Individualisation d'indices acoustiques pour la synthèse binaurale

Binaural synthesis is a sound spatialization technology, which is the closest to na-tural hearing. It allows the spatialization of a monophonic sound source with only twofilters for a given position. The filters are defined by the HRTFs (Head Related TransferFunction) corresponding to the left and right ear of the listener. The major drawback ofbinaural synthesis is that the HRTF, which are related to the listener's morphology, arestrongly individual. Listening with non-individual HRTF could lead to audible artifacts.Therefore binaural rendering of high quality requires individualized HRTF. This thesistackles the problem of the individualization of binaural synthesis in the framework ofits implementation as a pure delay, the interaural time di®erence (ITD), and a minimalphase filter determined by the magnitude of the HRTF. The work conducted on the ITDvalidates the implementation chosen even for the positions where the HRTF are poorlyminimum phase filters. In addition the ITD calculation methods which are close to per-ception are pointed out. An experimental study is also undertaken to investigate theresolution of the ITD with the elevation angle along the cones of confusion. Perceptualresults indicate that the ITD variation with the elevation angle needs to be reproduced.In order to account for this variation, a new formula is proposed on the basis of thespherical head model. Optimization of the parameters of this formula for a whole ITDdatabase provides an average formulation which is appropriate for a large number of sub-jects and for many applications. Concerning the modeling of the spectral cues (HRTFmagnitude), the Boundary Element Method (BEM) has been examined. It is concludedthat BEM methods are useful in combination with measurement for the modeling ofthe low frequency part. A new approach, which involves statistical learning technique, isproposed for the HRTF prediction. A neural network is built to compute HRTF in anydirection from a limited set of measured HRTF. Preliminary assessment of this modelingshows that the neural network succeeds well in individualizing spectral cues. This resultsuggests a simplified protocol of HRTF measurement : HRTF are measured for only afew directions and the HRTF for the other locations are obtained by the neural network.La synthèse binaurale est la technique de spatialisation sonore la plus proche del'écoute naturelle. Elle permet un rendu spatialisé d'une source monophonique à une po-sition donnée avec seulement deux filtres qui correspondent aux oreilles gauche et droite :les HRTF (Head Related Transfer Function). L'inconvénient majeur de la technique bi-naurale repose sur le fait que les HRTF, liées à la morphologie de l'auditeur, sont propresà chaque utilisateur. Une écoute avec des HRTF non-individuelles comporte des artefactsaudibles. Il faut donc acquérir des HRTF individuelles. Cette thèse aborde le problèmede l'individualisation de la synthèse binaurale dans le cadre de son implémentation en unretard pur, la différence interaurale de temps (ITD), et un filtre à phase minimale déter-miné par le module de la HRTF. Le travail sur l'ITD permet de valider l'implémentationchoisie même pour les positions où les HRTF sont mal décrites par des filtres à phaseminimale et permet de déterminer, parmi les méthodes classiques de calcul de l'ITD,celles qui estiment une ITD proche de la perception. Une étude expérimentale est aussimenée pour établir la résolution de l'ITD avec l'angle d'élévation. Les résultats indiquentla nécessité perceptive de reproduire les variations de l'ITD en élévation. Une nouvelleformule d'estimation de l'ITD créée sur la base d'un modèle de tête sphérique, la formulede déplacement des oreilles (FDO), est développée pour rendre compte de ces variations.L'optimisation des paramètres de cette formule aux ITD de toute une base de donnéesde HRTF permet d'entrevoir une formulation moyenne convenant pour un grand nombrede personne et pour de nombreuses applications. L'étude s'est ensuite focalisée sur lamodélisation du module spectral (filtre à phase minimale). Le travail réalisé sur l'appli-cation des méthodes de calcul par éléments de frontière (BEM pour Boundary ElementMethod) pour l'acquisition de HRTF, indique que cette méthode, peut notamment êtreutilisée en complément des mesures pour l'acquisition de la partie basse fréquence desHRTF. Une approche originale, qui applique des techniques d'apprentissage statistique,est proposée et étudiée pour la modélisation de HRTF. Un réseau de neurones artificiels(RNA) est entra^³né pour calculer des HRTF d'un individu à partir de la connaissancedes HRTF mesurées en un nombre réduit de positions. Les premiers résultats sont en-courageants : le modèle permet d'atteindre un degré assez fin d'individualisation, ce quisuggère un protocole simplifié d'acquisition de HRTF. Un faible nombre de mesures estacquis et les autres sont prédites par le modèle

Individualized HRTFs From Few Measurements: a Statistical Learning Approach

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEEInternational audienceVirtual Auditory Space (VAS) refers to the synthesis and simulation of spatial hearing using earphones and/or a speaker system. High-fidelity VAS requires the use of individualized head-related transfer functions (HRTFs) which describe the acoustic filtering properties of the listener's external auditory periphery. HRTFs serve the increasingly dominant role of implementation 3-D audio systems, which have been realized in some commercial applications. However, the cost of a 3-D audio system cannot be brought down because the efficiency of computation, the size of memory, and the synthesis of unmeasured HRTFs remain to be made better. Because HRTFs are unique for each user depending on his morphology, the economically realist synthesis of individualized HRTFs has to rely on some measurements. This paper presents a way to reduce the cost of a 3-D audio system using a statistical modeling which allows to use only few measurements for each user

Prodromal neuroinflammatory, cholinergic and metabolite dysfunction detected by PET and MRS in the TgF344-AD transgenic rat model of AD: a collaborative multi-modal study

Mouse models of Alzheimer's disease (AD) are valuable but do not fully recapitulate human AD pathology, such as spontaneous Tau fibril accumulation and neuronal loss, necessitating the development of new AD models. The transgenic (TG) TgF344-AD rat has been reported to develop age-dependent AD features including neuronal loss and neurofibrillary tangles, despite only expressing APP and PSEN1 mutations, suggesting an improved modelling of AD hallmarks. Alterations in neuronal networks as well as learning performance and cognition tasks have been reported in this model, but none have combined a longitudinal, multimodal approach across multiple centres, which mimics the approaches commonly taken in clinical studies. We therefore aimed to further characterise the progression of AD-like pathology and cognition in the TgF344-AD rat from young-adults (6 months (m)) to mid- (12 m) and advanced-stage (18 m, 25 m) of the disease.Methods: TgF344-AD rats and wild-type (WT) littermates were imaged at 6 m, 12 m and 18 m with [18F]DPA-714 (TSPO, neuroinflammation), [18F]Florbetaben (A beta) and [18F]ASEM (α7-nicotinic acetylcholine receptor) and with magnetic resonance spectroscopy (MRS) and with (S)-[18F]THK5117 (Tau) at 15 and 25 m. Behaviour tests were also performed at 6 m, 12 m and 18 m. Immunohistochemistry (CD11b, GFAP, Aβ, NeuN, NeuroChrom) and Tau (S)-[18F]THK5117 autoradiography, immunohistochemistry and Western blot were also performed.Results: [18F]DPA-714 positron emission tomography (PET) showed an increase in neuroinflammation in TG vs wildtype animals from 12 m in the hippocampus (+11%), and at the advanced-stage AD in the hippocampus (+12%), the thalamus (+11%) and frontal cortex (+14%). This finding coincided with strong increases in brain microgliosis (CD11b) and astrogliosis (GFAP) at these time-points as assessed by immunohistochemistry. In vivo [18F]ASEM PET revealed an age-dependent increase uptake in the striatum and pallidum/nucleus basalis of Meynert in WT only, similar to that observed with this tracer in humans, resulting in TG being significantly lower than WT by 18 m. In vivo [18F]Florbetaben PET scanning detected Aβ accumulation at 18 m, and (S)-[18F]THK5117 PET revealed subsequent Tau accumulation at 25m in hippocampal and cortical regions. Aβ plaques were low but detectable by immunohistochemistry from 6 m, increasing further at 12 and 18 m with Tau-positive neurons adjacent to Aβ plaques at 18 m. NeuroChrom (a pan neuronal marker) immunohistochemistry revealed a loss of neuronal staining at the Aβ plaques locations, while NeuN labelling revealed an age-dependent decrease in hippocampal neuron number in both genotypes. Behavioural assessment using the novel object recognition task revealed that both WT & TgF344-AD animals discriminated the novel from familiar object at 3 m and 6 m of age. However, low levels of exploration observed in both genotypes at later time-points resulted in neither genotype successfully completing the task. Deficits in social interaction were only observed at 3 m in the TgF344-AD animals. By in vivo MRS, we showed a decrease in neuronal marker N-acetyl-aspartate in the hippocampus at 18 m (-18% vs age-matched WT, and -31% vs 6 m TG) and increased Taurine in the cortex of TG (+35% vs age-matched WT, and +55% vs 6 m TG).Conclusions: This multi-centre multi-modal study demonstrates, for the first time, alterations in brain metabolites, cholinergic receptors and neuroinflammation in vivo in this model, validated by robust ex vivo approaches. Our data confirm that, unlike mouse models, the TgF344-AD express Tau pathology that can be detected via PET, albeit later than by ex vivo techniques, and is a useful model to assess and longitudinally monitor early neurotransmission dysfunction and neuroinflammation in AD.</p

Prodromal neuroinflammatory, cholinergic and metabolite dysfunction detected by PET and MRS in the TgF344-AD transgenic rat model of AD: a collaborative multi-modal study

Mouse models of Alzheimer's disease (AD) are valuable but do not fully recapitulate human AD pathology, such as spontaneous Tau fibril accumulation and neuronal loss, necessitating the development of new AD models. The transgenic (TG) TgF344-AD rat has been reported to develop age-dependent AD features including neuronal loss and neurofibrillary tangles, despite only expressing APP and PSEN1 mutations, suggesting an improved modelling of AD hallmarks. Alterations in neuronal networks as well as learning performance and cognition tasks have been reported in this model, but none have combined a longitudinal, multimodal approach across multiple centres, which mimics the approaches commonly taken in clinical studies. We therefore aimed to further characterise the progression of AD-like pathology and cognition in the TgF344-AD rat from young-adults (6 months (m)) to mid- (12 m) and advanced-stage (18 m, 25 m) of the disease. Methods: TgF344-AD rats and wild-type (WT) littermates were imaged at 6 m, 12 m and 18 m with [18F]DPA-714 (TSPO, neuroinflammation), [18F]Florbetaben (Aβ) and [18F]ASEM (α7-nicotinic acetylcholine receptor) and with magnetic resonance spectroscopy (MRS) and with (S)-[18F]THK5117 (Tau) at 15 and 25 m. Behaviour tests were also performed at 6 m, 12 m and 18 m. Immunohistochemistry (CD11b, GFAP, Aβ, NeuN, NeuroChrom) and Tau (S)-[18F]THK5117 autoradiography, immunohistochemistry and Western blot were also performed. Results: [18F]DPA-714 positron emission tomography (PET) showed an increase in neuroinflammation in TG vs wildtype animals from 12 m in the hippocampus (+11%), and at the advanced-stage AD in the hippocampus (+12%), the thalamus (+11%) and frontal cortex (+14%). This finding coincided with strong increases in brain microgliosis (CD11b) and astrogliosis (GFAP) at these time-points as assessed by immunohistochemistry. In vivo [18F]ASEM PET revealed an age-dependent increase uptake in the striatum and pallidum/nucleus basalis of Meynert in WT only, similar to that observed with this tracer in humans, resulting in TG being significantly lower than WT by 18 m. In vivo [18F]Florbetaben PET scanning detected Aβ accumulation at 18 m, and (S)-[18F]THK5117 PET revealed subsequent Tau accumulation at 25m in hippocampal and cortical regions. Aβ plaques were low but detectable by immunohistochemistry from 6 m, increasing further at 12 and 18 m with Tau-positive neurons adjacent to Aβ plaques at 18 m. NeuroChrom (a pan neuronal marker) immunohistochemistry revealed a loss of neuronal staining at the Aβ plaques locations, while NeuN labelling revealed an age-dependent decrease in hippocampal neuron number in both genotypes. Behavioural assessment using the novel object recognition task revealed that both WT & TgF344-AD animals discriminated the novel from familiar object at 3 m and 6 m of age. However, low levels of exploration observed in both genotypes at later time-points resulted in neither genotype successfully completing the task. Deficits in social interaction were only observed at 3 m in the TgF344-AD animals. By in vivo MRS, we showed a decrease in neuronal marker N-acetyl-aspartate in the hippocampus at 18 m (-18% vs age-matched WT, and -31% vs 6 m TG) and increased Taurine in the cortex of TG (+35% vs age-matched WT, and +55% vs 6 m TG). Conclusions: This multi-centre multi-modal study demonstrates, for the first time, alterations in brain metabolites, cholinergic receptors and neuroinflammation in vivo in this model, validated by robust ex vivo approaches. Our data confirm that, unlike mouse models, the TgF344-AD express Tau pathology that can be detected via PET, albeit later than by ex vivo techniques, and is a useful model to assess and longitudinally monitor early neurotransmission dysfunction and neuroinflammation in AD

Individualisation d'indices acoustiques pour la synthèse binaurale

Binaural synthesis is a sound spatialization technology, which is the closest to na-tural hearing. It allows the spatialization of a monophonic sound source with only twofilters for a given position. The filters are defined by the HRTFs (Head Related TransferFunction) corresponding to the left and right ear of the listener. The major drawback ofbinaural synthesis is that the HRTF, which are related to the listener's morphology, arestrongly individual. Listening with non-individual HRTF could lead to audible artifacts.Therefore binaural rendering of high quality requires individualized HRTF. This thesistackles the problem of the individualization of binaural synthesis in the framework ofits implementation as a pure delay, the interaural time di®erence (ITD), and a minimalphase filter determined by the magnitude of the HRTF. The work conducted on the ITDvalidates the implementation chosen even for the positions where the HRTF are poorlyminimum phase filters. In addition the ITD calculation methods which are close to per-ception are pointed out. An experimental study is also undertaken to investigate theresolution of the ITD with the elevation angle along the cones of confusion. Perceptualresults indicate that the ITD variation with the elevation angle needs to be reproduced.In order to account for this variation, a new formula is proposed on the basis of thespherical head model. Optimization of the parameters of this formula for a whole ITDdatabase provides an average formulation which is appropriate for a large number of sub-jects and for many applications. Concerning the modeling of the spectral cues (HRTFmagnitude), the Boundary Element Method (BEM) has been examined. It is concludedthat BEM methods are useful in combination with measurement for the modeling ofthe low frequency part. A new approach, which involves statistical learning technique, isproposed for the HRTF prediction. A neural network is built to compute HRTF in anydirection from a limited set of measured HRTF. Preliminary assessment of this modelingshows that the neural network succeeds well in individualizing spectral cues. This resultsuggests a simplified protocol of HRTF measurement : HRTF are measured for only afew directions and the HRTF for the other locations are obtained by the neural network.La synthèse binaurale est la technique de spatialisation sonore la plus proche del'écoute naturelle. Elle permet un rendu spatialisé d'une source monophonique à une po-sition donnée avec seulement deux filtres qui correspondent aux oreilles gauche et droite :les HRTF (Head Related Transfer Function). L'inconvénient majeur de la technique bi-naurale repose sur le fait que les HRTF, liées à la morphologie de l'auditeur, sont propresà chaque utilisateur. Une écoute avec des HRTF non-individuelles comporte des artefactsaudibles. Il faut donc acquérir des HRTF individuelles. Cette thèse aborde le problèmede l'individualisation de la synthèse binaurale dans le cadre de son implémentation en unretard pur, la différence interaurale de temps (ITD), et un filtre à phase minimale déter-miné par le module de la HRTF. Le travail sur l'ITD permet de valider l'implémentationchoisie même pour les positions où les HRTF sont mal décrites par des filtres à phaseminimale et permet de déterminer, parmi les méthodes classiques de calcul de l'ITD,celles qui estiment une ITD proche de la perception. Une étude expérimentale est aussimenée pour établir la résolution de l'ITD avec l'angle d'élévation. Les résultats indiquentla nécessité perceptive de reproduire les variations de l'ITD en élévation. Une nouvelleformule d'estimation de l'ITD créée sur la base d'un modèle de tête sphérique, la formulede déplacement des oreilles (FDO), est développée pour rendre compte de ces variations.L'optimisation des paramètres de cette formule aux ITD de toute une base de donnéesde HRTF permet d'entrevoir une formulation moyenne convenant pour un grand nombrede personne et pour de nombreuses applications. L'étude s'est ensuite focalisée sur lamodélisation du module spectral (filtre à phase minimale). Le travail réalisé sur l'appli-cation des méthodes de calcul par éléments de frontière (BEM pour Boundary ElementMethod) pour l'acquisition de HRTF, indique que cette méthode, peut notamment êtreutilisée en complément des mesures pour l'acquisition de la partie basse fréquence desHRTF. Une approche originale, qui applique des techniques d'apprentissage statistique,est proposée et étudiée pour la modélisation de HRTF. Un réseau de neurones artificiels(RNA) est entra^³né pour calculer des HRTF d'un individu à partir de la connaissancedes HRTF mesurées en un nombre réduit de positions. Les premiers résultats sont en-courageants : le modèle permet d'atteindre un degré assez fin d'individualisation, ce quisuggère un protocole simplifié d'acquisition de HRTF. Un faible nombre de mesures estacquis et les autres sont prédites par le modèle

Influence of the ears canals location on spherical head model for the individualized interaural time difference

cote interne IRCAM: Busson04aNone / NoneNational audienceThe spatialization rendering with binaural synthesis is still limited by the individualization of the spatial filters, which are usually composed of a pure delay for the interaural time difference (ITD) and a minimumphase filter for the spectral cues. This paper deals with the individualization of the ITD based on physical modeling. Individualized ITDs are well predicted by a spherical-head model with a customized radius derived from an empiric linear combination of three head anthropometric parameters describing the listener’s head. However it can be observed that the constant ITD contours computed from the spherical-head model are concentric circles, whereas the constant ITD contours extracted from measured HRTFs show deviations from these circles, especially for azimuths near to the interaural axis. The location of the ears with respect to the center of the head seems to be the main factor to reproduce these deviations. The authors propose to introduce a parameter governing the ears’ shifting, so as to break the symmetry of the spherical-head model. This idea leads to a new formula for the computation of individualized ITDs. The formula is tested by comparison with measured data. The authors also examine to what extent the deviations of the measured ITD along the circles contribute to the individualization. Psycho-acoustical experiments are performed to answer this question

Sono-proxy : un capteur non intrusif du comportement de la coquille Saint Jacques

National audienceDans cet article, nous prouvons la faisabilité dʼun suivi comportemental des organismes benthiques in situ sans dérangement en écoutant uniquement les sons quʼils produisent. Notre modèle dʼétude est la coquille Saint-Jacques (Pencten maximus). Ces travaux sont menés dʼune part pour identifier et caractériser les sources de bruit ambiant en milieu très côtier et dʼautre part pour définir un outil de suivi du comportement des organismes vivants marins utilisés par la communauté comme archives biologiques. A partir de mesures en laboratoire et de terrain, nous démontrons que lʼactivité de respiration de la coquille Saint-Jacques est associée à une production sonore mesurable. Cette activité, traduite par une ouverture et une fermeture rapide de la coquille, crée un son transitoire large bande à partir de 10 kilohertz dʼune durée de lʼordre dʼune seconde. Le niveau spectral de cette production sonore excède le bruit ambiant en rade de Brest ou dans lʼarchipel de Molène de 8 dB. Grâce à cet excédent, la portée de détection de ces sons est comprise entre 80 centimètres et 120 centimètres

Individualisation d'indices acoustiques pour la synthèse binaurale

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Higher-order statistics for bioacoustic click detection

National audienceThe passive acoustic monitoring (PAM) is a tool of choice for non-intrusive study of aquatic organisms in the wild. Anthropogenic disturbance may affect animal behavior and should generally be minimised. In this study, a PAM system was used to record the bioacoustic sound produced by the valve movements of the great scallop (\textit{Pecten maximus}). The primary function of PAM system is to detect bioacoustic emissions embedded in the background noise. Sounds produced by the great scallop are transients. Detecting them with power based detector could lead to misses particularly when signal to noise ratio is weak. In this paper, a click detection scheme based on higher-order statistics is applied to the monitoring of the great scallop in its habitat. The detector is effective in tracking the sound produced by the valve movements of the great scallop. The PAM system in association with the click detector represent a promising tool for monitoring, with minimal anthropogenic disturbance, the behavior of minimally mobile aquatic organisms in the wild