak; Loizou, Philipos C

    2011-09-01

    Most noise-reduction algorithms used in hearing aids apply a gain to the noisy envelopes to reduce noise interference. The present study assesses the impact of two types of speech distortion introduced by noise-suppressive gain functions: amplification distortion occurring when the amplitude of the target signal is over-estimated, and attenuation distortion occurring when the target amplitude is under-estimated. Sentences corrupted by steady noise and competing talker were processed through a noise-reduction algorithm and synthesized to contain either amplification distortion, attenuation distortion or both. The attenuation distortion was found to have a minimal effect on speech intelligibility. In fact, substantial improvements (>80 percentage points) in intelligibility, relative to noise-corrupted speech, were obtained when the processed sentences contained only attenuation distortion. When the amplification distortion was limited to be smaller than 6 dB, performance was nearly unaffected in the steady-noise conditions, but was severely degraded in the competing-talker conditions. Overall, the present data suggest that one reason that existing algorithms do not improve speech intelligibility is because they allow amplification distortions in excess of 6 dB. These distortions are shown in this study to be always associated with masker-dominated envelopes and should thus be eliminated.

  15. The Effect of Non-Harmonic Active Twist Actuation on BVI Noise

    Science.gov (United States)

    Fogarty, David E.; Wilbur, Matthew L.; Sekula, Martin K.

    2011-01-01

    The results of a computational study examining the effects of non-harmonic active-twist control on blade-vortex interaction (BVI) noise for the Apache Active Twist Rotor are presented. Rotor aeroelastic behavior was modeled using the Comprehensive Analytical Model of Rotorcraft Aerodynamics and Dynamics code and the rotor noise was predicted using the acoustics code PSU-WOPWOP. The application of non-harmonic active-twist inputs to the main rotor blade system comprised three parameters: azimuthal location to start actuation, azimuthal duration of actuation, and magnitude of actuation. The acoustic analysis was conducted for a single low-speed flight condition of advance ratio mu=0.14 and shaft angle-of-attack, a(sub s)=+6deg. BVI noise levels were predicted on a flat plane of observers located 1.1 rotor diameters beneath the rotor. The results indicate significant reductions of up to 10dB in BVI noise using a starting azimuthal location for actuation of 90?, an azimuthal duration of actuation of 90deg, and an actuation magnitude of +1.5 ft-lb.

  16. Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT

    Energy Technology Data Exchange (ETDEWEB)

    Maier, Andreas; Wigstroem, Lars; Hofmann, Hannes G.; Hornegger, Joachim; Zhu Lei; Strobel, Norbert; Fahrig, Rebecca [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Department of Radiology, Stanford University, Stanford, California 94305 (United States) and Center for Medical Image Science and Visualization, Linkoeping University, Linkoeping (Sweden); Pattern Recognition Laboratory, Department of Computer Science, Friedrich-Alexander University of Erlangen-Nuremberg, 91054, Erlangen (Germany); Nuclear and Radiological Engineering and Medical Physics Programs, George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Siemens AG Healthcare, Forchheim 91301 (Germany); Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2011-11-15

    Purpose: The combination of quickly rotating C-arm gantry with digital flat panel has enabled the acquisition of three-dimensional data (3D) in the interventional suite. However, image quality is still somewhat limited since the hardware has not been optimized for CT imaging. Adaptive anisotropic filtering has the ability to improve image quality by reducing the noise level and therewith the radiation dose without introducing noticeable blurring. By applying the filtering prior to 3D reconstruction, noise-induced streak artifacts are reduced as compared to processing in the image domain. Methods: 3D anisotropic adaptive filtering was used to process an ensemble of 2D x-ray views acquired along a circular trajectory around an object. After arranging the input data into a 3D space (2D projections + angle), the orientation of structures was estimated using a set of differently oriented filters. The resulting tensor representation of local orientation was utilized to control the anisotropic filtering. Low-pass filtering is applied only along structures to maintain high spatial frequency components perpendicular to these. The evaluation of the proposed algorithm includes numerical simulations, phantom experiments, and in-vivo data which were acquired using an AXIOM Artis dTA C-arm system (Siemens AG, Healthcare Sector, Forchheim, Germany). Spatial resolution and noise levels were compared with and without adaptive filtering. A human observer study was carried out to evaluate low-contrast detectability. Results: The adaptive anisotropic filtering algorithm was found to significantly improve low-contrast detectability by reducing the noise level by half (reduction of the standard deviation in certain areas from 74 to 30 HU). Virtually no degradation of high contrast spatial resolution was observed in the modulation transfer function (MTF) analysis. Although the algorithm is computationally intensive, hardware acceleration using Nvidia's CUDA Interface provided an 8

  17. Three-dimensional anisotropic adaptive filtering of projection data for noise reduction in cone beam CT.

    Science.gov (United States)

    Maier, Andreas; Wigstrom, Lars; Hofmann, Hannes G; Hornegger, Joachim; Zhu, Lei; Strobel, Norbert; Fahrig, Rebecca

    2011-11-01

    The combination of quickly rotating C-arm gantry with digital flat panel has enabled the acquisition of three-dimensional data (3D) in the interventional suite. However, image quality is still somewhat limited since the hardware has not been optimized for CT imaging. Adaptive anisotropic filtering has the ability to improve image quality by reducing the noise level and therewith the radiation dose without introducing noticeable blurring. By applying the filtering prior to 3D reconstruction, noise-induced streak artifacts are reduced as compared to processing in the image domain. 3D anisotropic adaptive filtering was used to process an ensemble of 2D x-ray views acquired along a circular trajectory around an object. After arranging the input data into a 3D space (2D projections + angle), the orientation of structures was estimated using a set of differently oriented filters. The resulting tensor representation of local orientation was utilized to control the anisotropic filtering. Low-pass filtering is applied only along structures to maintain high spatial frequency components perpendicular to these. The evaluation of the proposed algorithm includes numerical simulations, phantom experiments, and in-vivo data which were acquired using an AXIOM Artis dTA C-arm system (Siemens AG, Healthcare Sector, Forchheim, Germany). Spatial resolution and noise levels were compared with and without adaptive filtering. A human observer study was carried out to evaluate low-contrast detectability. The adaptive anisotropic filtering algorithm was found to significantly improve low-contrast detectability by reducing the noise level by half (reduction of the standard deviation in certain areas from 74 to 30 HU). Virtually no degradation of high contrast spatial resolution was observed in the modulation transfer function (MTF) analysis. Although the algorithm is computationally intensive, hardware acceleration using Nvidia's CUDA Interface provided an 8.9-fold speed-up of the

  18. Statistical-noise reduction in correlation analysis of high-energy nuclear collisions with event-mixing

    CERN Document Server

    Ray, R L

    2016-01-01

    The error propagation and statistical-noise reduction method of Reid and Trainor for two-point correlation applications in high-energy collisions is extended to include particle-pair references constructed by mixing two particles from all event-pair combinations within event subsets of arbitrary size. The Reid-Trainor method is also applied to other particle-pair mixing algorithms commonly used in correlation analysis of particle production from high-energy nuclear collisions. The statistical-noise reduction, inherent in the Reid-Trainor event-mixing procedure, is shown to occur for these other event-mixing algorithms as well. Monte Carlo simulation results are presented which verify the predicted degree of noise reduction. In each case the final errors are determined by the bin-wise particle-pair number, rather than by the bin-wise single-particle count.

  19. Statistical-noise reduction in correlation analysis of high-energy nuclear collisions with event-mixing

    Energy Technology Data Exchange (ETDEWEB)

    Ray, R.L., E-mail: ray@physics.utexas.edu; Bhattarai, P.

    2016-06-11

    The error propagation and statistical-noise reduction method of Reid and Trainor for two-point correlation applications in high-energy collisions is extended to include particle-pair references constructed by mixing two particles from all event-pair combinations within event subsets of arbitrary size. The Reid–Trainor method is also applied to other particle-pair mixing algorithms commonly used in correlation analysis of particle production from high-energy nuclear collisions. The statistical-noise reduction, inherent in the Reid–Trainor event-mixing procedure, is shown to occur for these other event-mixing algorithms as well. Monte Carlo simulation results are presented which verify the predicted degree of noise reduction. In each case the final errors are determined by the bin-wise particle-pair number, rather than by the bin-wise single-particle count.

  20. Improvement of vibration and noise by applying analysis technology. Development of active control technique of engine noise in a car cabin. Kaiseki gijutsu wo oyoshita shindo-soon no kaizen. Shashitsunai engine soon akutibu seigyo gijutsu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, H.; Nakao, N.; Butsuen, T. (Matsuda Motor Corp., Hiroshima (Japan). Technology Research Inst.)

    1994-06-01

    It is difficult to reduce engine noise which is principal noise in a car cabin without producing an adverse effect on low cost production. Active noise control technique (ANC) has been developed to reduce engine noise compatible with low cost production. This paper discusses its control algorithm and the system configuration and presents experimental results. The filtered-x least mean square method is a well-known ANC algorithm, however, it often requires large amount of calculation exceeding the present capacity of a digital signal processor. An effective ANC algorithm is developed by the use of the repetitiveness of the engine noise. This paper describes the basic theory of the control algorithm, the extension to a multiple input and output system, the system configuration and experimental results. A noise control system with three microphones is designed with consideration of the spatial distribution of the noise and reduces noise in the whole cabin by 8dB(A) in the largest case. Active noise control technique is applicable to many areas and can be used for the reduction of noise and vibration other than engine noise. 5 refs., 7 figs., 1 tab.

  1. Noise Exposure of Teachers in Nursery Schools—Evaluation of Measures for Noise Reduction When Dropping DUPLO Toy Bricks into Storage Cases by Sound Analyses

    Directory of Open Access Journals (Sweden)

    Konstanze Gebauer

    2016-07-01

    Full Text Available Background: Although noise is one of the leading work-related health risk factors for teachers, many nursery schools lack sufficient noise reduction measures. Methods: This intervention study evaluated the noise exposure of nursery school teachers when dropping DUPLO toy bricks into storage cases. Sound analyses of the impact included assessment of the maximum sound pressure level (LAFmax as well as frequency analyses with 1/3 octave band filter. For the purpose of standardization, a customized gadget was developed. Recordings were performed in 11 cases of different materials and designs to assess the impact on sound level reduction. Thereby, the acoustic effects of three damping materials (foam rubber, carpet, and PU-foam were investigated. Results: The lowest LAFmax was measured in cases consisting of “metal grid” (90.71 dB or of a woven willow “basket” (91.61 dB, whereas a case of “aluminium” (103.34 dB generated the highest impact LAFmax. The frequency analyses determined especially low LAFmax in the frequency bands between 80 and 2500 Hz in cases designs “metal grid” and “basket”. The insertion of PU-foam achieved the most significant attenuation of LAFmax (−13.88 dB and, in the frequency analyses, the best sound damping. Conclusion: The dropping of DUPLO bricks in cases contributes to the high noise level in nursery schools, but measured LAFmax show no evidence for the danger of acute hearing loss. However, continuous exposure may lead to functional impairment of the hair cells and trigger stress reactions. We recommend noise reduction by utilizing cases of woven “basket” with an insert of PU-foam.

  2. A Comparison of IIR and Wavelet Filtering for Noise Reduction of the ECG.

    Science.gov (United States)

    Sørensen, Js; Johannesen, L; Grove, Usl; Lundhus, K; Couderc, J-P; Graff, C

    2010-09-26

    This study compares the ability to preserve information and reduce noise contaminants on the ECG for five wavelet filters and three IIR filters. Two 3-lead Holter ECGs were used. White Gaussian Noise was added to the first ECG in increments of 10% coverage. The second ECG contained alternating muscle transients and noise-free segments. Computation times and SNR improvements for different noise coverages were calculated and compared. RMS errors were calculated from noise-free segments on the ECG with transient muscle noise. Wavelet filters improved SNR more than IIR filters when the signal coverage was more than 50% noise. In contrast, the computation times were shorter for IIR filters (6 s) than for wavelet filters (88 s). On the ECG with transient muscle noise there was a trade-off in performance between wavelet and IIR filtering. In a clinical setting where the amount of noise is unknown, using IIR filters appears to be preferred for consistent performance.

  3. Analysis of forces from the subframe into sidemembers for road noise reduction; Riya subframe keijo no saitekika ni yoru road noise no kaizen

    Energy Technology Data Exchange (ETDEWEB)

    Arakawa, M.; Asai, M.; Kiyota, Y.; Akiyama, A. [Toyota Motor Corp., Aichi (Japan)

    1995-04-20

    In a rigidity added rear subframe structure, an analysis was made of the internal force working on the joint with the sidemember, for studying how to reduce road noise. In the frequency domain giving rise to low noise related problems in a rigidity added rear subframe structure, the rear subframe and floor crossmember produces bending oscillation with the sidemember section serving as the point of articulation. Now that the floor is the location wherein the low noise originates, what is important in the effort to reduce noise is to suppress the up-and-down oscillation of the floor crossmember. The result of the analysis indicates that the floor oscillation, responding to the up-and-down force inputted by the rear subframe, reduces when the position of installation of the rear subframe is changed and rigidity is secured two times more than the rigidity required for optimization in the central cross section. In an application to a service vehicle, the road noise during a run along a tennis court evaluation road resulted in a 2.0dB reduction, which enables the conclusion that the technique introduced herein is better than the technique of providing a rear subframe with a dynamic damper. 2 refs., 14 figs.

  4. Prospective ECG-triggered coronary CT angiography: clinical value of noise-based tube current reduction method with iterative reconstruction.

    Directory of Open Access Journals (Sweden)

    Junlin Shen

    Full Text Available OBJECTIVES: To evaluate the clinical value of noise-based tube current reduction method with iterative reconstruction for obtaining consistent image quality with dose optimization in prospective electrocardiogram (ECG-triggered coronary CT angiography (CCTA. MATERIALS AND METHODS: We performed a prospective randomized study evaluating 338 patients undergoing CCTA with prospective ECG-triggering. Patients were randomly assigned to fixed tube current with filtered back projection (Group 1, n = 113, noise-based tube current with filtered back projection (Group 2, n = 109 or with iterative reconstruction (Group 3, n = 116. Tube voltage was fixed at 120 kV. Qualitative image quality was rated on a 5-point scale (1 = impaired, to 5 = excellent, with 3-5 defined as diagnostic. Image noise and signal intensity were measured; signal-to-noise ratio was calculated; radiation dose parameters were recorded. Statistical analyses included one-way analysis of variance, chi-square test, Kruskal-Wallis test and multivariable linear regression. RESULTS: Image noise was maintained at the target value of 35HU with small interquartile range for Group 2 (35.00-35.03HU and Group 3 (34.99-35.02HU, while from 28.73 to 37.87HU for Group 1. All images in the three groups were acceptable for diagnosis. A relative 20% and 51% reduction in effective dose for Group 2 (2.9 mSv and Group 3 (1.8 mSv were achieved compared with Group 1 (3.7 mSv. After adjustment for scan characteristics, iterative reconstruction was associated with 26% reduction in effective dose. CONCLUSION: Noise-based tube current reduction method with iterative reconstruction maintains image noise precisely at the desired level and achieves consistent image quality. Meanwhile, effective dose can be reduced by more than 50%.

  5. Simultaneous Reduction in Noise and Cross-Contamination Artifacts for Dual-Energy X-Ray CT

    Directory of Open Access Journals (Sweden)

    Baojun Li

    2013-01-01

    Full Text Available Purpose. Dual-energy CT imaging tends to suffer from much lower signal-to-noise ratio than single-energy CT. In this paper, we propose an improved anticorrelated noise reduction (ACNR method without causing cross-contamination artifacts. Methods. The proposed algorithm diffuses both basis material density images (e.g., water and iodine at the same time using a novel correlated diffusion algorithm. The algorithm has been compared to the original ACNR algorithm in a contrast-enhanced, IRB-approved patient study. Material density accuracy and noise reduction are quantitatively evaluated by the percent density error and the percent noise reduction. Results. Both algorithms have significantly reduced the noises of basis material density images in all cases. The average percent noise reduction is 69.3% and 66.5% with the ACNR algorithm and the proposed algorithm, respectively. However, the ACNR algorithm alters the original material density by an average of 13% (or 2.18 mg/cc with a maximum of 58.7% (or 8.97 mg/cc in this study. This is evident in the water density images as massive cross-contaminations are seen in all five clinical cases. On the contrary, the proposed algorithm only changes the mean density by 2.4% (or 0.69 mg/cc with a maximum of 7.6% (or 1.31 mg/cc. The cross-contamination artifacts are significantly minimized or absent with the proposed algorithm. Conclusion. The proposed algorithm can significantly reduce image noise present in basis material density images from dual-energy CT imaging, with minimized cross-contaminations compared to the ACNR algorithm.

  6. Low-Gain, Low-Noise Integrated Neuronal Amplifier for Implantable Artifact-Reduction Recording System

    Directory of Open Access Journals (Sweden)

    Abdelhamid Benazzouz

    2013-09-01

    Full Text Available Brain neuroprostheses for neuromodulation are being designed to monitor the neural activity of the brain in the vicinity of the region being stimulated using a single macro-electrode. Using a single macro-electrode, recent neuromodulation studies show that recording systems with a low gain neuronal amplifier and successive amplifier stages can reduce or reject stimulation artifacts. These systems were made with off-the-shelf components that are not amendable for future implant design. A low-gain, low-noise integrated neuronal amplifier (NA with the capability of recording local field potentials (LFP and spike activity is presented. In vitro and in vivo characterizations of the tissue/electrode interface, with equivalent impedance as an electrical model for recording in the LFP band using macro-electrodes for rodents, contribute to the NA design constraints. The NA occupies 0.15 mm2 and dissipates 6.73 µW, and was fabricated using a 0.35 µm CMOS process. Test-bench validation indicates that the NA provides a mid-band gain of 20 dB and achieves a low input-referred noise of 4 µVRMS. Ability of the NA to perform spike recording in test-bench experiments is presented. Additionally, an awake and freely moving rodent setup was used to illustrate the integrated NA ability to record LFPs, paving the pathway for future implantable systems for neuromodulation.

  7. Identification and reduction of vibration and noise of a glass tempering system

    Science.gov (United States)

    Ashhab, M. S.

    2015-05-01

    The vibration and noise of a glass tempering machine at a factory are studied. Experiments were conducted to identify the sources of vibration and noise. It was found that main sources for vibration and noise are two air barrels, the air pipes from the fans to the glass tempering machine and the fans location. Solutions were suggested to reduce vibration and noise from these three main sources. One of the solutions that were implemented is placing rubber dampers beneath the air barrels and pipes which almost cancelled the horizontal vibrations in the building structure and reduced the vertical vibrations to a low value most likely coming from noise. There are two types of noise, namely, radiation noise from the fans through the fans room walls and transmitted noise through the pipes caused by turbulence. A glass wool noise insulating layer was installed on the wall between the fans room and factory to reduce radiation noise through this wall. Part of the air pipe system in the factory is made of a light material which produced the highest levels of noise above 110 dBA. These air pipes were wrapped by glass wool rolls and the noise level near them was reduced to below 100 dBA which comes from other machine parts. In addition, noise levels were reduced between 2 and 15 dBA at different points in the factory.

  8. Reduction of phase noise to amplitude noise conversion in silicon waveguide-based phase-sensitive amplification.

    Science.gov (United States)

    Ma, Yonghua; Liu, Hongjun; Sun, Qibing; Huang, Nan; Wang, Zhaolu

    2016-04-20

    We use a vector phase sensitive amplification (PSA) scheme, which can eliminate the inherent phase noise (PN) to amplitude noise (AN) conversion in a conventional PSA process. A dispersion-engineered silicon strip waveguide is used to investigate the vector PSA scheme at the telecom wavelengths. The phase-dependent gain and phase-to-phase transfer functions as well as constellation diagram at different signal polarization states (SPSs) are numerically analyzed. It is found that the PN to AN conversion is completely suppressed when the SPS is identical to one of the pump polarization states. Moreover, the binary phase shift keying signal is regenerated by the proposed vector PSA scheme, and the error vector magnitude is calculated to assess the regeneration capacity. Our results have potential application in all-optical signal processing.

  9. Reduction of Striping Noise in Overlapping LIDAR Intensity Data by Radiometric Normalization

    Science.gov (United States)

    Yan, Wai Yeung; Shaker, Ahmed

    2016-06-01

    To serve seamless mapping, airborne LiDAR data are usually collected with multiple parallel strips with one or two cross strip(s). Nevertheless, the overlapping regions of LiDAR data strips are usually found with unbalanced intensity values, resulting in the appearance of stripping noise. Despite that physical intensity correction methods are recently proposed, some of the system and environmental parameters are assumed as constant or not disclosed, leading to such an intensity discrepancy. This paper presents a new normalization technique to adjust the radiometric misalignment found in the overlapping LiDAR data strips. The normalization technique is built upon a second-order polynomial function fitted on the joint histogram plot, which is generated with a set of pairwise closest data points identified within the overlapping region. The method was tested on Teledyne Optech's Gemini dataset (at 1064 nm wavelength), where the LiDAR intensity data were first radiometrically corrected based on the radar (range) equation. Five land cover features were selected to evaluate the coefficient of variation (cv) of the intensity values before and after implementing the proposed method. Reduction of cv was found by 19% to 59% in the Gemini dataset, where the striping noise was significantly reduced in the radiometrically corrected and normalized intensity data. The Gemini dataset was also used to conduct land cover classification, and the overall accuracy yielded a notable improvement of 9% to 18%. As a result, LiDAR intensity data should be pre-processed with radiometric correction and normalization prior to any data manipulation.

  10. Collisional Dephasing and the Reduction of Laser Phase-Noise to Amplitude-Noise Conversion in a Resonant Atomic Vapor

    Science.gov (United States)

    2007-11-02

    Further, since the samev alue of P, is obtained for both curves, this statement ap- Here, keg and iAeg are the transition wavelength and dipole pears to be...pressure to have no effect on the signal-to- 1 noise ratio and to simply increase Av, thereby degrading A 10-4 spectroscopic sensitivity. However, as shown...and evaluation. Space Materials Laboratory: Evaluation and characterizations of new materials and processing techniques: metals, alloys , ceramics

  11. Acoustics. Measurement of sound insulation in buildings and of building elements. Laboratory measurements of the reduction of transmitted impact noise by floor coverings on a heavyweight standard floor

    CERN Document Server

    British Standards Institution. London

    1998-01-01

    Acoustics. Measurement of sound insulation in buildings and of building elements. Laboratory measurements of the reduction of transmitted impact noise by floor coverings on a heavyweight standard floor

  12. Reduction of the radiating sound of a submerged finite cylindrical shell structure by active vibration control.

    Science.gov (United States)

    Kim, Heung Soo; Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok

    2013-02-06

    In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

  13. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    Directory of Open Access Journals (Sweden)

    Seung-Bok Choi

    2013-02-01

    Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

  14. A noise-reduction GWAS analysis implicates altered regulation of neurite outgrowth and guidance in autism

    Directory of Open Access Journals (Sweden)

    Hussman John P

    2011-01-01

    Full Text Available Abstract Background Genome-wide Association Studies (GWAS have proved invaluable for the identification of disease susceptibility genes. However, the prioritization of candidate genes and regions for follow-up studies often proves difficult due to false-positive associations caused by statistical noise and multiple-testing. In order to address this issue, we propose the novel GWAS noise reduction (GWAS-NR method as a way to increase the power to detect true associations in GWAS, particularly in complex diseases such as autism. Methods GWAS-NR utilizes a linear filter to identify genomic regions demonstrating correlation among association signals in multiple datasets. We used computer simulations to assess the ability of GWAS-NR to detect association against the commonly used joint analysis and Fisher's methods. Furthermore, we applied GWAS-NR to a family-based autism GWAS of 597 families and a second existing autism GWAS of 696 families from the Autism Genetic Resource Exchange (AGRE to arrive at a compendium of autism candidate genes. These genes were manually annotated and classified by a literature review and functional grouping in order to reveal biological pathways which might contribute to autism aetiology. Results Computer simulations indicate that GWAS-NR achieves a significantly higher classification rate for true positive association signals than either the joint analysis or Fisher's methods and that it can also achieve this when there is imperfect marker overlap across datasets or when the closest disease-related polymorphism is not directly typed. In two autism datasets, GWAS-NR analysis resulted in 1535 significant linkage disequilibrium (LD blocks overlapping 431 unique reference sequencing (RefSeq genes. Moreover, we identified the nearest RefSeq gene to the non-gene overlapping LD blocks, producing a final candidate set of 860 genes. Functional categorization of these implicated genes indicates that a significant proportion of

  15. Optical Fiber Sensors for Infrasonic Wind Noise Reduction and Earth Strain Measurement

    Science.gov (United States)

    DeWolf, Scott

    Fiber-based interferometers provide the means to sense very small displacements over long baselines, and have the advantage of being nearly completely passive in their operation, making them particularly well suited for geophysical applications. This work presents the development and results from four new systems: one in atmospheric acoustics and three in Earth strain. Turbulent pressure fluctuations (wind noise) are a significant limiting factor in low-frequency atmospheric acoustic measurements. The Optical Fiber Infrasound Sensor (OFIS) provides an alternative to traditional infrasonic wind noise reduction (WNR) techniques by providing an instantaneous average over a large spatial extent. This study shows that linear OFISs ranging in length from 30 to 270 m provide a WNR of up to 30 dB in winds up to 5 m/s, in good agreement with a new analytical model. Arrays of optical fiber strainmeters were deployed to measure sediment compaction at two sites in Bangladesh. One array at Jamalganj (in the north) consists of 20, 40, 60, and 100 m long strainmeters, while the second near Khulna (in the south) also includes lengths of 80 and 300 m. Two years of weekly measurements show a clear seasonal signal and subsidence at both sites that is in reasonable agreement with collocated GPS receivers. A new 250-meter, interferometric vertical borehole strainmeter has been developed based completely on passive optical components. Details of the prototyping, design, and deployment at the Pinon Flat Observatory (PFO) are presented. Power spectra show an intertidal noise level of -130 dB (re. 1 epsilon/Hz), consistent within 1-3 dB between redundant components. Examination of its response to Earth tides and earthquakes relative to the areal strain recorded by an orthogonal pair of collocated, 730 m horizontal laser strainmeters yield a Poisson's ratio of 0.26. Two prototype horizontal strainmeters were also developed to explore the use of similar interferometric optical fiber

  16. Reduction of diesel engine exhaust noise in the petroleum mining industry. [by resonator type diffuser

    Science.gov (United States)

    Marinov, T.

    1974-01-01

    An important noise source in a drilling plant is Diesel engine exhaust. In order to reduce this noise, a reactive silencer of the derivative resonator type was proposed, calculated from the acoustic and design point of view and applied. As a result of applying such a silencer on the exhaust conduit of a Diesel engine the noise level dropped down to 18 db.

  17. Efficient reduction of complex noise in passive millimeter-wavelength video utilizing Bayesian surprise

    Science.gov (United States)

    Mundhenk, T. Nathan; Baron, Josh; Matic, Roy M.

    2011-06-01

    Passive millimeter wavelength (PMMW) video holds great promise given its ability to see targets and obstacles through fog, smoke and rain. However, current imagers produce undesirable complex noise. This can come as a mixture of fast shot (snow like) noise and a slower forming circular fixed pattern. Shot noise can be removed by a simple gain style filter. However, this can produce blurring of objects in the scene. To alleviate this, we measure the amount of Bayesian surprise in videos. Bayesian surprise is feature change in time which is abrupt, but cannot be accounted for as shot noise. Surprise is used to attenuate the shot noise filter in locations of high surprise. Since high Bayesian surprise in videos is very salient to observers, this reduces blurring particularly in places where people visually attend. Fixed pattern noise is removed after the shot noise using a combination of Non-uniformity correction (NUC) and Eigen Image Wavelet Transformation. The combination allows for online removal of time varying fixed pattern noise even when background motion may be absent. It also allows for online adaptation to differing intensities of fixed pattern noise. The fixed pattern and shot noise filters are all efficient allowing for real time video processing of PMMW video. We show several examples of PMMW video with complex noise that is much cleaner as a result of the noise removal. Processed video clearly shows cars, houses, trees and utility poles at 20 frames per second.

  18. Integrated solid-state nanopore platform for nanopore fabrication via dielectric breakdown, DNA-speed deceleration and noise reduction

    Science.gov (United States)

    Goto, Yusuke; Yanagi, Itaru; Matsui, Kazuma; Yokoi, Takahide; Takeda, Ken-Ichi

    2016-08-01

    The practical use of solid-state nanopores for DNA sequencing requires easy fabrication of the nanopores, reduction of the DNA movement speed and reduction of the ionic current noise. Here, we report an integrated nanopore platform with a nanobead structure that decelerates DNA movement and an insulating polyimide layer that reduces noise. To enable rapid nanopore fabrication, we introduced a controlled dielectric breakdown (CDB) process into our system. DNA translocation experiments revealed that single nanopores were created by the CDB process without sacrificing performance in reducing DNA movement speed by up to 10 μs/base or reducing noise up to 600 pArms at 1 MHz. Our platform provides the essential components for proceeding to the next step in the process of DNA sequencing.

  19. Noise exposure immediately activates cochlear mitogen-activated protein kinase signaling

    Directory of Open Access Journals (Sweden)

    Kumar N Alagramam

    2014-01-01

    Full Text Available Noise-induced hearing loss (NIHL is a major public health issue worldwide. Uncovering the early molecular events associated with NIHL would reveal mechanisms leading to the hearing loss. Our aim is to investigate the immediate molecular responses after different levels of noise exposure and identify the common and distinct pathways that mediate NIHL. Previous work showed mice exposed to 116 decibels sound pressure level (dB SPL broadband noise for 1 h had greater threshold shifts than the mice exposed to 110 dB SPL broadband noise, hence we used these two noise levels in this study. Groups of 4-8-week-old CBA/CaJ mice were exposed to no noise (control or to broadband noise for 1 h, followed by transcriptome analysis of total cochlear RNA isolated immediately after noise exposure. Previously identified and novel genes were found in all data sets. Following exposure to noise at 116 dB SPL, the earliest responses included up-regulation of 243 genes and down-regulation of 61 genes, while a similar exposure at 110 dB SPL up-regulated 155 genes and down-regulated 221 genes. Bioinformatics analysis indicated that mitogen-activated protein kinase (MAPK signaling was the major pathway in both levels of noise exposure. Nevertheless, both qualitative and quantitative differences were noticed in some MAPK signaling genes, after exposure to different noise levels. Cacna1b , Cacna1g , and Pla2g6 , related to calcium signaling were down-regulated after 110 dB SPL exposure, while the fold increase in the expression of Fos was relatively lower than what was observed after 116 dB SPL exposure. These subtle variations provide insight on the factors that may contribute to the differences in NIHL despite the activation of a common pathway.

  20. Experimental study of the effect of viscoelastic damping materials on noise and vibration reduction within railway vehicles

    Science.gov (United States)

    Fan, Rongping; Meng, Guang; Yang, Jun; He, Caichun

    2009-01-01

    Interior noise and vibration reduction has become one important concern of railway operating environments due to the influence of increased speeds and reduced vehicle weights for energy efficiency. Three types of viscoelastic damping materials, bitumen-based damping material, water-based damping coating and butyl rubber damping material, were developed to reduce the vibration and noise within railway vehicles. Two sleeper carriages were furnished with the new materials in different patterns of constrained-layer and free-layer damping treatment. The measurements of vibration and noise were carried out in three running carriages. It is found that the reduction effect of damping treatments depends on the running speed. The unweighted root-mean-square acceleration is reduced by 0.08-0.79 and 0.06-0.49 m/s 2 for the carriage treated by bitumen-based as well as water-based damping materials and water-based damping material, respectively. The first two materials reduce vibration in a wider frequency range of 63-1000 Hz than the last. It turns out that the damping treatments of the first two reduce the interior noise level by 5-8 dBA within the carriage, and the last damping material by 1-6 dBA. However, the specific loudness analysis of noises shows that the noise components between 125 and 250 Hz are dominant for the overall loudness, although the low-frequency noise is noticeably decreased by the damping materials. The measure of loudness is shown to be more accurate to assess reduction effect of the damping material on the acoustic comfort.

  1. 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.

  2. Reduction of noise influence during the periodical inspection of the nuclear power plant

    Energy Technology Data Exchange (ETDEWEB)

    Hikono, Masaru [Inst. of Nuclear Safety System Inc., Mihama, Fukui (Japan)

    2002-09-01

    At the nuclear power plant under the regular inspection, the sound level and the worker's impression of the environmental noises were measured. The environmental noise was the level with a possibility to cause the noise-induced deafness and have the psychological influence on the workers such as ''Get irritated''. These results imply the necessity of the noise countermeasure. For the noise influence relaxation, we examined the effectiveness of ear protections (e.g., ear plugs) and the intelligibility improvement of the paging system, prepared the noise management manual and the educational leaflet for the support of worker's self-defense. The results of the examinations showed that ear plug was effective especially in the high-noise environment and that the improvement of paging system increased the intelligibility. (author)

  3. 智能软降噪算法研究%AN INTELLIGENT SOFT ACOUSTIC NOISE REDUCTION ALGORITHM

    Institute of Scientific and Technical Information of China (English)

    叶尔江·哈力木; 曼苏乐; 古丽米拉·克孜尔别克; 张秀彬

    2013-01-01

    In this paper, an intelligent soft acoustic noise reduction algorithm is proposed in light of the properties of complex, chaotic and unknown the noise spatial distribution has. Based on defining the description of typical "unknown noise signal groups" in the definition of " generalised noise" , the algorithm employs decomposition operation of transformation matrix to make the noise sources express their spatial location in polar coordinate, therefore it is able to decompose and locate the noise sources emerged from different positions of spatial regions with various emission direction angles. At the same time, this algorithm makes use of the " unknown noise signal groups containing foreseen specific frequency signals" , and extracts the useful "foreseen singles" in condition of removing all the noise interference to achieve the effect of effective cancelling out the noise signals.%针对噪声空间分布的复杂性、混沌性和未知性提出一种智能软降噪算法.该算法在建立“广义噪声”定义下典型“未知噪声信号群”描述的基础上,通过转换矩阵的分解运算,使得噪声源以极坐标来表达其空间位置,因此能够将来自空域不同位置及其发射方向角的噪声源进行分解与定位.同时利用“包含预知特定频率信号的未知噪声信号群”,将其中有用“预知信号”在去除所有噪声干扰的情况下提取出来,达到高效镇噪效果.

  4. The effects of digital image processing for noise reduction on observer performance

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Young Chul; Choi, Bo Ram; Huh, Kyung Hoi; Yi, Won Jin; Heo, Min Suk; Lee, Sam Sun; Choi, Soon Chul [School of Dentistry, Seoul National University, Seoul (Korea, Republic of)

    2010-09-15

    This study was performed to examine the effects of image filter on observer performance by counting the number of holes at each wedge step on a radiographic image. An aluminum step wedge with 11 steps ranged in thickness from 1.5 mm to 16.5 mm in 1.5 mm increments was fabricated for this study. Each step had 10 notched holes with 1.0 mm diameter on the bottom of the step wedge which were ranged in depths from 0.1 mm to 1.0 mm in 0.1 mm increments. Digital radiographic raw images of the aluminum step wedge were acquired by using CCD intraoral sensor. The images were processed using several types of noise reduction filters and kernel sizes. Three observers counted the number of holes which could be discriminated on each step. The data were analyzed by ANOVA. The number of holes at each step was decreased as the thickness of step was increased. The number of holes at each step on the raw images was significantly higher than that on the processed images. The number of holes was different according to the types and kernel sizes of the image filters. The types and kernel sizes of image filters on observer performance were important, therefore, they should be standardized for commercial digital imaging systems.

  5. Phasor Representation for Narrowband Active Noise Control Systems

    Directory of Open Access Journals (Sweden)

    Chen Fu-Kun

    2008-01-01

    Full Text Available The phasor representation is introduced to identify the characteristic of the active noise control (ANC systems. The conventional representation, transfer function, cannot explain the fact that the performance will be degraded at some frequency for the narrowband ANC systems. This paper uses the relationship of signal phasors to illustrate geometrically the operation and the behavior of two-tap adaptive filters. In addition, the best signal basis is therefore suggested to achieve a better performance from the viewpoint of phasor synthesis. Simulation results show that the well-selected signal basis not only achieves a better convergence performance but also speeds up the convergence for narrowband ANC systems.

  6. Phasor Representation for Narrowband Active Noise Control Systems

    Directory of Open Access Journals (Sweden)

    Fu-Kun Chen

    2008-05-01

    Full Text Available The phasor representation is introduced to identify the characteristic of the active noise control (ANC systems. The conventional representation, transfer function, cannot explain the fact that the performance will be degraded at some frequency for the narrowband ANC systems. This paper uses the relationship of signal phasors to illustrate geometrically the operation and the behavior of two-tap adaptive filters. In addition, the best signal basis is therefore suggested to achieve a better performance from the viewpoint of phasor synthesis. Simulation results show that the well-selected signal basis not only achieves a better convergence performance but also speeds up the convergence for narrowband ANC systems.

  7. An improved affine projection algorithm for active noise cancellation

    Science.gov (United States)

    Zhang, Congyan; Wang, Mingjiang; Han, Yufei; Sun, Yunzhuo

    2017-08-01

    Affine projection algorithm is a signal reuse algorithm, and it has a good convergence rate compared to other traditional adaptive filtering algorithm. There are two factors that affect the performance of the algorithm, which are step factor and the projection length. In the paper, we propose a new variable step size affine projection algorithm (VSS-APA). It dynamically changes the step size according to certain rules, so that it can get smaller steady-state error and faster convergence speed. Simulation results can prove that its performance is superior to the traditional affine projection algorithm and in the active noise control (ANC) applications, the new algorithm can get very good results.

  8. Proposal for a limit value reduction scenario for road vehicles compatible with the German national traffic noise prevention. Package II

    Energy Technology Data Exchange (ETDEWEB)

    Steven, Heinz [Data Analysis and Consultancy, Heinsberg (Germany)

    2012-03-15

    With COM(2011) 856 final from 09.12.2011 the EU Commission launched a proposal for a regulation of the European Parliament and of the Council on the sound level of motor vehicles. This proposal is related to motor vehicles having at least four wheels. Objective and aim are described as follows: ''The objective of the proposal is to ensure a high level of health and environmental protection and to safeguard the Internal Market for motor vehicles as regards their sound level. The proposal aims at reducing environmental noise by introducing a new test method for measuring noise emissions, by lowering the noise limit values, by including additional sound emission provisions in the type-approval procedure...'' (see paragraph 1 of the explanatory memorandum). Under the bullet point ''- new limit values'' of paragraph 1 of the explanatory memorandum the following statements are listed: ''On the basis of the results of the monitoring data an impact assessment has been prepared with different policy options for the noise test method and corresponding limit values. According to the most preferable option the limit values for light and medium size vehicles will be lowered in two steps of each 2 dB(A) and for heavy vehicles in a first step of 1 and a second step of 2 dB(A). This will result in a reduction of the noise impact of about 3 dB(A) for free flowing traffic and up to 4 dB(A) for intermittent traffic. The reduction of the number of highly annoyed people will be 25 %. The cost-benefit ratio for this measure is estimated to be around 20 times in favour of the noise reduction compared to no action taken.'' The forecast for the reduction of the noise impact in real traffic is far too optimistic. It is highly unlikely that the reduction of limit values by 3 to 4 dB will lead to a reduction of the noise impact in real traffic by the same amount without any deterioration factor. Own calculations with the TRANECAM

  9. Effect of advanced aircraft noise reduction technology on the 1990 projected noise environment around Patrick Henry Airport. [development of noise exposure forecast contours for projected traffic volume and aircraft types

    Science.gov (United States)

    Cawthorn, J. M.; Brown, C. G.

    1974-01-01

    A study has been conducted of the future noise environment of Patric Henry Airport and its neighboring communities projected for the year 1990. An assessment was made of the impact of advanced noise reduction technologies which are currently being considered. These advanced technologies include a two-segment landing approach procedure and aircraft hardware modifications or retrofits which would add sound absorbent material in the nacelles of the engines or which would replace the present two- and three-stage fans with a single-stage fan of larger diameter. Noise Exposure Forecast (NEF) contours were computed for the baseline (nonretrofitted) aircraft for the projected traffic volume and fleet mix for the year 1990. These NEF contours are presented along with contours for a variety of retrofit options. Comparisons of the baseline with the noise reduction options are given in terms of total land area exposed to 30 and 40 NEF levels. Results are also presented of the effects on noise exposure area of the total number of daily operations.

  10. Application of High Order X-LMS Filter for Active Noise Control

    Directory of Open Access Journals (Sweden)

    N.V.K.Mahalakshmi

    2014-06-01

    Full Text Available In this paper active noise is controlled by using higher order X-LMS (least mean square filter. This technique is based on X-NLMS (normalized least mean square, also known as traditional acoustic noise cancellation (ANC scheme. It cancels the wideband noise from the corrupted speech signal. The active noise reducing headphone is probably the most successful application of active control of sound – the technology of cancelling sound with sound i.e., by using anti-noise signal. This report presents an outlined technical review of noise cancellation in headphones. The principles of passive noise attenuation are presented after which active attenuation is introduced showing how the two complement the attenuation performance. In real-time environment, the number of different applications in which adaptive techniques are being successfully used that are echo cancellation, equalization of dispersive channels, system identification, signal enhancement, noise cancelling and control.

  11. 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.

  12. 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

  13. 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...

  14. 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.)

  15. Research of Noise Reduction with Steeper Approach%大角度进近减噪探索研究

    Institute of Scientific and Technical Information of China (English)

    闫国华; 费代祥

    2011-01-01

    随民航事业的蓬勃发展,机场周围的飞机噪声问题已变得不可小觑.基于噪声源研究已相当成熟,本文从飞机减噪程序入手,研究国内外常见的几种进近减噪程序,重点探索研究大角度(6度角)飞机进近减噪程序,结合国际民航组织的相关研究项目,用飞机着陆噪声区域面积的减少来阐述大角度进近的潜在益处.%With the development of civil aviation industry, the aircraft's noise around the airports has been becoming a serious problem. In this paper, several domestic and international noise reduction procedures are studied. The attention is paid mainly to the steeper (6 degrees) approach noise reduction procedures. The potential benefits of the steeper approach are evaluated by the reduction of the area covered by the noise of aircraft' s landing. This work is a part of the project supported by the International Civil Aviation Organization (ICAO).

  16. Study of active noise control system for a commercial HVAC unit

    Science.gov (United States)

    Devineni, Naga

    Acoustic noise is a common problem in everyday life. If the appliances that are present in the work and living areas generate noise then it's a serious problem. One such appliance is the Heating, Ventilation and Air-conditioning system (HVAC) in which blower fan and compressor units are housed together. Operation of a HVAC system creates two kinds of noise. One is the noise due to the air flow and the other is the result of the compressor. Both of them exhibit different signal properties and need different strategies to control them. There has been previous efforts in designing noise control systems that can control noise from the HVAC system. These include passive methods which use sound absorption materials to attenuate noise and active methods which cancel noise by generating anti-noise. Passive methods are effective in limiting the high frequency noise, but are inefficient in controlling low frequency noise from the compressor. Compressor noise is one of the strong low frequency components that propagate through the walls, therefore there is need for deploying active signal processing methods that consider the signal properties into consideration to cancel the noise acoustically. The quasi periodic nature of the compressor noise is exploited in noise modeling which aids in implementing an adaptive linear prediction filter in estimating the anti noise [12]. In this thesis, a multi channel architecture has been studied for a specific HVAC system in order to improve noise cancellation by creating larger quiet zone. In addition to the multi-channel architecture, a real time narrow band Active Noise Control (ANC) was employed to cancel noise under practical conditions.

  17. Multiple enhancements of rate oscillations by non-Gaussian noise in NO reduction with CO on Pt(100)

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The effect of the non-Gaussian colored noise(NGN) on the dynamics of nonlinear systems has attracted increasing attention.This work numerically studied the effect of a particular kind of the NGN,mainly in terms of its departure from Gaussian noise,on the rate oscillations(RO) in the catalytic reduction of NO with CO on Pt(100) surfaces.It was found that power spectrum density changes non-monotonically and the signal-to-noise ratio shows several peaks with increasing departure,demonstrating the presence of"departure-induced multiple resonance".Since the departure of the NGN determines the probability distribution and hence denotes the type of the noise,the phenomenon of"departure-induced multiple resonance"not only gives multiple enhancements of the RO by virtue of the departure of the NGN,but also implies that,besides Gaussian noise,various other types of noise may enhance the RO in the surface catalytic reaction systems.

  18. DFT-domain based single-microphone noise reduction for speech enhancement a survey of the state of the art

    CERN Document Server

    Hendriks, Richard C; Jensen, Jesper

    2013-01-01

    As speech processing devices like mobile phones, voice controlled devices, and hearing aids have increased in popularity, people expect them to work anywhere and at any time without user intervention. However, the presence of acoustical disturbances limits the use of these applications, degrades their performance, or causes the user difficulties in understanding the conversation or appreciating the device. A common way to reduce the effects of such disturbances is through the use of single-microphone noise reduction algorithms for speech enhancement.The field of single-microphone noise reducti

  19. Conceptual design study of advanced acoustic composite nacelle. [for achieving reductions in community noise and operating expense

    Science.gov (United States)

    Goodall, R. G.; Painter, G. W.

    1975-01-01

    Conceptual nacelle designs for wide-bodied and for advanced-technology transports were studied with the objective of achieving significant reductions in community noise with minimum penalties in airplane weight, cost, and in operating expense by the application of advanced composite materials to nacelle structure and sound suppression elements. Nacelle concepts using advanced liners, annular splitters, radial splitters, translating centerbody inlets, and mixed-flow nozzles were evaluated and a preferred concept selected. A preliminary design study of the selected concept, a mixed flow nacelle with extended inlet and no splitters, was conducted and the effects on noise, direct operating cost, and return on investment determined.

  20. High Temperature Smart Structures for Engine Noise Reduction and Performance Enhancement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Noise mitigation for subsonic transports is a continuing high priority, and recent work has identified successful exhaust mixing enhancement devices that have...

  1. High Temperature Smart Structures for Engine Noise Reduction and Performance Enhancement Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Noise mitigation for subsonic transports is a continuing high priority, and recent work has identified successful exhaust mixing enhancement devices (chevrons) that...

  2. The influence of preconceptions on perceived sound reduction by environmental noise barriers.

    Science.gov (United States)

    Joynt, Jennifer L R; Kang, Jian

    2010-09-15

    The paper presents research that answers three main questions: (1) Do preconceptions held about the constituent materials of an environmental noise barrier affect how people perceive the barrier will perform at attenuating noise? (2) Does aesthetic preference influence the perception of how a barrier will perform? (3) Are barriers, which are deemed more aesthetically pleasing, more likely to be perceived as better noise attenuators? In a virtual reality setting with film to improve the contextual realism of the intersensory interaction test, participants were required to compare the perceived effectiveness of five standard 'in-situ' noise barriers, including concrete, timber, metal, transparent acrylic and a vegetative screen. The audio stimulus was held at a constant sound pressure level (SPL), whilst the visual stimulus changed, as the influential factor. As the noise levels projected during the study were held constant, it was possible to attribute the participants' perception of noise attenuation by the barriers, to preconceptions of how the varying barrier material would attenuate noise. There was also an inverse correlation between aesthetics and perception of how a noise barrier would perform. The transparent and deciduous vegetation barriers, judged most aesthetically pleasing, were judged as the least effective at attenuating noise.

  3. Danish activities concerning noise in the environment (A)

    DEFF Research Database (Denmark)

    Ingerslev, Fritz

    1982-01-01

    the country in international collaboration. It is claimed that noise abatement will be diffuse and weak, if it is not based on a national strategy. The discussion of noise in the environment covers: external industrial noise, road traffic noise, and air traffic noise. The principles on which the maximum....... The regulations concerning road traffic noise are based on results of extensive interviews of persons living in areas with various exposure levels. The results of these interviews will be reported as well as the conclusions drawn....

  4. Application of Adaptive Filters to Active Noise Control

    Institute of Scientific and Technical Information of China (English)

    PEI Bingnan; LI Chuanguang

    2001-01-01

    A modified LMS algorithm for noise-control is suggested after a mathematical model ofsound-cancellation is established, on the basis of thesound wave interference principle and the physicalmodel of progressive waves in a duct. Its applicationin controlling noise with the frequency range from 100to 800 Hz can be implemented by using the adaptivedigital signal processing technique. The experimentson a pink noise, a broadband noise and a noise takenfrom a tank were made, which show that there existsan attenuation of 11 dB at the frequency of 500 Hzor so, and that the proposed adaptive noise controltechnique is very effective and valid.

  5. Performing Active Noise Control and Acoustic Experiments Remotely

    Directory of Open Access Journals (Sweden)

    Imran Khan

    2012-12-01

    Full Text Available This paper presents a novel and advanced remotely controlled laboratory for conducting Active Noise Control (ANC, acoustic and Digital Signal Processing (DSP experiments. The laboratory facility, recently developed by Blekinge Institute of Technology (BTH Sweden, supports remote learning through internet covering beginners level such as simple experimental measurements to advanced users and even researchers such as algorithm development and their performance evaluation on DSP. The required software development for ANC algorithms and equipment control are carried out anywhere in the world remotely from an internet-connected client PC using a standard web browser. The paper describes in detail how ANC, acoustic and DSP experiments can be performed remotely The necessary steps involved in an ANC experiment such as validity of ANC, forward path estimation and active control applied to a broad band random noise [0-200Hz] in a ventilation duct will be described in detail. The limitations and challenges such as the forward path and nonlinearities pertinent to the remote laboratory setup will be described for the guidance of the user. Based on the acoustic properties of the ventilation duct some of the possible acoustic experiments such as mode shapes analysis and standing waves analysis etc. will also be discussed in the paper.

  6. Smart Materials and Active Noise and Vibration Control in Vehicles

    NARCIS (Netherlands)

    Doppenberg, E.J.J.; Berkhoff, A.P.; Overbeek, van M.

    2001-01-01

    The paper presents the results for the reduction of sound radiated from a structure using different control methodologies, and discusses two approaches for active structural acoustic control: the acoustic approach or the vibro-acoustic approach. Integrated actuators in structure material are necessa

  7. Smart Materials and Active Noise and Vibration Control in Vehicles

    NARCIS (Netherlands)

    Doppenberg, E.J.J.; Berkhoff, Arthur P.; van Overbeek, M.; Gissinger, G.L.

    2001-01-01

    The paper presents the results for the reduction of sound radiated from a structure using different control methodologies, and discusses two approaches for active structural acoustic control: the acoustic approach or the vibro-acoustic approach. Integrated actuators in structure material are

  8. What kind of noise is brain noise? Anomalous scaling behavior of the resting brain activity fluctuations.

    Directory of Open Access Journals (Sweden)

    Daniel eFraiman

    2012-07-01

    Full Text Available The study of spontaneous fluctuations of brain activity, often referred as brain noise, is getting increasing attention in functional magnetic resonance imaging (fMRI studies. Despite important efforts, much of the statistical properties of such fluctuations remain largely unknown. This work scrutinize these fluctuations looking at specific statistical properties which are relevant to clarify its dynamical origins. Here, three statistical features which clearly differentiate brain data from naive expectations for random processes are uncovered: First, the variance of the fMRI mean signal as a function of the number of averaged voxels remains constant across a wide range of observed clusters sizes. Second, the anomalous behavior of the variance is originated by bursts of synchronized activity across regions, regardless of their widely different sizes. Finally, the correlation length (i.e., the length at which the correlation strength between two regions vanishes as well as mutual information diverges with the cluster's size considered, such that arbitrarily large clusters exhibit the same collective dynamics than smaller ones. These three properties are known to be exclusive of complex systems exhibiting critical dynamics, where the spatio-temporal dynamics show these peculiar type of fluctuations. Thus, these findings are fully consistent with previous reports of brain critical dynamics, and are relevant for the interpretation of the role of fluctuations and variability in brain function in health and disease.

  9. Pratt & Whitney/Boeing Engine Validation of Noise Reduction Concepts Final Report for NASA Contract NAS3-97144, Phase 2

    Science.gov (United States)

    Bock, Larry A.; Hauser, Joseph E.; Mathews, Douglas C.; Topol, David A.; Bielak, Gerald W.; Lan, Justin H.; Premo, John W.

    2014-01-01

    This report presents results of the work completed in Phase 2 of the Engine Validation of Noise Reduction Concepts (EVNRC) contract. The purpose of the program is to validate, through engine testing, advanced noise reduction concepts aimed at reducing engine noise up to 6 EPNdB and improving nacelle suppression by 50 percent relative to 1992 technology. Phase 1 of the program is completed and is summarized in NASA/CR-2014-218088.

  10. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    OpenAIRE

    Seung-Bok Choi; Juncheol Jeon; Jung Woo Sohn; Heung Soo Kim

    2013-01-01

    In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs) were used as actuators and sensors. One MFC was used as an excite...

  11. An efficient feedback active noise control algorithm based on reduced-order linear predictive modeling of FMRI acoustic noise.

    Science.gov (United States)

    Kannan, Govind; Milani, Ali A; Panahi, Issa M S; Briggs, Richard W

    2011-12-01

    Functional magnetic resonance imaging (fMRI) acoustic noise exhibits an almost periodic nature (quasi-periodicity) due to the repetitive nature of currents in the gradient coils. Small changes occur in the waveform in consecutive periods due to the background noise and slow drifts in the electroacoustic transfer functions that map the gradient coil waveforms to the measured acoustic waveforms. The period depends on the number of slices per second, when echo planar imaging (EPI) sequencing is used. Linear predictability of fMRI acoustic noise has a direct effect on the performance of active noise control (ANC) systems targeted to cancel the acoustic noise. It is shown that by incorporating some samples from the previous period, very high linear prediction accuracy can be reached with a very low order predictor. This has direct implications on feedback ANC systems since their performance is governed by the predictability of the acoustic noise to be cancelled. The low complexity linear prediction of fMRI acoustic noise developed in this paper is used to derive an effective and low-cost feedback ANC system.

  12. Research and application of inertia-gravity dedusting and noise reduction technology in mine airshaft outlet%Research and application of inertia-gravity dedusting and noise reduction technology in mine airshaft outlet

    Institute of Scientific and Technical Information of China (English)

    Wang Haiqiao; Li Yiqun; Chen Shiqiang

    2011-01-01

    Massive dust of exhausted airflow easily diffuses to the industrial square while hoisting shaft is used as return shaft in the retrograde ventilation, and certainly there is a problem of dust scattering and noise exceeding standard. In order to solve the problem, the coupled technology of dedusting and noise reduction in airshaft outlet was investigated and the device with the function of Dedusting and noise Reduction (DR) was originated. The device is named as DR diffuser, which comprehensively utilizes mechanisms of inertia-gravity dedusting and absorption-insulation sound. The DR diffuser has been applied to Xingdong Coal Mine, and the testing results show that: a. the resistance of DR diffuser is lower than 60 Pa; b. the noise level reaches to 49.2 dB(A) ; c. the dedusting efficiency of above 50 μm is higher than 85 % ; d. dynamic pressure recovered from the outlet of main fan is larger than 50 Pa. The above measured data illustrates that comprehensive benefit of the DR diffuser is good, and the device is worth of applying to engineering site.

  13. Investigation of Flow Conditioners for Compact Jet Engine Simulator Rig Noise Reduction

    Science.gov (United States)

    Doty, Michael J.; Haskin, Henry H.

    2011-01-01

    The design requirements for two new Compact Jet Engine Simulator (CJES) units for upcoming wind tunnel testing lead to the distinct possibility of rig noise contamination. The acoustic and aerodynamic properties of several flow conditioner devices are investigated over a range of operating conditions relevant to the CJES units to mitigate the risk of rig noise. An impinging jet broadband noise source is placed in the upstream plenum of the test facility permitting measurements of not only flow conditioner self-noise, but also noise attenuation characteristics. Several perforated plate and honeycomb samples of high porosity show minimal self-noise but also minimal attenuation capability. Conversely, low porosity perforated plate and sintered wire mesh conditioners exhibit noticeable attenuation but also unacceptable self-noise. One fine wire mesh sample (DP450661) shows minimal selfnoise and reasonable attenuation, particularly when combined in series with a 15.6 percent open area (POA) perforated plate upstream. This configuration is the preferred flow conditioner system for the CJES, providing up to 20 dB of broadband attenuation capability with minimal self-noise.

  14. Phase noise reduction by self-phase locking in semiconductor lasers using phase conjugate feedback

    DEFF Research Database (Denmark)

    Petersen, Lykke; Gliese, Ulrik Bo; Nielsen, Torben Nørskov

    1994-01-01

    A theoretical analysis of the behavior of the frequency/phase noise of semiconductor lasers with external phase conjugate feedback is presented. It is shown that the frequency noise is drastically reduced even for lasers with butt-coupled phase conjugate mirrors. In this laser system, the phase...

  15. Reduction of Non-stationary Noise using a Non-negative Latent Variable Decomposition

    DEFF Research Database (Denmark)

    Schmidt, Mikkel Nørgaard; Larsen, Jan

    2008-01-01

    We present a method for suppression of non-stationary noise in single channel recordings of speech. The method is based on a non-negative latent variable decomposition model for the speech and noise signals, learned directly from a noisy mixture. In non-speech regions an over complete basis...

  16. The design of the motor bracket for reduction of structure-borne noise in package air-conditioner

    Energy Technology Data Exchange (ETDEWEB)

    Sim, Hyoun Jin; Lee, Sung Jin; Oh, Jae Eung [Hanyang University, Seoul (Korea, Republic of); Kang, Tae Ho [WiniaMando, Asan (Korea, Republic of); Lee, Jung Yoon [Kyonggi University, Suwon (Korea, Republic of)

    2006-02-15

    As the economic power is improved and the customer's demand is hard to please, the noise and vibration is the most important yardstick that can determine the quality of the product. Especially, as the air-conditioner's demand increase suddenly, the product of quality and the noise is becoming a decisive factor of determining whether purchase the product or not. Therefore, every manufactory is investing a lot of money and research to cut down the unpleasantness induced from noise and vibration. And they are emphasizing their product's difference by advertising a silence very actively. With these reason, the demand of a silent indoor air-conditioner is the essential research filed when the product is developed. In this study, the noise and vibration is visualized in the space and frequency domain by using experimental methods such as Operational Deflection Shape (ODS), modal testing and sound intensity. Also the location of noise source and its characteristic is analyzed in an acoustical point of view to reduce the structure borne noise that come from the fan motor, and the pertinent control method is suggested. Furthermore, the most suitable shape of the motor bracket is suggested by applying FEM and DOE (Design of Experiments) in the noise and vibration point a view.

  17. Active noise canceling system for mechanically cooled germanium radiation detectors

    Science.gov (United States)

    Nelson, Karl Einar; Burks, Morgan T

    2014-04-22

    A microphonics noise cancellation system and method for improving the energy resolution for mechanically cooled high-purity Germanium (HPGe) detector systems. A classical adaptive noise canceling digital processing system using an adaptive predictor is used in an MCA to attenuate the microphonics noise source making the system more deployable.

  18. In situ calibration of atmospheric-infrasound sensors including the effects of wind-noise-reduction pipe systems.

    Science.gov (United States)

    Gabrielson, Thomas B

    2011-09-01

    A worldwide network of more than 40 infrasound monitoring stations has been established as part of the effort to ensure compliance with the Comprehensive Nuclear Test Ban Treaty. Each station has four to eight individual infrasound elements in a kilometer-scale array for detection and bearing determination of acoustic events. The frequency range of interest covers a three-decade range-roughly from 0.01 to 10 Hz. A typical infrasound array element consists of a receiving transducer connected to a multiple-inlet pipe network to average spatially over the short-wavelength turbulence-associated "wind noise." Although the frequency response of the transducer itself may be known, the wind-noise reduction system modifies that response. In order to understand the system's impact on detection and identification of acoustical events, the overall frequency response must be determined. This paper describes a technique for measuring the absolute magnitude and phase of the frequency response of an infrasound element including the wind-noise-reduction piping by comparison calibration using ambient noise and a reference-microphone system. Measured coherence between the reference and the infrasound element and the consistency between the magnitude and the phase provide quality checks on the process. © 2011 Acoustical Society of America

  19. Elastomeric Structural Attachment Concepts for Aircraft Flap Noise Reduction - Challenges and Approaches to Hyperelastic Structural Modeling and Analysis

    Science.gov (United States)

    Sreekantamurthy, Thammaiah; Turner, Travis L.; Moore, James B.; Su, Ji

    2014-01-01

    Airframe noise is a significant part of the overall noise of transport aircraft during the approach and landing phases of flight. Airframe noise reduction is currently emphasized under the Environmentally Responsible Aviation (ERA) and Fixed Wing (FW) Project goals of NASA. A promising concept for trailing-edge-flap noise reduction is a flexible structural element or link that connects the side edges of the deployable flap to the adjacent main-wing structure. The proposed solution is distinguished by minimization of the span-wise extent of the structural link, thereby minimizing the aerodynamic load on the link structure at the expense of increased deformation requirement. Development of such a flexible structural link necessitated application of hyperelastic materials, atypical structural configurations and novel interface hardware. The resulting highly-deformable structural concept was termed the FLEXible Side Edge Link (FLEXSEL) concept. Prediction of atypical elastomeric deformation responses from detailed structural analysis was essential for evaluating feasible concepts that met the design constraints. The focus of this paper is to describe the many challenges encountered with hyperelastic finite element modeling and the nonlinear structural analysis of evolving FLEXSEL concepts. Detailed herein is the nonlinear analysis of FLEXSEL concepts that emerged during the project which include solid-section, foamcore, hollow, extended-span and pre-stressed concepts. Coupon-level analysis performed on elastomeric interface joints, which form a part of the FLEXSEL topology development, are also presented.

  20. Comparison of Two Algorithms for the Reduction of Noise Events in Orbital Optical Lightning Data

    Science.gov (United States)

    Mach, D. M.; Bateman, M. G.

    2015-12-01

    The Geostationary Lightning Mapper (GLM) will be launched as part of the GOES-R satellite. The GLM on-board software is designed to allow a large amount of non-lightning data (noise) to be transmitted to the ground. This is done so that the ground software can remove the noise while at the same time preserving the weak lightning events in the data stream. The ground software has a noise filter that removes events that do not meet certain coherency requirements. The filter utilizes the location, time, and amplitude of the event, along with the background level to determine the likelihood that the event is actually due to lightning and not noise. Due to various constraints, the technique does not use all relevant information to determine the likelihood that the event is actually due to lightning. A more complete filter that uses the full extent of the information available, including clustering results, should produce better results. However, the extra coding and complexity needed to implement the full clustering based filter may not justify the slightly better results. To test the various filter options, this study uses GLM proxy data generated from numerous ground based and orbital sources that mimic the expected characteristics of the GLM lightning event data. These proxy data sets have noise data added, again based on the expected characteristics of GLM noise data. The full proxy data sets (noise and lightning) are filtered by the two methods and the results compared.