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Vandœuvre-lès-Nancy, France

Jean P.,French Scientific and Technical Center for Building | Schmich-Yamane I.,14 rue de Mortillet | Jagla J.,French Scientific and Technical Center for Building | Chevret P.,Institute National Of Recherche Et Securite Inrs
Applied Acoustics | Year: 2016

An original BEM approach is proposed to study the efficiency of desk screens in open plan offices. For large offices the volume geometry can be approximated by two horizontal planes - for floor and ceiling - and the source image approach is used to compute an approximated room Green function. When used in combination with the BEM approach, this allows reducing the discretised boundary to the desks only. The computation of the room Green functions is based on the modelling of the floor and ceiling response by means of the image source approach. The proposed approach is validated both numerically and experimentally. Very significant reductions of computation times have been obtained. The approach is used in an attempt to design efficient desk screens. © 2015 Elsevier Ltd. All rights reserved. Source


Khanfir A.,CNRS Acoustic Lab of Du Maine University | Faiz A.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Ducourneau J.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Chatillon J.,Institute National Of Recherche Et Securite Inrs | Lami S.S.,CNRS Mechanical Energy, Theories, and Applications Laboratory
Journal of Sound and Vibration | Year: 2016

Geometric or acoustical irregularities induces acoustic scattering. In this paper, a generalization of the model proposed by Khanfir et al. [8] (Journal of Sound and Vibration 332 (4) (2013)) to determine the scattered acoustic field above gratings of parallel rectangular cavities is developed, addressing the case of gratings of non-parallel rectangular cavities. The results provided by the model were compared both to numerical results, obtained with the finite element method, and to experimental ones. The observed agreement between the analytical predictions and the numerical and experimental results supports the validity of the proposed model. The coupling between the different cavities was investigated, in order to attain an explanation for its dependence on frequency and on the spacing between cavities. © 2015 Elsevier Ltd. Source


Khanfir A.,Institute National Of Recherche Et Securite Inrs | Faiz A.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Ducourneau J.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Chatillon J.,Institute National Of Recherche Et Securite Inrs | Skali Lami S.,CNRS Mechanical Energy, Theories, and Applications Laboratory
Journal of Sound and Vibration | Year: 2013

The aim of this research project was to predict the sound pressure above a wall facing composed of N parallel rectangular cavities. The diffracted acoustic field is processed by generalizing the Kobayashi Potential (KP) method used for determining the electromagnetic field diffracted by a rectangular cavity set in a thick screen. This model enables the diffracted field to be expressed in modal form. Modal amplitudes are subsequently calculated using matrix equations obtained by enforcing boundary conditions. Solving these equations allows the determination of the total reflected acoustic field above the wall facing. This model was compared with experimental results obtained in a semi-anechoic room for a single cavity, a periodic array of three rectangular cavities and an aperiodic grating of nine rectangular cavities of different size and spacing. These facings were insonified by an incident spherical acoustic field, which was decomposed into plane waves. The validity of this model is supported by the agreement between the numerical and experimental results observed. © 2012 Elsevier Ltd. All rights reserved. Source


Khanfir A.,Institute National Of Recherche Et Securite Inrs | Faiz A.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Ducourneau J.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Chatillon J.,Institute National Of Recherche Et Securite Inrs
41st International Congress and Exposition on Noise Control Engineering 2012, INTER-NOISE 2012 | Year: 2012

The "Institut national de recherche et sécurité" (INRS) is interested to reduce hearing risks in industrial workplaces by improving in situ noise conditions. INRS proposes appropriate solutions to improve the acoustic treatment of facings for noise control at workplace. This requires the development of theoretical and experimental methods of acoustic characterization of wall facings. These walls which possess periodic or aperiodic reliefs scatter sound waves. This work concerns the development of a theoretical model to predict the sound pressure field reflected and scattered over a periodic or an aperiodic grating of rectangular cavities. The chosen model is based on an electromagnetism study of thick slits. It has been adapted to study the acoustic behavior of a rectangular cavity by blocking the bottom of the slit. Then, the model has been generalized for several cavities with different sizes by taking into account effects of coupling. The model has been compared to experimental results obtained for a periodic and an aperiodic grating of 9 rectangular cavities with different sizes and spacings. These facings were insonified by an incident spherical acoustic field. The observed agreement between the numerical and experimental results supports the validity of our model on a wide frequency band. Source


Ducourneau J.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Faiz A.,CNRS Mechanical Energy, Theories, and Applications Laboratory | Chatillon J.,Institute National Of Recherche Et Securite Inrs
Applied Acoustics | Year: 2015

The interior wall facings that delimit industrial rooms are often uneven, i.e. they often have relief, and that causes the sound propagating in such premises to be acoustically scattered. Acoustic prediction software making it possible to plot maps of the sound field in workplaces needs characteristics such as the sound absorption or the sound scattering coefficient of such surfaces. In this work, we propose to obtain experimental this sound scattering coefficient of vertical surfaces in situ thanks to a new measurement. The experimental technique that was originally developed under free-field conditions was adapted to attenuate the echoes coming from reverberation and the noise coming from sources and machines present on the site. For that purpose, a first device has been developed containing a multipolar acoustic array and an impulsive source used respectively for achieving spatial filtering and for separating in time the different echoes. The new device developed and presented in this paper has been used on several measurement campaigns, and it has thus been possible to study, among other things, the reproducibility of the results. Installing a large multipolar array made it possible to obtain good accuracy for the results at low frequencies. The scattering coefficient of a vertical surface containing a rectangular cavity was measured for various angles of incidence in a noisy and reverberant environment. Finally, those measurements made it possible to map the sound scattering coefficient in the XY directions and thus to highlight the highly variable scattering mechanisms of a uneven structure depending on the measurement point. © 2014 Elsevier Ltd. All rights reserved. Source

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