Papers by Manell Zakharia
In a framework of acoustic comfort, an accurate localisation - in range and angles - of the sourc... more In a framework of acoustic comfort, an accurate localisation - in range and angles - of the sources transmitting noise to the driver has been investigated. Such a localisation permits to reduce the predominant sources in priority, in a given frequency range. An experiment has been conducted on a real truck cabin with a single point of excitation. The mechanical excitation was achieved using a shaker, and frequency-modulated signals have been used covering a very wide frequency. Two crossed line arrays of 112 microphones have been employed for reception. Standard wideband beamforming and beam steering have been used on both arrays. For each frequency, the 3D localisation of sources has been achieved. The major sources have been isolated using the Radon transform. A fine analysis was then performed in order to provide their spectral content, in addition to their 3D localisation. For the covering abstract see ITRD E107776.
The inversion of sea bottom properties and, in particular, the knowledge of the sound speed in th... more The inversion of sea bottom properties and, in particular, the knowledge of the sound speed in the seabed is an essential piece of information for sonar performance prediction. In shallow water, both bottom and surface roughness (sea state) can be a factor of error for inversion procedures. The aim of this paper is to assess, in simple cases, the error on inversion procedures due to a limited knowledge of surface roughness and to a mismatch between actual values and the ones used for inversion. Simulations were performed using a conventional normal-mode model (ORCA). Under small roughness approximations, the surface scattering phenomenon was introduced using modal attenuation coefficients. For a given environment and geometry, the acoustic field was computed for fixed sea state and roughness (reference field) and the inversion was achieved for other sets of values. The sound speed in the sediment was recovered by a conventional inversion method based on the Bartlett operator. Several simulations were realized for a wide range of frequency (50-350 Hz) and various sea states (0-4). The estimation error depends on both the mismatch and the frequency as well as on the geometry. It can reach several tens of m/s.
Archiv Fur Hydrobiologie, Feb 4, 1992
Evaluation de la faisabilite d'une detection acoustique de la fraie de l'ombre commun pou... more Evaluation de la faisabilite d'une detection acoustique de la fraie de l'ombre commun pour pallier l'absence de visibilite
Since its introduction in sonar (1975), the major application of synthetic aperture is in side-sc... more Since its introduction in sonar (1975), the major application of synthetic aperture is in side-scan geometry (bottom imaging and mine detection) where azimuthal compression can only be achieved along the sonar trajectory (1D). More recently (2000), other scanning geometries (2D) have been proposed (circular or planar), in order to take advantage of SAS processing in two directions, in particular for object identification or buried objects detection. In previous works, we have shown the possible extension of SAS techniques to planar scanning (longitude, latitude and depth). P-SAS was applied to sub-bottom profiler geometry. The concept was first validated on simulation and tank data and then on sea data obtained in a dump site in the Baltic sea (SITAR project). Extending SAS to a planar geometry is faced to the errors on a trajectory both within a track and between the tracks. Due to the additional degree of freedom, conventional auto-focusing techniques and even trajectory correctio...
Acta acustica (Les Ulis), 2020
The EAA is proud, to announce the "reborn" of Acta Acustica, our new Open Access journal. Acta Ac... more The EAA is proud, to announce the "reborn" of Acta Acustica, our new Open Access journal. Acta Acustica is the only full open access journal controlled by an acoustic association. Acta Acustica will cover all domains of acoustics. As you probably know, more than 20 research-funding agencies have agreed to support the so-called S-plan, that imposes that, starting in 2021, all the peer-reviewed results of projects funded by these agencies must be published in full open access journals and thus distributed worldwide. In order to avoid that the Article Processing Charges become an obstacle for publication for small-revenue institutions, the General Assembly of the EAA has agreed, under the principle of solidarity, to establish a financial support system for the authors belonging to the EAA National Societies. The support rules are detailed on the Journal website: https://www.edpsciences.org/en/publication-charges#aacus Thanks to the involvement and the professionalism of the Editor in Chief, the Associated Editors and all the Reviewers, the last issue of Acta Acustica united with Acustica has been published on time, despite all the operational difficulties encountered the last couple of months with our previous publisher. The same team has accepted to continue serving the EAA and will put both their enthusiasm and professionalism to make Acta Acustica, a top scientific level Journal and transform the first full open access Acoustics Journal controlled by a non-profit association in a great success. The year 2020 sounds like a very important for the EAA and a big challenge for the new board: launching of our new open access Journal, organizing our conference Forum Acusticum and above all make the International year of sound a big success.
The propagation of wideband pulses in multilayered periodic media shows a variable signal structu... more The propagation of wideband pulses in multilayered periodic media shows a variable signal structure depending on the pulse bandwidth B (time resolution). Depending on the ratio between travel time in a layer and the time resolution, the propagated signal can follow different regimes: pulse trains, null (extinction) or dispersive waveform (chirp). The phenomena have been observed both on experimental and simulated data. The simulations have allowed a better understanding the phenomena of velocity dispersion: the presence of a large number of thin layers that could not be separated individually (thickness << time resolution i.e. each individual layer is acoustically "transparent") can affect considerably the propagation and lead to a dispersive "equivalent medium". For such a case, increasing the bandwidth will lead to pulse train structure of propagated signal. Nevertheless, if layer thickness is reduced accordingly, velocity dispersion phenomenon occurs aga...
Sonochemical investigation in polyaniline non aqueous solutions provides useful information in un... more Sonochemical investigation in polyaniline non aqueous solutions provides useful information in understanding the behavior of liquid systems, since inter molecular and intramolecular association, complex formation and related structural changes affects the compressibility of the system which in turn produces variation in ultrasonic velocity. Nowadays the conducting polymers have become the center of gravity of polymers and materials science for the researchers due to their novel electronic and electrical properties. Among the conducting polymers, polyaniline has been extensively studied not alone for its conducting property which can be varied by the degree of doping, but also due to its environmental stability and economic feasibility. The present study seeks to ascertain the nature of the molecular interactions in the frame work of the thermodynamic and related parameters by using sonication. Doped polyaniline materials have been prepared through the oxidative polymerization of ani...
Les performances et limitations des systemes sonar "classiques" a vision laterale etant... more Les performances et limitations des systemes sonar "classiques" a vision laterale etant connues, le besoin croissant en resolution azimutale et en portee a suscite un regain d'interet pour la synthese d'ouverture. Les techniques de traitement d'antenne reposant sur l'hypothese de cibles ponctuelles, il est interessant d'aborder la synthese d'ouverture dans le cadre d'une approche plus complete incluant les proprietes en retrodiffusion de la scene analysee. La scene de reference comprend des cibles etendues rigides situees en champ libre ou posees sur un fond reverberant. Le champ retrodiffusant fait ainsi intervenir: 1) l'echo (deterministe) de la cible, 2) la reverberation de fond (aleatoire) et, 3) l'ombre acoustique de la cible sur le fond. Une premiere interpretation des images synthetiques est proposee, en termes de convolution spatiale, a l'aide de la reponse spatio-temporelle du systeme d'imagerie. On montre qu'une tel...
Dans ce travail, qui est une contribution a la caracterisation acoustique des fonds marins, des m... more Dans ce travail, qui est une contribution a la caracterisation acoustique des fonds marins, des methodes de caracterisation de zones sedimentaires presentant des risques d'instabilite ont ete tout particulierement etudiees. Celles-ci peuvent etre la consequence de la concentration de gaz qui modifie les proprietes de cohesion du sediment. Les travaux realises se decomposent en trois phases. Une etude experimentale en cuve a, tout d'abord, ete menee sur l'instabilite des pentes et de son controle par la mesure des fluctuations des parametres de cisaillement en fonction de la concentration de gaz piege dans le milieu. La combinaison d'approches sonar actif et passif a permis la correlation de la migration du gaz avec l'attenuation des ondes de cisaillement. Les proprietes de ces ondes etant difficiles a mesurer simplement in situ, nous nous sommes orientes vers l'utilisation d'ondes guidees de Stoneley-Scholte, dont les caracteristiques sont intimement liee...
CNRS-CDST / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc
Commonly used in ultrasonic pulse imaging, wideband transducers are becoming more and more popula... more Commonly used in ultrasonic pulse imaging, wideband transducers are becoming more and more popular in sonar area in various areas of application where the time resolution is a paramount issue such as: estimation of time of flight, communication, high resolution imaging, impedance and attenuation measurements, fine echo analysis…. While, for most ultrasonic transducers, the power involved is rather small (about ten watts), for sonar transducers the power may exceeds several tens of kilowatts.
Progress in Underwater Acoustics, 1987
Underwater acoustic navigation systems are based on the detection of responses from immersed tran... more Underwater acoustic navigation systems are based on the detection of responses from immersed transponders. Long baseline systems use a set of immersed transponders to localize a surface ship or an underwater vessel, with respect to the sea bottom.
Advances in experimental medicine and biology, 2012
IEEE Journal of Oceanic Engineering, 2006
The paper deals with a new concept of imaging technique based on planar synthetic aperture sonar ... more The paper deals with a new concept of imaging technique based on planar synthetic aperture sonar (P-SAS). P-SAS processing takes advantage of the overlap of both ping-to-ping and track to track footprints to improve the imaging resolution in both directions. After describing the method, its implementation is discussed. The exact implementation [three-dimensional (3-D)] is defined and an approximated and faster approach [2 two-dimensional (2-D)] is then proposed. The gain in computation time and the possible loss in performances (resolutions, echo amplitude) are investigated by simulating a simple point target. The point spread function is studied in details. The new concept is finally validated by tank experiments (scale about 100) for both proud and buried target imaging.
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Papers by Manell Zakharia