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Sample records for acoustic source localization

  1. Acoustic source localization : exploring theory and practice

    Wind, Jelmer Wilco

    2009-01-01

    Over the past few decades, noise pollution became an important issue in modern society. This has led to an increased effort in the industry to reduce noise. Acoustic source localization methods determine the location and strength of the vibrations which are the cause of sound based onmeasurements of the sound field. This thesis describes a theoretical study of many facets of the acoustic source localization problem as well as the development, implementation and validation of new source locali...

  2. Acoustic source localization : exploring theory and practice

    Wind, Jelmer Wilco

    2009-01-01

    Over the past few decades, noise pollution became an important issue in modern society. This has led to an increased effort in the industry to reduce noise. Acoustic source localization methods determine the location and strength of the vibrations which are the cause of sound based onmeasurements of

  3. Acoustic sources' localization in presence of reverberation

    Julliard, E.; Pauzin, S.; Simon, F.; Biron, D.

    2005-09-01

    For several years, aeronautical industries have wished to improve internal acoustical comfort. In order to make it, they need metrological tools which are able to help them to spot acoustical sources and the associated path in a specific frequency range (i.e., for helicopters' internal noise: 1000-5000 Hz). Two major source' localization' tools exist: holography and beamforming, but these two techniques are based on a free field's hypothesis. So, problems appear when these techniques are used in a reverberant medium. This paper deals with the study and the comparison of holography and beamforming results in an enclosed area. To complete the study, intensimetry is also implemented to have information on the energy propagation. In order to test the performances of each method, two reflecting panels are put at right angles to create a reverberant environment, in an anechoic chamber. We seek to locate loudspeakers clamped in one panel, in the presence of parasite loudspeakers located on the other one. Then, a parametrical study is led: localization and number of sources, coherent or noncoherent sources. Thus, using limitations, precautions to take, and a base of comparison three methods are put forward. Finally, some envisaged solutions to limit problems of reflections (signal processing, overturning, etc.) are presented.

  4. Sound source localization using distributed elevated acoustic sensors

    Di, Xiao; Wagstaff, Ronald A.; Anderson, John D.; Gilbert, Kenneth E.

    2009-05-01

    Detecting and localizing impulsive acoustic sources in the daytime using distributed elevated acoustic sensors with large baseline separations has distinct advantages over small ground-based arrays. There are generally two reasons for this: first, during the daytime, because of more direct and less encumbered propagation paths, signal levels are generally larger at altitude than near the ground. Second, larger baselines provide improved localization accuracy. Results are reported from a distributed array of acoustic sensors deployed during an experiment near Bourges, France during June of 2008. The distributed array consisted of microphones and GPS receivers attached to the tether lines of three widely separated aerostats. The sound sources were various impulsive devices. Results from the measurements are presented and discussed. Localization errors (GPS accuracy, propagation calculation, and aerostat motion, etc) are discussed. Possible ways to improve the localization accuracy are suggested.

  5. Localization of multiple acoustic sources in a room environment

    Highlights: • Direction estimation of multiple acoustic sources in a room environment. • A new method was tested and implemented to reduce source direction ambiguity. • Suppression of undesired cross-correlation between different signals. • Localization of multiple acoustic sources in a room environment. • Effectiveness of hyperbolic position location algorithm for multiple sources. - Abstract: Combustion systems results in high pollution and low performance due to lack of uniform thermal and chemical behavior in the entire reactor zone. Localization of multiple acoustic sources using an array of microphones and time difference of arrival (TDOA) method is examined. Adaptations of such a scheme into high speed jet flows, combustors or reactors can help assist in the identification of local acoustic sources in a system to seek improved performance of the system. Linear microphones can be used for acoustic source localization in a practical room environment using time delay estimation. Hyperbolic position algorithm based on TDOA provides good localization of a single acoustic in both two dimensional and three dimensional space. The time delay between the signals acquired by two microphones is obtained from maximum of cross-correlation between the two signals. Noise and reverberation effects can introduce ambiguity in the time delay estimation from multiple peaks in the delay estimator. In addition directional incidence from multiple sources can result in cross talk between different sources to degrade localization accuracy. CPSP (Cross-power spectral phase analysis) is examined here for localization of multiple sound sources present in a room environment. The CPSP method localizes a sound source as a crossing point of sound directions estimated using different microphone pairs but it degrades due to cross-correlation between different sound sources. A new method based on averaging of CPSP coefficients has been examined here to reduce the directional

  6. Energy-Based Collaborative Source Localization Using Acoustic Microsensor Array

    Li Dan

    2003-01-01

    Full Text Available A novel sensor network source localization method based on acoustic energy measurements is presented. This method makes use of the characteristics that the acoustic energy decays inversely with respect to the square of distance from the source. By comparing energy readings measured at surrounding acoustic sensors, the source location during that time interval can be accurately estimated as the intersection of multiple hyperspheres. Theoretical bounds on the number of sensors required to yield unique solution are derived. Extensive simulations have been conducted to characterize the performance of this method under various parameter perturbations and noise conditions. Potential advantages of this approach include low intersensor communication requirement, robustness with respect to parameter perturbations and measurement noise, and low-complexity implementation.

  7. Localization of acoustic sources using a decentralized particle filter

    Gerstoft Peter

    2011-01-01

    Full Text Available Abstract This paper addresses the decentralized localization of an acoustic source in a (wireless sensor network based on the underlying partial differential equation (PDE. The PDE is transformed into a distributed state-space model and augmented by a source model. Inferring the source state amounts to a non-linear non-Gaussian Bayesian estimation problem for whose solution we implement a decentralized particle filter (PF operating within and across clusters of sensor nodes. The aggregation of the local posterior distributions from all clusters is achieved via an enhanced version of the maximum consensus algorithm. Numerical simulations illustrate the performance of our scheme.

  8. Acoustic Source Localization and Beamforming: Theory and Practice

    Chen Joe C

    2003-01-01

    Full Text Available We consider the theoretical and practical aspects of locating acoustic sources using an array of microphones. A maximum-likelihood (ML direct localization is obtained when the sound source is near the array, while in the far-field case, we demonstrate the localization via the cross bearing from several widely separated arrays. In the case of multiple sources, an alternating projection procedure is applied to determine the ML estimate of the DOAs from the observed data. The ML estimator is shown to be effective in locating sound sources of various types, for example, vehicle, music, and even white noise. From the theoretical Cramér-Rao bound analysis, we find that better source location estimates can be obtained for high-frequency signals than low-frequency signals. In addition, large range estimation error results when the source signal is unknown, but such unknown parameter does not have much impact on angle estimation. Much experimentally measured acoustic data was used to verify the proposed algorithms.

  9. Acoustic source localization in mixed field using spherical microphone arrays

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

  10. Localization of acoustic emission sources in geometrically sparse structures

    Převorovský, Zdeněk; Chlada, Milan

    Berlín : Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.V, 2014. ISBN 978-3-940283-63-4. [Conference of the European Working Group on Acoustic Emission : EWGAE 2014 /31./. Drážďany (DE), 03.09.2014-05.09.2014] Institutional support: RVO:61388998 Keywords : civil structures * structures health monitoring ( SHM) * acoustic emission * source location Subject RIV: BI - Acoustics

  11. Pitch and TDOA-Based Localization of Acoustic Sources with Distributed Arrays

    Hansen, Martin Weiss; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

    2015-01-01

    In this paper, a method for acoustic source localization using distributed microphone arrays based on time-differences of arrival (TDOAs) is presented. The TDOAs are used to estimate the location of an acoustic source using a recently proposed method, based on a 4D parameter space defined by the 3D...... location of the source, and the TDOAs. The performance of the proposed method for acoustic source localization is compared to the performance of a method based on generalized cross-correlation with phase transform (GCC-PHAT) using synthetic and speech signals with varying source position. Results show a...

  12. Acoustic emission source localization based on distance domain signal representation

    Gawronski, M.; Grabowski, K.; Russek, P.; Staszewski, W. J.; Uhl, T.; Packo, P.

    2016-04-01

    Acoustic emission is a vital non-destructive testing technique and is widely used in industry for damage detection, localisation and characterization. The latter two aspects are particularly challenging, as AE data are typically noisy. What is more, elastic waves generated by an AE event, propagate through a structural path and are significantly distorted. This effect is particularly prominent for thin elastic plates. In these media the dispersion phenomenon results in severe localisation and characterization issues. Traditional Time Difference of Arrival methods for localisation techniques typically fail when signals are highly dispersive. Hence, algorithms capable of dispersion compensation are sought. This paper presents a method based on the Time - Distance Domain Transform for an accurate AE event localisation. The source localisation is found through a minimization problem. The proposed technique focuses on transforming the time signal to the distance domain response, which would be recorded at the source. Only, basic elastic material properties and plate thickness are used in the approach, avoiding arbitrary parameters tuning.

  13. Localization of acoustic emission sources. Possibilities and limits

    It is necessary to dispose of a system capable of data acquisition and processing in real time. The coordinates of emissive sources must be calculated either immediately after the detection of information or after a brief storage time. Emphasis is laid on the various parameters liable to affect the measurement precision: transducers (type, selectivity, form of signal), threshold device (dynamics, influence on the precision), screening device (influence on the number of data received). Four-transducer patterns are now in common use: square, centred equilateral triangle, lozenge mesh ... Each geometry possesses zones of indetermination. The accuracy on the coordinates of the source varies according to the position of this source with respect to the four-transducer mesh, which leads to a case-by-case study of the arrangement and dimensions of the meshes placed on the structure to be observed. Detection and localization equipment must be designed as a whole system flexible and easy to adapt to any structure

  14. Acoustic Source Localization via Subspace Based Method Using Small Aperture MEMS Arrays

    Xin Zhang

    2014-01-01

    Full Text Available Small aperture microphone arrays provide many advantages for portable devices and hearing aid equipment. In this paper, a subspace based localization method is proposed for acoustic source using small aperture arrays. The effects of array aperture on localization are analyzed by using array response (array manifold. Besides array aperture, the frequency of acoustic source and the variance of signal power are simulated to demonstrate how to optimize localization performance, which is carried out by introducing frequency error with the proposed method. The proposed method for 5 mm array aperture is validated by simulations and experiments with MEMS microphone arrays. Different types of acoustic sources can be localized with the highest precision of 6 degrees even in the presence of wind noise and other noises. Furthermore, the proposed method reduces the computational complexity compared with other methods.

  15. Biology-inspired acoustic sensors for sound source localization

    Liu, Haijun; Chen, Zhong; Yu, Miao

    2008-03-01

    In this article, the design of a biology-inspired miniature directional microphone is presented. This microphone consists of two clamped circular diaphragms, which are mechanically coupled by a connecting bridge that is pivoted at its center. A theoretical model is constructed to determine the microphone response to sound incident from an arbitrary direction. Both the simulation and preliminary experimental results show that the proposed microphone provides a remarkable amplification of the time delay associated with the sound induced diaphragm responses. This study should be relevant to various sound source localization applications.

  16. Source Localization with Acoustic Sensor Arrays Using Generative Model Based Fitting with Sparse Constraints

    Javier Macias-Guarasa

    2012-10-01

    Full Text Available This paper presents a novel approach for indoor acoustic source localization using sensor arrays. The proposed solution starts by defining a generative model, designed to explain the acoustic power maps obtained by Steered Response Power (SRP strategies. An optimization approach is then proposed to fit the model to real input SRP data and estimate the position of the acoustic source. Adequately fitting the model to real SRP data, where noise and other unmodelled effects distort the ideal signal, is the core contribution of the paper. Two basic strategies in the optimization are proposed. First, sparse constraints in the parameters of the model are included, enforcing the number of simultaneous active sources to be limited. Second, subspace analysis is used to filter out portions of the input signal that cannot be explained by the model. Experimental results on a realistic speech database show statistically significant localization error reductions of up to 30% when compared with the SRP-PHAT strategies.

  17. New approaches for automatic threedimensional source localization of acoustic emissions--Applications to concrete specimens.

    Kurz, Jochen H

    2015-12-01

    The task of locating a source in space by measuring travel time differences of elastic or electromagnetic waves from the source to several sensors is evident in varying fields. The new concepts of automatic acoustic emission localization presented in this article are based on developments from geodesy and seismology. A detailed description of source location determination in space is given with the focus on acoustic emission data from concrete specimens. Direct and iterative solvers are compared. A concept based on direct solvers from geodesy extended by a statistical approach is described which allows a stable source location determination even for partly erroneous onset times. The developed approach is validated with acoustic emission data from a large specimen leading to travel paths up to 1m and therefore to noisy data with errors in the determined onsets. The adaption of the algorithms from geodesy to the localization procedure of sources of elastic waves offers new possibilities concerning stability, automation and performance of localization results. Fracture processes can be assessed more accurately. PMID:26233938

  18. Time-distance domain transformation for Acoustic Emission source localization in thin metallic plates.

    Grabowski, Krzysztof; Gawronski, Mateusz; Baran, Ireneusz; Spychalski, Wojciech; Staszewski, Wieslaw J; Uhl, Tadeusz; Kundu, Tribikram; Packo, Pawel

    2016-05-01

    Acoustic Emission used in Non-Destructive Testing is focused on analysis of elastic waves propagating in mechanical structures. Then any information carried by generated acoustic waves, further recorded by a set of transducers, allow to determine integrity of these structures. It is clear that material properties and geometry strongly impacts the result. In this paper a method for Acoustic Emission source localization in thin plates is presented. The approach is based on the Time-Distance Domain Transform, that is a wavenumber-frequency mapping technique for precise event localization. The major advantage of the technique is dispersion compensation through a phase-shifting of investigated waveforms in order to acquire the most accurate output, allowing for source-sensor distance estimation using a single transducer. The accuracy and robustness of the above process are also investigated. This includes the study of Young's modulus value and numerical parameters influence on damage detection. By merging the Time-Distance Domain Transform with an optimal distance selection technique, an identification-localization algorithm is achieved. The method is investigated analytically, numerically and experimentally. The latter involves both laboratory and large scale industrial tests. PMID:26950889

  19. Localizing Near and Far Field Acoustic Sources with Distributed Microhone Arrays

    Hansen, Martin Weiss; Jensen, Jesper Rindom; Christensen, Mads Græsbøll

    2014-01-01

    In this paper, we consider the problem of acoustic source localization using distributed microphone arrays. Time differences of arrival (TDOAs) are estimated using a recently proposed method based on joint direction of arrival (DOA) and range estimation. The TDOAs are used to estimate the location...... method based on joint DOA and pitch estimation, using synthesized harmonic signals with varying source position. Results show a decrease in the error of the estimated position when joint DOA and range estimation is used for TDOA estimation, compared to the GCC-PHAT and joint DOA and pitch methods....

  20. Localization of acoustic emission sources in tensile and ct specimens using a broadband acquisition technique.

    Fleischmann, P; Rouby, D; Malaprade, G; Lanchon, I

    1981-11-01

    The acoustic emission sources in a conventional cylindrical tensile test sample of short transversely-cut carbon manganese steel are localized. There is not always a good correlation between the localization of the first signals and the zone which eventually fractures. During the Lüder's plateau, the ae signals are emitted in the deformation band and, in the hardening range, there is no significant ae in the gauge length of the sample. In ct samples precracked by fatigue, the signals are due to the growth of the plastic zone around the crack tip, and the plastic zone size, measured by source localization, agrees with those provided by models derived from fracture mechanics. PMID:7292774

  1. Localization of Directional Sound Sources Supported by A Priori Information of the Acoustic Environment

    András Radványi

    2007-11-01

    Full Text Available Speaker localization with microphone arrays has received significant attention in the past decade as a means for automated speaker tracking of individuals in a closed space for videoconferencing systems, directed speech capture systems, and surveillance systems. Traditional techniques are based on estimating the relative time difference of arrivals (TDOA between different channels, by utilizing crosscorrelation function. As we show in the context of speaker localization, these estimates yield poor results, due to the joint effect of reverberation and the directivity of sound sources. In this paper, we present a novel method that utilizes a priori acoustic information of the monitored region, which makes it possible to localize directional sound sources by taking the effect of reverberation into account. The proposed method shows significant improvement of performance compared with traditional methods in “noise-free” condition. Further work is required to extend its capabilities to noisy environments.

  2. Structural Health Monitoring of Wind Turbine Blades: Acoustic Source Localization Using Wireless Sensor Networks

    Omar Mabrok Bouzid

    2015-01-01

    Full Text Available Structural health monitoring (SHM is important for reducing the maintenance and operation cost of safety-critical components and systems in offshore wind turbines. This paper proposes an in situ wireless SHM system based on an acoustic emission (AE technique. By using this technique a number of challenges are introduced due to high sampling rate requirements, limitations in the communication bandwidth, memory space, and power resources. To overcome these challenges, this paper focused on two elements: (1 the use of an in situ wireless SHM technique in conjunction with the utilization of low sampling rates; (2 localization of acoustic sources which could emulate impact damage or audible cracks caused by different objects, such as tools, bird strikes, or strong hail, all of which represent abrupt AE events and could affect the structural health of a monitored wind turbine blade. The localization process is performed using features extracted from aliased AE signals based on a developed constraint localization model. To validate the performance of these elements, the proposed system was tested by testing the localization of the emulated AE sources acquired in the field.

  3. Sub-sampling-based 2D localization of an impulsive acoustic source in reverberant environments

    Omer, Muhammad

    2014-07-01

    This paper presents a robust method for two-dimensional (2D) impulsive acoustic source localization in a room environment using low sampling rates. The proposed method finds the time delay from the room impulse response (RIR) which makes it robust against room reverberations. We consider the RIR as a sparse phenomenon and apply a recently proposed sparse signal reconstruction technique called orthogonal clustering (OC) for its estimation from the sub-sampled received signal. The arrival time of the direct path signal at a pair of microphones is identified from the estimated RIR, and their difference yields the desired time delay estimate (TDE). Low sampling rates reduces the hardware and computational complexity and decreases the communication between the microphones and the centralized location. Simulation and experimental results of an actual hardware setup are presented to demonstrate the performance of the proposed technique.

  4. Localized Acoustic Surface Modes

    Farhat, Mohamed

    2015-08-04

    We introduce the concept of localized acoustic surface modes (ASMs). We demonstrate that they are induced on a two-dimensional cylindrical rigid surface with subwavelength corrugations under excitation by an incident acoustic plane wave. Our results show that the corrugated rigid surface is acoustically equivalent to a cylindrical scatterer with uniform mass density that can be represented using a Drude-like model. This, indeed, suggests that plasmonic-like acoustic materials can be engineered with potential applications in various areas including sensing, imaging, and cloaking.

  5. Acoustic emission source modeling

    Hora, Petr; Červená, Olga

    2010-01-01

    Roč. 4, č. 1 (2010), s. 25-36. ISSN 1802-680X R&D Projects: GA ČR GA101/09/1630 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission source * wave propagation * FEM Subject RIV: BI - Acoustics

  6. Accurate sound source localization in a reverberant environment using multiple acoustic sensors

    This paper introduces a new method for the estimation of sound source distance and direction using at least three microphone sensors in indoor environments. Unlike the other methods that normally use approximations in obtaining the time difference between sensors, this method exploits the existed geometrical relationships of the sensors to form an exact solution to estimating the source position. To overcome reverberation, an enhancing pre-process has been used for different sound sources with different spectra, e.g., single frequency, multiple frequencies and different noise shapes. Source direction and distances are estimated from time of sound wave travel and distances of acoustic sensors. Using the method described in this paper a level of 1° accuracy is obtained. Several experimental tests have been undertaken that verify the results. Conclusions and future work are also described

  7. Passive Acoustic Source Localization at a Low Sampling Rate Based on a Five-Element Cross Microphone Array

    Yue Kan

    2015-06-01

    Full Text Available Accurate acoustic source localization at a low sampling rate (less than 10 kHz is still a challenging problem for small portable systems, especially for a multitasking micro-embedded system. A modification of the generalized cross-correlation (GCC method with the up-sampling (US theory is proposed and defined as the US-GCC method, which can improve the accuracy of the time delay of arrival (TDOA and source location at a low sampling rate. In this work, through the US operation, an input signal with a certain sampling rate can be converted into another signal with a higher frequency. Furthermore, the optimal interpolation factor for the US operation is derived according to localization computation time and the standard deviation (SD of target location estimations. On the one hand, simulation results show that absolute errors of the source locations based on the US-GCC method with an interpolation factor of 15 are approximately from 1/15- to 1/12-times those based on the GCC method, when the initial same sampling rates of both methods are 8 kHz. On the other hand, a simple and small portable passive acoustic source localization platform composed of a five-element cross microphone array has been designed and set up in this paper. The experiments on the established platform, which accurately locates a three-dimensional (3D near-field target at a low sampling rate demonstrate that the proposed method is workable.

  8. Acoustic emission source modeling

    Hora, Petr; Červená, Olga

    Plzeň : University of West Bohemia, 2009 - (Adámek, V.; Zajíček, M.). s. 1-2 ISBN 978-80-7043-824-4. [Výpočtová mechanika 2009. 09.11.2009-11.11.2009, Nečtiny] R&D Projects: GA ČR GA101/09/1630 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission source * wave propagation * FEM Subject RIV: BI - Acoustics

  9. MEMS Biomimetic Acoustic Pressure Gradient Sensitive Structure for Sound Source Localization

    Sen Ren

    2009-07-01

    Full Text Available The parasitoid fly Ormia ochracea shows an astonishing localization ability with its tiny hearing organ. A novel MEMS biomimetic acoustic pressure gradient sensitive structure was designed and fabricated by mimicking the mechanically coupled tympana of the fly. Firstly, the analytic representation formulas of the resultant force and resultant moment of the incoming plane wave acting on the structure were derived. After that, structure modal analysis was performed and the results show that the structure has out-of-phase and in-phase vibration modes, and the corresponding eigenfrequency is decided by the stiffness of vertical torsional beam and horizontal beam respectively. Acoustic-structural coupled analysis was performed and the results show that phase difference and amplitude difference between the responses of the two square diaphragms of the sensitive structure are effectively enlarged through mechanical coupling beam. The phase difference and amplitude difference increase with increasing incident angle and can be used to distinguish the direction of sound arrival. At last, the fabrication process and results of the device is also presented.

  10. Acoustic emission source modeling

    Hora P.

    2010-07-01

    Full Text Available The paper deals with the acoustic emission (AE source modeling by means of FEM system COMSOL Multiphysics. The following types of sources are used: the spatially concentrated force and the double forces (dipole. The pulse excitation is studied in both cases. As a material is used steel. The computed displacements are compared with the exact analytical solution of point sources under consideration.

  11. Acoustic source for generating an acoustic beam

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2016-05-31

    An acoustic source for generating an acoustic beam includes a housing; a plurality of spaced apart piezo-electric layers disposed within the housing; and a non-linear medium filling between the plurality of layers. Each of the plurality of piezoelectric layers is configured to generate an acoustic wave. The non-linear medium and the plurality of piezo-electric material layers have a matching impedance so as to enhance a transmission of the acoustic wave generated by each of plurality of layers through the remaining plurality of layers.

  12. Software for neutrino acoustic detection and localization

    The evidence of the existing of UHE (E>1019eV) cosmic rays and its possible connection to UHE neutrino suggests the building of an acoustic telescope for neutrino, exploiting thermo-acoustic effect. We present software for neutrino acoustic signal detection and localization. The main points discussed here are the sea noise model, the determination of time differences of arrival (TDOA) between hydrophones signals, the source localization algorithm, and the telescope geometry effect. The effect of TDOAs errors and telescope geometry on the localization accuracy is also discussed.

  13. Software for neutrino acoustic detection and localization

    Bouhadef, B. [INFN Sezione Pisa, Polo Fibonacci, Largo Bruno Pontecorvo 3, 56127 Pisa (Italy); Dipartimento di Fisica, ' E. Fermi' University of Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy)], E-mail: bouhadef@df.unipi.it

    2009-06-01

    The evidence of the existing of UHE (E>10{sup 19}eV) cosmic rays and its possible connection to UHE neutrino suggests the building of an acoustic telescope for neutrino, exploiting thermo-acoustic effect. We present software for neutrino acoustic signal detection and localization. The main points discussed here are the sea noise model, the determination of time differences of arrival (TDOA) between hydrophones signals, the source localization algorithm, and the telescope geometry effect. The effect of TDOAs errors and telescope geometry on the localization accuracy is also discussed.

  14. Software for neutrino acoustic detection and localization

    Bouhadef, B.

    2009-06-01

    The evidence of the existing of UHE (E>10eV) cosmic rays and its possible connection to UHE neutrino suggests the building of an acoustic telescope for neutrino, exploiting thermo-acoustic effect. We present software for neutrino acoustic signal detection and localization. The main points discussed here are the sea noise model, the determination of time differences of arrival (TDOA) between hydrophones signals, the source localization algorithm, and the telescope geometry effect. The effect of TDOAs errors and telescope geometry on the localization accuracy is also discussed.

  15. Localization of Directional Sound Sources Supported by A Priori Information of the Acoustic Environment

    András Radványi; Zoltán Fodróczi

    2007-01-01

    Speaker localization with microphone arrays has received significant attention in the past decade as a means for automated speaker tracking of individuals in a closed space for videoconferencing systems, directed speech capture systems, and surveillance systems. Traditional techniques are based on estimating the relative time difference of arrivals (TDOA) between different channels, by utilizing crosscorrelation function. As we show in the context of speaker localization, these estimates yiel...

  16. The use of cluster analysis method for the localization of acoustic emission sources detected during the hydrotest of PWR pressure vessels

    The acoustic emission method is a promising tool for checking reactor pressure vessel integrity. Localization of emission sources is the first and the most important step in processing emission signals. The paper describes the emission sources localization method which is based on cluster analysis of a set of points depicting the emission events in the plane of coordinates of their occurrence. The method is based on using this set of points for constructing the minimum spanning tree and its partition into fragments corresponding to point clusters. Furthermore, the laws are considered of probability distribution of the minimum spanning tree edge length for one and several clusters with the aim of finding the optimum length of the critical edge for the partition of the tree. Practical application of the method is demonstrated on localizing the emission sources detected during a hydrotest of a pressure vessel used for testing the reactor pressure vessel covers. (author)

  17. Jedan pristup u oceni efektivnosti sistema za zvukometrijsko izviđanje 'Boomerang' / One approach to the evaluation of the effectiveness of the boomerang system for acoustic source localization and identification

    Miroslav R. Terzić

    2010-07-01

    Full Text Available U radu je prikazan jedan pristup u oceni efektivnosti sistema za zvukometrijsko izviđanje. Sistem za zvukometrijsko izviđanje modelovan je kao sistem masovnog opsluživanja, opisana su stanja sistema, parametri i izveden izraz za određivanje verovatnoće opsluživanja sistema za zvukometrijskao izviđanje, kao kriterijuma za ocenu efektivnosti. / One approach to the evaluation of the effectiveness of a system for acoustic source localization and identification has been shown in this article. The system for acoustic source localization and identification has been presented as a model of mass servicing system. The states of the system as well as its features have been described while the formula for service probability determination has been derived as a criterion for effectiveness evaluation. The introductory part of the article describes the system for acoustic source localization and identification and shows a model for quantity estimation of the function of technical system effectiveness E (t. The system effectiveness represents a probability of system initiation as well as a probability of its successful mission accomplishment on the basis of designed capabilities within the given time period and operational conditions. The basic characteristics of the Boomerang system for acoustic source localization and identification show the system elements and its designed capability to detect, analyse and distribute acoustic source location data. The analytical model for the evaluation of the effectiveness of the Boomerang system for acoustic source localization and identification shows that 'n' stations for acoustic source localization can exchange information with each other using the network link. The system conditions are described and the expression for the determination of service probability as a criterion for system effectiveness evaluation is derived. The evaluation of the effectiveness of the Boomerang system for acoustic source

  18. Acoustic emission source localization and velocity determination of the fundamental mode A0 using wavelet analysis and a Newton-based optimization technique

    This paper investigates the development of an in situ impact detection monitoring system able to identify in real-time the acoustic emission location. The proposed algorithm is based on the differences of stress waves measured by surface-bonded piezoelectric transducers. A joint time–frequency analysis based on the magnitude of the continuous wavelet transform was used to determine the time of arrival of the wavepackets. A combination of unconstrained optimization technique associated with a local Newton's iterative method was employed to solve a set of nonlinear equations in order to assess the impact location coordinates and the wave speed. With the proposed approach, the drawbacks of a triangulation method in terms of estimating a priori the group velocity and the need to find the best time–frequency technique for the time-of-arrival determination were overcome. Moreover, this algorithm proved to be very robust since it was able to converge from almost any guess point and required little computational time. A comparison between the theoretical and experimental results carried out with piezoelectric film (PVDF) and acoustic emission transducers showed that the impact source location and the wave velocity were predicted with reasonable accuracy. In particular, the maximum error in estimation of the impact location was less than 2% and about 1% for the flexural wave velocity

  19. Acoustic Emission Defects Localized by Means of Geodetic Iterative Procedure - Algorithms, Tests, AE Experiment

    Kůs, V.; Záveský, M.; Převorovský, Zdeněk

    Granada : University of Granada, 2012 - (Gallego, A.; Ono, K.), s. 1-12 ISBN 978-84-615-9941-7. [Europen Conference on Acoustic Emission Testing/30./ & International Conference on Acoustic Emission/7./. Granada (ES), 12.09.2012-15.09.2012] Institutional support: RVO:61388998 Keywords : acoustic emissio * geodesic * Newton -Raphson method * iterative source localization Subject RIV: BI - Acoustics

  20. STRAIN LOCALIZATION PECULIARITIES AND DISTRIBUTION OF ACOUSTIC EMISSION SOURCES IN ROCK SAMPLES TESTED BY UNIAXIAL COMPRESSION AND EXPOSED TO ELECTRIC PULSES

    V. A. Mubassarova

    2015-09-01

    Full Text Available Results of uniaxial compression tests of rock samples in electromagnetic fields are presented. The experiments were performed in the Laboratory of Basic Physics of Strength, Institute of Continuous Media Mechanics, Ural Branch of RAS (ICMM. Deformation of samples was studied, and acoustic emission (AE signals were recorded. During the tests, loads varied by stages. Specimens of granite from the Kainda deposit in Kyrgyzstan (similar to samples tested at the Research Station of RAS, hereafter RS RAS were subject to electric pulses at specified levels of compression load. The electric pulses supply was galvanic; two graphite electrodes were fixed at opposite sides of each specimen. The multichannel Amsy-5 Vallen System was used to record AE signals in the six-channel mode, which provided for determination of spatial locations of AE sources. Strain of the specimens was studied with application of original methods of strain computation based on analyses of optical images of deformed specimen surfaces in LaVISION Strain Master System.Acoustic emission experiment data were interpreted on the basis of analyses of the AE activity in time, i.e. the number of AE events per second, and analyses of signals’ energy and AE sources’ locations, i.e. defects.The experiment was conducted at ICMM with the use of the set of equipment with advanced diagnostic capabilities (as compared to earlier experiments described in [Zakupin et al., 2006a, 2006b; Bogomolov et al., 2004]. It can provide new information on properties of acoustic emission and deformation responses of loaded rock specimens to external electric pulses.The research task also included verification of reproducibility of the effect (AE activity when fracturing rates responded to electrical pulses, which was revealed earlier in studies conducted at RS RAS. In terms of the principle of randomization, such verification is methodologically significant as new effects, i.e. physical laws, can be considered

  1. Characterizing Acoustic Sources in Pressure Vessels

    李路明; 郑鹏; 刘时风; 施克仁

    2002-01-01

    The "dream" of acoustic emission (AE) testing is to get the acoustic source characteristics from AE signals, especially when evaluating aging pressure vessels. In this paper, the wavelet transform was used to analyze different AE signals from cracks (surface and inner), pencil-lead-breakage and leakage. These acoustic sources were applied on an actual pressure vessel. While the vessel experienced hydraulic pressure, their AE signals were acquired by a digital AE testing system with a wide frequency band transducer and a high speed A/D converter. Then, the digital signals were analyzed using the wavelet transform method. Correlation coefficients of the transformed data show that the different acoustic sources can be easily identified.

  2. Simulating neurobiological localization of acoustic signals based on temporal and volumetric differentiations

    Dattani, Nikesh S.

    2008-01-01

    The localization of sound sources by the human brain is computationally simulated from a neurobiological perspective. The simulation includes the neural representation of temporal differences in acoustic signals between the ipsilateral and contralateral ears for constant sound intensities (angular localization), and of volumetric differences in acoustic signals for constant azimuthal angles (radial localization). The transmission of the original acoustic signal from the environment, through e...

  3. Calculating room acoustic parameters from pseudo-impulsive acoustic sources

    San Martin, Maria L.; Vela, Antonio; San Martin, Ricardo; Arana, Miguel A.

    2002-11-01

    The impulse response function provides complete information to predict the acoustic response of a room to an acoustic input of arbitrary characteristics. At this job study, small explosions of firecrackers are proposed to be used as pseudo-impulsive acoustics sources to determine some acoustic parameters of a room such as reverberation time, definition, and clarity, comparing these results to those obtained with other techniques. A previous characterization of these sources allows us to state that they can be used for this purpose because they are, in practice, omnidirectional, their temporary pattern is highly repetitive and their spectral power is, as well, repetitive and with enough power in octave bands from 125 Hz to 8 kHz. If the linear time-invariant system impulse response h(t) is known, output signal s(t) regarding any arbitrary signal s(t) can be obtained. For our pseudo-impulsive sources, the output signal s(t) has been taken as impulse response h(t). Using the integrated impulse response method suggested by Schroeder, it has been stated that both the mean values and standard deviations for some parameters are practically identical to results obtained with other usual techniques. (To be presented in Spanish.)

  4. Identification of Turbomachinery Noise Sources Using Acoustical Holography Project

    National Aeronautics and Space Administration — Evaluation and enhancement of the acoustical performance of turbomachinery requires knowledge of the acoustic sources. However, the noise generation mechanisms...

  5. Acoustic and non-acoustic factors in modeling listener-specific performance of sagittal-plane sound localization

    PiotrMajdak

    2014-04-01

    Full Text Available The ability of sound-source localization in sagittal planes (along the top-down and front-back dimension varies considerably across listeners. The directional acoustic spectral features, described by head-related transfer functions (HRTFs, also vary considerably across listeners, a consequence of the listener-specific shape of the ears. It is not clear whether the differences in localization ability result from differences in the encoding of directional information provided by the HRTFs, i.e., acoustic factors, or from differences in auditory processing of those cues (e.g., spectral-shape sensitivity, i.e., non-acoustic factors.We addressed this issue by analyzing the listener-specific localization ability in terms of localization performance. Directional responses to spatially distributed broadband stimuli from 18 listeners were used. A model of sagittal-plane localization was fit individually for each listener by considering the actual localization performance, the listener-specific HRTFs representing the acoustic factor, and an uncertainty parameter representing the non-acoustic factors. The model was configured to simulate the condition of complete calibration of the listener to the tested HRTFs. Listener-specifically calibrated model predictions yielded correlations of, on average, 0.93 with the actual localization performance. Then, the model parameters representing the acoustic and non-acoustic factors were systematically permuted across the listener group.While the permutation of HRTFs affected the localization performance, the permutation of listener-specific uncertainty had a substantially larger impact. Our findings suggest that across-listener variability in sagittal-plane localization ability is only marginally determined by the acoustic factor, i.e., the quality of directional cues found in typical human HRTFs. Rather, the non-acoustic factor, supposed to represent the listeners' efficiency in processing directional cues, appears

  6. Acoustic source strength of propeller cavitation

    Bruijn, A. de

    1979-01-01

    The acoustic source strength i.e. the volume velocity of propeller cavitation for six single-screw ships are presented. Plotting the data in the form of dimensionleee volume velocity and as a function of the cavitation number based on the rotation speed and the immersion depth, a certain differentia

  7. Acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials

    Using the multilayered cylinder model, we study acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials, which exhibit locally negative effective mass densities. A spring model is introduced to replace the traditional transfer matrix, which may be singular in the negative mass region. The backscattering form function and the scattering cross section are calculated to discuss the acoustic properties of the coated submerged cylindrical shell. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. Acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials

    Li Li; Wen Ji-Hong; Cai Li; Zhao Hong-Gang; Wen Xi-Sen

    2013-01-01

    Using the multilayered cylinder model,we study acoustic scattering from a submerged cylindrical shell coated with locally resonant acoustic metamaterials,which exhibit locally negative effective mass densities.A spring model is introduced to replace the traditional transfer matrix,which may be singular in the negative mass region.The backscattering form function and the scattering cross section are calculated to discuss the acoustic properties of the coated submerged cylindrical shell.

  9. Measuring Acoustic Wave Transit Time in Furnace Based on Active Acoustic Source Signal

    Zhen Luo; Feng Tian; Xiao-Ping Sun

    2007-01-01

    Accurate measurement of transit time for acoustic wave between two sensors installed on two sides of a furnace is a key to implementing the temperature field measurement technique based on acoustical method. A new method for measuring transit time of acoustic wave based on active acoustic source signal is proposed in this paper, which includes the followings: the time when the acoustic source signal arrives at the two sensors is measured first; then, the difference of two arriving time arguments is computed, thereby we get the transit time of the acoustic wave between two sensors installed on the two sides of the furnace. Avoiding the restriction on acoustic source signal and background noise, the new method can get the transit time of acoustic wave with higher precision and stronger ability of resisting noise interference.

  10. Hyperbolic source location of crack related acoustic emission in bone.

    O'Toole, John; Creedon, Leo; Hession, John; Muir, Gordon

    2013-01-01

    Little work has been done on the localization of microcracks in bone using acoustic emission. Microcrack localization is useful to study the fracture process in bone and to prevent fractures in patients. Locating microcracks that occur before fracture allows one to predict where fracture will occur if continued stress is applied to the bone. Two source location algorithms were developed to locate microcracks on rectangular bovine bone samples. The first algorithm uses a constant velocity approach which has some difficulty dealing with the anisotropic nature of bone. However, the second algorithm uses an iterative technique to estimate the correct velocity for the acoustic emission source location being located. In tests with simulated microcracks, the constant velocity algorithm achieves a median error of 1.78 mm (IQR 1.51 mm) and the variable velocity algorithm improves this to a median error of 0.70 mm (IQR 0.79 mm). An experiment in which the bone samples were loaded in a three point bend test until they fractured showed a good correlation between the computed location of detected microcracks and where the final fracture occurred. Microcracks can be located on bovine bone samples using acoustic emission with good accuracy and precision. PMID:23363217

  11. A localization model to localize multiple sources using Bayesian inference

    Dunham, Joshua Rolv

    Accurate localization of a sound source in a room setting is important in both psychoacoustics and architectural acoustics. Binaural models have been proposed to explain how the brain processes and utilizes the interaural time differences (ITDs) and interaural level differences (ILDs) of sound waves arriving at the ears of a listener in determining source location. Recent work shows that applying Bayesian methods to this problem is proving fruitful. In this thesis, pink noise samples are convolved with head-related transfer functions (HRTFs) and compared to combinations of one and two anechoic speech signals convolved with different HRTFs or binaural room impulse responses (BRIRs) to simulate room positions. Through exhaustive calculation of Bayesian posterior probabilities and using a maximal likelihood approach, model selection will determine the number of sources present, and parameter estimation will result in azimuthal direction of the source(s).

  12. Localization based on acoustic and seismic array processing

    J.Z. Stafsudd; Asgari, S; C. E. Chen; Ali, A.; R. E. Hudson; Lorenzelli, F.; Yao, K.; E. Taciroglu

    2005-01-01

    In this poster, we consider the analysis, implementation, and application of wideband sources using both seismic and acoustic sensors. We use the AML algorithm to perform acoustic DOA. For non-uniform noise spectra, whitening filtering was applied to the received acoustic signals before the AML operation. For short-range seismic DOA applications, one method was based on eigen-decomposition of the covariance matrix and a second method was based on surface wave analysis. Experimental estimatio...

  13. Acoustic communications considerations for collaborative simultaneous localization and mapping

    Hilger, Ryan Peter

    2014-01-01

    Approved for public release; distribution is unlimited This thesis considers the use of acoustic communications in reducing position uncertainty for collaborating autonomous underwater vehicles. The foundation of the work relies on statistical techniques for accurate navigation without access to GPS, known as Simultaneous Localization and Mapping (SLAM). Multiple AUVs permit increased coverage, system redundancy and reduced mission times. Collaboration through acoustic communications can m...

  14. Intelligent location of simultaneously active acoustic emission sources: Part II

    Kosel, T

    2007-01-01

    Part I describes an intelligent acoustic emission locator, while Part II discusses blind source separation, time delay estimation and location of two continuous acoustic emission sources. Acoustic emission (AE) analysis is used for characterization and location of developing defects in materials. AE sources often generate a mixture of various statistically independent signals. A difficult problem of AE analysis is separation and characterization of signal components when the signals from various sources and the mode of mixing are unknown. Recently, blind source separation (BSS) by independent component analysis (ICA) has been used to solve these problems. The purpose of this paper is to demonstrate the applicability of ICA to locate two independent simultaneously active acoustic emission sources on an aluminum band specimen. The method is promising for non-destructive testing of aircraft frame structures by acoustic emission analysis.

  15. Enhanced directional sensitivity of a biomimetic MEMS acoustic localization sensor

    Gee, Danny; Liu, Haijun; Currano, Luke; Yu, Miao

    2010-04-01

    We present an improved microfabricated sound localization sensor for unobtrusive surveillance systems inspired by the tympanic membranes of the parasitoid fly, Ormia ochracea. The device consists of two silicon diaphragms mechanically coupled by a suspended beam that amplifies the difference in time response, dependent on the incident angle of the sound source. Fabrication techniques were modified to reduce residual stresses and improve device uniformity. Enhanced acoustic cues for devices with central pivoting anchors were measured with laser Doppler vibrometry. Device responses to weak excitations demonstrated good sensitivity over environmental noise. An order of magnitude in time difference amplification was measured at 90° incident angles with a directional sensitivity of .39μs/degree. These results provide a foundation for realizing an accurate bio-inspired MEMS directional microphone.

  16. Chemical plume source localization.

    Pang, Shuo; Farrell, Jay A

    2006-10-01

    This paper addresses the problem of estimating a likelihood map for the location of the source of a chemical plume using an autonomous vehicle as a sensor probe in a fluid flow. The fluid flow is assumed to have a high Reynolds number. Therefore, the dispersion of the chemical is dominated by turbulence, resulting in an intermittent chemical signal. The vehicle is capable of detecting above-threshold chemical concentration and sensing the fluid flow velocity at the vehicle location. This paper reviews instances of biological plume tracing and reviews previous strategies for a vehicle-based plume tracing. The main contribution is a new source-likelihood mapping approach based on Bayesian inference methods. Using this Bayesian methodology, the source-likelihood map is propagated through time and updated in response to both detection and nondetection events. Examples are included that use data from in-water testing to compare the mapping approach derived herein with the map derived using a previously existing technique. PMID:17036813

  17. Acoustic metamaterials: From local resonances to broad horizons

    Ma, Guancong; Sheng, Ping

    2016-01-01

    Within a time span of 15 years, acoustic metamaterials have emerged from academic curiosity to become an active field driven by scientific discoveries and diverse application potentials. This review traces the development of acoustic metamaterials from the initial findings of mass density and bulk modulus frequency dispersions in locally resonant structures to the diverse functionalities afforded by the perspective of negative constitutive parameter values, and their implications for acoustic wave behaviors. We survey the more recent developments, which include compact phase manipulation structures, superabsorption, and actively controllable metamaterials as well as the new directions on acoustic wave transport in moving fluid, elastic, and mechanical metamaterials, graphene-inspired metamaterials, and structures whose characteristics are best delineated by non-Hermitian Hamiltonians. Many of the novel acoustic metamaterial structures have transcended the original definition of metamaterials as arising from the collective manifestations of constituent resonating units, but they continue to extend wave manipulation functionalities beyond those found in nature. PMID:26933692

  18. Acoustic metamaterials: From local resonances to broad horizons.

    Ma, Guancong; Sheng, Ping

    2016-02-01

    Within a time span of 15 years, acoustic metamaterials have emerged from academic curiosity to become an active field driven by scientific discoveries and diverse application potentials. This review traces the development of acoustic metamaterials from the initial findings of mass density and bulk modulus frequency dispersions in locally resonant structures to the diverse functionalities afforded by the perspective of negative constitutive parameter values, and their implications for acoustic wave behaviors. We survey the more recent developments, which include compact phase manipulation structures, superabsorption, and actively controllable metamaterials as well as the new directions on acoustic wave transport in moving fluid, elastic, and mechanical metamaterials, graphene-inspired metamaterials, and structures whose characteristics are best delineated by non-Hermitian Hamiltonians. Many of the novel acoustic metamaterial structures have transcended the original definition of metamaterials as arising from the collective manifestations of constituent resonating units, but they continue to extend wave manipulation functionalities beyond those found in nature. PMID:26933692

  19. Study of acoustic emission sources and signals

    Pumarega, M. I. López; Armeite, M.; Oliveto, M. E.; Piotrkowski, R.; Ruzzante, J. E.

    2002-05-01

    Methods of acoustic emission (AE) signal analysis give information about material conditions, since AE generated in stressed solids can be used to indicate cracks and defect positions so as their damaging potential. We present a review of results of laboratory AE tests on metallic materials. Rings of seamless steel tubes, with and without oxide layers, were cut and then deformed by opening their ends. Seamless Zry-4 tubes were submitted to hydraulic stress tests until rupture with a purposely-constructed hydraulic system. In burst type signals, their parameters, Amplitude (A), Duration (D) and Risetime (R), were statistically studied. Amplitudes were found to follow the Log-normal distribution. This led to infer that the detected AE signal, is the complex consequence of a great number of random independent sources, which individual effects are linked. We could show, using cluster analysis for A, D and R mean values, with 5 clusters, coincidence between the clusters and the test types. A slight linear correlation was obtained for the parameters A and D. The arrival time of the AE signals was also studied, which conducted to discussing Poisson and Polya processes. The digitized signals were studied as (1/f)β noises. The general results are coherent if we consider the AE phenomena in the frame of Self Organized Criticality theory.

  20. Localization and tracing of early acoustic reflections in enclosures

    Tervo, Sakari

    2011-01-01

    Objective room acoustic studies are conducted by measuring room impulse responses. The standard techniques include the use of an omni-directional source and, in most cases, one omni-directional microphone. This approach is well defined when measuring the standard room acoustic parameters. Recently, early reflections, the first arriving sound waves in the room impulse response after the direct sound, have gained attention in research. The spatial location of the early reflections, i.e., t...

  1. Combination of acoustical radiosity and the image source method

    Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho;

    2013-01-01

    A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part. The...... model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated...... studio hall. The proposed model turns out to be promising for acoustic predictions providing a high level of detail and accuracy....

  2. The application of Shuffled Frog Leaping Algorithm to Wavelet Neural Networks for acoustic emission source location

    Cheng, Xinmin; Zhang, Xiaodan; Zhao, Li; Deng, Aideng; Bao, Yongqiang; Liu, Yong; Jiang, Yunliang

    2014-04-01

    When using acoustic emission to locate the friction fault source of rotating machinery, the effects of strong noise and waveform distortion make accurate locating difficult. Applying neural network for acoustic emission source location could be helpful. In the BP Wavelet Neural Network, BP is a local search algorithm, which falls into local minimum easily. The probability of successful search is low. We used Shuffled Frog Leaping Algorithm (SFLA) to optimize the parameters of the Wavelet Neural Network, and the optimized Wavelet Neural Network to locate the source. After having performed the experiments of friction acoustic emission's source location on the rotor friction test machine, the results show that the calculation of SFLA is simple and effective, and that locating is accurate with proper structure of the network and input parameters.

  3. Localization with a Mobile Beacon in Underwater Acoustic Sensor Networks

    Sangho Lee; Kiseon Kim

    2012-01-01

    Localization is one of the most important issues associated with underwater acoustic sensor networks, especially when sensor nodes are randomly deployed. Given that it is difficult to deploy beacon nodes at predetermined locations, localization schemes with a mobile beacon on the sea surface or along the planned path are inherently convenient, accurate, and energy-efficient. In this paper, we propose a new range-free Localization with a Mobile Beacon (LoMoB). The mobile beacon periodically br...

  4. Premiliniary Study of Outdoor Positioning Acoustic Source Direction of Arrival

    M.Mayilvaganan; Devaki

    2012-01-01

    Wireless sensor network systems have become revolutionize in recent years.Acoustic source Direction Of Arrival(DOA) is one of the essential phenomenon in manyapplications. Acoustic sensor network can provide a way to simulatenous monitor and interactionof many sources. This paper provides an preliminary study of Direction Of Arrival(DOA) foroutdoor positioning and attempt to classify the different approaches. We focus on DominantFrequency Selection(DFSE) ,Approximate Maximum Likelihood(AML) a...

  5. Modeling Large sound sources in a room acoustical calculation program

    Christensen, Claus Lynge

    1999-01-01

    A room acoustical model capable of modelling point, line and surface sources is presented. Line and surface sources are modelled using a special ray-tracing algorithm detecting the radiation pattern of the surfaces in the room. Point sources are modelled using a hybrid calculation method combining...... this ray-tracing method with Image source modelling. With these three source types, it is possible to model large and complex sound sources in workrooms....

  6. Intelligent location of simultaneously active acoustic emission sources: Part I

    Kosel, T

    2007-01-01

    The intelligent acoustic emission locator is described in Part I, while Part II discusses blind source separation, time delay estimation and location of two simultaneously active continuous acoustic emission sources. The location of acoustic emission on complicated aircraft frame structures is a difficult problem of non-destructive testing. This article describes an intelligent acoustic emission source locator. The intelligent locator comprises a sensor antenna and a general regression neural network, which solves the location problem based on learning from examples. Locator performance was tested on different test specimens. Tests have shown that the accuracy of location depends on sound velocity and attenuation in the specimen, the dimensions of the tested area, and the properties of stored data. The location accuracy achieved by the intelligent locator is comparable to that obtained by the conventional triangulation method, while the applicability of the intelligent locator is more general since analysis o...

  7. Modeling huge sound sources in a room acoustical calculation program

    Christensen, Claus Lynge

    1999-01-01

    A room acoustical model capable of modeling point sources, line sources, and surface sources is presented. Line and surface sources are modeled using a special ray-tracing algorithm detecting the radiation pattern of the surfaces of the room. Point sources are modeled using a hybrid calculation...... method combining this ray-tracing method with image source modeling. With these three source types it is possible to model huge and complex sound sources in industrial environments. Compared to a calculation with only point sources, the use of extended sound sources is shown to improve the agreement with...

  8. Transversal Anderson localization of sound in acoustic waveguide arrays

    We present designs of one-dimensional acoustic waveguide arrays and investigate wave propagation inside. Under the condition of single identical waveguide mode and weak coupling, the acoustic wave motion in waveguide arrays can be modeled with a discrete mode-coupling theory. The coupling constants can be retrieved from simulations or experiments as the function of neighboring waveguide separations. Sound injected into periodic arrays gives rise to the discrete diffraction, exhibiting ballistic or extended transport in transversal direction. But sound injected into randomized waveguide arrays readily leads to Anderson localization transversally. The experimental results show good agreement with simulations and theoretical predictions. (paper)

  9. Eigenbeamforming array systems for sound source localization

    Tiana Roig, Elisabet

    D study aims at enhancing the performance of uniform circular ar- rays, and to a lesser extent, spherical arrays, for two- and three-dimensional localization problems, respectively. These array geometries allow to perform eigenbeamforming, beamforming based on the decomposition of the sound field in a...... spherical scatterer is recommended instead. A better visualization in the entire frequency range can be achieved with deconvo- lution methods, as they allow the recovery of the sound source distribution from a given beamformed map. Three efficient methods based on spectral procedures, originally conceived...... for planar-sparse arrays, are adapted to circular arrays. They rely on the fact that uniform circular arrays present an azimuthal response that is rather independent on the focusing direction. Finally, a method based on the combination of beamforming and acoustic holog- raphy is introduced for both...

  10. 3D Finite-Difference Modeling of Acoustic Radiation from Seismic Sources

    Chael, E. P.; Aldridge, D. F.; Jensen, R. P.

    2013-12-01

    Shallow seismic events, earthquakes as well as explosions, often generate acoustic waves in the atmosphere observable at local or even regional distances. Recording both the seismic and acoustic signals can provide additional constraints on source parameters such as epicenter coordinates, depth, origin time, moment, and mechanism. Recent advances in finite-difference (FD) modeling methods enable accurate numerical treatment of wave propagation across the ground surface between the (solid) elastic and (fluid) acoustic domains. Using a fourth-order, staggered-grid, velocity-stress FD algorithm, we are investigating the effects of various source parameters on the acoustic (or infrasound) signals transmitted from the solid earth into the atmosphere. Compressional (P), shear (S), and Rayleigh waves all radiate some acoustic energy into the air at the ground surface. These acoustic wavefronts are typically conical in shape, since their phase velocities along the surface exceed the sound speed in air. Another acoustic arrival with a spherical wavefront can be generated from the vicinity of the epicenter of a shallow event, due to the strong vertical ground motions directly above the buried source. Images of acoustic wavefields just above the surface reveal the radiation patterns and relative amplitudes of the various arrivals. In addition, we compare the relative effectiveness of different seismic source mechanisms for generating acoustic energy. For point sources at a fixed depth, double-couples with almost any orientation produce stronger acoustic signals than isotropic explosions, due to higher-amplitude S and Rayleigh waves. Of course, explosions tend to be shallower than most earthquakes, which can offset the differences due to mechanism. Low-velocity material in the shallow subsurface acts to increase vertical seismic motions there, enhancing the coupling to acoustic waves in air. If either type of source breaks the surface (e.g., an earthquake with surface rupture

  11. Scaling of membrane-type locally resonant acoustic metamaterial arrays.

    Naify, Christina J; Chang, Chia-Ming; McKnight, Geoffrey; Nutt, Steven R

    2012-10-01

    Metamaterials have emerged as promising solutions for manipulation of sound waves in a variety of applications. Locally resonant acoustic materials (LRAM) decrease sound transmission by 500% over acoustic mass law predictions at peak transmission loss (TL) frequencies with minimal added mass, making them appealing for weight-critical applications such as aerospace structures. In this study, potential issues associated with scale-up of the structure are addressed. TL of single-celled and multi-celled LRAM was measured using an impedance tube setup with systematic variation in geometric parameters to understand the effects of each parameter on acoustic response. Finite element analysis was performed to predict TL as a function of frequency for structures with varying complexity, including stacked structures and multi-celled arrays. Dynamic response of the array structures under discrete frequency excitation was investigated using laser vibrometry to verify negative dynamic mass behavior. PMID:23039544

  12. Acoustic emission source location based on signal features

    Blaháček, Michal; Chlada, Milan; Převorovský, Zdeněk

    Uetikon-Zuerich : Trans Tech Publications, 2006 - (Pullin, R.), s. 77-82 ISBN 0-87849-420-0. ISSN 1022-6680. [European Conference on AE Testing /27./. Cardiff (GB), 20.09.2006-22.09.2006] R&D Projects: GA MPO(CZ) FT-TA/026 EU Projects: European Commission(XE) 502927 - AERO-NEWS Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission * source location Subject RIV: BI - Acoustics

  13. ADVANCED ACOUSTIC EMISSION SOURCE LOCATION IN COMPLEX AIRCRAFT STRUCTURE

    Blaháček, Michal; Převorovský, Zdeněk

    Krakow: University of Technology Krakov, 2008 - (Kanji, O.), s. 172-177 ISBN 978-83-7242-478-5. [European Conference on Acoustic Emission Testing EWGAE /28./. Krakow (PL), 17.09.2008-19.09.2008] R&D Projects: GA ČR GA101/07/1518 Institutional research plan: CEZ:AV0Z20760514 Keywords : source location * aircraft structure * fuzzy Subject RIV: BI - Acoustics

  14. Locating the acoustic source in thin glass plate using low sampling rate data.

    Hoseini Sabzevari, S Amir; Moavenian, Majid

    2016-08-01

    Acoustic source localization is an important step for structural health monitoring (SHM). There are many research studies dealing with localization based on high sampling rate data. In this paper, for the first time, acoustic source is localized on an isotropic plate using low sampling rate data. Previous studies have mainly used a cluster of specific sensors to easily record high sampling rate signals containing qualitative time domain features. This paper proposes a novel technique to localize the acoustic source on isotropic plates by simply implementing a combination of two simple electret microphones and Loci of k-Tuple Distances (LkTD) from the two sensors with low sampling rate data. In fact the method proposes substitution of previous methods based on solving the system of equations and increasing the number of sensors by implementing the selection of LkTD. Unlike most previous studies, estimation of time difference of arrival (TDOA) is based on the frequency properties of the signal rather than it's time properties. An experimental set-up is prepared and experiments are conducted to validate the proposed technique by prediction of the acoustic source location. The experimental results show that TDOA estimations based on low sampling rate data can produce more accurate predictions in comparison with previous studies. It is also shown that the selection of LkTD on the plate has noticeable effects on the performance of this technique. PMID:27110914

  15. AUV Local Path Planning Based on Acoustic Image Processing

    LI Ye; CHANG Wen-tian; JIANG Da-peng; ZHANG Tie-dong; SU Yu-min

    2006-01-01

    The forward-looking image sonar is a necessary vision device for Autonomous Underwater Vehicles (AUV). Based on the acoustic image received from forward-looking image sonar, AUV local path is planned. When the environment model is made to adapt to local path planning, an iterative algorithm of binary conversion is used for image segmentation. Raw data of the acoustic image, which were received from serial port, are processed. By the use of "Mathematic Morphology" to filter noise, a mathematic model of environment for local path planning is established after coordinate transformation. The optimal path is searched by the distant transmission (Dt) algorithm. Simulation is conducted for the analysis of the algorithm. Experiment on the sea proves it reliable.

  16. Modelling Large sound sources in a room acoustical calculation program

    Christensen, Claus Lynge

    1999-01-01

    A room acoustical model capable of modelling point, line and surface sources is presented. Line and surfacesources are modelled using a special ray-tracing algorithm detecting the radiation pattern of the surfaces in the room.Point sources are modelled using a hybrid calculation method combining...... this ray-tracing method with Image sourcemodelling. With these three source types, it is possible to model large and complex sound sources in workrooms....

  17. Localization in an acoustic cavitation cloud

    Miao, Boya

    2016-01-01

    Using a nonlinear sound wave equation for a bubbly liquid in conjunction with an equation for bubble pulsation, we predict and experimentally demonstrate the appearance of a gap in the frequency spectrum of a sound wave propagating in a cavitation cloud comprising bubbles. For bubbles with an ambient radius of 100 {\\mu}m, the calculations revealed that this gap corresponds to the phenomenon of sound wave localization. For bubbles with an ambient radius of 120 {\\mu}m, this spectral gap relates to a forbidden band of the sound wave. In the experiment, we observed the predicted gap in the frequency spectrum in soda water; however, in tap water, no spectral gap was present because the bubbles were much smaller than 100 {\\mu}m.

  18. Effective zero index in locally resonant acoustic material

    Zhu, Xue-Feng, E-mail: ernestzhu.nju@gmail.com

    2013-10-30

    Here in locally resonant acoustic material, it is shown that effective zero refractive index can be constructed by the resonant unit-cells with coherent degenerate monopole–dipole momenta. Due to strong local resonances, the material layers with effective zero refractive index can function as a resonant cavity of high Q factor, where a subtle deviation from the resonant frequency may result in distinct increase of reflection. Full-wave simulations are performed to demonstrate some unusual wave transport properties such as invisibility cloaking, super-reflection, local field enhancement, and wavefronts rotation.

  19. Microphones' directivity for the localization of sound sources

    Rizzo, Piervincenzo; Tajari, Mahdi; Spada, Antonino

    2011-06-01

    In a recent paper [P. Rizzo, G. Bordoni, A. Marzani, and J. Vipperman, "Localization of Sound Sources by Means of Unidirectional Microphones, Meas. Sci. Tech., 20, 055202 (12pp), 2009] the proof-of-concept of an approach for the localization of acoustic sources was presented. The method relies on the use of unidirectional microphones and amplitude-based signals' features to extract information about the direction of the incoming sound. By intersecting the directions identified by a pair of microphones, the position of the emitting source can be identified. In this paper we expand the work presented previously by assessing the effectiveness of the approach for the localization of an acoustic source in an indoor setting. As the method relies on the accurate knowledge of the microphones directivity, analytical expression of the acoustic sensors polar pattern were derived by testing them in an anechoic chamber. Then an experiment was conducted in an empty laboratory by using an array of three unidirectional microphones. The ability to locate the position of a commercial speaker placed at different positions in the room is discussed. The objective of this study is to propose a valid alternative to the common application of spaced arrays and therefore to introduce a new generation of reduced size sound detectors and localizers. The ability of the proposed methodology to locate the position of a commercial speaker placed at different positions in the room was evaluated and compared to the accuracy provided by a conventional time delay estimate algorithm.

  20. Patch near-field acoustic holography: The influence of acoustic contributions from outside the source

    Fernandez Grande, Efren; Jacobsen, Finn; Zhang, Yong-Bin

    2009-01-01

    to the patch. The purpose of this paper is to investigate how the acoustic radiation from outside the patch area influences the reconstruction of the sound field close to the source. The reconstruction is based on simulated measurements of sound pressure and particle velocity. The methods used in this paper...

  1. Localization with a Mobile Beacon in Underwater Acoustic Sensor Networks

    Sangho Lee

    2012-04-01

    Full Text Available Localization is one of the most important issues associated with underwater acoustic sensor networks, especially when sensor nodes are randomly deployed. Given that it is difficult to deploy beacon nodes at predetermined locations, localization schemes with a mobile beacon on the sea surface or along the planned path are inherently convenient, accurate, and energy-efficient. In this paper, we propose a new range-free Localization with a Mobile Beacon (LoMoB. The mobile beacon periodically broadcasts a beacon message containing its location. Sensor nodes are individually localized by passively receiving the beacon messages without inter-node communications. For location estimation, a set of potential locations are obtained as candidates for a node’s location and then the node’s location is determined through the weighted mean of all the potential locations with the weights computed based on residuals.

  2. Harnessing buckling to design tunable locally resonant acoustic metamaterials.

    Wang, Pai; Casadei, Filippo; Shan, Sicong; Weaver, James C; Bertoldi, Katia

    2014-07-01

    We report a new class of tunable and switchable acoustic metamaterials comprising resonating units dispersed into an elastic matrix. Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves. We first use numerical analysis to show the evolution of the locally resonant band gap, fully accounting for the effect of nonlinear pre-deformation. Then, we experimentally measure the transmission of vibrations as a function of the applied loading in a finite-size sample and find excellent agreement with our numerical predictions. The proposed concept expands the ability of existing acoustic metamaterials by enabling tunability over a wide range of frequencies. Furthermore, we demonstrate that in our system the deformation can be exploited to turn on or off the band gap, opening avenues for the design of adaptive switches. PMID:25032927

  3. Acoustic source identification using a Generalized Weighted Inverse Beamforming technique

    Presezniak, Flavio; Zavala, Paulo A. G.; Steenackers, Gunther; Janssens, Karl; Arruda, Jose R. F.; Desmet, Wim; Guillaume, Patrick

    2012-10-01

    In the last years, acoustic source identification has gained special attention, mainly due to new environmental norms, urbanization problems and more demanding acoustic comfort expectation of consumers. From the current methods, beamforming techniques are of common use, since normally demands affordable data acquisition effort, while producing clear source identification in most of the applications. In order to improve the source identification quality, this work presents a method, based on the Generalized Inverse Beamforming, that uses a weighted pseudo-inverse approach and an optimization procedure, called Weighted Generalized Inverse Beamforming. To validate this method, a simple case of two compact sources in close vicinity in coherent radiation was investigated by numerical and experimental assessment. Weighted generalized inverse results are compared to the ones obtained by the conventional beamforming, MUltiple Signal Classification, and Generalized Inverse Beamforming. At the end, the advantages of the proposed method are outlined together with the computational effort increase compared to the Generalized Inverse Beamforming.

  4. Invariant currents in lossy acoustic waveguides with complete local symmetry

    Kalozoumis, P A; Diakonos, F K; Theocharis, G; Schmelcher, P

    2015-01-01

    We implement the concept of complete local symmetry in lossy acoustic waveguides. Despite the presence of losses, the existence of a spatially invariant current is shown theoretically and observed experimentally. We demonstrate how this invariant current leads to the generalization of the Bloch and parity theorems for lossy systems defining a mapping of the pressure field between symmetry related spatial domains. Using experimental data we verify this mapping with remarkable accuracy. For the performed experiment we employ a construction technique based on local symmetries which allows the design of setups with prescribed perfect transmission resonances in the lossless case. Our results reveal the fundamental role of symmetries in restricted spatial domains and clearly indicate that completely locally symmetric devices constitute a promising class of setups, regarding the manipulation of wave propagation.

  5. A device for locating acoustic wave emitting sources

    The invention relates to a device for locating acoustic wave emitting sources. A two dimensional sensor network, with diamond-shaped (or the like) meshes, is placed on the surface of a structure in which acoustic wave emitting sources are to be located. The sensors are arranged according to two groups, each of which is connected to a clock and a counter. Every signal fed into a mesh of the network inhibits all the other sensors not belonging to said mesh; the location of the source within the diamond-shaped mesh is achieved by triangulation. This can be applied to the detection of flaws in metal structures, e.g. in nuclear reactor vessels

  6. Passive Source Localization Using Compressively Sensed Towed Array

    N. Suresh Kumar

    2013-12-01

    Full Text Available The objective of this work is to estimate the sparse angular power spectrum using a towed acoustic pressure sensor (APS array. In a passive towed array sonar, any reduction in the analog sensor signal conditioning receiver hardware housed inside the array tube, significantly improves the signal integrity and hence the localization performance. In this paper, a novel sparse acoustic pressure sensor (SAPS array architecture is proposed to estimate the direction of arrival (DOA of multiple acoustic sources. Bearing localization is effectively achieved by customizing the Capons spatial filter algorithm to suit the SAPS array architecture. Apart from the Monte Carlo simulations, the acoustic performance of the SAPS array with compressively sensed minimum variance distortionless response (CS-MVDR filter is demonstrated using a real passive towed array data. The proposed sparse towed array architecture promises a significant reduction in the analog signal acquisition receiver hardware, transmission data rate, number of snapshots and software complexity.Defence Science Journal, 2013, 63(6, pp.630-635, DOI:http://dx.doi.org/10.14429/dsj.63.5765

  7. Robotic vehicle uses acoustic array for detection and localization in urban environments

    Young, Stuart H.; Scanlon, Michael V.

    2001-09-01

    Sophisticated robotic platforms with diverse sensor suites are quickly replacing the eyes and ears of soldiers on the complex battlefield. The Army Research Laboratory (ARL) in Adelphi, Maryland has developed a robot-based acoustic detection system that will detect an impulsive noise event, such as a sniper's weapon firing or door slam, and activate a pan-tilt to orient a visible and infrared camera toward the detected sound. Once the cameras are cued to the target, onboard image processing can then track the target and/or transmit the imagery to a remote operator for navigation, situational awareness, and target detection. Such a vehicle can provide reconnaissance, surveillance, and target acquisition for soldiers, law enforcement, and rescue personnel, and remove these people from hazardous environments. ARL's primary robotic platforms contain 16-in. diameter, eight-element acoustic arrays. Additionally, a 9- in. array is being developed in support of DARPA's Tactical Mobile Robot program. The robots have been tested in both urban and open terrain. The current acoustic processing algorithm has been optimized to detect the muzzle blast from a sniper's weapon, and reject many interfering noise sources such as wind gusts, generators, and self-noise. However, other detection algorithms for speech and vehicle detection/tracking are being developed for implementation on this and smaller robotic platforms. The collaboration between two robots, both with known positions and orientations, can provide useful triangulation information for more precise localization of the acoustic events. These robots can be mobile sensor nodes in a larger, more expansive, sensor network that may include stationary ground sensors, UAVs, and other command and control assets. This report will document the performance of the robot's acoustic localization, describe the algorithm, and outline future work.

  8. Patch nearfield acoustic holography based on the equivalent source method

    2008-01-01

    On the basis of nearfield acoustic holography (NAH) based on the equivalent source method (ESM), patch NAH based on the ESM is proposed. The method overcomes the shortcoming in the conventional NAH that the hologram surface should be larger than the source surface. It need not to discretize the whole source and its measurement need not to cover the whole source. The measurement may be performed over the region of interest, and the reconstruction can be done in the region directly. The method is flexible in applications, stable in computation, and very easy to implement. It has good potential applications in engineering. The numerical simulations show the invalidity of the conventional NAH based on the ESM and prove the validities of the proposed method for reconstructing a partial source and the regularization for reducing the error effect of the pressure measured on the hologram surface.

  9. Patch nearfield acoustic holography based on the equivalent source method

    2008-01-01

    On the basis of nearfield acoustic holography (NAH) based on the equivalent source method (ESM), patch NAH based on the ESM is proposed. The method overcomes the shortcoming in the conventional NAH that the hologram surface should be larger than the source surface. It need not to discretize the whole source and its measurement need not to cover the whole source. The measurement may be performed over the region of interest, and the reconstruction can be done in the region directly. The method is flexible in applications, stable in computation, and very easy to implement. It has good potential applications in engineering. The nu- merical simulations show the invalidity of the conventional NAH based on the ESM and prove the validities of the proposed method for reconstructing a partial source and the regularization for reducing the error effect of the pressure measured on the hologram surface.

  10. Fly-ear inspired acoustic sensors for gunshot localization

    Liu, Haijun; Currano, Luke; Gee, Danny; Yang, Benjamin; Yu, Miao

    2009-05-01

    The supersensitive ears of the parasitoid fly Ormia ochracea have inspired researchers to develop bio-inspired directional microphone for sound localization. Although the fly ear is optimized for localizing the narrow-band calling song of crickets at 5 kHz, experiments and simulation have shown that it can amplify directional cues for a wide frequency range. In this article, a theoretical investigation is presented to study the use of fly-ear inspired directional microphones for gunshot localization. Using an equivalent 2-DOF model of the fly ear, the time responses of the fly ear structure to a typical shock wave are obtained and the associated time delay is estimated by using cross-correlation. Both near-field and far-field scenarios are considered. The simulation shows that the fly ear can greatly amplify the time delay by ~20 times, which indicates that with an interaural distance of only 1.2 mm the fly ear is able to generate a time delay comparable to that obtained by a conventional microphone pair with a separation as large as 24 mm. Since the parameters of the fly ear structure can also be tuned for muzzle blast and other impulse stimulus, fly-ear inspired acoustic sensors offers great potential for developing portable gunshot localization systems.

  11. Source localization of rhythmic ictal EEG activity

    Beniczky, Sándor; Lantz, Göran; Rosenzweig, Ivana;

    2013-01-01

    Although precise identification of the seizure-onset zone is an essential element of presurgical evaluation, source localization of ictal electroencephalography (EEG) signals has received little attention. The aim of our study was to estimate the accuracy of source localization of rhythmic ictal...... EEG activity using a distributed source model....

  12. System and method for sonic wave measurements using an acoustic beam source

    Vu, Cung Khac; Sinha, Dipen N.; Pantea, Cristian

    2015-08-11

    A method and system for investigating structure near a borehole are described herein. The method includes generating an acoustic beam by an acoustic source; directing at one or more azimuthal angles the acoustic beam towards a selected location in a vicinity of a borehole; receiving at one or more receivers an acoustic signal, the acoustic signal originating from a reflection or a refraction of the acoustic wave by a material at the selected location; and analyzing the received acoustic signal to characterize features of the material around the borehole.

  13. Propagation and localization of acoustic waves in Fibonacci phononic circuits

    Aynaou, H [Laboratoire de Dynamique et d' Optique des Materiaux, Departement de Physique, Faculte des Sciences, Universite Mohamed Premier, 60000 Oujda (Morocco); Boudouti, E H El [Laboratoire de Dynamique et d' Optique des Materiaux, Departement de Physique, Faculte des Sciences, Universite Mohamed Premier, 60000 Oujda (Morocco); Djafari-Rouhani, B [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, UMR CNRS 8024, UFR de Physique, Universite de Lille 1, F-59655 Villeneuve d' Ascq (France); Akjouj, A [Laboratoire de Dynamique et Structure des Materiaux Moleculaires, UMR CNRS 8024, UFR de Physique, Universite de Lille 1, F-59655 Villeneuve d' Ascq (France); Velasco, V R [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2005-07-13

    A theoretical investigation is made of acoustic wave propagation in one-dimensional phononic bandgap structures made of slender tube loops pasted together with slender tubes of finite length according to a Fibonacci sequence. The band structure and transmission spectrum is studied for two particular cases. (i) Symmetric loop structures, which are shown to be equivalent to diameter-modulated slender tubes. In this case, it is found that besides the existence of extended and forbidden modes, some narrow frequency bands appear in the transmission spectra inside the gaps as defect modes. The spatial localization of the modes lying in the middle of the bands and at their edges is examined by means of the local density of states. The dependence of the bandgap structure on the slender tube diameters is presented. An analysis of the transmission phase time enables us to derive the group velocity as well as the density of states in these structures. In particular, the stop bands (localized modes) may give rise to unusual (strong normal) dispersion in the gaps, yielding fast (slow) group velocities above (below) the speed of sound. (ii) Asymmetric tube loop structures, where the loops play the role of resonators that may introduce transmission zeros and hence new gaps unnoticed in the case of simple diameter-modulated slender tubes. The Fibonacci scaling property has been checked for both cases (i) and (ii), and it holds for a periodicity of three or six depending on the nature of the substrates surrounding the structure.

  14. Influence of sound source width on human sound localization.

    Greene, Nathaniel T; Paige, Gary D

    2012-01-01

    Free-field sound localization experiments generally assume that a loudspeaker can be approximated by a point-source; however, a large loudspeaker may extend beyond the width that two sources can be discriminated. Humans can accurately discriminate sound source locations within a few degrees, thus one might expect localization precision to decrease as a function of sound source diameter, much as precision is lower for localizing the center of a wide, blurry light source. In order to test the degree to which humans differentially localize small and large sound sources, auditory targets were presented using a single 25.4 cm by 10.2 cm elliptical loudspeaker with the primary axis oriented both horizontally and vertically in different sessions. Subjects were seated with their heads fixed by a bite bar in a darkened, echo-attenuating room facing a cylindrical, acoustically transparent screen at a distance of 2 meters. Auditory targets consisted of repeating bursts (5 Hz) of low frequency band-pass noise (0.2 - 1 kHz, 75 dB SPL). Subjects were instructed to quickly and accurately guide a laser pointer mounted on a cylindrical joystick towards targets, presented randomly within a field ± 40° in azimuth by ± 10° in elevation, with oversampled points located every ten degrees along the primary meridians. Localization accuracy and precision (mean and standard deviation of localization error at oversampled locations) were not significantly different between speaker orientations, and were comparable to baseline measurements recorded using a 7.6 cm circular speaker. We conclude that low frequency sound localization performance is not dependent upon the size of the sound source as predicted theoretically, and is well approximated by a point source. PMID:23367407

  15. Algorithms for regional source localization

    Dandach, S. H.; Bullo, F.

    2009-01-01

    In this paper we use the MAP criterion to locate a region containing a source. Sensors placed in a field of interest divide the latter into smaller regions and take measurements that are transmitted over noisy wireless channels. We propose implementations of our algorithm that consider complete and limited communication among sensors and seek to choose the most likely hypothesis. Each hypothesis corresponds to the event that a given region contains the source. Corrupted measurements are used ...

  16. Localization from near-source quasi-static electromagnetic fields

    Mosher, J.C.

    1993-09-01

    A wide range of research has been published on the problem of estimating the parameters of electromagnetic and acoustical sources from measurements of signals measured at an array of sensors. In the quasi-static electromagnetic cases examined here, the signal variation from a point source is relatively slow with respect to the signal propagation and the spacing of the array of sensors. As such, the location of the point sources can only be determined from the spatial diversity of the received signal across the array. The inverse source localization problem is complicated by unknown model order and strong local minima. The nonlinear optimization problem is posed for solving for the parameters of the quasi-static source model. The transient nature of the sources can be exploited to allow subspace approaches to separate out the signal portion of the spatial correlation matrix. Decomposition techniques are examined for improved processing, and an adaptation of MUtiple SIgnal Characterization (MUSIC) is presented for solving the source localization problem. Recent results on calculating the Cramer-Rao error lower bounds are extended to the multidimensional problem here. This thesis focuses on the problem of source localization in magnetoencephalography (MEG), with a secondary application to thunderstorm source localization. Comparisons are also made between MEG and its electrical equivalent, electroencephalography (EEG). The error lower bounds are examined in detail for several MEG and EEG configurations, as well as localizing thunderstorm cells over Cape Canaveral and Kennedy Space Center. Time-eigenspectrum is introduced as a parsing technique for improving the performance of the optimization problem.

  17. Resolving the source of the solar acoustic oscillations: What will be possible with DKIST?

    Rast, Mark; Martinez Pillet, Valentin

    2016-05-01

    The solar p-modes are likely excited by small-scale convective dynamics in the solar photosphere, but the detailed source properties are not known. Theoretical models differ and observations are yet unable to differentiate between them. Resolving the underlying source events is more than a curiosity. It is important to the veracity of global helioseismic measurements (including local spectral methods such as ring diagram analysis) because global p-mode line shapes and thus accurate frequency determinations depend critically on the relationship between intensity and velocity during the excitation events. It is also fundamental to improving the accuracy of the local time-distance measurements because in these kernel calculations depend on knowledge of the source profile and the properties of the excitation noise. The Daniel K. Inouye Solar Telescope (DKIST) will have the spatial resolution and spectral range needed to resolve the solar acoustic excitation events in both time and space (horizontally and with height) using multi-wavelength observations. Inversions to determine the dynamic and thermodynamic evolution of the discrete small-scale convective events that serve as acoustic sources may also be possible, though determination of the pressure fluctuations associated with the sources is a challenge. We describe the DKIST capabilities anticipated and the preliminary work needed to prepare for them.

  18. Escaping "localisms" in IT sourcing

    Mola, L.; Carugati, Andrea

    2012-01-01

    Organizations are limited in their choices by the institutional environment in which they operate. This is particularly true for IT sourcing decisions that go beyond cost considerations and are constrained by traditions, geographical location, and social networks. This article investigates how a ...

  19. Acoustic multipole source model for volcanic explosions and inversion for source parameters

    Kim, Keehoon; Lees, Jonathan M.; Ruiz, Mario

    2012-12-01

    Volcanic explosions are accompanied by strong acoustic pressure disturbances in the atmosphere. With a proper source model, these acoustic signals provide invaluable information about volcanic explosion dynamics. Far-field solutions to volcanic infrasound radiation have been derived above a rigid half-space boundary, and a simple inversion method was developed based on the half-space model. Acoustic monopole and dipole sources were estimated simultaneously from infrasound waveforms. Stability of the inversion procedure was assessed in terms of variances of source parameters, and the procedure was reliable with at least three stations around the infrasound source. Application of this method to infrasound observations recorded at Tungurahua volcano in Ecuador successfully produced a reasonable range of source parameters with acceptable variances. Observed strong directivity of infrasound radiation from explosions at Tungurahua are successfully explained by the directivity of a dipole source model. The resultant dipole axis, in turn, shows good agreement with the opening direction of the vent at Tungurahua, which is considered to be the origin of the dipole source. The method is general and can be utilized to study any monopole, dipole or combined sources generated by explosions.

  20. An autonomous surveillance system for blind sources localization and separation

    Wu, Sean; Kulkarni, Raghavendra; Duraiswamy, Srikanth

    2013-05-01

    This paper aims at developing a new technology that will enable one to conduct an autonomous and silent surveillance to monitor sound sources stationary or moving in 3D space and a blind separation of target acoustic signals. The underlying principle of this technology is a hybrid approach that uses: 1) passive sonic detection and ranging method that consists of iterative triangulation and redundant checking to locate the Cartesian coordinates of arbitrary sound sources in 3D space, 2) advanced signal processing to sanitizing the measured data and enhance signal to noise ratio, and 3) short-time source localization and separation to extract the target acoustic signals from the directly measured mixed ones. A prototype based on this technology has been developed and its hardware includes six B and K 1/4-in condenser microphones, Type 4935, two 4-channel data acquisition units, Type NI-9234, with a maximum sampling rate of 51.2kS/s per channel, one NI-cDAQ 9174 chassis, a thermometer to measure the air temperature, a camera to view the relative positions of located sources, and a laptop to control data acquisition and post processing. Test results for locating arbitrary sound sources emitting continuous, random, impulsive, and transient signals, and blind separation of signals in various non-ideal environments is presented. This system is invisible to any anti-surveillance device since it uses the acoustic signal emitted by a target source. It can be mounted on a robot or an unmanned vehicle to perform various covert operations, including intelligence gathering in an open or a confined field, or to carry out the rescue mission to search people trapped inside ruins or buried under wreckages.

  1. Sensitivity of thin-film bulk acoustic resonators (FBAR) to localized mechanical forces

    We report on the sensitivity of thin-film bulk acoustic resonators (FBARs) to localized contact mechanical forces, their design for high sensitivity and the performance under different forcing conditions and mechanisms. Cantilever and membrane structures are the examples chosen for structure and process flow design, finite element modeling and experimental characterization. To leverage on the high sensitivity of FBAR devices at the 2 GHz radio frequency, we carried out electrical bulk acoustic wave excitation and readout of the first longitudinal acoustic mode. Experiments to extract actual sensitivities included atomic force microscopy-driven force excitation, nanoindentation and manual force loading. A force sensitivity function with extracted values S (MHz N−1) from 50 to 270 MHz N−1 shows its dependence on the thin-film stack configuration, the extent of force which determines the linear regime and the spatial location of the force loading source. The discussion provides a force range and sensitivity benchmarking, possible manufacturing and application scenarios, and design guidelines for future integrated devices. (paper)

  2. Progressive Approaches to Localization and Identification of AE Sources

    Převorovský, Zdeněk; Krofta, Josef; Chlada, Milan; Farová, Zuzana; Kůs, V.

    Granada : University of Granada, 2012 - (Gallego, A.; Ono, K.), s. 1-2 ISBN 978-84-615-9941-7. [Europen Conference on Acoustic Emission Testing/30./ & International Conference on Acoustic Emission/7./. Granada (ES), 12.09.2012-15.09.2012] R&D Projects: GA MPO(CZ) FR-TI1/274; GA ČR(CZ) GAP104/10/1430; GA MPO(CZ) FR-TI1/198 Institutional support: RVO:61388998 Keywords : acoustic emission * source location and identification * time reversal acoustics * signal deconvolution * inverse problem solution Subject RIV: BI - Acoustics

  3. A comparison of methods for 3D target localization from seismic and acoustic signatures

    ELBRING,GREGORY J.; GARBIN,H. DOUGLAS; LADD,MARK D.

    2000-04-03

    An important application of seismic and acoustic unattended ground sensors (UGS) is the estimation of the three dimensional position of an emitting target. Seismic and acoustic data derived from UGS systems provide the taw information to determine these locations, but can be processed and analyzed in a number of ways using varying amounts of auxiliary information. Processing methods to improve arrival time picking for continuous wave sources and methods for determining and defining the seismic velocity model are the primary variables affecting the localization accuracy. Results using field data collected from an underground facility have shown that using an iterative time picking technique significantly improves the accuracy of the resulting derived target location. Other processing techniques show little advantage over simple crosscorrelation along in terms of accuracy, but may improve the ease with which time picks can be made. An average velocity model found through passive listening or a velocity model determined from a calibration source near the target source both result in similar location accuracies, although the use of station correction severely increases the location error.

  4. Maximum Likelihood Localization of Radiation Sources with unknown Source Intensity

    Baidoo-Williams, Henry E

    2016-01-01

    In this paper, we consider a novel and robust maximum likelihood approach to localizing radiation sources with unknown statistics of the source signal strength. The result utilizes the smallest number of sensors required theoretically to localize the source. It is shown, that should the source lie in the open convex hull of the sensors, precisely $N+1$ are required in $\\mathbb{R}^N, ~N \\in \\{1,\\cdots,3\\}$. It is further shown that the region of interest, the open convex hull of the sensors, is entirely devoid of false stationary points. An augmented gradient ascent algorithm with random projections should an estimate escape the convex hull is presented.

  5. Underwater Broadband Source Localization Based on Modal Filtering and Features Extraction

    Cristol Xavier

    2010-01-01

    Full Text Available Passive source localization is a crucial issue in underwater acoustics. In this paper, we focus on shallow water environment (0 to 400 m and broadband Ultra-Low Frequency acoustic sources (1 to 100 Hz. In this configuration and at a long range, the acoustic propagation can be described by normal mode theory. The propagating signal breaks up into a series of depth-dependent modes. These modes carry information about the source position. Mode excitation factors and mode phases analysis allow, respectively, localization in depth and distance. We propose two different approaches to achieve the localization: multidimensional approach (using a horizontal array of hydrophones based on frequency-wavenumber transform ( method and monodimensional approach (using a single hydrophone based on adapted spectral representation ( method. For both approaches, we propose first complete tools for modal filtering, and then depth and distance estimators. We show that adding mode sign and source spectrum informations improves considerably the localization performance in depth. The reference acoustic field needed for depth localization is simulated with the new realistic propagation modelMoctesuma. The feasibility of both approaches, and , are validated on data simulated in shallow water for different configurations. The performance of localization, in depth and distance, is very satisfactory.

  6. LARA: Expert system for acoustic localization of robot in a LMFBR

    The expert system LARA (Acoustic Localization of Autonomic Robot) has been developed to show the interest of introducing artificial intelligency for fine automatic positioning of refuelling machine in a LMFBR reactor. LARA which is equipped with an acoustic detector gives rapidly a good positioning on the fuel

  7. Determination of the acoustic source power levels of wind turbines

    Debruijn, A.; Stam, W. J.; Dewolf, W. B.

    To facilitate Wind Energy Conversin System (WECS) licensing, it is recommended to obtain the immission-relevant sound power from the WECS, since this quantity fits into most recommendations for industrial installations. Measurements on small and medium-scale WECS show that rotor rotation speed is a more important parameter than the wind velocity with regard to the radiated noise. An acoustic telescope was used to identify noise sources on two medium-size wind turbines. The mechanical noise from the nacelle is mostly predominant but the trailing edge aerodynamic noise is not negligible. A prediction model for this type of noise, which leads to good agreement with experimental data was developed. A method to suppress turbulence signals around WECS is a set-up with twin microphones, using correlation techniques on both signals.

  8. Detection of impulsive sources from an aerostat-based acoustic array data collection system

    Prather, Wayne E.; Clark, Robert C.; Strickland, Joshua; Frazier, Wm. Garth; Singleton, Jere

    2009-05-01

    An aerostat based acoustic array data collection system was deployed at the NATO TG-53 "Acoustic Detection of Weapon Firing" Joint Field Experiment conducted in Bourges, France during the final two weeks of June 2008. A variety of impulsive sources including mortar, artillery, gunfire, RPG, and explosive devices were fired during the test. Results from the aerostat acoustic array will be presented against the entire range of sources.

  9. Geodesic acoustic mode in tokamaks: local consideration and eigenvalue analysis

    A set of magnetohydrodynamic equations describing the geodesic acoustic mode (GAM) in tokamak plasmas is derived. The obtained equations take into account the presence of the energetic ions and allow to study energetic-ion-driven GAM instability perturbatively or non-perturbatively (EGAM mode). They are applicable to plasmas with β-bar q2≲1, where β-bar =βs/(1+βs), βs=cs2/vA2, cs is the sound velocity, vA is the Alfvén velocity, q is the tokamak safety factor. Using these equations, GAM/EGAM instability is studied in a local approach and by means of the eigenvalue analysis. It is shown that β-coupling (the coupling of Fourier harmonics of the perturbation due to finite β—ratio of the plasma pressure to the magnetic field pressure—and the curvature of the field lines) can be responsible for the radial structure of the GAM-mode. A conclusion is drawn that conditions for the GAM/EGAM instability to arise are mildest in the case of counter-injection of energetic ions with pitch angles χ2 < 0.6 and large ratio of Larmor radius of the energetic ions to a characteristic length of inhomogeneity of these ions. A numerical code solving the derived equations is developed. Specific calculations are carried out for tokamaks with a non-monotonic safety factor. On the other hand, it is found that due to the presence of the energetic ions the GAM/EGAM continuum can have an extremum even when the safety factor q(r) is monotonic, which indicates that global modes can exist also in this case. (paper)

  10. Flat acoustic sources with frequency response correction based on feedback and feed-forward distributed control

    Ho, Jen-Hsuan; Berkhoff, A.P.

    2015-01-01

    This paper presents an acoustic source with a small thickness and high bending stiffness. The high bending stiffness is obtained with a sandwich structure in which the face of the sandwich structure internal to the source is perforated to increase the acoustic compliance, thereby leading to increase

  11. Brief communication "Seismic and acoustic-gravity signals from the source of the 2004 Indian Ocean Tsunami"

    A. Raveloson

    2012-02-01

    Full Text Available The great Sumatra-Andaman earthquake of 26 December 2004 caused seismic waves propagating through the solid Earth, tsunami waves propagating through the ocean and infrasound or acoustic-gravity waves propagating through the atmosphere. Since the infrasound wave travels faster than its associated tsunami, it is for warning purposes very intriguing to study the possibility of infrasound generation directly at the earthquake source. Garces et al. (2005 and Le Pichon et al. (2005 emphasized that infrasound was generated by mountainous islands near the epicenter and by tsunami propagation along the continental shelf to the Bay of Bengal. Mikumo et al. (2008 concluded from the analysis of travel times and amplitudes of first arriving acoustic-gravity waves with periods of about 400–700 s that these waves are caused by coseismic motion of the sea surface mainly to the west of the Nicobar islands in the open seas. We reanalyzed the acoustic-gravity waves and corrected the first arrival times of Mikumo et al. (2008 by up to 20 min. We found the source of the first arriving acoustic-gravity wave about 300 km to the north of the US Geological Survey earthquake epicenter. This confirms the result of Mikumo et al. (2008 that sea level changes at the earthquake source cause long period acoustic-gravity waves, which indicate that a tsunami was generated. Therefore, a denser local network of infrasound stations may be helpful for tsunami warnings, not only for very large earthquakes.

  12. Linearized versus non-linear inverse methods for seismic localization of underground sources

    Oh, Geok Lian; Jacobsen, Finn

    2013-01-01

    the Bayes nonlinear inversion method. The travel times used in the beamformer are derived from solving the Eikonal equation. In the linearized inversion method, we assume that the elastic waves are predominantly acoustic waves, and the acoustic approximation is applied. For the nonlinear inverse......The problem of localization of underground sources from seismic measurements detected by several geophones located on the ground surface is addressed. Two main approaches to the solution of the problem are considered: a beamforming approach that is derived from the linearized inversion problem, and...... Difference elastic wave-field numerical method. In this paper, the accuracy and performance of the linear beamformer and nonlinear inverse methods to localize a underground seismic source are checked and compared using computer generated synthetic experimental data. © 2013 Acoustical Society of America....

  13. LOCAL TO BASIN SCALE ARRAYS FOR PASSIVE ACOUSTIC MONITORING IN THE ATLANTIC SECTOR OF THE SOUTHERN OCEAN

    Rettig, Stefanie; Boebel, Olaf; Menze, Sebastian; Kindermann, Lars; Thomisch, Karolin; Van Opzeeland, Ilse

    2013-01-01

    Passive acoustic data provide a prime source of information on marine mammal distribution and behaviour. Particularly in the Southern Ocean, where ship-based data collection can be severely hampered by weather and ice conditions, passive acoustic monitoring (PAM) of marine mammals forms an important source of year-round information on acoustic presence. Array data can be used to obtain directional information on the species present in the recordings to derive movement patterns. Acoustic array...

  14. Noise caused by cavitating Butterfly and Monovar Valves. Effects of cavitation on acoustic sources; numerical simulation

    An experimental study of the effects of cavitation was carried out through an analysis of cavitating Butterfly and Monovar valves. For each variation case, the nature of the dominant source is determined in relation to frequency. Once the parameters of the cavitation zone are identified, a three-zone model is used in order to pinpoint the acoustic sources with cavitation. In order to determine acoustic sources, we present a numerical simulation using a bubbles population. (authors)

  15. Functional delay and sum beamforming for three-dimensional acoustic source identification with solid spherical arrays

    Yang, Yang; Chu, Zhigang; Shen, Linbang; Xu, Zhongming

    2016-07-01

    parameter, when the focus distance is unequal to the distance from the source to the array center or the focus directions do not embrace the source direction. Fortunately, the deviation can be commendably compensated for by the introduced scale-and-integrate method. This study will be of great significance to the accurate and quick localization and quantification of acoustic sources in cabin environments.

  16. Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure

    The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of different samples were measured by the pulse tube. Measurement results show that the new material possesses excellent underwater acoustic effects in a wide frequency range. Moreover, in order to investigate impacts of locally resonant units, some defects are introduced into the sample. The experimental result and the theoretical calculation both show that locally resonant units being connected to a network structure play an important role in achieving a wide band strong acoustic absorption. (condensed matter: structure, thermal and mechanical properties)

  17. Automatic estimation of position and orientation of an acoustic source by a microphone array network.

    Nakano, Alberto Yoshihiro; Nakagawa, Seiichi; Yamamoto, Kazumasa

    2009-12-01

    A method which automatically provides the position and orientation of a directional acoustic source in an enclosed environment is proposed. In this method, different combinations of the estimated parameters from the received signals and the microphone positions of each array are used as inputs to the artificial neural network (ANN). The estimated parameters are composed of time delay estimates (TDEs), source position estimates, distance estimates, and energy features. The outputs of the ANN are the source orientation (one out of four possible orientations shifted by 90 degrees and either the best array which is defined as the nearest to the source) or the source position in two dimensional/three dimensional (2D/3D) space. This paper studies the position and orientation estimation performances of the ANN for different input/output combinations (and different numbers of hidden units). The best combination of parameters (TDEs and microphone positions) yields 21.8% reduction in the average position error compared to the following baselines and a correct orientation ratio greater than 99%. Position localization baselines consist of a time delay of arrival based method with an average position error of 34.1 cm and the steered response power with phase transform method with an average position error of 29.8 cm in 3D space. PMID:20000922

  18. Color Filtering Localization for Three-Dimensional Underwater Acoustic Sensor Networks

    Zhihua Liu; Han Gao; Wuling Wang; Shuai Chang; Jiaxing Chen

    2015-01-01

    Accurate localization of mobile nodes has been an important and fundamental problem in underwater acoustic sensor networks (UASNs). The detection information returned from a mobile node is meaningful only if its location is known. In this paper, we propose two localization algorithms based on color filtering technology called PCFL and ACFL. PCFL and ACFL aim at collaboratively accomplishing accurate localization of underwater mobile nodes with minimum energy expenditure. They both adopt the o...

  19. On Building Immersive Audio Applications Using Robust Adaptive Beamforming and Joint Audio-Video Source Localization

    Beracoechea JA

    2006-01-01

    Full Text Available This paper deals with some of the different problems, strategies, and solutions of building true immersive audio systems oriented to future communication applications. The aim is to build a system where the acoustic field of a chamber is recorded using a microphone array and then is reconstructed or rendered again, in a different chamber using loudspeaker array-based techniques. Our proposal explores the possibility of using recent robust adaptive beamforming techniques for effectively estimating the original sources of the emitting room. A joint audio-video localization method needed in the estimation process as well as in the rendering engine is also presented. The estimated source signal and the source localization information drive a wave field synthesis engine that renders the acoustic field again at the receiving chamber. The system performance is tested using MUSHRA-based subjective tests.

  20. Real-Time Source Classification with an Waveform Parameter Filtering of Acoustic Emission Signals

    Cho, Seung Hyun; Park, Jae Ha; Ahn, Bong Young [Chonnam National University, Gwangju (Korea, Republic of)

    2011-04-15

    The acoustic emission(AE) technique is a well established method to carry out structural health monitoring(SHM) of large structures. However, the real-time monitoring of the crack growth in the roller coaster support structures is not easy since the vehicle operation produces very large noise as well as crack growth. In this investigation, we present the waveform parameter filtering method to classify acoustic sources in real-time. This method filtrates only the AE hits by the target acoustic source as passing hits in a specific parameter band. According to various acoustic sources, the waveform parameters were measured and analyzed to verify the present filtering method. Also, the AE system employing the waveform parameter filter was manufactured and applied to the roller coaster support structure in an actual amusement park

  1. LDB: Localization with Directional Beacons for Sparse 3D Underwater Acoustic Sensor Networks

    Hanjiang Luo

    2010-01-01

    Full Text Available In this paper, we propose a novel distributed localization scheme LDB, a 3D localization scheme with directional beacons for Underwater Acoustic Sensor Networks (UWA-SNs. LDB localizes sensor nodes using an Autonomous Underwater Vehicle (AUV as a mobile beacon sender. Mounted with a directional transceiver which creates conical shaped directional acoustic beam, the AUV patrols over the 3D deployment volume with predefined trajectory sending beacons with constant interval towards the sensor nodes. By listening two or more beacons sent from the AUV, the nodes can localize themselves silently. Through theoretical analysis, we provide the upper bound of the estimation error of the scheme. We also evaluate the scheme by simulations and the results show that our scheme can achieve a high localization accuracy, even in sparse networks.

  2. Improving the efficiency of deconvolution algorithms for sound source localization

    Lylloff, Oliver Ackermann; Fernandez Grande, Efren; Agerkvist, Finn T.;

    2015-01-01

    unknown acoustic source distribution and the beamformer's response to a point source, i.e., point-spread function. A significant limitation of deconvolution is, however, an additional computational effort compared to beamforming. In this paper, computationally efficient deconvolution algorithms are...

  3. Investigations of incorporating source directivity into room acoustics computer models to improve auralizations

    Vigeant, Michelle C.

    Room acoustics computer modeling and auralizations are useful tools when designing or modifying acoustically sensitive spaces. In this dissertation, the input parameter of source directivity has been studied in great detail to determine first its effect in room acoustics computer models and secondly how to better incorporate the directional source characteristics into these models to improve auralizations. To increase the accuracy of room acoustics computer models, the source directivity of real sources, such as musical instruments, must be included in the models. The traditional method for incorporating source directivity into room acoustics computer models involves inputting the measured static directivity data taken every 10° in a sphere-shaped pattern around the source. This data can be entered into the room acoustics software to create a directivity balloon, which is used in the ray tracing algorithm to simulate the room impulse response. The first study in this dissertation shows that using directional sources over an omni-directional source in room acoustics computer models produces significant differences both in terms of calculated room acoustics parameters and auralizations. The room acoustics computer model was also validated in terms of accurately incorporating the input source directivity. A recently proposed technique for creating auralizations using a multi-channel source representation has been investigated with numerous subjective studies, applied to both solo instruments and an orchestra. The method of multi-channel auralizations involves obtaining multi-channel anechoic recordings of short melodies from various instruments and creating individual channel auralizations. These auralizations are then combined to create a total multi-channel auralization. Through many subjective studies, this process was shown to be effective in terms of improving the realism and source width of the auralizations in a number of cases, and also modeling different

  4. A Wide Band Strong Acoustic Absorption in a Locally Network Anechoic Coating

    Composite materials with interpenetrating network structures usually exhibit unexpected merit due to the cooperative interaction. Locally resonant phononic crystals (LRPC) exhibit excellent sound attenuation performance based on a periodical arrangement of sound wave scatters. Inspired by the interpenetrating network structure and the LRPC concept, we develop a locally network anechoic coating (LNAC) that can achieve a wide band of underwater strong acoustic absorption. The experimental results show that the LNAC possesses an excellent underwater acoustic absorbing capacity in a wide frequency range. Moreover, in order to investigate the impact of the interpenetrating network structure, we fabricate a faultage structure sample and the network is disconnected by hard polyurethane (PU). The experimental comparison between the LNAC and the faultage structure sample shows that the interpenetrating network structure of the LNAC plays an important role in achieving a wide band strong acoustic absorption

  5. Acoustic detection and localization of weapons fire by unattended ground sensors and aerostat-borne sensors

    Naz, P.; Marty, Ch.; Hengy, S.; Miller, L. S.

    2009-05-01

    The detection and localization of artillery guns on the battlefield is envisaged by means of acoustic and seismic waves. The main objective of this work is to examine the different frequency ranges usable for the detection of small arms, mortars, and artillery guns on the same hardware platform. The main stages of this study have consisted of: data acquisition of the acoustic signals of the different weapons used, signal processing and evaluation of the localization performance for various types of individual arrays, and modeling of the wave propagation in the atmosphere. The study of the propagation effects on the signatures of these weapons is done by comparing the acoustic signals measured during various days, at ground level and at the altitude of our aerostat (typically 200 m). Numerical modeling has also been performed to reinforce the interpretation of the experimental results.

  6. GPS-less Localization Protocol for Underwater Acoustic Networks

    Al-Khalid Othman

    2008-02-01

    Full Text Available The problem of underwater positioning is increasingly crucial due to the emerging importance of sub-sea activities. Knowledge of node location is essential for many applications for which sensor networks can be used. At the surface, positioning problems have been resolved by the extended use of GPS, which is straightforward and effective. Unfortunately, using GPS in the sub-sea environment is impossible and positioning requires the use of special systems. One of the major challenges in the underwater acoustic networks (UANs area of research is the development of a networking protocol that can cope with the management of a dynamic sub-sea network. We propose a scheme to perform node discovery, using only one seed node (primary seed in a known position. The discovery protocol can be divided into two parts: First, building up the relative co-ordinate system. Second, involving more remote nodes becoming seed nodes for further discoveries. Four different algorithms have been investigated; (i Farthest/Farthest Algorithm, (ii Farthest/Nearest Algorithm, (iii Nearest/Farthest Algorithm and (iv Nearest/Nearest Algorithm. We investigated the performances of random and fixed (grid network topologies. Different locations of primary seed node were exercised and statistics for node discovery will be reported.

  7. Analysis of underwater decoupling properties of a locally resonant acoustic metamaterial coating

    Ling-Zhi, Huang; Yong, Xiao; Ji-Hong, Wen; Hai-Bin, Yang; Xi-Sen, Wen

    2016-02-01

    This paper presents a semi-analytical solution for the vibration and sound radiation of a semi-infinite plate covered by a decoupling layer consisting of locally resonant acoustic metamaterial. Formulations are derived based on a combination use of effective medium theory and the theory of elasticity for the decoupling material. Theoretical results show good agreements between the method developed in this paper and the conventional finite element method (FEM), but the method of this paper is more efficient than FEM. Numerical results also show that system with acoustic metamaterial decoupling layer exhibits significant noise reduction performance at the local resonance frequency of the acoustic metamaterial, and such performance can be ascribed to the vibration suppression of the base plate. It is demonstrated that the effective density of acoustic metamaterial decoupling layer has a great influence on the mechanical impedance of the system. Furthermore, the resonance frequency of locally resonant structure can be effectively predicted by a simple model, and it can be significantly affected by the material properties of the locally resonant structure. Project supported by the National Natural Science Foundation of China (Grant Nos. 51305448 and 51275519).

  8. Analogy electromagnetism-acoustics: Validation and application to local impedance active control for sound absorption

    Nicolas, Laurent; Furstoss, M.; Galland, Marie-Annick

    1998-01-01

    An analogy between electromagnetism and acoustics is presented in 2D. The propagation of sound in presence of absorbing material is modeled using an open boundary microwave package. Validation is performed through analytical and experimental results. Application to local impedance active control for free field sound absorption is finally described.

  9. Enlargement of locally resonant sonic band gap by using composite plate-type acoustic metamaterial

    We numerically investigate the propagation characteristics of Lamb waves in composite plate-type acoustic metamaterial constituted of one-side cylindrical stubs deposited on a two-dimensional binary locally resonant phononic plate. Numerical results show that, with the introduction of composite plate-type acoustic metamaterial, locally resonant band gap shifts to lower frequency, and a significant enlargement of the relative bandwidth by a factor of 3 can be obtained, compared to one-side locally resonant stubbed plates. We show that the band gap enlargement is attributed to the coupling between the local resonant Lamb modes of two-dimensional phononic plate and the resonant modes of the stubs. - Highlights: • An original composite plate-type locally resonant acoustic metamaterial is proposed. • A significant enlargement of the relative bandwidth by a factor of 3 can be obtained. • The band gap enlargement is attributed to the locally resonant complex effect. • The band gap is significantly dependent upon the geometrical parameters

  10. Battlefield acoustics

    Damarla, Thyagaraju

    2015-01-01

    This book presents all aspects of situational awareness in a battlefield using acoustic signals. It starts by presenting the science behind understanding and interpretation of sound signals. The book then goes on to provide various signal processing techniques used in acoustics to find the direction of sound source, localize gunfire, track vehicles, and detect people. The necessary mathematical background and various classification and fusion techniques are presented. The book contains majority of the things one would need to process acoustic signals for all aspects of situational awareness in one location. The book also presents array theory, which is pivotal in finding the direction of arrival of acoustic signals. In addition, the book presents techniques to fuse the information from multiple homogeneous/heterogeneous sensors for better detection. MATLAB code is provided for majority of the real application, which is a valuable resource in not only understanding the theory but readers, can also use the code...

  11. Design of acoustic logging signal source of imitation based on field programmable gate array

    An acoustic logging signal source of imitation is designed and realized, based on the Field Programmable Gate Array (FPGA), to improve the efficiency of examining and repairing acoustic logging tools during research and field application, and to inspect and verify acoustic receiving circuits and corresponding algorithms. The design of this signal source contains hardware design and software design,and the hardware design uses an FPGA as the control core. Four signals are made first by reading the Random Access Memory (RAM) data which are inside the FPGA, then dealing with the data by digital to analog conversion, amplification, smoothing and so on. Software design uses VHDL, a kind of hardware description language, to program the FPGA. Experiments illustrate that the ratio of signal to noise for the signal source is high, the waveforms are stable, and also its functions of amplitude adjustment, frequency adjustment and delay adjustment are in accord with the characteristics of real acoustic logging waveforms. These adjustments can be used to imitate influences on sonic logging received waveforms caused by many kinds of factors such as spacing and span of acoustic tools, sonic speeds of different layers and fluids, and acoustic attenuations of different cementation planes. (paper)

  12. Effects of individual sound sources on the subjective loudness and acoustic comfort in underground shopping streets.

    Kang, Jian; Meng, Qi; Jin, Hong

    2012-10-01

    Previous studies have demonstrated that human evaluation of subjective loudness and acoustic comfort depends on a series of factors in a particular situation rather than only on sound pressure levels. In the present study, a large-scale subjective survey has been undertaken on underground shopping streets in Harbin, China, to determine how individual sound sources influence subjective loudness and acoustic comfort evaluation. Based on the analysis of case study results, it has been shown that all individual sound sources can increase subjective loudness to a certain degree. However, their levels of influence on acoustic comfort are different. Background music and the public address system can increase acoustic comfort, with a mean difference of 0.18 to 0.32 and 0.21 to 0.27, respectively, where a five-point bipolar category scale is used. Music from shops and vendor shouts can decrease acoustic comfort, with a mean difference of -0.11 to -0.38 and -0.39 to -0.62, respectively. The feasibility of improving acoustic comfort by changing certain sound sources is thus demonstrated. PMID:22846767

  13. Helmet-mounted acoustic array for hostile fire detection and localization in an urban environment

    Scanlon, Michael V.

    2008-04-01

    The detection and localization of hostile weapons firing has been demonstrated successfully with acoustic sensor arrays on unattended ground sensors (UGS), ground-vehicles, and unmanned aerial vehicles (UAVs). Some of the more mature systems have demonstrated significant capabilities and provide direct support to ongoing counter-sniper operations. The Army Research Laboratory (ARL) is conducting research and development for a helmet-mounted system to acoustically detect and localize small arms firing, or other events such as RPG, mortars, and explosions, as well as other non-transient signatures. Since today's soldier is quickly being asked to take on more and more reconnaissance, surveillance, & target acquisition (RSTA) functions, sensor augmentation enables him to become a mobile and networked sensor node on the complex and dynamic battlefield. Having a body-worn threat detection and localization capability for events that pose an immediate danger to the soldiers around him can significantly enhance their survivability and lethality, as well as enable him to provide and use situational awareness clues on the networked battlefield. This paper addresses some of the difficulties encountered by an acoustic system in an urban environment. Complex reverberation, multipath, diffraction, and signature masking by building structures makes this a very harsh environment for robust detection and classification of shockwaves and muzzle blasts. Multifunctional acoustic detection arrays can provide persistent surveillance and enhanced situational awareness for every soldier.

  14. Acoustic source identification in an enclosed space using the inverse phased beam tracing at medium frequencies

    Ih, Jeong-Guon; Jeong, Cheol-Ho

    2008-01-01

    to the identification of the acoustic sources inside a chamber. In the simulation tests, spherical and rectangular shaped sources operating in a room were taken as examples. When the source pressure distribution was reconstructed by this numerical inverse technique, the sound power spectrum radiated from the source...... could be estimated by eliminating the contribution from surface reflections. Reconstruction error was investigated by the Monte Carlo simulation in terms of the signal-to-noise ratio...

  15. The sound power emitted by a source of low acoustic impedance

    Jacobsen, Finn; Verholt, Lars M.

    1998-01-01

    Several authors have maintained that a source of low acoustic impedance (which includes standardised reference sources of the aerodynamic type) would radiate less than the free field power in a reverberation room. However, neither computer simulations nor experiments have confirmed this assertion....

  16. Underwater Acoustic Localization and Tracking of Pacific Walruses in the Northeastern Chukchi Sea

    Rideout, Brendan Pearce

    This thesis develops and demonstrates an approach for estimating the three-dimensional (3D) location of a vocalizing underwater marine mammal using acoustic arrival time measurements at three spatially separated receivers while providing rigorous location uncertainties. To properly account for uncertainty in the measurements of receiver parameters (e.g., 3D receiver locations and synchronization times) and environmental parameters (water depth and sound speed correction), these quantities are treated as unknowns constrained with prior estimates and prior uncertainties. While previous localization algorithms have solved for an unknown scaling factor on the prior uncertainties as part of the inversion, in this work unknown scaling factors on both the prior and arrival time uncertainties are estimated. Maximum a posteriori estimates for sound source locations and times, receiver parameters, and environmental parameters are calculated simultaneously. Posterior uncertainties for all unknowns are calculated and incorporate both arrival time and prior uncertainties. Simulation results demonstrated that, for the case considered here, linearization errors are generally small and that the lack of an accurate sound speed profile does not necessarily cause large uncertainties or biases in the estimated positions. The primary motivation for this work was to develop an algorithm for locating underwater Pacific walruses in the coastal waters around Alaska. In 2009, an array of approximately 40 underwater acoustic receivers was deployed in the northeastern Chukchi Sea (northwest of Alaska) from August to October to record the vocalizations of marine mammals including Pacific walruses and bowhead whales. Three of these receivers were placed in a triangular arrangement approximately 400 m apart near the Hanna Shoal (northwest of Wainwright, Alaska). A sequence of walrus knock vocalizations from this data set was processed using the localization algorithm developed in this thesis

  17. Transient acoustic response in car cabins with localization of reflections

    Cebrián Lindström, Víctor

    2013-01-01

    Due to its small size and the restrictions on source and listener positions, the design of sound reproduction systems for car cabins is particularly cumbersome. In the present project the measurement of the impulse response between a single loudspeaker and a listener position, with special emphasis on the directional characteristics, will be examined. The propagation paths inside a car are very short, meaning that it is very difficult for the existing commercial measurement systems to reso...

  18. Distributed Remote Vector Gaussian Source Coding for Wireless Acoustic Sensor Networks

    Zahedi, Adel; Østergaard, Jan; Jensen, Søren Holdt;

    2014-01-01

    and the estimates of the source resulting from decoding the received messages are then jointly encoded and transmitted to a neighboring node in the network. We show that for this distributed source coding scenario, one can encode a so-called conditional sufficient statistic of the sources instead of......In this paper, we consider the problem of remote vector Gaussian source coding for a wireless acoustic sensor network. Each node receives messages from multiple nodes in the network and decodes these messages using its own measurement of the sound field as side information. The node’s measurement...... jointly encoding multiple sources. We focus on the case where node measurements are in form of noisy linearly mixed combinations of the sources and the acoustic channel mixing matrices are invertible. For this problem, we derive the rate-distortion function for vector Gaussian sources and under covariance...

  19. Acoustics

    Goodman, Jerry R.; Grosveld, Ferdinand

    2007-01-01

    The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

  20. Eccentricity effects on acoustic radiation from a spherical source suspended within a thermoviscous fluid sphere.

    Hasheminejad, Seyyed M; Azarpeyvand, Mahdi

    2003-11-01

    Acoustic radiation from a spherical source undergoing angularly periodic axisymmetric harmonic surface vibrations while eccentrically suspended within a thermoviscous fluid sphere, which is immersed in a viscous thermally conducting unbounded fluid medium, is analyzed in an exact fashion. The formulation uses the appropriate wave-harmonic field expansions along with the translational addition theorem for spherical wave functions and the relevant boundary conditions to develop a closed-form solution in form of infinite series. The analytical results are illustrated with a numerical example in which the vibrating source is eccentrically positioned within a chemical fluid sphere submerged in water. The modal acoustic radiation impedance load on the source and the radiated far-field pressure are evaluated and discussed for representative values of the parameters characterizing the system. The proposed model can lead to a better understanding of dynamic response of an underwater acoustic lens. It is equally applicable in miniature transducer analysis and design with applications in medical ultrasonics. PMID:14682628

  1. Quad Cities Unit 2 Main Steam Line Acoustic Source Identification and Load Reduction

    The Quad Cities Units 1 and 2 have a history of steam line vibration issues. The implementation of an Extended Power Up-rate resulted in significant increases in steam line vibration as well as acoustic loading of the steam dryers, which led to equipment failures and fatigue cracking of the dryers. This paper discusses the results of extensive data collection on the Quad Cities Unit 2 replacement dryer and the Main Steam Lines. This data was taken with the intent of identifying acoustic sources in the steam system. Review of the data confirmed that vortex shedding coupled column resonance in the relief and safety valve stub pipes were the principal sources of large magnitude acoustic loads in the main steam system. Modifications were developed in sub-scale testing to alter the acoustic properties of the valve standpipes and add acoustic damping to the system. The modifications developed and installed consisted of acoustic side branches that were attached to the Electromatic Relief Valve (ERV) and Main Steam Safety Valve (MSSV) attachment pipes. Subsequent post-modification testing was performed in plant to confirm the effectiveness of the modifications. The modifications have been demonstrated to reduce vibration loads at full Extended Power Up-rate (EPU) conditions to levels below those at Original Licensed Thermal Power (OLTP). (authors)

  2. Military jet noise source imaging using multisource statistically optimized near-field acoustical holography.

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M

    2016-04-01

    The identification of acoustic sources is critical to targeted noise reduction efforts for jets on high-performance tactical aircraft. This paper describes the imaging of acoustic sources from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated source location; sources farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped source regions, which is a phenomenon relatively recently reported for full-scale jets. PMID:27106340

  3. Exploiting AML algorithm for multiple acoustic source 2D and 3D DOA estimations

    2011-01-01

    The approximate maximum likelihood (AML) algorithm shows promises for joint estimations of acoustic source spectrum and direction-of-arrival (DOA). For the multisource case, the AML algorithm remains feasible as one considers an alternating projection procedure based on sequential iterative search on single source parameters. In order to perform multisource beamforming operations, earlier, we used a two-dimensional (2D) sensor array with 2D AML to obtain the DOA estimations for sources in the far field of t...

  4. The Doppler Effect based acoustic source separation for a wayside train bearing monitoring system

    Zhang, Haibin; Zhang, Shangbin; He, Qingbo; Kong, Fanrang

    2016-01-01

    Wayside acoustic condition monitoring and fault diagnosis for train bearings depend on acquired acoustic signals, which consist of mixed signals from different train bearings with obvious Doppler distortion as well as background noises. This study proposes a novel scheme to overcome the difficulties, especially the multi-source problem in wayside acoustic diagnosis system. In the method, a time-frequency data fusion (TFDF) strategy is applied to weaken the Heisenberg's uncertainty limit for a signal's time-frequency distribution (TFD) of high resolution. Due to the Doppler Effect, the signals from different bearings have different time centers even with the same frequency. A Doppler feature matching search (DFMS) algorithm is then put forward to locate the time centers of different bearings in the TFD spectrogram. With the determined time centers, time-frequency filters (TFF) are designed with thresholds to separate the acoustic signals in the time-frequency domain. Then the inverse STFT (ISTFT) is taken and the signals are recovered and filtered aiming at each sound source. Subsequently, a dynamical resampling method is utilized to remove the Doppler Effect. Finally, accurate diagnosis for train bearing faults can be achieved by applying conventional spectrum analysis techniques to the resampled data. The performance of the proposed method is verified by both simulated and experimental cases. It shows that it is effective to detect and diagnose multiple defective bearings even though they produce multi-source acoustic signals.

  5. Acoustical “transparency” induced by local resonance in Bragg bandgaps

    We show that sound waves can resonantly transmit through Bragg bandgaps in an acoustical duct periodically attached with an array of Helmholtz resonators, forming within the normally forbidden band a transparency window with group velocity smaller than the normal speed of sound. The transparency occurs for the locally resonant frequency so much close to the Bragg one that both the local-resonance-induced bandgap and the Bragg one heavily overlap with each other. The phenomenon seems an acoustical analog of the well-known electromagnetically induced transparency by quantum interference. Different from the Fano-like interference explanation, we also provide a mechanism for the transparency window phenomenon which makes it possible to extend the phenomenon in general

  6. Acoustical “transparency” induced by local resonance in Bragg bandgaps

    Yu, Gaokun; Wang, Xinlong, E-mail: xlwang@nju.edu.cn [Key Laboratory of Modern Acoustics and Institute of Acoustics, Nanjing University, Nanjing 210093 (China)

    2014-01-28

    We show that sound waves can resonantly transmit through Bragg bandgaps in an acoustical duct periodically attached with an array of Helmholtz resonators, forming within the normally forbidden band a transparency window with group velocity smaller than the normal speed of sound. The transparency occurs for the locally resonant frequency so much close to the Bragg one that both the local-resonance-induced bandgap and the Bragg one heavily overlap with each other. The phenomenon seems an acoustical analog of the well-known electromagnetically induced transparency by quantum interference. Different from the Fano-like interference explanation, we also provide a mechanism for the transparency window phenomenon which makes it possible to extend the phenomenon in general.

  7. Acoustic wavefield evolution as a function of source location perturbation

    Alkhalifah, Tariq Ali

    2010-12-01

    The wavefield is typically simulated for seismic exploration applications through solving the wave equation for a specific seismic source location. The direct relation between the form (or shape) of the wavefield and the source location can provide insights useful for velocity estimation and interpolation. As a result, I derive partial differential equations that relate changes in the wavefield shape to perturbations in the source location, especially along the Earth\\'s surface. These partial differential equations have the same structure as the wave equation with a source function that depends on the background (original source) wavefield. The similarity in form implies that we can use familiar numerical methods to solve the perturbation equations, including finite difference and downward continuation. In fact, we can use the same Green\\'s function to solve the wave equation and its source perturbations by simply incorporating source functions derived from the background field. The solutions of the perturbation equations represent the coefficients of a Taylor\\'s series type expansion of the wavefield as a function of source location. As a result, we can speed up the wavefield calculation as we approximate the wavefield shape for sources in the vicinity of the original source. The new formula introduces changes to the background wavefield only in the presence of lateral velocity variation or in general terms velocity variations in the perturbation direction. The approach is demonstrated on the smoothed Marmousi model.

  8. AE source localization on the material with unknown elastic wave propagation velocity

    The ability to locate defects in materials is one of the major attractions of the acoustic emission technique. The standard method of planar source location is to place three or more transducers on the surface of a specimen and to triangulate the source position by using the differences in arrival times of the acoustic emission wave at the sensors. But the standard method have limited applications if the propagation velocity in the medium is riot known. In this paper, we propose a method for AE source localization on the material with unknown elastic wave propagation velocity. In this method, it is not needed to know the propagation velocity previously, that is, we can apply this method to arbitrary materials of which properties is not known exactly. We discuss the robustness of detecting AE source location algorithm according to the errors, and signal processing for measurement of the differences in arrival times of acoustic emission wave at the sensors. For performance evaluation of this algorithm, experiments performed using a lead break as the AE source on the surface of an aluminum plate.

  9. Improving reconstruction of the baryon acoustic peak : the effect of local environment

    Achitouv, Ixandra; Blake, Chris

    2015-01-01

    Precise measurements of the baryon acoustic oscillation (BAO) scale as a standard ruler in the clustering pattern of large-scale structure is a central goal of current and future galaxy surveys. The BAO peak may be sharpened using the technique of density-field reconstruction, in which the bulk displacements of galaxies are estimated using a Zel'dovitch approximation. We use numerical simulations to demonstrate how the accuracy of this approximation depends strongly on local environment, and ...

  10. Local-linear-prediction analysis for underwater acoustic target radiated noise

    LIANG Juan; LU Jiren

    2002-01-01

    Local-linear-prediction in phase space is performed for the underwater acoustic target radiated noise. Relation curve of average prediction error versus neighboring points' number is calculated. The result is used in judging the nonlinearity of radiated noise time series, and obtaining the appropriate form and coefficients of predicting model. The line and continuous spectral component are predicted respectively. Choice of some model parameters minimizing the prediction error is also discussed.

  11. Acoustic emission non-destructive testing of structures using source location techniques.

    Beattie, Alan G.

    2013-09-01

    The technology of acoustic emission (AE) testing has been advanced and used at Sandia for the past 40 years. AE has been used on structures including pressure vessels, fire bottles, wind turbines, gas wells, nuclear weapons, and solar collectors. This monograph begins with background topics in acoustics and instrumentation and then focuses on current acoustic emission technology. It covers the overall design and system setups for a test, with a wind turbine blade as the object. Test analysis is discussed with an emphasis on source location. Three test examples are presented, two on experimental wind turbine blades and one on aircraft fire extinguisher bottles. Finally, the code for a FORTRAN source location program is given as an example of a working analysis program. Throughout the document, the stress is on actual testing of real structures, not on laboratory experiments.

  12. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers

    Zhang, Y.-B.; Chen, X.-Z.; Jacobsen, Finn

    2009-01-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recen...... generated by sources on the two sides of the hologram plane is also examined....

  13. Mesospheric airglow and ionospheric responses to upward-propagating acoustic and gravity waves above tropospheric sources

    Snively, J. B.; Zettergren, M. D.

    2013-12-01

    The existence of acoustic waves (periods ~1-5 minutes) and gravity waves (periods >4 minutes) in the ionosphere above active tropospheric convection has been appreciated for more than forty years [e.g., Georges, Rev. Geophys. and Space Phys., 11(3), 1973]. Likewise, gravity waves exhibiting cylindrical symmetry and curvature of phase fronts have been observed via imaging of the mesospheric airglow layers [e.g., Yue et al., JGR, 118(8), 2013], clearly associated with tropospheric convection; gravity wave signatures have also recently been detected above convection in ionospheric total electron content (TEC) measurements [Lay et al., GRL, 40, 2013]. We here investigate the observable features of acoustic waves, and their relationship to upward-propagating gravity waves generated by the same sources, as they arrive in the mesosphere, lower-thermosphere, and ionosphere (MLTI). Numerical simulations using a nonlinear, cylindrically-axisymmetric, compressible atmospheric dynamics model confirm that acoustic waves generated by transient tropospheric sources may produce "concentric ring" signatures in the mesospheric hydroxyl airglow layer that precede the arrival of gravity waves. As amplitudes increase with altitude and decreasing neutral density, the modeled acoustic waves achieve temperature and vertical wind perturbations on the order of ~10s of Kelvin and m/s throughout the E- and F-region. Using a coupled multi-fluid ionospheric model [Zettergren and Semeter, JGR, 117(A6), 2012], extended for low-latitudes using a 2D dipole magnetic field coordinate system, we investigate acoustic wave perturbations to the ionosphere in the meridional direction. Resulting perturbations are predicted to be detectable by ground-based radar and GPS TEC measurements, or via in situ instrumentation. Although transient and short-lived, the acoustic waves' airglow and ionospheric signatures are likely to in some cases be observable, and may provide important insight into the regional

  14. Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

    The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.

  15. Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials

    Wen, Jihong; Shen, Huijie; Yu, Dianlong; Wen, Xisen

    2013-11-01

    The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.

  16. Embedded Acoustic Sensor Array for Engine Fan Noise Source Diagnostic Test: Feasibility of Noise Telemetry via Wireless Smart Sensors

    Zaman, Afroz; Bauch, Matthew; Raible, Daniel

    2011-01-01

    Aircraft engines have evolved into a highly complex system to meet ever-increasing demands. The evolution of engine technologies has primarily been driven by fuel efficiency, reliability, as well as engine noise concerns. One of the sources of engine noise is pressure fluctuations that are induced on the stator vanes. These local pressure fluctuations, once produced, propagate and coalesce with the pressure waves originating elsewhere on the stator to form a spinning pressure pattern. Depending on the duct geometry, air flow, and frequency of fluctuations, these spinning pressure patterns are self-sustaining and result in noise which eventually radiate to the far-field from engine. To investigate the nature of vane pressure fluctuations and the resulting engine noise, unsteady pressure signatures from an array of embedded acoustic sensors are recorded as a part of vane noise source diagnostics. Output time signatures from these sensors are routed to a control and data processing station adding complexity to the system and cable loss to the measured signal. "Smart" wireless sensors have data processing capability at the sensor locations which further increases the potential of wireless sensors. Smart sensors can process measured data locally and transmit only the important information through wireless communication. The aim of this wireless noise telemetry task was to demonstrate a single acoustic sensor wireless link for unsteady pressure measurement, and thus, establish the feasibility of distributed smart sensors scheme for aircraft engine vane surface unsteady pressure data transmission and characterization.

  17. Acoustic noise associated with the MOD-1 wind turbine: its source, impact, and control

    Kelley, N.D.; McKenna, H.E.; Hemphill, R.R.; Etter, C.L.; Garrelts, R.L.; Linn, N.C.

    1985-02-01

    This report summarizes extensive research by staff of the Solar Energy Research Institute and its subcontractors conducted to establish the origin and possible amelioration of acoustic disturbances associated with the operation of the DOE/NASA MOD-1 wind turbine installed in 1979 near Boone, North Carolina. Results have shown that the source of this acoustic annoyance was the transient, unsteady aerodynamic lift imparted to the turbine blades as they passed through the lee wakes of the large, cylindrical tower supports. Nearby residents were annoyed by the low-frequency, acoustic impulses propagated into the structures in which the complainants lived. The situation was aggravated further by a complex sound propagation process controlled by terrain and atmospheric focusing. Several techniques for reducing the abrupt, unsteady blade load transients were researched and are discussed in the report.

  18. Local helioseismic and spectroscopic analyses of interactions between acoustic waves and a sunspot

    Rajaguru, S P; Sankarasubramanian, K; Couvidat, S; 10.1088/2041-8205/721/2/L86

    2010-01-01

    Using a high cadence imaging spectropolarimetric observation of a sunspot and its surroundings in magnetically sensitive (FeI 6173 A) and insensitive (FeI 7090 A) upper photospheric absorption lines, we map the instantaneous wave phases and helioseismic travel times as a function of observation height and inclination of magnetic field to the vertical. We confirm the magnetic inclination angle dependent transmission of incident acoustic waves into upward propagating waves, and derive (1) proof that helioseismic travel times receive direction dependent contributions from such waves and hence cause errors in conventional flow inferences, (2) evidences for acoustic wave sources beneath the umbral photosphere, and (3) significant differences in travel times measured from the chosen magnetically sensitive and insensitive spectral lines.

  19. Internal gravity waves from a non-local perturbation source

    Bulatov, Vitaly V.; Vladimirov, Yuriy V.

    2009-01-01

    The internal gravity waves far field exited by a non-local perturbation sources was considered. A separate wave mode asymptomatic presentation was constructed, describing the wave field key features depending on the source geometry.

  20. Source identification in acoustics and structural mechanics using Sierra/SD.

    Walsh, Timothy Francis; Aquino, Wilkins [Duke University Durham, NC; Ross, Michael

    2013-03-01

    In this report we derive both time and frequency-domain methods for inverse identification of sources in elastodynamics and acoustics. The inverse/design problem is cast in a PDE-constrained optimization framework with efficient computation of gradients using the adjoint method. The implementation of source inversion in Sierra/SD is described, and results from both time and frequency domain source inversion are compared to actual experimental data for a weapon store used in captive carry on a military aircraft. The inverse methodology is advantageous in that it provides a method for creating ground based acoustic and vibration tests that can reduce the actual number of flight tests, and thus, saving costs and time for the program.

  1. Surface response of a viscoelastic medium to subsurface acoustic sources with application to medical diagnosis

    Royston, Thomas J.; Yazicioglu, Yigit; Loth, Francis

    2003-02-01

    The response at the surface of an isotropic viscoelastic medium to buried fundamental acoustic sources is studied theoretically, computationally and experimentally. Finite and infinitesimal monopole and dipole sources within the low audible frequency range (40-400 Hz) are considered. Analytical and numerical integral solutions that account for compression, shear and surface wave response to the buried sources are formulated and compared with numerical finite element simulations and experimental studies on finite dimension phantom models. It is found that at low audible frequencies, compression and shear wave propagation from point sources can both be significant, with shear wave effects becoming less significant as frequency increases. Additionally, it is shown that simple closed-form analytical approximations based on an infinite medium model agree well with numerically obtained ``exact'' half-space solutions for the frequency range and material of interest in this study. The focus here is on developing a better understanding of how biological soft tissue affects the transmission of vibro-acoustic energy from biological acoustic sources below the skin surface, whose typical spectral content is in the low audible frequency range. Examples include sound radiated from pulmonary, gastro-intestinal and cardiovascular system functions, such as breath sounds, bowel sounds and vascular bruits, respectively.

  2. Laser-generated thermoelastic acoustic sources and acoustic waves in anisotropic plate

    XU BaiQiang; WANG Feng; FENG Jun; WANG JiJun; SUN HongXiang; LUO Ying

    2009-01-01

    The effect of anisotropy on the ultrasound wave generation and propagation in the unidirectional fi-ber-reinforced composite plate has been investigated. A quantitative numerical model for the la-ser-generated ultrasound in the thermoelastic regime was presented by using a finite element method.All factors, such as spatial and time distributions of the incident laser beam, optical penetration, ther-mal diffusivity, and source-receiver distance can be taken into account. Numerical results show that the effect on ultrasound waveform of the size of the laser volume source produces strong bipolar Iongitu-dinal waves and improves the amplitude and directivity of the longitudinal waves. A fiber-reinforced composite material exhibits isotropic or homogenous behavior for ultrasonic wave propagation per-pendicular to the fiber direction. For ultrasonic propagation along the fiber direction, ultrasonic dis-persion resulting from the inhomogeneous nature of the material affects the laser ultrasonic waveforms. As the dimensions of the laser pulse are increased in space and time, the displacement waveform be-comes broader and its magnitude decreases.

  3. Laser-generated thermoelastic acoustic sources and acoustic waves in anisotropic plate

    2009-01-01

    The effect of anisotropy on the ultrasound wave generation and propagation in the unidirectional fi- ber-reinforced composite plate has been investigated. A quantitative numerical model for the la- ser-generated ultrasound in the thermoelastic regime was presented by using a finite element method. All factors, such as spatial and time distributions of the incident laser beam, optical penetration, ther- mal diffusivity, and source-receiver distance can be taken into account. Numerical results show that the effect on ultrasound waveform of the size of the laser volume source produces strong bipolar longitu- dinal waves and improves the amplitude and directivity of the longitudinal waves. A fiber-reinforced composite material exhibits isotropic or homogenous behavior for ultrasonic wave propagation per- pendicular to the fiber direction. For ultrasonic propagation along the fiber direction, ultrasonic dis- persion resulting from the inhomogeneous nature of the material affects the laser ultrasonic waveforms. As the dimensions of the laser pulse are increased in space and time, the displacement waveform be- comes broader and its magnitude decreases.

  4. Data-driven and calibration-free Lamb wave source localization with sparse sensor arrays.

    Harley, Joel B; Moura, José M F

    2015-08-01

    Most Lamb wave localization techniques require that we know the wave's velocity characteristics; yet, in many practical scenarios, velocity estimates can be challenging to acquire, are unavailable, or are unreliable because of the complexity of Lamb waves. As a result, there is a significant need for new methods that can reduce a system's reliance on a priori velocity information. This paper addresses this challenge through two novel source localization methods designed for sparse sensor arrays in isotropic media. Both methods exploit the fundamental sparse structure of a Lamb wave's frequency-wavenumber representation. The first method uses sparse recovery techniques to extract velocities from calibration data. The second method uses kurtosis and the support earth mover's distance to measure the sparseness of a Lamb wave's approximate frequency-wavenumber representation. These measures are then used to locate acoustic sources with no prior calibration data. We experimentally study each method with a collection of acoustic emission data measured from a 1.22 m by 1.22 m isotropic aluminum plate. We show that both methods can achieve less than 1 cm localization error and have less systematic error than traditional time-of-arrival localization methods. PMID:26276960

  5. The model of local mode analysis for structural acoustics of box structures

    Ngai, King-Wah

    Structure-borne noise is a new noise pollution problem emerging from railway concrete box structures in Hong Kong. Its low frequency noise with intermittent effect can cause considerable nuisance to neighborhoods. The tonal noise peaks in this low frequency range should be one of the important factors in structure-borne noise analysis. In the acoustic field, the deterministic analysis of all the resonant modes of vibration is generally considered as not practical. Many acoustic experts use the statistical energy analysis as the main tool for the noise investigation whereas the application of the experimental modal analysis in the structural acoustic problem is comparatively rare. In the past, most studies mainly focused on the structure-borne noise measurement and analysis. The detail study of the cause of structure-borne noise is lack, especially for the rectangular concrete box structure. In this dissertation, an experimental and analytical approach is adopted to study a typical concrete box model. This thesis aims at confirming the importance of modal analysis in the structure-borne noise study and then at identifying the local vibration modes along the cross-section of box structure. These local modes are responsible for the structure-borne noise radiation. The findings of this study suggest that the web of viaduct cross-section is not as rigid as assumed in the conventional viaduct design and the web face is likely to be more flexible in the vertical displacement of the concrete viaduct. Two types of local vibration modes along the cross-section are identified: the centre mode and the web mode. At the top panel of the viaduct, the centre mode has movement in the middle but not at the edges. The web mode has movement at the edges with the middle fixed. The combined centre and web mode has been found to be important in the structural acoustics of the concrete box structure. In the actual concrete viaduct, the coincidence frequency is especially low (often around

  6. Homogenization of locally resonant acoustic metamaterials towards an emergent enriched continuum

    Sridhar, A.; Kouznetsova, V. G.; Geers, M. G. D.

    2016-03-01

    This contribution presents a novel homogenization technique for modeling heterogeneous materials with micro-inertia effects such as locally resonant acoustic metamaterials. Linear elastodynamics is used to model the micro and macro scale problems and an extended first order Computational Homogenization framework is used to establish the coupling. Craig Bampton Mode Synthesis is then applied to solve and eliminate the microscale problem, resulting in a compact closed form description of the microdynamics that accurately captures the Local Resonance phenomena. The resulting equations represent an enriched continuum in which additional kinematic degrees of freedom emerge to account for Local Resonance effects which would otherwise be absent in a classical continuum. Such an approach retains the accuracy and robustness offered by a standard Computational Homogenization implementation, whereby the problem and the computational time are reduced to the on-line solution of one scale only.

  7. EEG dipole source localization using artificial neural networks

    Localization of focal electrical activity in the brain using dipole source analysis of the electroencephalogram (EEG), is usually performed by iteratively determining the location and orientation of the dipole source, until optimal correspondence is reached between the dipole source and the measured potential distribution on the head. In this paper, we investigate the use of feed-forward layered artificial neural networks (ANNs) to replace the iterative localization procedure, in order to decrease the calculation time. The localization accuracy of the ANN approach is studied within spherical and realistic head models. Additionally, we investigate the robustness of both the iterative and the ANN approach by observing the influence on the localization error of both noise in the scalp potentials and scalp electrode mislocalizations. Finally, after choosing the ANN structure and size that provides a good trade-off between low localization errors and short computation times, we compare the calculation times involved with both the iterative and ANN methods. An average localization error of about 3.5 mm is obtained for both spherical and realistic head models. Moreover, the ANN localization approach appears to be robust to noise and electrode mislocations. In comparison with the iterative localization, the ANN provides a major speed-up of dipole source localization. We conclude that an artificial neural network is a very suitable alternative for iterative dipole source localization in applications where large numbers of dipole localizations have to be performed, provided that an increase of the localization errors by a few millimetres is acceptable. (author)

  8. A GPS-free passive acoustic localization scheme for underwater wireless sensor networks

    Mirza, Md Aquil

    2011-10-01

    Seaweb is an acoustic communication technology that enables communication between sensor nodes. Seaweb interconnects the underwater nodes through digital signal processing (DSP)-based modem by using acoustic links between the neighbouring sensors. In this paper, we design and investigate a global positioning system (GPS)-free passive localization protocol using seaweb technology. This protocol uses the range data and planar trigonometry to estimate the positions of the discovered nodes. We take into consideration the small displacement of sensor nodes due to watch circles and placement of sensor nodes on non-uniform underwater surface, for precise localization. Once the nodes are localized, we divide the whole network .eld into circular levels that minimizes the traf.c complexity and thereby increases the lifetime of the sensor network .eld. We then form the mesh network inside each of the circular levels that increases the reliability. The algorithm is designed in such a way that it overcomes the ambiguous nodes errata and re.ected paths and makes the algorithm more robust. The synthetic network geometries are so designed which can evaluate the algorithm in the presence of perfect or imperfect ranges or in case of incomplete data. A comparative study is made with the existing algorithms which proves our newly proposed algorithm to be more effective. © 2011 IEEE.

  9. Optimizing stepwise rotation of dodecahedron sound source to improve the accuracy of room acoustic measures.

    Martellotta, Francesco

    2013-09-01

    Dodecahedron sound sources are widely used for acoustical measurement purposes as they produce a good approximation of omnidirectional radiation. Evidence shows that such an assumption is acceptable only in the low-frequency range (namely below 1 kHz), while at higher frequencies sound radiation is far from being uniform. In order to improve the accuracy of acoustical measurements obtained from dodecahedron sources, international standard ISO 3382 suggests an averaging of results after a source rotation. This paper investigates the effects of such rotations, both in terms of variations in acoustical parameters and spatial distribution of sound reflections. Taking advantage of a spherical microphone array, the different reflection patterns were mapped as a function of source rotation, showing that some reflections may be considerably attenuated for different aiming directions. This paper investigates the concept of averaging results while changing rotation angles and the minimum number of rotations required to improve the accuracy of the average value. Results show that averages of three measurements carried out at 30° angular steps are closer to actual values and show much less fluctuation. In addition, an averaging of the directional intensity components of the selected responses stabilizes the spatial distribution of the reflections. PMID:23967936

  10. INFORMATION CRITERIA FOR A SOUND SOURCE LOCALIZATION BY HUMAN

    Dubrovskiy, N.; Tarasova, M.; Baronkin, V.

    1992-01-01

    Some information measure is suggested for analysis of sound source localization efficiency by human. Using this measure the influence of signal-noise ratio, observation time and frequency analysis bandwidth was studied, as well as presence of local source of interference.

  11. Using Distant Sources in Local Seismic Tomography

    Julian, Bruce; Foulgr, Gillian

    2014-05-01

    Seismic tomography methods such as the 'ACH' method of Aki, Christoffersson & Husebye (1976, 1977) are subject to significant bias caused by the unknown wave-speed structure outside the study volume, whose effects are mathematically of the same order as the local-structure effects being studied. Computational experiments using whole-mantle wave-speed models show that the effects are also of comparable numerical magnitude (Masson & Trampert, 1997). Failure to correct for these effects will significantly corrupt computed local structures. This bias can be greatly reduced by solving for additional parameters defining the shapes, orientations, and arrival times of the incident wavefronts. The procedure is exactly analogous to solving for hypocentral locations in local-earthquake tomography. For planar incident wavefronts, each event adds three free parameters and the forward problem is surprisingly simple: The first-order change in the theoretical arrival time at observation point B resulting from perturbations in the incident-wave time t0 and slowness vector s is δtB ≡ δt0 + δs · rA = δtA, the change in the time of the plane wave at the point A where the un-perturbed ray enters the study volume (Julian and Foulger, submitted). This consequence of Fermat's principle apparently has not previously been recognized. In addition to eliminating the biasing effect of structure outside the study volume, this formalism enables us to combine data from local and distant events in studies of local structure, significantly improving resolution of deeper structure, particularly in places such as volcanic and geothermal areas where seismicity is confined to shallow depths. Many published models that were derived using ACH and similar methods probably contain significant artifacts and are in need of re-evaluation.

  12. Sources of Competitiveness in Tourist Local Systems

    Boix Domenech, Rafael; Capone, Francesco

    2006-01-01

    At the end of the XIX Century, Marshall described the existence of some concentrations of small and medium enterprises specialised in a specific production activity in certain districts of some industrial English cities. Starting from his contribute, Italian scholars have paid particular attention to this local system of production coined by Marshall under the term "industrial district”. In other countries, different but related territorial models have played a central role as the "milieu” or...

  13. The Relationship between Conductivity Uncertainties and EEG Source Localization Accuracy

    Wang, Gang; Yang, Lin; Worrell, Gregory; He, Bin

    2009-01-01

    The brain-to-skull conductivity ratio (BSCR) is an important parameter in EEG source imaging and localization. Misspecification of this value may introduce localization errors in the estimation of brain electrical activity. However, the effect of this ratio has not been well understood despite many investigations. In the present study, we conducted a series of computer simulations to investigate the relationship between BSCR and EEG source localization accuracy. Furthermore, we have attempted...

  14. Eccentricity effects on acoustic radiation from a spherical source suspended within a thermoviscous fluid sphere

    Hasheminejad, S.M.; Azarpeyvand, M.

    2003-01-01

    Acoustic radiation from a spherical source undergoing angularly periodic axisymmetric harmonic surface vibrations while eccentrically suspended within a thermoviscous fluid sphere, which is immersed in a viscous thermally conducting unbounded fluid medium, is analyzed in an exact fashion. The formulation uses the appropriate wave-harmonic field expansions along with the translational addition theorem for spherical wave functions and the relevant boundary conditions to develop a closed-form so...

  15. Investigation of model based beamforming and Bayesian inversion signal processing methods for seismic localization of underground sources

    Oh, Geok Lian; Brunskog, Jonas

    2014-01-01

    frequency-wavenumber processing to determine the location of the underground tunnel. Considering the case of determining the location of an underground tunnel, this paper proposed two physical models, the acoustic approximation ray tracing model and the finite difference time domain three-dimensional (3D......Techniques have been studied for the localization of an underground source with seismic interrogation signals. Much of the work has involved defining either a P-wave acoustic model or a dispersive surface wave model to the received signal and applying the time-delay processing technique and...

  16. Local Measurement of Electron Density and Temperature in High Temperature Laser Plasma Using the Ion-Acoustic Dispersion

    The dispersion of ion-acoustic fluctuations has been measured using a novel technique that employs multiple color Thomson-scattering diagnostics to measure the frequency spectrum for two separate thermal ion-acoustic fluctuations with significantly different wave vectors. The plasma fluctuations are shown to become dispersive with increasing electron temperature. We demonstrate that this technique allows a time resolved local measurement of electron density and temperature in inertial confinement fusion plasmas

  17. Use of unidirectional microphones and signal processing for the localization of sound sources

    Rizzo, Piervincenzo; Bordoni, Giacomo; Marzani, Alessandro

    2009-05-01

    Targeting people or objects by passive acoustic sensors is of relevant interest in several military and civil applications, spanning from surveillance and patrolling systems to teleconferencing and human-robot interaction. To date methods and patents focused solely on the use of beamforming algorithms to compute the time of arrival of sounds detected by using omnidirectional microphones (OM) sparsely deployed. This paper describes the preliminary results of a novel approach devoted to the localization of ground borne acoustic sources. It is demonstrated that an array made of at least three unidirectional microphones can be exploited to detect the position the source. Pulse features extracted either in the time domain or in the frequency domain are used to identify the direction of the incoming sound. This information is then fed into a semi-analytical algorithm devoted to the identification of the source location. The novelty of the method presented here consists on the use of unidirectional microphones rather than omnidirectional microphones and on the ability to extract the sound direction by considering features like the pulse amplitude rather than the pulse arrival time. It is believed that this method may pave the road toward a new generation of reduced size sound detectors and localizers.

  18. Sound Source Localization by Using Two Microphones

    Yilmaz, Gulay

    2014-01-01

    This thesis work presents the way of locating the sound source by using two microphone. The idea to approach the goal is based on the Time di fference of Arrival Estimation (TDOA). There are several ways to the TDOA such as the generalized cross-correlation (GCC) and Steered Response Power (SRP).The most common technique used in TDOA estimation is the generalized cross-correlation (GCC). But Steered Response Power PHAT (SRP-PHAT) together with the Windowed Discrete Fourier Transform(WDFT) are...

  19. Acoustic source location in the secondary mixing region of a jet-blown flap using a cross-correlation technique

    Becker, R. S.; Maus, J. R.

    1977-01-01

    An experimental investigation of the acoustic sources in the secondary mixing region of a laboratory-scale jet-flap was made using a causality correlation technique. The processed signal of a hot-film anemometer probe was cross correlated with the output signal of a far-field microphone. Axial acoustic source strength distributions were measured for three far-field microphone locations: plus or minus 45 deg in the flyover plane and 45 deg in the sideline plane. These measurements showed that the acoustic sources in the secondary mixing region are highly directional, radiating much more effectively to the -45 deg-microphone, located below the plane of the flap surface. A relative maximum in the acoustic source strength measured for the microphones in the flyover plane occurred very near the flap trailing edge, which may be due to an edge amplification effect predicted by the theoretical work of Ffowcs Williams and Hall.

  20. Detection and localization of leak of pipelines of RBMK reactor. Methods of processing of acoustic noise

    For realization of leak detection of input pipelines and output pipelines of RBMK reactor the method, based on detection and control of acoustic leak signals, was designed. In this report the review of methods of processing and analysis of acoustic noise is submitted. These methods were included in the software of the leak detection system and are used for the decision of the following problems: leak detection by method of sound pressure level in conditions of powerful background noise and strong attenuation of a signal; detection of a small leak in early stage by high-sensitivity correlation method; determination of a point of a sound source in conditions of strong reflection of a signal by a correlation method and sound pressure method; evaluation of leak size by the analysis of a sound level and point of a sound source. The work of considered techniques is illustrated on an example of test results of a fragment of the leak detection system. This test was executed on a Leningrad NPP, operated at power levels of 460, 700, 890 and 1000 MWe. 16 figs

  1. A smart pattern recognition system for the automatic identification of aerospace acoustic sources

    Cabell, R. H.; Fuller, C. R.

    1989-01-01

    An intelligent air-noise recognition system is described that uses pattern recognition techniques to distinguish noise signatures of five different types of acoustic sources, including jet planes, propeller planes, a helicopter, train, and wind turbine. Information for classification is calculated using the power spectral density and autocorrelation taken from the output of a single microphone. Using this system, as many as 90 percent of test recordings were correctly identified, indicating that the linear discriminant functions developed can be used for aerospace source identification.

  2. An efficient closed-form solution for acoustic emission source location in three-dimensional structures

    Xibing Li

    2014-02-01

    Full Text Available This paper presents an efficient closed-form solution (ECS for acoustic emission(AE source location in three-dimensional structures using time difference of arrival (TDOA measurements from N receivers, N ≥ 6. The nonlinear location equations of TDOA are simplified to linear equations. The unique analytical solution of AE sources for unknown velocity system is obtained by solving the linear equations. The proposed ECS method successfully solved the problems of location errors resulting from measured deviations of velocity as well as the existence and multiplicity of solutions induced by calculations of square roots in existed close-form methods.

  3. Locating Acoustic Events Based on Large-Scale Sensor Networks

    Hojung Cha; Yungeun Kim; Junho Ahn

    2009-01-01

    Research on acoustic source localization is actively being conducted to enhance accuracy and coverage. However, the performance is inherently limited due to the use of expensive sensor nodes and inefficient communication methods. This paper proposes an acoustic source localization algorithm for a large area that uses low-cost sensor nodes. The proposed mechanism efficiently handles multiple acoustic sources by removing false-positive errors that arise from the different propagation ranges of ...

  4. Modelling of wind tunnel wall effects on the radiation characteristics of acoustic sources

    Eversman, W.; Baumeister, K. J.

    1984-01-01

    It is pointed out that the relatively high fuel economy available from propeller-driven aircraft has renewed interest in high speed, highly loaded multiple blade turboprop propulsion systems. Undesirable features related to community noise and the high intensity cabin noise have stimulated new research on the acoustic characteristics of turboprops. The present investigation has the objective to develop a mathematical model of the essential features of the radiation of acoustic disturbances from propellers in a duct and in free space in order to quantify the success with which duct testing can be expected to approximate free field conditions. In connection with the importance of source directionality, a detailed model is considered which consists of a finite element representation of the Gutin propeller theory valid in both the near and far field.

  5. Response of the ionosphere to natural and man-made acoustic sources

    O. A. Pokhotelov

    Full Text Available A review is presented of the effects influencing the ionosphere which are caused by acoustic emission from different sources (chemical and nuclear explosions, bolides, meteorites, earthquakes, volcanic eruptions, hurricanes, launches of spacecrafts and flights of supersonic jets. A terse statement is given of the basic theoretical principles and simplified theoretical models underlying the physics of propagation of infrasonic pulses and gravity waves in the upper atmosphere. The observations of "quick" response by the ionosphere are pointed out. The problem of magnetic disturbances and magnetohydrodynamic (MHD wave generation in the ionosphere is investigated. In particular, the supersonic propagation of ionospheric disturbances, and the conversion of the acoustic energy into the so-called gyrotropic waves in the ionospheric E-layer are considered.

  6. Acoustic flight tests of rotorcraft noise-abatement approaches using local differential GPS guidance

    Chen, Robert T. N.; Hindson, William S.; Mueller, Arnold W.

    1995-01-01

    This paper presents the test design, instrumentation set-up, data acquisition, and the results of an acoustic flight experiment to study how noise due to blade-vortex interaction (BVI) may be alleviated. The flight experiment was conducted using the NASA/Army Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) research helicopter. A Local Differential Global Positioning System (LDGPS) was used for precision navigation and cockpit display guidance. A laser-based rotor state measurement system on board the aircraft was used to measure the main rotor tip-path-plane angle-of-attack. Tests were performed at Crows Landing Airfield in northern California with an array of microphones similar to that used in the standard ICAO/FAA noise certification test. The methodology used in the design of a RASCAL-specific, multi-segment, decelerating approach profile for BVI noise abatement is described, and the flight data pertaining to the flight technical errors and the acoustic data for assessing the noise reduction effectiveness are reported.

  7. Source localization analysis using seismic noise data acquired in exploration geophysics

    Roux, P.; Corciulo, M.; Campillo, M.; Dubuq, D.

    2011-12-01

    Passive monitoring using seismic noise data shows a growing interest at exploration scale. Recent studies demonstrated source localization capability using seismic noise cross-correlation at observation scales ranging from hundreds of kilometers to meters. In the context of exploration geophysics, classical localization methods using travel-time picking fail when no evident first arrivals can be detected. Likewise, methods based on the intensity decrease as a function of distance to the source also fail when the noise intensity decay gets more complicated than the power-law expected from geometrical spreading. We propose here an automatic procedure developed in ocean acoustics that permits to iteratively locate the dominant and secondary noise sources. The Matched-Field Processing (MFP) technique is based on the spatial coherence of raw noise signals acquired on a dense array of receivers in order to produce high-resolution source localizations. Standard MFP algorithms permits to locate the dominant noise source by matching the seismic noise Cross-Spectral Density Matrix (CSDM) with the equivalent CSDM calculated from a model and a surrogate source position that scans each position of a 3D grid below the array of seismic sensors. However, at exploration scale, the background noise is mostly dominated by surface noise sources related to human activities (roads, industrial platforms,..), which localization is of no interest for the monitoring of the hydrocarbon reservoir. In other words, the dominant noise sources mask lower-amplitude noise sources associated to the extraction process (in the volume). Their location is therefore difficult through standard MFP technique. The Multi-Rate Adaptative Beamforming (MRABF) is a further improvement of the MFP technique that permits to locate low-amplitude secondary noise sources using a projector matrix calculated from the eigen-value decomposition of the CSDM matrix. The MRABF approach aims at cancelling the contributions of

  8. Complex space source theory of spatially localized electromagnetic waves

    Seshadri, SR

    2013-01-01

    The author highlights that there is a need obtain exact full-wave solutions that reduce to the paraxial beams in the appropriate limit. Complex Space Source Theory of Spatially Localized Electromagnetic Waves treats the exact full-wave generalizations of all the basic types of paraxial beam solutions. These are developed by the use of Fourier and Bessel transform techniques and the complex space source theory of spatially localized electromagnetic waves is integrated as a branch of Fourier optics.

  9. Communication Acoustics

    Blauert, Jens

    Communication Acoustics deals with the fundamentals of those areas of acoustics which are related to modern communication technologies. Due to the advent of digital signal processing and recording in acoustics, these areas have enjoyed an enormous upswing during the last 4 decades. The book...... the book a source of valuable information for those who want to improve or refresh their knowledge in the field of communication acoustics - and to work their way deeper into it. Due to its interdisciplinary character Communication Acoustics is bound to attract readers from many different areas, such as......: acoustics, cognitive science, speech science, and communication technology....

  10. Local elasticity and mobility of twin boundaries in martensitic films studied by atomic force acoustic microscopy

    Nanoscale elastic properties of twinned martensite NiMnGa films were characterized by means of atomic force acoustic microscopy using cantilever contact-resonance spectra to measure the local contact stiffness k* and the local damping Q−1, which contains information on the crystallographic anisotropy of martensitic twin variants and the dissipative motion of twin boundaries (TBs). Images of k* and indentation modulus maps were obtained. Similar to topography images measured by conventional atomic force microscopy in contact mode, they show the nature of the twin structure and thus a regular variation in local elastic modulus. A correlation between k* and Q−1 was observed and mirrors the motion of the TB accompanied by a viscoelastic procedure. The k*-image and the topography image measured are opposite in contrast, which likely arises from mobile and immobile TBs depending on the geometry of twinning. Multi-resonance spectra were measured, which can be related to martensitic multivariants and are explainable as different types of nanotwins. A critical stress, defined as the starting point of softening due to TB movement was determined to be about 0.5 GPa for a thick film (1 μm) and 0.75 GPa for a thin film (0.15 μm), respectively. The values are much larger than that measured for bulk materials, but reasonable due to a large internal stress in the films. (paper)

  11. Source localization for active control of turbofan rotor-stator broadband noise

    Walker, Bruce E.

    2005-09-01

    In order to identify a reference signal source for an active noise cancellation system, cross-correlation techniques were used to localize broadband noise source regions on exit guide vanes of the NASA Glenn Research Center Advance Noise Control Fan (ANCF). Arrays of surface pressure sensors were imbedded in one guide vane and in the wall of the fan. Synchronous sampling was used with a multichannel data acquisition system to allow removal of periodic components from the signals. The signals were then cross-correlated to assess radiation directivity and the relationship between vane surface pressure and in-duct acoustic noise. The results of these measurements indicated that broadband unsteady pressures near the leading edge tip of the guide vane were well enough correlated with acoustic radiation that 2-3 dB active noise cancellation could be achieved using a simple gain-delay control algorithm and actuator array. After successful simulation in a wind tunnel environment the concept was incorporated on 15 guide vanes and tested in ANCF. Cross-correlation measurements were further used to evaluate system performance and to identify competing noises from rotating and stationary sources within the fan.

  12. An Analytical Solution for Acoustic Emission Source Location for Known P Wave Velocity System

    Longjun Dong

    2014-01-01

    Full Text Available This paper presents a three-dimensional analytical solution for acoustic emission source location using time difference of arrival (TDOA measurements from N receivers, N⩾5. The nonlinear location equations for TDOA are simplified to linear equations, and the direct analytical solution is obtained by solving the linear equations. There are not calculations of square roots in solution equations. The method solved the problems of the existence and multiplicity of solutions induced by the calculations of square roots in existed close-form methods. Simulations are included to study the algorithms' performance and compare with the existing technique.

  13. LARA. Localization of an automatized refueling machine by acoustical sounding in breeder reactors - implementation of artificial intelligence techniques

    The automatic control of the machine which handles the nuclear subassemblies in fast neutron reactors requires autonomous perception and decision tools. An acoustical device allows the machine to position in the work area. Artificial intelligence techniques are implemented to interpret the data: pattern recognition, scene analysis. The localization process is managed by an expert system. 6 refs.; 8 figs

  14. Sparsity and super-resolution in sound source localization with sensor arrays

    Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus

    2014-01-01

    Sound source localization with sensor arrays involves the estimation of the direction-of-arrival (DOA) from a limited number of observations. Compressive sensing (CS) is a method for solving such undetermined problems which achieves simultaneously sparsity, thus super-resolution, and computational...... speed. We formulate the DOA estimation as a sparse signal reconstruction problem and show that methods which exploit sparsity have superior performance compared to traditional methods for DOA estimation. To demonstrate the high-resolution capabilities and the robustness of CS and other sparsity...... promoting optimization techniques in DOA estimation, the methods are applied to experimental data from underwater acoustic measurements in the challenging scenario of source tracking from single snapshot data....

  15. The statistical distributed source boundary point method to calculate the acoustic radiation from the random vibrating body

    WANGXiufeng; CHENXinzhao; LIUZhao

    2003-01-01

    The statistical distributed source boundary point method (SDSBPM) put forward is applied to calculate the acoustic radiation from the random vibrating body. A detailed description of this method is presented. A test for the SDSBPM is carried out through the random vibrating sphere and the random vibrating cuboid. An experiment on the exterior acoustic radiation of a random vibrating simulation axial box of the lathe tool is performed in a semi-anechoic chamber.

  16. Localization of Vibrating Noise Sources in Nuclear Reactor Cores

    In this thesis the possibility of locating vibrating noise sources in a nuclear reactor core from the neutron noise has been investigated using different localization methods. The influence of the vibrating noise source has been considered to be a small perturbation of the neutron flux inside the reactor. Linear perturbation theory has been used to construct the theoretical framework upon which the localization methods are based. Two different cases have been considered: one where a one-dimensional one-group model has been used and another where a two-dimensional two-energy group noise simulator has been used. In the first case only one localization method is able to determine the position with good accuracy. This localization method is based on finding roots of an equation and is sensitive to other perturbations of the neutron flux. It will therefore work better with the assistance of approximative methods that reconstruct the noise source to determine if the results are reliable or not. In the two-dimensional case the results are more promising. There are several different localization techniques that reproduce both the vibrating noise source position and the direction of vibration with enough precision. The approximate methods that reconstruct the noise source are substantially better and are able to support the root finding method in a more constructive way. By combining the methods, the results will be more reliable

  17. Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

    Shahab, S.; Gray, M.; Erturk, A., E-mail: alper.erturk@me.gatech.edu [G. W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-03-14

    Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acoustic energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver.

  18. Ultrasonic power transfer from a spherical acoustic wave source to a free-free piezoelectric receiver: Modeling and experiment

    Contactless powering of small electronic components has lately received growing attention for wireless applications in which battery replacement or tethered charging is undesired or simply impossible, and ambient energy harvesting is not a viable solution. As an alternative to well-studied methods of contactless energy transfer, such as the inductive coupling method, the use of ultrasonic waves transmitted and received by piezoelectric devices enables larger power transmission distances, which is critical especially for deep-implanted electronic devices. Moreover, energy transfer by means of acoustic waves is well suited in situations where no electromagnetic fields are allowed. The limited literature of ultrasonic acoustic energy transfer is mainly centered on proof-of-concept experiments demonstrating the feasibility of this method, lacking experimentally validated modeling efforts for the resulting multiphysics problem that couples the source and receiver dynamics with domain acoustics. In this work, we present fully coupled analytical, numerical, and experimental multiphysics investigations for ultrasonic acoustic energy transfer from a spherical wave source to a piezoelectric receiver bar that operates in the 33-mode of piezoelectricity. The fluid-loaded piezoelectric receiver under free-free mechanical boundary conditions is shunted to an electrical load for quantifying the electrical power output for a given acoustic source strength of the transmitter. The analytical acoustic-piezoelectric structure interaction modeling framework is validated experimentally, and the effects of system parameters are reported along with optimal electrical loading and frequency conditions of the receiver

  19. Quantitative and qualitative analyses of under-balcony acoustics with real and simulated arrays of multiple sources

    Kwon, Youngmin

    The objective of this study was to quantitatively and qualitatively identify the acoustics of the under-balcony areas in music performance halls under realistic conditions that are close to an orchestral performance in consideration of multiple music instrumental sources and their diverse sound propagation patterns. The study executed monaural and binaural impulse response measurements with an array of sixteen directional sources (loudspeakers) for acoustical assessments. Actual measurements in a performance hall as well as computer simulations were conducted for the quantitative assessments. Psycho-acoustical listening tests were conducted for the qualitative assessments using the music signals binaurally recorded in the hall with the same source array. The results obtained from the multiple directional source tests were analyzed by comparing them to those obtained from the tests performed with a single omni-directional source. These two sets of results obtained in the under-balcony area were also compared to those obtained in the main orchestra area. The quantitative results showed that the use of a single source conforming to conventional measurement protocol seems to be competent for measurements of the room acoustical parameters such as EDTmid, RTmid, C80500-2k, IACCE3 and IACCL3. These quantitative measures, however, did not always agree with the results of the qualitative assessments. The primary reason is that, in many other acoustical analysis respects, the acoustical phenomena shown from the multiple source measurements were not similar to those shown from the single source measurements. Remarkable differences were observed in time-domain impulse responses, frequency content, spectral distribution, directional distribution of the early reflections, and in sound energy density over time. Therefore, the room acoustical parameters alone should not be the acoustical representative characterizing a performance hall or a specific area such as the under

  20. Visualizing underwater acoustic matched-field processing

    Rosenblum, Lawrence; Kamgar-Parsi, Behzad; Karahalios, Margarida; Heitmeyer, Richard

    1991-06-01

    Matched-field processing is a new technique for processing ocean acoustic data measured by an array of hydrophones. It produces estimates of the location of sources of acoustic energy. This method differs from source localization techniques in other disciplines in that it uses the complex underwater acoustic environment to improve the accuracy of the source localization. An unexplored problem in matched-field processing has been to separate multiple sources within a matched-field ambiguity function. Underwater acoustic processing is one of many disciplines where a synthesis of computer graphics and image processing is producing new insight. The benefits of different volume visualization algorithms for matched-field display are discussed. The authors show how this led to a template matching scheme for identifying a source within the matched-field ambiguity function that can help move toward an automated source localization process.

  1. Characterisation of an airborne sound source for use in a virtual acoustic prototype

    Moorhouse, A. T.; Seiffert, G.

    2006-09-01

    An approach is outlined suitable for constructing 'virtual acoustic prototypes' of machines. Here, the machine is 'sub-structured' into: active components (vibro-acoustic sources), and frame (the remaining passive parts of the machine). The approach is validated using the illustrative example of an electric motor installed in a machine frame. The motor is characterised by a line of four monopoles on its axis, the complex source strengths for which are obtained from the measured anechoic sound field around the motor using an inverse method. A singular value decomposition is carried out both to aid the solution and to shed light on the dominant mechanisms. A set of compatible transfer functions of a machine frame is then measured using a reciprocal technique. The sound power of the assembled machine is then predicted using a 'virtual prototype' approach of combining motor and frame data in the computer. Reasonable agreement is obtained with measurements made on a real prototype, although the agreement was limited at least in part by difficulties in repeating the same operating conditions for the motor. A simplified characterisation, using a single monopole, and with improved motor control produced excellent agreement.

  2. Multiple incoherent sound source localization using a single vector sensor

    Basten, T.G.H.; Bree, H.E. de; Druyvesteyn, W.F.; Wind, J.W.

    2009-01-01

    With the Microflown acoustic particle velocity sensor, broadband acoustic vector sensors in air have become available. An assembled probe version is based upon three orthogonally placed acoustic particle velocity sensors and a single sound pressure sensor. This probe has also become available as a m

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

    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.

  4. Moment tensor analysis of the acoustic emission source in the rock damage process

    YU Huaizhong; ZHU Qingyong; YIN Xiangchu; WANG Yucang

    2005-01-01

    To further investigate the mechanism of acoustic emission (AE) in the rock fracture experiment, moment tensor analysis was carried out. The AE sources characterized by crack sizes, orientations and fracture modes, are represented by a time-dependent moment tensor. Since the waveforms recorded by AE monitors correlate to the moment tensors, we prefer to select the P wave amplitude from the full-space Green's function of homogeneous and isotropic materials to determine the six independent components of the moment tensor. The moment tensor analysis was used to investigate the AE sources recorded in the experiment, and three types of micro-cracks were found, which are tensile mode, shear mode and mixture of the tensile and shear mode. In addition, the motion of micro-cracks was decided by eigenvectors of moment tensor. Results indicate that the moment tensor analysis may be used as a measurement to reflect the damage evolution of rock specimen.

  5. An alternative subspace approach to EEG dipole source localization

    In the present study, we investigate a new approach to electroencephalography (EEG) three-dimensional (3D) dipole source localization by using a non-recursive subspace algorithm called FINES. In estimating source dipole locations, the present approach employs projections onto a subspace spanned by a small set of particular vectors (FINES vector set) in the estimated noise-only subspace instead of the entire estimated noise-only subspace in the case of classic MUSIC. The subspace spanned by this vector set is, in the sense of principal angle, closest to the subspace spanned by the array manifold associated with a particular brain region. By incorporating knowledge of the array manifold in identifying FINES vector sets in the estimated noise-only subspace for different brain regions, the present approach is able to estimate sources with enhanced accuracy and spatial resolution, thus enhancing the capability of resolving closely spaced sources and reducing estimation errors. The present computer simulations show, in EEG 3D dipole source localization, that compared to classic MUSIC, FINES has (1) better resolvability of two closely spaced dipolar sources and (2) better estimation accuracy of source locations. In comparison with RAP-MUSIC, FINES' performance is also better for the cases studied when the noise level is high and/or correlations among dipole sources exist

  6. An alternative subspace approach to EEG dipole source localization

    Xu Xiaoliang [KC Science and Technologies Inc., Naperville, IL 60565 (United States); Xu, Bobby [Illinois Mathematics and Science Academy, Aurora, IL 60506 (United States); He Bin [Department of Bioengineering, University of Illinois, Chicago, IL 60607 (United States)

    2004-01-21

    In the present study, we investigate a new approach to electroencephalography (EEG) three-dimensional (3D) dipole source localization by using a non-recursive subspace algorithm called FINES. In estimating source dipole locations, the present approach employs projections onto a subspace spanned by a small set of particular vectors (FINES vector set) in the estimated noise-only subspace instead of the entire estimated noise-only subspace in the case of classic MUSIC. The subspace spanned by this vector set is, in the sense of principal angle, closest to the subspace spanned by the array manifold associated with a particular brain region. By incorporating knowledge of the array manifold in identifying FINES vector sets in the estimated noise-only subspace for different brain regions, the present approach is able to estimate sources with enhanced accuracy and spatial resolution, thus enhancing the capability of resolving closely spaced sources and reducing estimation errors. The present computer simulations show, in EEG 3D dipole source localization, that compared to classic MUSIC, FINES has (1) better resolvability of two closely spaced dipolar sources and (2) better estimation accuracy of source locations. In comparison with RAP-MUSIC, FINES' performance is also better for the cases studied when the noise level is high and/or correlations among dipole sources exist.

  7. An alternative subspace approach to EEG dipole source localization

    Xu, Xiao-Liang; Xu, Bobby; He, Bin

    2004-01-01

    In the present study, we investigate a new approach to electroencephalography (EEG) three-dimensional (3D) dipole source localization by using a non-recursive subspace algorithm called FINES. In estimating source dipole locations, the present approach employs projections onto a subspace spanned by a small set of particular vectors (FINES vector set) in the estimated noise-only subspace instead of the entire estimated noise-only subspace in the case of classic MUSIC. The subspace spanned by this vector set is, in the sense of principal angle, closest to the subspace spanned by the array manifold associated with a particular brain region. By incorporating knowledge of the array manifold in identifying FINES vector sets in the estimated noise-only subspace for different brain regions, the present approach is able to estimate sources with enhanced accuracy and spatial resolution, thus enhancing the capability of resolving closely spaced sources and reducing estimation errors. The present computer simulations show, in EEG 3D dipole source localization, that compared to classic MUSIC, FINES has (1) better resolvability of two closely spaced dipolar sources and (2) better estimation accuracy of source locations. In comparison with RAP-MUSIC, FINES' performance is also better for the cases studied when the noise level is high and/or correlations among dipole sources exist.

  8. Acoustic emission source location in complex structures using full automatic delta T mapping technique

    Al-Jumaili, Safaa Kh.; Pearson, Matthew R.; Holford, Karen M.; Eaton, Mark J.; Pullin, Rhys

    2016-05-01

    An easy to use, fast to apply, cost-effective, and very accurate non-destructive testing (NDT) technique for damage localisation in complex structures is key for the uptake of structural health monitoring systems (SHM). Acoustic emission (AE) is a viable technique that can be used for SHM and one of the most attractive features is the ability to locate AE sources. The time of arrival (TOA) technique is traditionally used to locate AE sources, and relies on the assumption of constant wave speed within the material and uninterrupted propagation path between the source and the sensor. In complex structural geometries and complex materials such as composites, this assumption is no longer valid. Delta T mapping was developed in Cardiff in order to overcome these limitations; this technique uses artificial sources on an area of interest to create training maps. These are used to locate subsequent AE sources. However operator expertise is required to select the best data from the training maps and to choose the correct parameter to locate the sources, which can be a time consuming process. This paper presents a new and improved fully automatic delta T mapping technique where a clustering algorithm is used to automatically identify and select the highly correlated events at each grid point whilst the "Minimum Difference" approach is used to determine the source location. This removes the requirement for operator expertise, saving time and preventing human errors. A thorough assessment is conducted to evaluate the performance and the robustness of the new technique. In the initial test, the results showed excellent reduction in running time as well as improved accuracy of locating AE sources, as a result of the automatic selection of the training data. Furthermore, because the process is performed automatically, this is now a very simple and reliable technique due to the prevention of the potential source of error related to manual manipulation.

  9. Modeling the Underwater Acoustic Field Excited by an Airborne Rapidly Moving Source Using Wavenumber Integration

    Zhang Yipeng; Ma Yuanliang

    2007-01-01

    It is complicated to model the acoustic field in stratified ocean for airborne aircraft, due to high speed of the source and air-to-water sound transmission. To our knowledge, there are very few papers in the open literature dealing with this complicated problem; but, in our opinion,they all require great amount of computation. We now propose a different method that requires much less computation. We improve the wavenumber integration method to model the received temporal signal for a moving source in stratified ocean and sum up in a concise form the core of our paper as follows: (A) Eq. (11) can be calculated by means of fast Chirp Z transform and the signals at all N time points are generated simultaneously; (B) direct numerical evaluation of the wavenumber integral in Eq. (4) produces large numerical errors; so it is necessary to shift the integration slightly below the real axis; (C) we compare the computation cost of direct calculation method with that of our fast calculation method ; from the results presented in table 1,we can see that the fast calculation method consumes much less computation time, particularly for long duration signals; (D) for an airborne rapidly moving source, we compute the Dopplershifted signals in shallow water and analyze their short-time Fourier transform; from Fig. 1b, we can see that the received signals have multiple frequency components for a tonal source due to source motion and that each component corresponds to an arrival path.

  10. Adaptively Reevaluated Bayesian Localization (ARBL): A novel technique for radiological source localization

    Miller, Erin A.; Robinson, Sean M.; Anderson, Kevin K.; McCall, Jonathon D.; Prinke, Amanda M.; Webster, Jennifer B.; Seifert, Carolyn E.

    2015-06-01

    We present a novel technique for the localization of radiological sources in urban or rural environments from an aerial platform. The technique is based on a Bayesian approach to localization, in which measured count rates in a time series are compared with predicted count rates from a series of pre-calculated test sources to define likelihood. This technique is expanded by using a localized treatment with a limited field of view (FOV), coupled with a likelihood ratio reevaluation, allowing for real-time computation on commodity hardware for arbitrarily complex detector models and terrain. In particular, detectors with inherent asymmetry of response (such as those employing internal collimation or self-shielding for enhanced directional awareness) are leveraged by this approach to provide improved localization. Results from the localization technique are shown for simulated flight data using monolithic as well as directionally-aware detector models, and the capability of the methodology to locate radioisotopes is estimated for several test cases. This localization technique is shown to facilitate urban search by allowing quick and adaptive estimates of source location, in many cases from a single flyover near a source. In particular, this method represents a significant advancement from earlier methods like full-field Bayesian likelihood, which is not generally fast enough to allow for broad-field search in real time, and highest-net-counts estimation, which has a localization error that depends strongly on flight path and cannot generally operate without exhaustive search.

  11. Adaptively Reevaluated Bayesian Localization (ARBL). A Novel Technique for Radiological Source Localization

    Miller, Erin A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Robinson, Sean M. [Pacific Northwest National Lab. (PNNL), Seattle, WA (United States); Anderson, Kevin K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McCall, Jonathon D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Prinke, Amanda M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Webster, Jennifer B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Seifert, Carolyn E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-01-19

    Here we present a novel technique for the localization of radiological sources in urban or rural environments from an aerial platform. The technique is based on a Bayesian approach to localization, in which measured count rates in a time series are compared with predicted count rates from a series of pre-calculated test sources to define likelihood. Furthermore, this technique is expanded by using a localized treatment with a limited field of view (FOV), coupled with a likelihood ratio reevaluation, allowing for real-time computation on commodity hardware for arbitrarily complex detector models and terrain. In particular, detectors with inherent asymmetry of response (such as those employing internal collimation or self-shielding for enhanced directional awareness) are leveraged by this approach to provide improved localization. Our results from the localization technique are shown for simulated flight data using monolithic as well as directionally-aware detector models, and the capability of the methodology to locate radioisotopes is estimated for several test cases. This localization technique is shown to facilitate urban search by allowing quick and adaptive estimates of source location, in many cases from a single flyover near a source. In particular, this method represents a significant advancement from earlier methods like full-field Bayesian likelihood, which is not generally fast enough to allow for broad-field search in real time, and highest-net-counts estimation, which has a localization error that depends strongly on flight path and cannot generally operate without exhaustive search

  12. Adaptively Reevaluated Bayesian Localization (ARBL): A novel technique for radiological source localization

    We present a novel technique for the localization of radiological sources in urban or rural environments from an aerial platform. The technique is based on a Bayesian approach to localization, in which measured count rates in a time series are compared with predicted count rates from a series of pre-calculated test sources to define likelihood. This technique is expanded by using a localized treatment with a limited field of view (FOV), coupled with a likelihood ratio reevaluation, allowing for real-time computation on commodity hardware for arbitrarily complex detector models and terrain. In particular, detectors with inherent asymmetry of response (such as those employing internal collimation or self-shielding for enhanced directional awareness) are leveraged by this approach to provide improved localization. Results from the localization technique are shown for simulated flight data using monolithic as well as directionally-aware detector models, and the capability of the methodology to locate radioisotopes is estimated for several test cases. This localization technique is shown to facilitate urban search by allowing quick and adaptive estimates of source location, in many cases from a single flyover near a source. In particular, this method represents a significant advancement from earlier methods like full-field Bayesian likelihood, which is not generally fast enough to allow for broad-field search in real time, and highest-net-counts estimation, which has a localization error that depends strongly on flight path and cannot generally operate without exhaustive search

  13. Estimation of glottal source features from the spectral envelope of the acoustic speech signal

    Torres, Juan Felix

    Speech communication encompasses diverse types of information, including phonetics, affective state, voice quality, and speaker identity. From a speech production standpoint, the acoustic speech signal can be mainly divided into glottal source and vocal tract components, which play distinct roles in rendering the various types of information it contains. Most deployed speech analysis systems, however, do not explicitly represent these two components as distinct entities, as their joint estimation from the acoustic speech signal becomes an ill-defined blind deconvolution problem. Nevertheless, because of the desire to understand glottal behavior and how it relates to perceived voice quality, there has been continued interest in explicitly estimating the glottal component of the speech signal. To this end, several inverse filtering (IF) algorithms have been proposed, but they are unreliable in practice because of the blind formulation of the separation problem. In an effort to develop a method that can bypass the challenging IF process, this thesis proposes a new glottal source information extraction method that relies on supervised machine learning to transform smoothed spectral representations of speech, which are already used in some of the most widely deployed and successful speech analysis applications, into a set of glottal source features. A transformation method based on Gaussian mixture regression (GMR) is presented and compared to current IF methods in terms of feature similarity, reliability, and speaker discrimination capability on a large speech corpus, and potential representations of the spectral envelope of speech are investigated for their ability represent glottal source variation in a predictable manner. The proposed system was found to produce glottal source features that reasonably matched their IF counterparts in many cases, while being less susceptible to spurious errors. The development of the proposed method entailed a study into the aspects

  14. Robust Source Localization in a Random Shallow Water Channel

    Sazontov, Alexander; Matveyev, Alexander

    2014-01-01

    This paper addresses source localization problem in a random shallow water channel. We present an extension of the generalized MUSIC method to the case, %in which when the signal correlation matrix is imprecisely known. The algorithm is validated by %simulations and its application to the experimental data observed in the Barents Sea. It has been found that the approach proposed demonstrates its excellent performance.

  15. Turbulence generation through intense localized sources of energy

    Maqui, Agustin; Donzis, Diego

    2015-11-01

    Mechanisms to generate turbulence in controlled conditions have been studied for nearly a century. Most common methods include passive and active grids with a focus on incompressible turbulence. However, little attention has been given to compressible flows, and even less to hypersonic flows, where phenomena such as thermal non-equilibrium can be present. Using intense energy from lasers, extreme molecule velocities can be generated from photo-dissociation. This creates strong localized changes in both the hydrodynamics and thermodynamics of the flow, which may perturb the flow in a way similar to an active grid to generate turbulence in hypersonic flows. A large database of direct numerical simulations (DNS) are used to study the feasibility of such an approach. An extensive analysis of single and two point statistics, as well as spectral dynamics is used to characterize the evolution of the flow towards realistic turbulence. Local measures of enstrophy and dissipation are studied to diagnose the main mechanisms for energy exchange. As commonly done in compressible flows, dilatational and solenoidal components are separated to understand the effect of acoustics on the development of turbulence. Further results for cases that assimilate laboratory conditions will be discussed. The authors gratefully acknowledge the support of AFOSR.

  16. MEG source localization using invariance of noise space.

    Zhang, Junpeng; Raij, Tommi; Hämäläinen, Matti; Yao, Dezhong

    2013-01-01

    We propose INvariance of Noise (INN) space as a novel method for source localization of magnetoencephalography (MEG) data. The method is based on the fact that modulations of source strengths across time change the energy in signal subspace but leave the noise subspace invariant. We compare INN with classical MUSIC, RAP-MUSIC, and beamformer approaches using simulated data while varying signal-to-noise ratios as well as distance and temporal correlation between two sources. We also demonstrate the utility of INN with actual auditory evoked MEG responses in eight subjects. In all cases, INN performed well, especially when the sources were closely spaced, highly correlated, or one source was considerably stronger than the other. PMID:23505502

  17. MEG source localization using invariance of noise space.

    Junpeng Zhang

    Full Text Available We propose INvariance of Noise (INN space as a novel method for source localization of magnetoencephalography (MEG data. The method is based on the fact that modulations of source strengths across time change the energy in signal subspace but leave the noise subspace invariant. We compare INN with classical MUSIC, RAP-MUSIC, and beamformer approaches using simulated data while varying signal-to-noise ratios as well as distance and temporal correlation between two sources. We also demonstrate the utility of INN with actual auditory evoked MEG responses in eight subjects. In all cases, INN performed well, especially when the sources were closely spaced, highly correlated, or one source was considerably stronger than the other.

  18. The design and calibration of particular geometry piezoelectric acoustic emission transducer for leak detection and localization

    Yalcinkaya, Hazim; Ozevin, Didem

    2013-09-01

    Pipeline leak detection using an acoustic emission (AE) method requires highly sensitive transducers responding to less attenuative and dispersive wave motion in order to place the discrete transducer spacing in an acceptable approach. In this paper, a new piezoelectric transducer geometry made of PZT-5A is introduced to increase the transducer sensitivity to the tangential direction. The finite element analysis of the transducer geometry is modeled in the frequency domain to identify the resonant frequency, targeting 60 kHz, and the loss factor. The numerical results are compared with the electromechanical characterization tests. The transducer response to wave motion generated in different directions is studied using a multiphysics model that couples mechanical and electrical responses of structural and piezoelectric properties. The directional dependence and the sensitivity of the transducer response are identified using the laser-induced load function. The transducer response is compared with a conventional thickness mode AE transducer under simulations and leak localization in a laboratory scale steel pipe.

  19. Sparse cortical source localization using spatio-temporal atoms.

    Korats, Gundars; Ranta, Radu; Le Cam, Steven; Louis-Dorr, Valérie

    2015-08-01

    This paper addresses the problem of sparse localization of cortical sources from scalp EEG recordings. Localization algorithms use propagation model under spatial and/or temporal constraints, but their performance highly depends on the data signal-to-noise ratio (SNR). In this work we propose a dictionary based sparse localization method which uses a data driven spatio-temporal dictionary to reconstruct the measurements using Single Best Replacement (SBR) and Continuation Single Best Replacement (CSBR) algorithms. We tested and compared our methods with the well-known MUSIC and RAP-MUSIC algorithms on simulated realistic data. Tests were carried out for different noise levels. The results show that our method has a strong advantage over MUSIC-type methods in case of synchronized sources. PMID:26737185

  20. A persistent localized microseismic source near the Kyushu Island, Japan

    Zeng, Xiangfang; Ni, Sidao

    2010-12-01

    Very strong signals with apparent velocity higher than Rayleigh wave velocity are observed on noise correlation functions (NCFs) between seismic stations in East Asia. These signals are present on one-month NCFs in ten years period with stable arrival times, indicating their persistent and localized nature. The signals are strong in the frequency band of 0.07-0.12Hz, and their amplitudes show inter-annual but not seasonal variation. Location obtained from two algorithms with GSN and FNET data indicates that the source is situated in Kyushu Island, Japan. After an earthquake is used to account for heterogeneity effects, the location is closer to the Ariake bay but still in the island. The non-seasonal amplitude variation and the peak frequency of 0.1Hz suggest the signals are probably not generated by oceanic sources. This persistent localized microseismic source needs to be taken into consideration in ambient noise tomography studies in East Asia.

  1. Inverse Problem Solution in Acoustic Emission Source Analysis : Classical and Artificial Neural Network Approach

    Převorovský, Zdeněk; Chlada, Milan; Vodička, Josef

    New York : Springer, 2006 - (Delsanto, P.), s. 515-529 ISBN 0-387-33860-8 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission * artificial neural network s * inverse problems Subject RIV: BI - Acoustics

  2. A Study of the Development of PC-Based Source Location System using Acoustic Emission Technique

    Acoustic emission (AE) technique has been applied to not only mechanical property testing but also on-line monitoring of the el)tire structure or a limit zone only. Although several AE devices have already been developed for the on-line monitoring, the price of these systems is very high and it is difficult for the field to apply yet. In this study, wc developed a specially designed PC-based source location system using the A/D board. The source location technique is very important to identify the source, such as crack, leak detection. However, since the AE waveforms obtained from transducers are very difficult to distinguish the defect signals, therefore, it is necessary to consider the signal analyses of the transient waveform. Wavelet Transform (WT) is a powerful tool for processing transient signals with temporally varying spectra that helps to resolve high and low frequency transients components effectively In this study, the analyses of the AE signals are presented by employing the WT analyses. AE results are compared the PC-based source location system using A/D board with the commercial AE system

  3. Localization of Narrow-Band Sources in Unknown Spatially Correlated Noise

    Bourennane Salah

    2010-01-01

    Full Text Available In subspace-based method for direction-of-arrival (DOA estimation of signal wavefronts, the additive noise term is often assumed to be spatially white or known to within a multiplicative scalar. When the noise is nonwhite but has a known covariance matrix, we can still handle the problem through prewhitening. However, the problem turns to be complex when the noise field is completely unknown. In this paper, we study the localization of the sources, when the noise covariance matrix is one unknown band matrix. An iterative denoising algorithm based on the noise subspace spanned by the eigenvectors associated with the smallest eigenvalues is developed. The performance of the proposed algorithm is evaluated by computer simulations. We also test the proposed algorithm with some experimental data recorded during an underwater acoustic experiment.

  4. Time delay estimation in a reverberant environment by low rate sampling of impulsive acoustic sources

    Omer, Muhammad

    2012-07-01

    This paper presents a new method of time delay estimation (TDE) using low sample rates of an impulsive acoustic source in a room environment. The proposed method finds the time delay from the room impulse response (RIR) which makes it robust against room reverberations. The RIR is considered a sparse phenomenon and a recently proposed sparse signal reconstruction technique called orthogonal clustering (OC) is utilized for its estimation from the low rate sampled received signal. The arrival time of the direct path signal at a pair of microphones is identified from the estimated RIR and their difference yields the desired time delay. Low sampling rates reduce the hardware and computational complexity and decrease the communication between the microphones and the centralized location. The performance of the proposed technique is demonstrated by numerical simulations and experimental results. © 2012 IEEE.

  5. Minimum variance brain source localization for short data sequences.

    Ravan, Maryam; Reilly, James P; Hasey, Gary

    2014-02-01

    In the electroencephalogram (EEG) or magnetoencephalogram (MEG) context, brain source localization methods that rely on estimating second-order statistics often fail when the number of samples of the recorded data sequences is small in comparison to the number of electrodes. This condition is particularly relevant when measuring evoked potentials. Due to the correlated background EEG/MEG signal, an adaptive approach to localization is desirable. Previous work has addressed these issues by reducing the adaptive degrees of freedom (DoFs). This reduction results in decreased resolution and accuracy of the estimated source configuration. This paper develops and tests a new multistage adaptive processing technique based on the minimum variance beamformer for brain source localization that has been previously used in the radar statistical signal processing context. This processing, referred to as the fast fully adaptive (FFA) approach, can significantly reduce the required sample support, while still preserving all available DoFs. To demonstrate the performance of the FFA approach in the limited data scenario, simulation and experimental results are compared with two previous beamforming approaches; i.e., the fully adaptive minimum variance beamforming method and the beamspace beamforming method. Both simulation and experimental results demonstrate that the FFA method can localize all types of brain activity more accurately than the other approaches with limited data. PMID:24108457

  6. A Numerical Investigation of Turbine Noise Source Hierarchy and Its Acoustic Transmission Characteristics

    VanZante, Dale; Envia, Edmane

    2008-01-01

    Understanding the relative importance of the various turbine noise generation mechanisms and the characteristics of the turbine acoustic transmission loss are essential ingredients in developing robust reduced-order models for predicting the turbine noise signature. A computationally based investigation has been undertaken to help guide the development of a turbine noise prediction capability that does not rely on empiricism. The investigation relies on highly detailed numerical simulations of the unsteady flowfield inside a modern high-pressure turbine (HPT). The simulations are developed using TURBO, which is an unsteady Reynolds-averaged Navier-Stokes (URANS) code capable of multi-stage simulations. The purpose of this study is twofold. First, to determine an estimate of the relative importance of the contributions to the coherent part of the acoustic signature of a turbine from the three potential sources of turbine noise generation, namely, blade-row viscous interaction, potential field interaction, and entropic source associated with the interaction of the blade rows with the temperature nonuniformities caused by the incomplete mixing of the hot fluid and the cooling flow. Second, to develop an understanding of the turbine acoustic transmission characteristics and to assess the applicability of existing empirical and analytical transmission loss models to realistic geometries and flow conditions for modern turbine designs. The investigation so far has concentrated on two simulations: (1) a single-stage HPT and (2) a two-stage HPT and the associated inter-turbine duct/strut segment. The simulations are designed to resolve up to the second harmonic of the blade passing frequency tone in accordance with accepted rules for second order solvers like TURBO. The calculations include blade and vane cooling flows and a radial profile of pressure and temperature at the turbine inlet. The calculation can be modified later to include the combustor pattern factor at the

  7. Source localization using recursively applied and projected (RAP) MUSIC

    Mosher, J.C. [Los Alamos National Lab., NM (United States); Leahy, R.M. [Univ. of Southern California, Los Angeles, CA (United States). Signal and Image Processing Inst.

    1998-03-01

    A new method for source localization is described that is based on a modification of the well known multiple signal classification (MUSIC) algorithm. In classical MUSIC, the array manifold vector is projected onto an estimate of the signal subspace, but errors in the estimate can make location of multiple sources difficult. Recursively applied and projected (RAP) MUSIC uses each successively located source to form an intermediate array gain matrix, and projects both the array manifold and the signal subspace estimate into its orthogonal complement. The MUSIC projection is then performed in this reduced subspace. Using the metric of principal angles, the authors describe a general form of the RAP-MUSIC algorithm for the case of diversely polarized sources. Through a uniform linear array simulation, the authors demonstrate the improved Monte Carlo performance of RAP-MUSIC relative to MUSIC and two other sequential subspace methods, S and IES-MUSIC.

  8. Particle Filter with Integrated Voice Activity Detection for Acoustic Source Tracking

    Anders M. Johansson

    2007-01-01

    Full Text Available In noisy and reverberant environments, the problem of acoustic source localisation and tracking (ASLT using an array of microphones presents a number of challenging difficulties. One of the main issues when considering real-world situations involving human speakers is the temporally discontinuous nature of speech signals: the presence of silence gaps in the speech can easily misguide the tracking algorithm, even in practical environments with low to moderate noise and reverberation levels. A natural extension of currently available sound source tracking algorithms is the integration of a voice activity detection (VAD scheme. We describe a new ASLT algorithm based on a particle filtering (PF approach, where VAD measurements are fused within the statistical framework of the PF implementation. Tracking accuracy results for the proposed method is presented on the basis of synthetic audio samples generated with the image method, whereas performance results obtained with a real-time implementation of the algorithm, and using real audio data recorded in a reverberant room, are published elsewhere. Compared to a previously proposed PF algorithm, the experimental results demonstrate the improved robustness of the method described in this work when tracking sources emitting real-world speech signals, which typically involve significant silence gaps between utterances.

  9. Localization of source with unknown amplitude using IPMC sensor arrays

    Abdulsadda, Ahmad T.; Zhang, Feitian; Tan, Xiaobo

    2011-04-01

    The lateral line system, consisting of arrays of neuromasts functioning as flow sensors, is an important sensory organ for fish that enables them to detect predators, locate preys, perform rheotaxis, and coordinate schooling. Creating artificial lateral line systems is of significant interest since it will provide a new sensing mechanism for control and coordination of underwater robots and vehicles. In this paper we propose recursive algorithms for localizing a vibrating sphere, also known as a dipole source, based on measurements from an array of flow sensors. A dipole source is frequently used in the study of biological lateral lines, as a surrogate for underwater motion sources such as a flapping fish fin. We first formulate a nonlinear estimation problem based on an analytical model for the dipole-generated flow field. Two algorithms are presented to estimate both the source location and the vibration amplitude, one based on the least squares method and the other based on the Newton-Raphson method. Simulation results show that both methods deliver comparable performance in source localization. A prototype of artificial lateral line system comprising four ionic polymer-metal composite (IPMC) sensors is built, and experimental results are further presented to demonstrate the effectiveness of IPMC lateral line systems and the proposed estimation algorithms.

  10. High Power Local Oscillator Sources for 1-2 THz

    Mehdi, Imran; Thomas, Bertrand; Lin, Robert; Maestrini, Alain; Ward, John; Schlecht, Erich; Gill, John; Lee, Choonsup; Chattopadhyay, Goutam; Maiwald, Frank

    2010-01-01

    Recent results from the Heterodyne Instrument for Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore the current status of tunable local oscillator sources beyond HIFI and provide demonstration of how power combining of GaAs Schottky diodes can be used to increase both power and upper operating frequency for heterodyne receivers. Availability of power levels greater than 1 watt in the W-band now makes it possible to design a 1900 GHz source with more than 100 microwatts of expected output power.

  11. Sources and characteristics of acoustic emissions from mechanically stressed geologic granular media — A review

    Michlmayr, Gernot; Cohen, Denis; Or, Dani

    2012-05-01

    The formation of cracks and emergence of shearing planes and other modes of rapid macroscopic failure in geologic granular media involve numerous grain scale mechanical interactions often generating high frequency (kHz) elastic waves, referred to as acoustic emissions (AE). These acoustic signals have been used primarily for monitoring and characterizing fatigue and progressive failure in engineered systems, with only a few applications concerning geologic granular media reported in the literature. Similar to the monitoring of seismic events preceding an earthquake, AE may offer a means for non-invasive, in-situ, assessment of mechanical precursors associated with imminent landslides or other types of rapid mass movements (debris flows, rock falls, snow avalanches, glacier stick-slip events). Despite diverse applications and potential usefulness, a systematic description of the AE method and its relevance to mechanical processes in Earth sciences is lacking. This review is aimed at providing a sound foundation for linking observed AE with various micro-mechanical failure events in geologic granular materials, not only for monitoring of triggering events preceding mass mobilization, but also as a non-invasive tool in its own right for probing the rich spectrum of mechanical processes at scales ranging from a single grain to a hillslope. We review first studies reporting use of AE for monitoring of failure in various geologic materials, and describe AE generating source mechanisms in mechanically stressed geologic media (e.g., frictional sliding, micro-crackling, particle collisions, rupture of water bridges, etc.) including AE statistical features, such as frequency content and occurrence probabilities. We summarize available AE sensors and measurement principles. The high sampling rates of advanced AE systems enable detection of numerous discrete failure events within a volume and thus provide access to statistical descriptions of progressive collapse of systems

  12. Improved Bayesian Infrasonic Source Localization for regional infrasound

    Blom, Philip S.; Marcillo, Omar; Arrowsmith, Stephen J.

    2015-12-01

    The mathematical framework used in the Bayesian Infrasonic Source Localization (BISL) methodology is examined and simplified providing a generalized method of estimating the source location and time for an infrasonic event. The likelihood function describing an infrasonic detection used in BISL has been redefined to include the von Mises distribution developed in directional statistics and propagation-based, physically derived celerity-range and azimuth deviation models. Frameworks for constructing propagation-based celerity-range and azimuth deviation statistics are presented to demonstrate how stochastic propagation modelling methods can be used to improve the precision and accuracy of the posterior probability density function describing the source localization. Infrasonic signals recorded at a number of arrays in the western United States produced by rocket motor detonations at the Utah Test and Training Range are used to demonstrate the application of the new mathematical framework and to quantify the improvement obtained by using the stochastic propagation modelling methods. Using propagation-based priors, the spatial and temporal confidence bounds of the source decreased by more than 40 per cent in all cases and by as much as 80 per cent in one case. Further, the accuracy of the estimates remained high, keeping the ground truth within the 99 per cent confidence bounds for all cases.

  13. EEG and MEG source localization using recursively applied (RAP) MUSIC

    Mosher, J.C. [Los Alamos National Lab., NM (United States); Leahy, R.M. [University of Southern California, Los Angeles, CA (United States). Signal and Image Processing Inst.

    1996-12-31

    The multiple signal characterization (MUSIC) algorithm locates multiple asynchronous dipolar sources from electroencephalography (EEG) and magnetoencephalography (MEG) data. A signal subspace is estimated from the data, then the algorithm scans a single dipole model through a three-dimensional head volume and computes projections onto this subspace. To locate the sources, the user must search the head volume for local peaks in the projection metric. Here we describe a novel extension of this approach which we refer to as RAP (Recursively APplied) MUSIC. This new procedure automatically extracts the locations of the sources through a recursive use of subspace projections, which uses the metric of principal correlations as a multidimensional form of correlation analysis between the model subspace and the data subspace. The dipolar orientations, a form of `diverse polarization,` are easily extracted using the associated principal vectors.

  14. Source location of artificial acoustic emission in elbow-pipe joint using neural network

    A new technique to locate a defect, combining acoustic emission (AE) and neural network, is proposed to assess the structural integrity of a pipeline in operation. Computer simulations and experiments to locate the defect using artificial AE by means of a pencil lead break are conducted at an elbow-pipe joint. Arrival time differences of the AE wave from the AE source to four sensors with 150kHz resonance frequency are measured using an AE digital measuring system with four channel devices. Half the data and all data are used for leaning of the neural network and for estimating the locations, respectively. Source location error of the elbow-pipe joint in the experiment, as well as the simulation, was less than 1%. To confirm the detection of a crack extension in a pipe joint by the system, crack tip locations due to extension are obtained from a welded defect of a tensile specimen are determined. Results are obtained for the detection of the crack extension. (author)

  15. Source location of artificial acoustic emission in elbow-pipe joint using neural network

    Homma, Kyoji; Okamura, Yuka [The Univ. of Electro-communications, Chofu, Tokyo (Japan)

    2002-11-01

    A new technique to locate a defect, combining acoustic emission (AE) and neural network, is proposed to assess the structural integrity of a pipeline in operation. Computer simulations and experiments to locate the defect using artificial AE by means of a pencil lead break are conducted at an elbow-pipe joint. Arrival time differences of the AE wave from the AE source to four sensors with 150kHz resonance frequency are measured using an AE digital measuring system with four channel devices. Half the data and all data are used for leaning of the neural network and for estimating the locations, respectively. Source location error of the elbow-pipe joint in the experiment, as well as the simulation, was less than 1%. To confirm the detection of a crack extension in a pipe joint by the system, crack tip locations due to extension are obtained from a welded defect of a tensile specimen are determined. Results are obtained for the detection of the crack extension. (author)

  16. Importance of Including the Acoustic Medium in Rooms on the Transmission Path between Source and Receiver Rooms within a Building

    Andersen, Lars; Kirkegaard, Poul Henning; Dickow, Kristoffer Ahrens;

    2011-01-01

    Low-frequency noise is a potential nuisance to inhabitants in lightweight building structures. Hence, development of efficient and accurat methods for prediction of noice in such buildings is important. The aim of this paper is to assess the necessity of including the acoustic medium in rooms along...... the transmission path from one room to another. For this purpose, analyses are carried out in frequency domain by a finite-element model, employing a fully couples model of sound waves within an acoustic medium and vibrations in a building structure. Focus is on modelling the room between the source...... and receiver rooms. A model including the acoustic medium in the middle room is compared to a model with no air in the room, and different transmissions paths for flanking niose (walls and floors) are studied. The study concerns the frequency range 50-250 Hz....

  17. Brain source localization based on fast fully adaptive approach.

    Ravan, Maryam; Reilly, James P

    2012-01-01

    In the electroencephalogram (EEG) or magnetoencephalogram (MEG) context, brain source localization (beamforming) methods often fail when the number of observations is small. This is particularly true when measuring evoked potentials, especially when the number of electrodes is large. Due to the nonstationarity of the EEG/MEG, an adaptive capability is desirable. Previous work has addressed these issues by reducing the adaptive degrees of freedom (DoFs). This paper develops and tests a new multistage adaptive processing for brain source localization that has been previously used for radar statistical signal processing application with uniform linear antenna array. This processing, referred to as the fast fully adaptive (FFA) approach, could significantly reduce the required sample support and computational complexity, while still processing all available DoFs. The performance improvement offered by the FFA approach in comparison to the fully adaptive minimum variance beamforming (MVB) with limited data is demonstrated by bootstrapping simulated data to evaluate the variability of the source location. PMID:23367106

  18. Evolutions of friction properties and acoustic emission source parameters associated with large sliding

    Yabe, Y.; Tsuda, H.; Iida, T.

    2015-12-01

    It was demonstrated by Yabe (2002) that friction properties and AE (acoustic emission) activities evolve with accumulation of sliding. However, large sliding distances of ~65 mm in his experiments were achieved by recurring ~10 mm sliding on the same fault. The evolution of friction coefficient was discontinuous, when rock samples were reset. Further, normal stress was not kept constant. To overcome these problems and to reexamine the evolutions of friction properties and AE activities with continuous large sliding under a constant normal stress, we developed a rotary shear apparatus. The evolutions of friction and AE up to ~80 mm sliding under a normal stress of 5 MPa were investigated. Rate dependence of friction was the velocity strengthening (a-b>0 in rate and state friction law) at the beginning. The value of a-b gradually decreased with sliding to negative (velocity weakening). Then, it took a constant negative value, when the sliding reached a critical distance. The m-value of Ishimoto-Iida's relation of AE activity increased with sliding at the beginning and converged to a constant value at the critical sliding distance. The m-value showed a negative rate dependence at the beginning, but became neutral after sliding of the critical distance. The sliding distances required to converge the a-b value, the m-value and the rate dependence of the m-value are almost identical to one another. These results are the same as those by Yabe (2002), suggesting the intermission of sliding little affected the evolutions. We, then, examined evolutions of AE source parameters such as source radii and stress drops. The average source radius was constant over the whole sliding distance, while the average stress drop decreased at the beginning of sliding, and converged to a constant value. The sliding distance required to the conversion was the same as that for the above mentioned evolutions of friction property or AE activity.

  19. Field Trial of Distributed Acoustic Sensing Using Active Sources at Garner Valley, California

    Wang, H. F.; Lord, N. E.; Chalari, A.; Lancelle, C.; Baldwin, J. A.; Castongia, E.; Fratta, D.; Nigbor, R. L.; Karaulanov, R.

    2014-12-01

    An optical fiber Distributed Acoustic Sensor array was deployed in a shallow trench at the site of the Garner Valley Downhole Array (GVDA) in southern California. The site was operated as a collaborator of the Network for Earthquake Engineering Simulation (NEES) by UCSB. The fiber-optic cable layout approximated a rectangle whose dimensions were roughly 160 meters by 80 meters. The layout included two subdiagonals to provide a variety of orientations of the cable relative to source locations. The study included different seismic sources deployed at a number of surveyed positions: a 45 kN shear shaker operated at the site by NEES@UCLA, a portable 450 N shaker, a small Vibroseis truck, and hammer blows on a steel plate to map cable locations. Several dozen separate tests were recorded in which each test typically included ten repeats. The data were utilized for several studies. First, the characteristics of the recorded signals were analyzed for directivity and sensitivity of the cable response (Lancelle et al., 2014, this meeting). The DAS system recorded dynamic ground events in the direction of the cable and hence comparisons with geophones required signal processing. The one-meter spacing of DAS traces could be well correlated over distances of a few meters. Second, swept-sine sources were used to obtain surface-wave velocity dispersion to determine near-surface shear-wave velocity distribution using Multispectral Analysis of Surface Waves (MASW) (Baldwin et al., 2014, this meeting). The results were in good agreement with previous Vibroseis results at the site (Stokoe et al. 2004). Third, a new method for time-frequency filtering was developed for extracting the surface-wave phase velocities from uncorrelated receiver traces (Lord et al., 2014, this meeting).

  20. Production of Local Acoustic Radiation Force to Constrain Direction of Microcapsules in Flow

    Masuda, Kohji; Watarai, Nobuyuki; Nakamoto, Ryusuke; Muramatsu, Yusuke

    2010-07-01

    We have ever reported our attempt to control the direction of microcapsules in flow by acoustic radiation force. However, the diameter of capsules was too large to be applied in vivo. Furthermore, the acoustic radiation force affected only the focal area because focused ultrasound was used. Thus, we have improved our experiment by using microcapsules as small as blood cells and introducing a plane wave of ultrasound. We prepared an artificial blood vessel including a Y-form bifurcation established in two observation areas. Then, we newly defined the induction index to evaluate the difference in capsule density in two downstream paths. As a result, the optimum angle of ultrasound emission to induct to the desired path was derived. The induction index increased in proportion to the central frequency of ultrasound, which is affected by the aggregation of capsules to receive more acoustic radiation force.

  1. Source localization of brain activity using helium-free interferometer

    To detect extremely small magnetic fields generated by the human brain, currently all commercial magnetoencephalography (MEG) systems are equipped with low-temperature (low-Tc) superconducting quantum interference device (SQUID) sensors that use liquid helium for cooling. The limited and increasingly expensive supply of helium, which has seen dramatic price increases recently, has become a real problem for such systems and the situation shows no signs of abating. MEG research in the long run is now endangered. In this study, we report a MEG source localization utilizing a single, highly sensitive SQUID cooled with liquid nitrogen only. Our findings confirm that localization of neuromagnetic activity is indeed possible using high-Tc SQUIDs. We believe that our findings secure the future of this exquisitely sensitive technique and have major implications for brain research and the developments of cost-effective multi-channel, high-Tc SQUID-based MEG systems.

  2. Sourcing semiclassical gravity from spontaneously localized quantum matter

    Tilloy, Antoine

    2015-01-01

    The possibility that a classical space-time and quantum matter cohabit at the deepest level, i.e. the possibility of having a fundamental and not phenomenological semiclassical gravity, is often disregarded for lack of a good candidate theory. The standard semiclassical theory suffers from fundamental inconsistencies (e.g.: Schr\\"odinger cat sources, faster-than-light communication and violation of the Born rule) which can only be ignored in simple typical situations. We harness the power of spontaneous localization models, historically constructed to solve the measurement problem in quantum mechanics, to build a consistent theory of (stochastic) semiclassical gravity in the Newtonian limit. Our model makes quantitative and testable predictions: we recover the Newtonian pair potential up to a short distance cut-off and uncover an additional gravitational decoherence term which depends on the specifics of the underlying spontaneous localization model considered. We hint at a possible program to go past the New...

  3. Use of a Single Nanoparticle as Localized Light Source

    Full text: In this work, we have identified different types of inorganic spherical nanoparticles that can be trapped by near-infrared (IR) laser tweezers and simultaneously used as a local near-field light source. Visible light emission is then exclusively induced by the IR trapping laser. In particular, we show that we can detect electromagnetic non-linear optical field enhancement resulting from surface plasmon excitation on a trapped gold nanosphere. Furthermore, we demonstrate optical trapping of a single KNbO3 nanoparticle along with second harmonic excitation by the IR laser. In parallel, we can quantify the forces acting on the trapped nanoparticle by measuring its 3D Brownian fluctuations with nanometer spatial and microsecond temporal resolutions through interferometric position detection. The long term goal is to use a single near-field probe for versatile and multidimensional microspectroscopy to obtain local information, such as fluorescence, dynamical and mechanical properties of molecules surrounding the particle. (author)

  4. Ictal source localization in presurgical patients with refractory epilepsy.

    Boon, Paul; D'Havé, Michel; Vanrumste, Bart; Van Hoey, Gert; Vonck, Kristl; Van Walleghem, Phyllis; Caemaert, Jacques; Achten, Eric; De Reuck, Jacques

    2002-10-01

    Source localization of epileptic foci using ictal spatiotemporal dipole modeling (ISDM) yields reliable anatomic information in presurgical candidates. It requires substantial resources from EEG and neuroimaging laboratories. The profile and number of patients who may benefit from it are currently unknown. The purpose of this study is to demonstrate the clinical usefulness of source localization in a prospectively analyzed series. One hundred patients (51 male and 49 female patients) with mean age of 31 years (range, 2 to 63 years) and mean duration of refractory epilepsy of 20 years (range, 1 to 49 years) were enrolled consecutively in a presurgical protocol. Ictal EEG was available in 93 patients. ISDM was performed when suitable ictal EEG files were available. The clinical applicability of ISDM was examined in three patients groups: 37 patients in whom ictal EEG recording and MRI were congruent (group I), 30 patients in whom results were not completely congruent but not incongruent (group II), and 26 patients in whom the results were incongruent (group III). ISDM could be performed in 31 of 100 patients: 11 in group I, 8 in group II, and 12 in group III. ISDM influenced decision making in none of the patients in group I, in 4 of 8 patients in group II, and in 10 of 12 patients in group III. Typically, the results of ISDM directed avoiding intracranial EEG recordings in what appeared to be unsuitable candidates for resection by clearly confirming the incongruency between ictal EEG and MRI findings. In this series of 100 presurgical candidates, ictal source localization could be performed in 31% of patients. In 14% of patients, it proved to be a key element in the surgical decision process. PMID:12477991

  5. Inverse Problem Solution in Acoustic Emission Source Analysis: Classical and Artificial Neural Network Approaches

    Převorovský, Zdeněk; Chlada, Milan; Vodička, Josef

    Torino : Springer, 2007 - (Delsanto, P.), s. 515-529 ISBN 0-387-33860-8 R&D Projects: GA ČR GA205/03/0071; GA ČR GA201/04/2102 Institutional research plan: CEZ:AV0Z20760514 Keywords : acoustic emission * artificial neural network s * inverse problems Subject RIV: BI - Acoustics

  6. Phase patterns of dispersive waves from moving localized sources

    A general approach is proposed within which the phase structure of wave perturbations caused by a moving localized source can be described based on the wave dispersion law alone. Applying this approach, a simple analytical expression for the phase surfaces is obtained. It is used to study the details of phase patterns of gravity-capillary waves, the structure of wave trains in the ocean in the wake of a moving tropical hurricane, and the system of lee waves in Earth's atmosphere. (methodological notes)

  7. Chemical Source Localization using Mobile Robots in Indoor Arena

    Yuli Zhang

    2013-07-01

    Full Text Available This paper presents a virtual-physics force based control strategy for swarm robotic chemical source localization. The control force includes: structure formation force, goal force, and obstacle avoidant force. For swarm formation, the robots maintain the regular polygon formation and a virtual robot is located at the center of the polygon. The motion of the virtual robot depends on the goal force which obtained from the sensor observations of the robots. Once the virtual robot moved to a new place, the robots would also move as a single body with the structure formation force and obstacle avoidant force. In this paper, we adopted chemotaxis as plume tracing algorithms. Simulation experiments in indoor arena without obstacle and with obstacles using different robot number are carried out respectively, and the results show that the proposed strategy can effectively navigate the mobile robotics swarms to the chemical source once selecting proper number of robots.  

  8. Combining bayesian source imaging with equivalent dipole approach to solve the intracranial EEG source localization problem.

    Le Cam, Steven; Caune, Vairis; Ranta, Radu; Korats, Gundars; Louis-Dorr, Valerie

    2015-08-01

    The brain source localization problem has been extensively studied in the past years, yielding a large panel of methodologies, each bringing their own strengths and weaknesses. Combining several of these approaches might help in enhancing their respective performance. Our study is carried out in the particular context of intracranial recordings, with the objective to explain the measurements based on a reduced number of dipolar activities. We take benefit of the sparse nature of the Bayesian approaches to separate the noise from the source space, and to distinguish between several source contributions on the electrodes. This first step provides accurate estimates of the dipole projections, which can be used as an entry to an equivalent current dipole fitting procedure. We demonstrate on simulations that the localization results are significantly enhanced by this post-processing step when up to five dipoles are activated simultaneously. PMID:26736344

  9. Detection and localization of defects in complex structures by Nonlinear Elastic Wave Spectroscopy and Acoustic Emission

    Převorovský, Zdeněk; Chlada, Milan; Krofta, Josef; Kober, Jan; Dos Santos, S.

    Le Mans: The University of Maine in Le Mans, 2013 - (Bentahar, M.; Kenderian, S.; Green, R.). s. 95 [Internanational Symposium on Nondestructive Characterization of Materials /13./. 20.05.2013-24.05.2013, Le Mans] Institutional support: RVO:61388998 Keywords : nonlinear elastic wave spectroscopy * acoustic emission * nondestructive testing * damage initiation * civil structure Subject RIV: JS - Reliability ; Quality Management, Testing

  10. DEVELOPING LOW TEMPERATURE SOURCE LOCAL HEATING FOR PIGLETS

    Chus R. V.

    2015-04-01

    Full Text Available During the research, we have developed a low-temperature zonal heating panels with an infrared emitter to create a local microclimate for piglets in the suckling period. This heater is lightweight and durable frame in the form of an inverted box size 400 mm x 1800 mm, attached to the wall of the building swivel. Top frame mounted thermostat is connected to a temperature sensor mounted directly on a metal plate with a thickness of 1 mm, painted in black color. In the upper part of the inner carcass layer is a light insulating material, which is located directly under the low-temperature heat source is electric. Study of the optimal size of the heating panel revealed that in view of the limitations associated with the area of the machine and biological characteristics of the optimum size of the sow for 11 piglets are: width – 400 mm; length – 1500 mm (at ventral position and 1800 mm (lateral position. Comparison of different heating sources for piglets revealed that the use of infrared lamps enables newborn piglets seating area by 55.6%, while in 28 days – by 88.9%. Infrared lamps can not completely meet the recommended specifications as to ensure a more intense heat lamp to be lowered towards the floor surface, which leads to a reduction in the useful area heated. Using as a source of local heating mats and low-temperature panels satisfies pigs in the area of the den in the early suckling period at 138.9 and 200.0%, to weaning, respectively – by 48.5 and 65.5%. Thus, we have developed a low-temperature heating panels contributed to a more uniform distribution of heat in a recreation area of suckling piglets and to provide a comfortable environment at temperatures of 2-3 C lower in comparison with other methods of heating