550 research outputs found
Design and implementation of a multi-octave-band audio camera for realtime diagnosis
Noise pollution investigation takes advantage of two common methods of
diagnosis: measurement using a Sound Level Meter and acoustical imaging. The
former enables a detailed analysis of the surrounding noise spectrum whereas
the latter is rather used for source localization. Both approaches complete
each other, and merging them into a unique system, working in realtime, would
offer new possibilities of dynamic diagnosis. This paper describes the design
of a complete system for this purpose: imaging in realtime the acoustic field
at different octave bands, with a convenient device. The acoustic field is
sampled in time and space using an array of MEMS microphones. This recent
technology enables a compact and fully digital design of the system. However,
performing realtime imaging with resource-intensive algorithm on a large amount
of measured data confronts with a technical challenge. This is overcome by
executing the whole process on a Graphic Processing Unit, which has recently
become an attractive device for parallel computing
Acoustic survey of the pelagic resources in Senegal, Gambia and Mauretania waters in 1980 : main results from cruises Echosar 1 and Echosar 2 of R/V Capricorne
Block-sparse approach for the identification of complex sound sources in a room
International audienceGeometrical acoustic softwares are necessary to produce auralizations for specific sound environment. Whether the room impulse response computation require point-source and receiver to be of omnidirectional sensitivity, the influence of their directivity on the resulting virtual audio rendering Is relevant. It is then crucial to account for when simulating accurately a calibrate acoustic model.We treats here the case of the source directivity. The use of a spherical surrounding microphone array remains the most natural way to measure it. The source is located inside the delimiting volume. The radiated pressure is sampled at fixed points. The directivity pattern is then computed in term of spherical harmonics functions. But due to hardware complexity, most of the spherical antennas in the litterature have a few number of microphones. This limits the performance of the antenna in term of resolution and bandwidth. Also, decomposition errors can appear with a possible mismatch between the acoustic center of the source and the origin of the array. An additional optimization task is required which increases the complexity of the process.In this paper, we propose a practical strategy, comprising a dedicated algorithm and an array design, to estimate the directivity pattern of complex sound sources. The study takes place in reverberant rooms.Firstly, we describe a greedy-sparse algorithm called Block Orthogonal Matching Pursuit. By this iterative approach, the identification and characterization tasks can be joint in a unique scheme. This facilitates the acoustic center research. However, under non-anechoic conditions, BlockOMP fails because of the free-field propagation assumption. Considering the first reflections to approximate the room transfer function permits to solve the inverse problem. The notion of virtual microphone arrays, based on an analogy with the Image Source Method, is introduced to extend the validity of BlockOMP. Numerical results supply a proof of the concept in a scenario including multiple acoustic sources.Secondly, a large three-dimensional microphone array is deployed. Largeness concerns here in both its dimensions and the number of microphones. The array consists of five sub-planes which surround the entire room where sources are located. The acquisition system comprises digital MEMS microphones chips. The entire signal processing chain is directly integrated on the captor. The microphones are flush mounted on the walls of the room. The true location of the sensors is known, given by an acoustic geometrical calibration step. The 1024 MEMS record synchronously the pressure signal emitted by the sources. From each harmonic spectral component, a sparse spherical harmonics decomposition of each target can be achieved.An experiment is performed to assert the efficiency of the proposed strategy. The goal is to recover the nature of two prototypes of source. They are build from an unbaffled loudspeaker, arranged to show a dipole and a quadripole behaviour. Their directivity pattern are previously measured under controlled conditions using a semi-circular array of 64 microphones. This database serves here as reference. For the experiment, they emit the same signal simultaneous. The results with our system indicates good correlations. Separating both the sound radiating contribution is well achieved. Our last study case deals with the voice directivity measurements. If the dependence with the frequency has been established, the effect of the phonema variation is rarely identified. We demonstrate here that our apparatus constitutes a powerful tool to examine this aspect
Le dimorphisme sexuel de conformation de lâos coxal humain. Bases biologiques et nouvelles applications possibles
Lâimportance du dimorphisme sexuel de lâos coxal humain est une propriĂ©tĂ© trĂšs abondamment exploitĂ©e pour la diagnose sexuelle du squelette. Une analyse morphomĂ©trique basĂ©e sur les concepts de la morphologie mathĂ©matique permet de mettre en Ă©vidence les zones de lâos coxal qui prĂ©sentent le plus fort dimorphisme de conformation. Il sâagit essentiellement de lâilium dans son ensemble, du plan sacrĂ© et du pubis. Le pubis est dĂ©jĂ trĂšs largement utilisĂ© dans les techniques de diagnose sexuelle. Il pourrait ĂȘtre possible de dĂ©velopper et de tester des approches exploitant davantage le dimorphisme sexuel de conformation de lâilium et de sa partie postĂ©rieure. Ceci serait un avantage pour les os coxaux fragmentaires et pourrait Ă©ventuellement ĂȘtre applicable Ă la diagnose sexuelle dâos coxaux de reprĂ©sentants non-modernes du genre Homo.The extent of sexual dimorphism of the human hip bone is a characteristic widely exploited in sex diagnosis of the skeleton. A morphometrical analysis based on the concepts of mathematical morphology allows clear attribution of the areas of the pelvic bone which present the greatest dimorphism in shape. These are the ilium in its entirety, the sacral plane and the pubis. The pubis is already very widely used in techniques of sexual diagnosis. It should be possible to develop and test new approaches which deal more with the conformational dimorphism of the ilium and its posterior part. This would be an advantage in the case of fragmentary pelvic bones and could possibly be used for assessing the sex of pelvic remains of non-modern fossil Homo
Résultats des campagnes Echosar 1 (février 1980) et Echosar 2 (septembre 1980) : prospection des stocks pélagiques le long des cÎtes du Sénégal, de la Gambie et de la Mauritanie
Obstetrical Constraints and the Origin of Extended Postnatal Brain Maturation in Hominin Evolution
The origin of difficult birth is still a matter of debate in obstetrics. Recent studies hypothesized that early hominins already experienced obstructed labor even with reduced neonatal head sizes. The aim of this work is to test this hypothesis using an extant obstetrical sample with known delivery outcomes. Three delivery outcomes (i.e., instrument-assisted, Caesarean section, and vaginal birth) were evaluated using a discriminant analysis based on 131 motherâbaby dyads and 36 feto-pelvic variables. This obstetrical sample was compared with 20 australopithecine âdyadsâ generated from the combination of six pelvic reconstructions (three for Australopithecus afarensis, two for A. africanus, and one for A. sediba) and three fetal head size estimations. The obstetrical analysis revealed that dystocic births can be predicted by pelvic features such as an anteroposteriorly flattened pelvic inlet. Australopithecines shared these pelvic morphologies with humans and had eutocic birth only for infants of 110 g brain size or smaller, equaling a human-like neonatal/adult brain size ratio of 25â28%. Although birth mechanism cannot be deduced, the newborn/adult brain size ratio was likely more human-like than previously thought, suggesting that australopithecines were secondarily altricial to circumvent instances of obstructed labor and subsequently require a prolonged postnatal brain growth period, implying some aspects of life history pattern similar to modern humans
BipĂ©die du babouin olive (Papio anubis) : Ă©tude de la cinĂ©matique articulaire du membre infĂ©rieur au cours de lâontogenĂšse
La bipĂ©die habituelle reprĂ©sente un marqueur morpho- logique, fonctionnel et comportemental de la lignĂ©e humaine. Tous les primates non-humains (PNHs) pratiquent la bipĂ©die spontanĂ©ment, cependant son utilisation reste occasionnelle chez ces espĂšces. LâĂ©tude de la bipĂ©die dans un cadre comparatif est donc primordiale pour comprendre notre Ă©volution. Des Ă©tudes ont rĂ©vĂ©lĂ© que la frĂ©quence dâutilisation de la bipĂ©die semble plus importante chez les jeunes. Le sujet abordĂ© ici est de savoir si u..
Evolution du niveau d'agglomération de nanopoudres d'aluminium : une approche rhéologique
National audienceFrom micrometric size to nanometric size, the increase of the surface energies allows the agglomeration to be preponderant and then, the risks linked to powders are changed. When the toxicity, the inflammation and explosion risks of nanoparticles are mentioned, the agglomerates must be taken into account. The effect of agglomeration in the behavior of nanopowders has been studied from experimental observation of agglomerated nanopowders of aluminum subjected to shear in a powder rheometer. In order to understand the effect of deagglomeration on the powders, the agglomerate strength has been estimated thanks to the porosity of the powder bed contained in the rheometer cell. This one is ranged between 10 kPa and 1 MPa. The rheological tests show that, compared with the micrometric aluminum, the aluminum nanopowders have a peculiar behavior in the Geldart's classification, being in both class A and C. This fact is due to the facility of nanoparticles to agglomerate and to stay agglomerated.Lorsque l'on passe de la dimension micrométrique à la dimension nanométrique, l'augmentation importante des énergies de surface rend prépondérants les phénomÚnes d'agglomération. Ceci modifie l'appréhension des risques liés aux poudres. Pour parler de toxicité, de risques d'inflammation et d'explosion des nanoparticules, nous devons prendre en compte la présence d'agglomérats. L'effet de l'agglomération sur la dispersibilité des nanopoudres a été étudié à partir d'observations expérimentales de nanopoudres agglomérées d'aluminium soumises au cisaillement fourni par un rhéomÚtre à poudres. Pour comprendre l'effet de la désagglomération sur les poudres, nous avons déjà estimé la contrainte d'agglomération mise en jeu à partir de la porosité du lit de poudres contenues dans la cellule du rhéomÚtre. Cette contrainte est globalement ici comprise entre 10 kPa et 1MPa. Les tests en rhéologie ont montré qu'en comparaison avec une poudre d'aluminium micrométrique, les nanopoudres d'aluminium ont un comportement particulier vis-à -vis de la classification de Geldart, appartenant à la fois aux classes A et C, ceci étant du à la facilité des nanoparticules à s'agglomérer et à le rester
The effect of agglomeration on the emission of particles from nanopowders flow
International audienceThis paper suggests an original method to evaluate the possible emission of particles from a nanopowder submitted to a shear stress in dense phase and the resulting degree of agglomeration of the particles released. The method is based upon the monitoring of the rheological signature of the nanopowders, thanks to a powder rheometer. As a function of the increasing shear rate, the powder flow will evolve from the newtonian state (dense powder) to the coulombian state (dense rheofluidified phase). If the shear rate is high enough, the powder will be set in suspension and the kinetic state (a leaner dense phase submitted to particles collisions) will be reached. The shear stress in this state is dependent on the particle or the agglomerate diameter for cohesive powders, which can be then calculated from rheograms. Carbon black and silica nanopowders have been tested and compared to other experiments carried out on non cohesive glass beads microparticles, chosen as reference. For the different glass beads powders, the average value of their 'agglomerate' diameter is 12% different of the primary diameter, indicating agglomeration of less than two particles. Nanometric agglomerates were found to be of hundred micrometers diameter. That is in line with the high tendency of the nanoparticles to agglomerate. This work can be used to evaluate the current safety tests, such as Hartmann's tube or 20 L sphere apparatuses, to verify whether the standard equipment for microparticles is suitable for the use of nanoparticles. This is linked to research projects like NanoSafe 2
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