Male sperm whale acoustic behavior observed from multipaths at a single hydrophone

Sperm whales generate transient sounds (clicks) when foraging. These clicks have been described as echolocation sounds, a result of having measured the source level and the directionality of these signals and having extrapolated results from biosonar tests made on some small odontocetes. The authors propose a passive acoustic technique requiring only one hydrophone to investigate the acoustic behavior of free-ranging sperm whales. They estimate whale pitch angles from the multipath distribution of click energy. They emphasize the close bond between the sperm whale’s physical and acoustic activity, leading to the hypothesis that sperm whales might, like some small odontocetes, control click level and rhythm. An echolocation model estimating the range of the sperm whale’s targets from the interclick interval is computed and tested during different stages of the whale’s dive. Such a hypothesis on the echolocation process would indicate that sperm whales echolocate their prey layer when initiating their dives and follow a methodic technique when foraging

WG1N5315 - Response to Call for AIC evaluation methodologies and compression technologies for medical images: LAR Codec

This document presents the LAR image codec as a response to Call for AIC evaluation methodologies and compression technologies for medical images.This document describes the IETR response to the specific call for contributions of medical imaging technologies to be considered for AIC. The philosophy behind our coder is not to outperform JPEG2000 in compression; our goal is to propose an open source, royalty free, alternative image coder with integrated services. While keeping the compression performances in the same range as JPEG2000 but with lower complexity, our coder also provides services such as scalability, cryptography, data hiding, lossy to lossless compression, region of interest, free region representation and coding

Étude par acoustique passive du comportement de chasse du grand cachalot

PARIS12-CRETEIL BU Multidisc. (940282102) / SudocSudocFranceF

UTILISATION DU DOSSIER MEDICAL COMME A PRIORI D'OPTIMISATION DU TRAITEMENT DES POTENTIELS EVOQUES AUDITIFS PRECOCES

PARIS12-CRETEIL BU Multidisc. (940282102) / SudocSudocFranceF

Acquisition et construction automatique de la courbe latence-intensité des potentiels évoqués auditifs précoces

International audienc

Détection et reconnaissance des signaux stochastiques transitoires (application à l'identification des mammifères marins)

Ce travail de thèse porte sur la détection et la reconnaissance des clics émis par les cachalots (Physeter macrocephalus). Ces signaux sont de très courte durée, non stationnaire, noyé dans un bruit dont les caractéristiques peuvent varier au cours du temps. Nous proposons une approche originale basée sur la méthode de Schur. Le recours à cette technique paramétrique est intéressant pour plusieurs raisons. Premièrement, la mise à jour des coefficients se fait de façon récursive à la présentation d'un nouvel échantillon de l'enregistrement acoustique. En choisissant un facteur d'oubli adaptatif, il est possible de réduire la phase de convergence et de suivre au plus près les variations des signaux. Deuxièmement, nous déduisons, de l'ensemble des coefficients, l'information permettant de caractériser les clics des cachalots. Nous pouvons ainsi les distinguer des clics de dauphins bleus et blancs (Stenella Coeruleoalba). Troisièmement, nous avons comparé notre détecteur à d'autres techniques classiques utilisées en bioacoustique. Et les performances obtenues justifient notre choix, y compris pour des rapports signal-sur-bruit défavorable. Quatrièmement, nous avons montré que la complexité de calcul permet d'envisager des applications temps-réel. Ceci est particulièrement important dans l'objectif d'implanter cette méthode dans des stations d'observations acoustiques des mammifères marins.This PhD work is based on the detection and the recognition of sperm whale (Physeter macrocephalus) clicks. These signals are short, non-stationary, recorded with time-variant noise. We propose an original approach based on the Schur method. We chose this parametric technique for meany reasons. Firstly, the coefficients are recursively updated at the presentation of each new sample of the acoustic recordings. Because f an adaptative forgetting factor, the convergence step is reduced and the method is well adapted to the variations of these signals. Secondly, the Schur coefficients contain information necessary for characterizing the sperm whale clicks. We can also distinguish these clicks from the striped dolphin (Stenella Coeruleoalba) clicks. Thirdly, we compared our detector to other classical techniques used in bioacoustics. The obtained performance justifies our choice, even for signals with a weak signal-to-noise ratio. Fourthly, we showed that the computation complexity is compatible with real-time applications. This is essential in the objective of applying this algorithm on marine mammal observation stations using passive acoustics.PARIS12-Bib. électronique (940280011) / SudocSudocFranceF

Objective detection of brainstem auditory evoked potentials with a priori information from higher presentation levels

International audienceThis paper describes a brainstem auditory evoked potentials (BAEPs) detection method based on supervised pattern recognition. A previously used pattern recognition technique relying on cross-correlation with a template was modified in order to include a priori information allowing detection accuracy. Reference is made to the patient’s audiogram and to the latency–intensity (LI) curve with respect to physiological mechanisms. Flexible and adaptive constraints are introduced in the optimization procedure by means of eight rules. Several data samples were used in this study. The determination of parameters was performed through 270 BAEPs from 20 subjects with normal and high audiometric thresholds and through additional BAEPs from 123 normal ears and 14 ears showing prominent wave VI BAEPs. The evaluation of the detection performance was performed in two steps: first, the sensitivity, specificity and accuracy were estimated using 283 BAEPs from 20 subjects showing normal and high audiometric thresholds and secondly, the sensitivity, specificity and accuracy of the detection and the accuracy of the response threshold were estimated using 213 BAEPs from 18 patients in clinic.Taking into account some a priori information, the accuracy in BAEPs detection was enhanced from 76 to 90%. The patient response thresholds were determined with a mean error of 5 dB and a standard deviation error of 8.3 dB. Results were obtained using experimental data; therefore, they are promising for routine use in clinic

Acquisition et construction automatique de la courbe latence-intensité des potentiels évoqués auditifs précoces

International audienc