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7. Influence of the scattering effect on acoustic image obtained with a spherical microphone array

Author

St-Jacques, Julien, Rouard, Kevin, Sgard, Franck, Nélisse, Hugues, Berry, Alain, Quaegebeur, Nicolas, Grondin, François, Boileau, Loic, Doutres, Olivier, Padois, Thomas, St-Jacques, Julien, Rouard, Kevin, Sgard, Franck, Nélisse, Hugues, Berry, Alain, Quaegebeur, Nicolas, Grondin, François, Boileau, Loic, Doutres, Olivier, and Padois, Thomas

Abstract

Longterm exposure to noise in the workplace can lead hearing loss and other psychosocial effects. Among the most effective noise reduction methods is to apply efforts directly at the source. To do so, each source must be characterized by their spatial location and contribution. In the workplace, a Spherical Microphone Array (SMA) can be used. When the microphones are held on a wireframe structure or on thin rods, the SMA is considered acoustically transparent, and the Conventional Beamforming in the Frequency domain (CBF) algorithm can be used. The CBF, however, does not compensate for the scattering effect of a diffracting object. On the other hand, rigid SMAs are usually made of a solid sphere with flush-mounted microphones and may scatter the acoustic waves. Although the literature has shown the advantages of using a rigid SMA with the spherical harmonics decomposition, the influence of the scattering effect on the acoustic image when not accounted for remains under-examined. This study aims to assess the influence of the uncompensated scattering effects on acoustic images obtained with a SMA. Images obtained with a rigid SMA are compared to those obtained from a theoretical perfectly transparent SMA using the CBF. First, a spherical wave field is simulated using a finite element analysis model to generate the microphone signals for both SMAs. Then, the images are generated using the CBF and three image quality criteria are used to assess the scattering effects, i.e., the ellipse area ratio, the mainlobe-to-sidelobe ratio and the mainlobe level. Results show that the influence of the scattering effect, if not corrected, will reduce the width of the mainlobe and amplify the level of the sidelobes. The effect on the estimated source level is not significant in this case.

Published
2023

8. A criterion based on the calculation of a solid angle to assess the quality of acoustic images obtained with a SMA

Author

Rouard, Kevin, St-Jacques, Julien, Sgard, Franck, Doutres, Olivier, Nélisse, Hugues, Boileau, Loic, Berry, Alain, Quaegebeur, Nicolas, Grondin, François, Padois, Thomas, Rouard, Kevin, St-Jacques, Julien, Sgard, Franck, Doutres, Olivier, Nélisse, Hugues, Boileau, Loic, Berry, Alain, Quaegebeur, Nicolas, Grondin, François, and Padois, Thomas

Abstract

The quality of an acoustic image is evaluated based on criteria such as the source level, the mainlobe-to-sidelobes ratio and the spatial resolution. Spatial resolution can be evaluated by the mainlobe area. For spherical microphone arrays, polar projection and ellipse area can be used. These methods are however applied in a plane and not in a spherical plane. In particular, the covariance ellipsemethod may exceed the spherical coordinate frame of the acoustic image when the mainlobe is large, typically at low frequencies, or when there are numerous sidelobes at high frequencies. In addition, the mainlobe may not be centered in the acoustic image and may be distorted around the poles. In order to overcome these limitations, a criterion based on the solid angle is introduced in this paper.The performance of the method based on the solid angle computation is compared with that based on the ellipse. Numerical simulations are performed using a spherical microphone array with a rigid t-design geometry, and spherical harmonics are used to generate the acoustic images. The results show that the solid angle method provides a more stable value compared to the covariance ellipse method when the source is not centered. When the source is centered, the results are similar except when sidelobes occur. In conclusion, the solid angle method provides a robust approach for evaluating the spatial resolution of acoustic images obtained with spherical microphone arrays.

Published
2023

9. Evaluation of vibration emission values of nailers: Can an automatic test stand be used instead of human operators?

Author

Vincent, Maxime, Padois, Thomas, Gaudreau, Marc-André, Dupont, Thomas, Marcotte, Pierre, Vincent, Maxime, Padois, Thomas, Gaudreau, Marc-André, Dupont, Thomas, and Marcotte, Pierre

Abstract

To protect workers, it is necessary to characterize the noise and vibration emissions value of nailers. Standardized characterization methods exist but require three trained human operators, which leads to a dispersion in the results and a difficult implementation. An automatic test stand (ATS) was developed to characterize those values without the participation of human operators. It is proposed here that we compare the results obtained by the two methods. Preliminary results suggest that further refinement of the ATS is needed to better mimic the biodynamics of the human hand–arm and that a larger number of operators would be required for validation.

Published
2023

10. ACOUSTICS WEEK IN CANADA 2023.

Author

Doutres, Olivier, Padois, Thomas, and Voix, Jérémie

Abstract

The Canadian Acoustical Association hosted the Acoustics Week in Canada (AWC) in Montreal from October 3rd to October 6th, 2023. This event was a resounding success, bringing together over 260 participants over the 4 days of the conference, setting a record for AWC. More than 160 presentations were given on various topics in acoustics, such as speech and hearing science, architectural acoustics, hearing protection, and materials for noise and vibration control. The acoustics community was able to come together and share memorable moments, such as during the 'Powerpoint Karaoke' or the musical jam organized on the sidelines of the gala dinner. This report presents the highlights of the conference for the benefits of AWC23 participants and future conference convenors. [ABSTRACT FROM AUTHOR]

Published
2023

16. Numerical investigation of the effects of model uncertainties on component-based transfer path analysis method with dynamic substructuring applied to aircraft-like components.

Author

Prenant, Simon, Padois, Thomas, Dupont, Thomas, and Doutres, Olivier

Subjects
TRANSFER path analysis, ACOUSTICAL engineering, AIRCRAFT noise, SOUND design, NOISE control, SOUNDPROOFING
Abstract

The hydraulic pumps are considered to have a major contribution to the structure borne noise generated inside aircrafts. Methods such as Component-Based Transfer Path Analysis (CB-TPA) are promising tools for aircraft manufacturers to build internal processes for the specification, design and validation of the impact of vibrating systems on new aircrafts. However, the experimental applicability of these methods remains limited due to some experimental difficulties. CB-TPA' formulation is based on dynamical quantities, which require the determination of terms related to rotational degrees of freedom. Indirect methods such as Virtual Point (VP) are commonly employed for this purpose, but it results in more cumbersome experimental set-ups and increased measurement uncertainties. The implementation of these methods can also be difficult in the case of a flat and thin receiving structure as commonly encountered in aircraft applications, since in-plane translational excitations have to be applied and the access to the vibrating system/structure interface points is limited. In this work, a decoupling procedure is used to overcome these issues. A numerical model is used to investigate the influence of model uncertainties on the CB-TPA' predictions, when the dynamical quantities are provided by VP method including the decoupling procedure. [ABSTRACT FROM AUTHOR]

Published
2023
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17. Comparison of road noise policies across Australia, Europe, and North America

Author

Perna, Maxime, Padois, Thomas, Trudeau, Christopher, Bild, Edda, Laplace, Josée, Dupont, Thomas, Guastavino, Catherine, Perna, Maxime, Padois, Thomas, Trudeau, Christopher, Bild, Edda, Laplace, Josée, Dupont, Thomas, and Guastavino, Catherine

Abstract

Developing innovative noise policies that build on international best practices is difficult when policies around the world differ along many dimensions, ranging from different sources covered to different levels of governance involved. This is particularly critical in the context of road traffic, identified as one of the main culprits leading to noise-associated complaints and health issues. In this article, we document the wide range of specifications observed in road traffic policies and propose a methodology to compare noise limits across noise policies. First, we present the responsibilities of administrative governments according to the scope (e.g., emission vs. exposure). Second, we compare noise limits by scope and geographic areas by separating acoustic indicators (overall and event indicators). Third, we convert overall outdoor noise limits into a common basis using the method described by Brink and his associates (2018) and compare them with the World Health Organization (WHO)’s recommendations (2018). Finally, measurement protocols are also compared across outdoor noise policies. This paper shows that road noise is managed at several administrative levels using approaches that are either centralized or decentralized. We also observed disparities in the associated noise limits across geographic areas. The converted outdoor noise limits generally exceeded the WHO’s recommendations (2018). Finally, this paper outlines how outdoor measurement protocols vary across geographic areas. However, similarities were identified between state and provincial noise policies within the same country.

Published
2022

21. Noise from outdoor music activities: selected recommendations dedicated to Quebec municipalities

Author

Perna, Maxime, Padois, Thomas, Doutres, Olivier, Dupont, Thomas, Laboratoire d'Analyse Vibratoire et Acoustique (LAVA), École Polytechnique de Montréal (EPM), Département de génie mécanique, and Ecole de Technologie Supérieure [Montréal] (ETS)

Subjects
[PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], outdoor leisure activities, environmental noise, limit values, noise management, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph]
Abstract

International audience; Through a governmental health prevention policy, the Quebec government decided to take actions in order to reduce the effects of environmental noise on the health and quality of life of the population. According to a recent interdepartmental action plan, a priority action was to give recommendations to municipalities and event promoters for the following outdoor leisure activities: music, fireworks, shooting ranges, and car racing. The population of interest were the attendees potentially exposed to high noise levels and the residents living close to the venues. This study is based on: (i) a literature review of regulations, scientific papers and reports from Quebec, Europe and Australia, (ii) a consultation campaign involving Quebec municipalities, event promoters and acoustic consultants and (iii) acoustic measurements carried out during leisure activities in Quebec. Acoustic descriptors, limit values, monitoring methods, planning methods, management plan and mitigation practices are presented. The documents analysis shows that the limit values should be set for all Quebec municipalities in order to protect the hearing health of attendees (limit values defined by the province of Quebec or Canada). To protect the well-being of residents, it is recommended that each regulations be defined and adapted to the local context of each municipality and events.

Published
2020
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22. Municipal noise regulations in Quebec

Author

Trudeau, Christopher, Bild, Edda, Padois, Thomas, Perna, Maxime, Dumoulin, Romain, Dupont, Thomas, Guastavino, Catherine, Département de génie mécanique, Ecole de Technologie Supérieure [Montréal] (ETS), Laboratoire d'Analyse Vibratoire et Acoustique (LAVA), École Polytechnique de Montréal (EPM), Institut de Chimie de Clermont-Ferrand (ICCF), SIGMA Clermont (SIGMA Clermont)-Institut de Chimie du CNRS (INC)-Université Clermont Auvergne [2017-2020] (UCA [2017-2020])-Centre National de la Recherche Scientifique (CNRS), McGill University = Université McGill [Montréal, Canada], Centre Interdisciplinaire de Recherche en Musique, Médias et Technologie [Montréal] (CIRMMT), Schulich School of Music [Montréal], and McGill University = Université McGill [Montréal, Canada]-McGill University = Université McGill [Montréal, Canada]

Subjects
[PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], 13. Climate action, 11. Sustainability, Quebec, noise regulations, environmental noise, limit values, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph]
Abstract

International audience; In Canada, there are three levels of governance (federal, provincial and municipal). We focus here on regulations related to environmental noise at the municipal level in the province of Quebec. We report on the main findings of a systematic review of 114 municipal regulations. The review covered regulations from 74 cities in Quebec, selected based on five criteria: size, geographical region, economic activity, proximity to major transportation infrastructure, and presence of outdoor recreational events. All official and up-to-date legal documents related to environmental noise were considered, including noise ordinances, rules of peace and order, and environmental protection acts. A qualitative analysis of definitions across documents indicates that environmental noise can be conceived as an acoustic phenomenon, an environmental pollutant, a public health concern, or a quality of life indicator. Other elements refer to the context in which it is experienced, in terms of time of day, zoning, activities and communities affected, as well as the agents producing noise. Furthermore, 35 municipalities include exposure limits in dBA mostly for overall sound level and 16 of them describe the measurement protocol. Most regulations rely on the energetic indicator LAeq,T, sometimes with corrections considering noise characteristics and emergence from the background noise. Despite variations across cities, limits typically center around: - 65 dBA outdoors and 45 dBA indoors for daytime, - 50 dBA outdoors and 40 dBA indoors for nighttime. The findings are discussed in light of best practices at the international level, including the World Health Organization guidelines. This research is funded by the Quebec ministries of Health (MSSS) and Environment (MELCC).

Published
2020
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23. Experimental validation of acoustic metamaterials noise attenuation performance for aircraft cabin applications

Author

Ghinet, Sebastian, Bouche, Patrick, Padois, Thomas, Pires, Louis, Doutres, Olivier, Kone, Tenon Charly, Triki, Khaled, Abdelkader, Fahmi, Panneton, Raymond, and Atalla, Noureddine

Subjects
acoustic resonators, cabins (aircraft), yarn, noise abatement, sound insulation, metamaterials, vehicle performance, acoustic noise, architectural acoustics, wool, acoustic variables control, aircraft, porous materials, glass
Abstract

Over the past few decades, various low frequency noise control technology concepts incorporating acoustic metamaterials have been proposed in the literature. The proposed technologies showed promising performance, with a significant noise attenuation rate per thickness unit and are considered as an improved solution when compared to conventional sound insulation materials. Previously presented approaches with layered porous materials and embedded Helmholtz resonators (HR) exhibited considerable potential when tuned at tonal, multi-tonal or narrow frequency bands. In the present study, two noise control solutions were investigated numerically and their noise control performance was validated experimentally in single and double wall configurations when attached to a stiffened curved panel under diffuse field excitation in a sound transmission loss (STL) facility. The first solution comprised glass wool layers and a high flow resistivity micro-perforated screen for broad band noise attenuation. The second solution comprised glass wool layers with embedded HR designed to attenuate the effect of the ring frequency of the curved fuselage panel under diffuse field excitation. The paper discusses the main mechanisms involved in the STL performance of the two noise control solutions in single and double wall configurations., 49th International Congress and Exposition on Noise Control Engineering, INTER-NOISE 2020, August 23-26, 2020, Seoul, Korea

Published
2020

24. Influence of mobility completeness and source behavior on the robustness of component-based transfer path analysis methods: A numerical study

Author

Dare, T., Bolton, S., Davies, P., Xue, Y., Ebbitt, G., Prenant, Simon, Padois, Thomas, Dupont, Thomas, Doutres, Olivier, Dare, T., Bolton, S., Davies, P., Xue, Y., Ebbitt, G., Prenant, Simon, Padois, Thomas, Dupont, Thomas, and Doutres, Olivier

Abstract

Structure borne noise is considered a major contribution to the noise generated inside aircrafts. In order to analyze it, engineering methods have been developed such as Transfer Path Analysis (TPA) and Source Characterisation (SC). These methods are based on active and passive properties of the source and the receiving structure being coupled or decoupled. The theoretical formulation requires mobility according to all Degrees Of Freedom (DOFs) and rotational DOFs represent a challenge for experimental application. To fulfill the mobility matrix, indirect method have been developed and specific sensors have been proposed, resulting in a more complex experimental set-up and an increase in measurement uncertainties. The necessity of assessing the full matrix completeness is thus still questionable. The robustness of these methods with respect to the matrix completeness and the source behavior is investigated numerically in this work. A numerical model has been developed to simulate vibrating sources with simple or complex vibratory behavior and to assess the mobility matrices for any completenesses. Velocity on the receiving structure is used as a target indicator. The influence of source behavior and completeness are discussed and the results show that the required mobility completeness depends on the source behavior.

Published
2021

25. A review of acoustic imaging methods using phased microphone arrays

Author

Merino-Martínez, Roberto, Sijtsma, Pieter, Snellen, Mirjam, Ahlefeldt, Thomas, Antoni, Jerome, Bahr, Christopher J., Blacodon, Daniel, Ernst, Daniel, Finez, Arthur, Funke, Stefan, Geyer, THomas F., Haxter, Stefan, Herold, Gert, Huang, Xun, Humphreys, WIllam M., Leclére, Quentin, Malgoezar, Anwar, Michel, Ulf, Padois, Thomas, Picard, Christophe, Sarradj, Ennes, Siller, Henri, Simons, Dick G., and Spehr, Carsten

Subjects
Phased microphone arrays, Acoustic imaging, Beamforming, Deconvolution, Aeroacoustic measurements
Published
2019
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28. Comparison of the reception plate method and the inverse force method for assessing the power of a dummy vibratory source

Author

Padois, Thomas, Prenant, Simon, Rolland, Valentin, Chérif, Raef, Robin, Olivier, Atalla, Noureddine, Etchessahar, Manuel, Klop, Richard, Laurier Chapleau, Sebastien, Dupont, Thomas, Doutres, Olivier, Padois, Thomas, Prenant, Simon, Rolland, Valentin, Chérif, Raef, Robin, Olivier, Atalla, Noureddine, Etchessahar, Manuel, Klop, Richard, Laurier Chapleau, Sebastien, Dupont, Thomas, and Doutres, Olivier

Abstract

Multiple vibratory sources are integrated in the aircraft. The vibrational power of these sources is injected to the receiving structure through their connections points resulting in annoying acoustic levels in the cabin. This noise, referred to as structure borne noise, could be mitigated if vibrating systems, receiving structures and interfaces between them are well designed. Methods, such as Reception Plate Method (RPM), Inverse Force Method (IFM) or Component-Based Transfer Path Analysis (CB-TPA) have been developed to specify proper design guidelines related to noise mitigation during the design phase. This work focuses on the RPM and IFM, which allow for measuring the power from a vibratory source into a reception plate. Previous works, based on a round-robin evaluation, have shown that the RPM is very sensitive to the experimental test setup. The main errors come from the plate loss factor measurement and spatially-averaged plate velocity, which contribute directly into the power computation. In this work, a similar experimental setup has been developed. The experimental loss factor is obtained with the impulse response decay method and several automatic dB-decays are considered. The number of accelerometers and their positions are also investigated for assessing the spatially-averaged plate velocity. Both analyses allow for determining the RPM power with minimum-maximum deviation curves. The RPM results are compared with the IFM considering one and three translational degrees of freedom using a custom-made dummy source with a controlled tonal behavior varying from low (100 Hz) to high (1200 Hz) frequencies.

Published
2019

29. Using transfer path analysis methods for assessing the velocity response on a plate generated by a dummy vibratory source

Author

Prenant, Simon, Rolland, Valentin, Padois, Thomas, Chérif, Raef, Etchessahar, Manuel, Klop, Richard, Laurier Chapleau, Sebastien, Dupont, Thomas, Doutres, Olivier, Prenant, Simon, Rolland, Valentin, Padois, Thomas, Chérif, Raef, Etchessahar, Manuel, Klop, Richard, Laurier Chapleau, Sebastien, Dupont, Thomas, and Doutres, Olivier

Abstract

Multiple vibratory sources are integrated in the aircraft and rotorcraft. The vibrational power of these sources is injected to the receiving structure through their connection points resulting in annoying acoustic levels in the cabin. This noise, referred to as structure borne noise, could be mitigated if vibrating systems, receiving structures and interfaces between them are well designed. Methods such as Reception Plate Method (RPM) and Component-Based Transfer Path Analysis (CB-TPA) have been developed to specify proper design guidelines related to noise mitigation during the design phase. This paper focuses on the CB-TPA. The main advantage of this method is to predict the vibra-tory behavior of an assembly (source and receiving structure) from the intrinsic properties of its sub-systems. Nevertheless, it is not straightforward to assess these properties because of several experi-mental difficulties such as the completeness of the mobility matrices, a passive property required for both subsystems. The objective of this work is to assess the experimental applicability of two CB-TPA methods on a small scale laboratory setup comprising of a controlled vibratory source mounted onto a flat panel. Two controlled vibratory sources with more or less complex vibratory behaviors have been designed in order to assess the CB-TPA methods sensitivity to matrices incompleteness. Passive and active properties of subsystems are assessed, taking into account 3 translational degrees of freedom. The vibratory response of the assembly generated by the source coupled to the plate is estimated and the impact of the completeness of the subsystem’s characterization is discussed.

Published
2019

30. Acoustic imaging using different weighting functions with the generalized cross correlation based on the generalized mean

Author

Padois, Thomas, Doutres, Olivier, Nelisse, Hugues, Sgard, Franck, Padois, Thomas, Doutres, Olivier, Nelisse, Hugues, and Sgard, Franck

Abstract

The generalized cross correlation (GCC) is a standard technique for estimating time delay between microphone signals. A prefiltering operation by a weighting function may be included to whiten the cross spectrum of the microphones signals. The expected result is a narrow cross correlation function and a more accurate estimation of the time delay. Among the classic weighting functions, the most known is the PHAse Transform (PHAT). The ability of the PHAT weighting function to whiten the cross spectrum of the microphone signals can be improved by adding an exponent or the minimum value of the coherence function to the denominator. Both approaches have shown promising results for time delay estimation. In this work, the aforementioned modifications of the PHAT weighting function are considered for performing acoustic imaging with the classic GCC and the GCC based on the geometric mean. Numerical and experimental measurements are carried out in the case of two acoustic sources in front of a regular microphones array.

Published
2019

31. Noise from outdoor music activities: selected examples of regulations and recommendations

Author

Perna, Maxime, Padois, Thomas, Dumoulin, Romain, Doutres, Olivier, Dupont, Thomas, Perna, Maxime, Padois, Thomas, Dumoulin, Romain, Doutres, Olivier, and Dupont, Thomas

Abstract

According to the World Health Organization, environmental noise features among the top environ-mental risks to physical and mental health and well-being. Environmental noise includes noise pro-duced by transport traffic, industrial activities, neighborhood and leisure activities. Among the lei-sure activities which may cause hearing impairment and environmental noise annoyance include fireworks, shooting ranges, car racing and outdoor music activities; this study focuses on the latter. Examples of regulations from Australia, Belgium, France, United Kingdom and Canada (Québec city and Montréal) are presented. It is shown that regulations are not harmonized, many different indicators, limit values, measurement locations, and measurement times are used to protect attendees or residents living in noise sensitive areas.

Published
2019

34. Earplug comfort: From subjective assessment on the field to objective measurement and simulation using augmented artificial heads

Author

Doutres, Olivier, primary, Sgard, Franck C., additional, Benacchio, Simon, additional, Terroir, Jonathan, additional, Perrin, Nellie, additional, Trompette, Nicolas, additional, Negrini, Alessia, additional, Gaudreau, Marc-André, additional, Jolly, Caroline, additional, Berry, Alain, additional, Gauthier, Philippe-Aubert, additional, Padois, Thomas, additional, and Gauvin, Chantal, additional

Published
2018
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35. BINAURAL BEAMFORMER: AN EARLY PROOF OF CONCEPT FOR WEARABLES AUDIO DEVICES.

Author

Dedieu, Stéphane, Padois, Thomas, and Voix, Jérémie

Abstract

The article focuses on binaural beamforming as a method to enhance speech intelligibility in wearable audio devices by reducing interfering noise sources. Topics discussed include the design and validation of small microphone arrays for behind-the-ear headsets, the implementation of Minimum Variance Distortionless Response (MVDR) beamforming, and the application of a General Sidelobe Canceller (GSC) strategy to further improve noise reduction in real-world conditions.

Published
2023

40. On the use of geometric and harmonic means with the generalized cross-correlation in the time domain to improve noise source maps

Author

Padois, Thomas, Doutres, Olivier, Sgard, Franck, Berry, Alain, Padois, Thomas, Doutres, Olivier, Sgard, Franck, and Berry, Alain

Abstract

Microphone array techniques are an efficient tool to detect acoustic source positions. The delay and sum beamforming is the standard method. In the time domain, the generalized cross-correlation can be used to compute the noise source map. This technique is based on the arithmetic mean of the spatial likelihood functions. In this study, the classical arithmetic mean is replaced by the more standard generalized mean. The noise source maps provide by the arithmetic, geometric and harmonic means are compared in the case of numerical and experimental data obtained in a reverberant room. The geometric and harmonic means provide the best noise source maps with no side lobes and a better source level estimation.

Published
2016

41. Time domain source localization technique based on generalized cross correlation and generalized mean

Author

Padois, Thomas, Doutres, Olivier, Sgard, Franck, Berry, Alain, Padois, Thomas, Doutres, Olivier, Sgard, Franck, and Berry, Alain

Abstract

Microphone arrays have become efficient tools to localize sound acoustic sources. The standard method is the delay and sum beamforming which can be used in the frequency or time domain. In the frequency domain, the cross spectral matrix of the microphone signals is used to generate the noise source map. Therefore, the processing has to be done frequency by frequency. To improve noise source maps, deconvolution or inverse methods can be utilized. However, these methods increase the computation time and may require user-defined parameters. In the time domain, the generalized cross-correlation of the microphone signals is used to compute the noise source map. The generalized cross-correlation of a microphone pair signal provides the spatial likelihood functions. Then, these spatial likelihood functions are averaged to generate the noise source map. This map is composed of a main lobe which leads to the source position together with side and spurious lobes which may prevent the localization of the source. The spatial likelihood functions averaging process is commonly based on the arithmetic mean. In this study, averaging based on the generalized mean is considered to improve the source localization. Several source-microphone array configurations are numerically computed. Noise source maps obtained with geometric and harmonic means are compared with that based on the classical arithmetic mean. The geometric and harmonic means are shown to provide the best noise source maps with few side lobes. The effect of the number of microphones on the noise source map quality is also investigated.

Published
2016

45. Localisation de source acoustique en soufflerie anéchoïque par deux techniques d’antennerie : formation de voies et retournement temporel numérique

Author

Padois, Thomas, Université de Poitiers, Christian Prax, and Vincent Valeau

Subjects
[SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], aeroacoustic, time reversal, soufflerie anéchoïque, beamforming, formation de voies, retournement temporel, localisation, linearized Euler equations, équations d’Euler linéarisées, aéroacoustique, méthodes numériques, numerical methods, anechoic wind tunnel
Abstract

Beamforming (BF) is a powerful technique to localise sound sources in a wind-tunnel, but theflow effects on the acoustic propagation should be taken into account. An experiment is carried outin an anechoic wind-tunnel in order to validate the BF treatment associated to flow corrections.The results show that the BF technique can estimate very accurately the position of the source. However, the experiments are limited by the low speed of the wind-tunnel. So, a numerical code solving the linearized Euler equations (EEL) is used to simulate different flow conditions. We show that the apparent position shifting of the source, due to the effects of the flow is roughly proportional to the product of the Mach number by the thickness of the uniform flow. Furthermore, we show that the corrections remain robust for a higher Mach number. Then we present a new method for localising a source in a wind-tunnel based on the time-reversal technique. We show that EEL are invariant under time-reversal in changing the direction of the flow velocity. The experimental signals obtained are time-reversed and the backpropagation is performed numerically. The results show that it is possible to localise the source position, without BF assumptions and without flow corrections. The ability of the method to localise an intermittent aeroacoustic source is highlighted.; Le développement croissant des moyens de transport a engendré des nuisances sonores en zone urbaine et périurbaine. Pour pallier ce problème les industriels sont amenés à effectuer des études en vue de la réduction du bruit. La première étape de ce travail consiste à localiser les zones responsables de la production sonore. Le traitement d’antenne microphonique associé à la formation de voies (beamforming) est une méthode classique et robuste de localisation de sources sonores. Dans le cas de sources aéroacoustiques, cette technique d’imagerie peut être appliquée in situ, engendrant un coût important, ou en soufflerie anéchoïque. L’application de cette technique à des mesures en soufflerie permet ainsi de localiser des sources de bruits dans un écoulement, mais les effets de l’écoulement sur la propagation doivent être pris en compte pour une localisation optimale. Une expérience de localisation de source est mise en place dans la soufflerie anéchoïque Eole afin de valider le traitement par formation de voies associé aux corrections des effets de l’écoulement. Deux modèles correctifs distincts sont testés (modèle d’Amiet et modèle de Koop). Les résultats montrent que cette technique permet d’estimer très précisément la position de la source acoustique. De plus, nous montrons que les effets de l’écoulement sur la propagation sont bien indépendants de la longueur d’onde acoustique. Cependant, les moyens techniques limitent l’étude sur la localisation de source à de faibles vitesses, ainsi un code numérique résolvant les équations d’Euler linéarisées est utilisé afin de simuler des conditions d’écoulement plus diverses. Nous mettons en évidence que le décalage apparent de la position de la source, dû aux effets de convection et réfraction des ondes acoustiques, est approximativement proportionnel au produit du nombre de Mach par l’épaisseur d’écoulement uniforme. De plus, nous montrons que les deux corrections testées demeurent robustes même pour un nombre de Mach élevé. Dans une seconde partie nous présentons une méthode originale de localisation de source pour l’aéroacoustique s’appuyant sur une technique connue en acoustique, le retournement temporel. Contrairement à la formation de voies, cette méthode ne fait aucune hypothèse sur le rayonnement de la source et sur la distance source-antenne. Nous montrons que les équations d’Euler linéarisées autour d’un écoulement moyen sont invariantes par retournement temporel en changeant le sens de l’écoulement moyen. Puis une étude numérique des capacités d’un miroir à retournement temporel pour la localisation de source monopolaire ou dipolaire en soufflerie est réalisée. Finalement des expériences sont menées en soufflerie; les signaux obtenus sont retournés temporellement et la phase de rétropropagation est réalisée numériquement. Les résultats montrent qu’il est possible de localiser la position de la source sans les hypothèses liées à la formation de voies et sans correction des effets de l’écoulement. De plus, les capacités de la méthode à localiser une source aéroacoustique intermittente sont mises en évidence.

Published
2011

46. Sound source localisation in a anechoic wind-tunnel by two microphone array techniques : Beamforming and numerical time reversal

Author

Padois, Thomas and Legrand, Mathias

Subjects
[SPI.ACOU] Engineering Sciences [physics]/Acoustics [physics.class-ph], aeroacoustic, time reversal, soufflerie anéchoïque, beamforming, formation de voies, retournement temporel, localisation, linearized Euler equations, équations d’Euler linéarisées, aéroacoustique, méthodes numériques, numerical methods, anechoic wind tunnel
Abstract

Beamforming (BF) is a powerful technique to localise sound sources in a wind-tunnel, but theflow effects on the acoustic propagation should be taken into account. An experiment is carried outin an anechoic wind-tunnel in order to validate the BF treatment associated to flow corrections.The results show that the BF technique can estimate very accurately the position of the source. However, the experiments are limited by the low speed of the wind-tunnel. So, a numerical code solving the linearized Euler equations (EEL) is used to simulate different flow conditions. We show that the apparent position shifting of the source, due to the effects of the flow is roughly proportional to the product of the Mach number by the thickness of the uniform flow. Furthermore, we show that the corrections remain robust for a higher Mach number. Then we present a new method for localising a source in a wind-tunnel based on the time-reversal technique. We show that EEL are invariant under time-reversal in changing the direction of the flow velocity. The experimental signals obtained are time-reversed and the backpropagation is performed numerically. The results show that it is possible to localise the source position, without BF assumptions and without flow corrections. The ability of the method to localise an intermittent aeroacoustic source is highlighted., Le développement croissant des moyens de transport a engendré des nuisances sonores en zone urbaine et périurbaine. Pour pallier ce problème les industriels sont amenés à effectuer des études en vue de la réduction du bruit. La première étape de ce travail consiste à localiser les zones responsables de la production sonore. Le traitement d’antenne microphonique associé à la formation de voies (beamforming) est une méthode classique et robuste de localisation de sources sonores. Dans le cas de sources aéroacoustiques, cette technique d’imagerie peut être appliquée in situ, engendrant un coût important, ou en soufflerie anéchoïque. L’application de cette technique à des mesures en soufflerie permet ainsi de localiser des sources de bruits dans un écoulement, mais les effets de l’écoulement sur la propagation doivent être pris en compte pour une localisation optimale. Une expérience de localisation de source est mise en place dans la soufflerie anéchoïque Eole afin de valider le traitement par formation de voies associé aux corrections des effets de l’écoulement. Deux modèles correctifs distincts sont testés (modèle d’Amiet et modèle de Koop). Les résultats montrent que cette technique permet d’estimer très précisément la position de la source acoustique. De plus, nous montrons que les effets de l’écoulement sur la propagation sont bien indépendants de la longueur d’onde acoustique. Cependant, les moyens techniques limitent l’étude sur la localisation de source à de faibles vitesses, ainsi un code numérique résolvant les équations d’Euler linéarisées est utilisé afin de simuler des conditions d’écoulement plus diverses. Nous mettons en évidence que le décalage apparent de la position de la source, dû aux effets de convection et réfraction des ondes acoustiques, est approximativement proportionnel au produit du nombre de Mach par l’épaisseur d’écoulement uniforme. De plus, nous montrons que les deux corrections testées demeurent robustes même pour un nombre de Mach élevé. Dans une seconde partie nous présentons une méthode originale de localisation de source pour l’aéroacoustique s’appuyant sur une technique connue en acoustique, le retournement temporel. Contrairement à la formation de voies, cette méthode ne fait aucune hypothèse sur le rayonnement de la source et sur la distance source-antenne. Nous montrons que les équations d’Euler linéarisées autour d’un écoulement moyen sont invariantes par retournement temporel en changeant le sens de l’écoulement moyen. Puis une étude numérique des capacités d’un miroir à retournement temporel pour la localisation de source monopolaire ou dipolaire en soufflerie est réalisée. Finalement des expériences sont menées en soufflerie; les signaux obtenus sont retournés temporellement et la phase de rétropropagation est réalisée numériquement. Les résultats montrent qu’il est possible de localiser la position de la source sans les hypothèses liées à la formation de voies et sans correction des effets de l’écoulement. De plus, les capacités de la méthode à localiser une source aéroacoustique intermittente sont mises en évidence.

Published
2011

49. Traitement d'antenne appliqué aux mesures en soufflerie: Prise en compte des effets de l'écoulement sur la propagation au moyen d'un modèle numérique

Author

Padois, Thomas, Prax, Christian, Valeau, Vincent, Leclere, Quentin, Société Française d'Acoustique - SFA, Institut Pprime (PPRIME), and ENSMA-Centre National de la Recherche Scientifique (CNRS)-Université de Poitiers

Subjects
[SPI.ACOU]Engineering Sciences [physics]/Acoustics [physics.class-ph], Traitement d'antenne, [SPI.ACOU] Engineering Sciences [physics]/Acoustics [physics.class-ph], Écoulement cisaillé, Équations d'Euler linéarisées, Réfraction, [PHYS.MECA.ACOU] Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph]
Abstract

National audience; Les trente dernières années ont vu une réduction importante du niveau de bruit des moteurs. Ainsi, l'attention s'est recentrée sur les sources de bruit aérodynamique et la localisation de sources aéroacoustiques est devenue un enjeu considérable. Une méthode de localisation classique et robuste est le traitement d'antenne microphonique associé à la formation de voies (beamforming). L'application de cette technique à des mesures en soufflerie permet ainsi de localiser des sources de bruits dans un écoulement mais les effets de l'écoulement sur la propagation doivent être pris en compte pour une localisation optimale. Ainsi, nous avons mis en place un code de propagation acoustique basé sur la résolution des équations d'Euler linéarisées (EEL). Ce code numérique nous permet de simuler la propagation acoustique d'un monopole rayonnant dans un écoulement uniforme séparé de l'air au repos par une couche de cisaillement, puis d'obtenir la pression acoustique sur une antenne microphonique. Un traitement d'antenne associé à une correction des phénomènes de convection dans la zone de l'écoulement uniforme et de réfraction dans la couche de cisaillement nous permettent ainsi de localiser avec précision la source pour différents nombres de Mach et différentes épaisseurs de la couche de cisaillement. Nous montrons que le rapport de la longueur d'onde sur l'épaisseur de couche de cisaillement n'influe pas sur la correction et que la correction est robuste suivant le nombre de Mach. La validité des corrections obtenues à partir d'un modèle analytique est également vérifiée. Enfin le traitement d'antenne corrigé est validé par des expériences menées en soufflerie anéchoïque.

Published
2010

50. EFFECT OF THE ERROR ON THE SOUND SPEED AND MICROPHONE POSITION ON ACOUSTIC IMAGE OBTAINED WITH A SPHERICAL MICROPHONE ARRAY.

Author

St-Jacques, Julien, Rouard, Kevin, Sgard, Franck, Nélisse, Hugues, Berry, Alain, Quaegebeur, Nicolas, Grondin, François, Boileau, Loic, Doutres, Olivier, and Padois, Thomas

Subjects
ACOUSTIC imaging, MICROPHONE arrays, MICROPHONES, ACOUSTIC wave effects
Abstract

The article discusses the effect of an error on the sound speed and microphones position on the acoustic image. Topics include reducing the noise level in a workplace by using spherical microphone array (SMA); measuring the scattering effect using Spherical Harmonic Beamforming (SHB) and Generalized Cross-Correlation (GCC) algorithm; and it was observed that the SHB is sensitive to an error committed on the microphones position while the GCC is more robust.

Published
2022

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