Processus de séparation perceptive des sources sonores simultanées
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Paris 3Disciplines:
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Abstract EN:
This research seeks to identify the auditory mechanisms at the origin of the segregation of concurrent sound sources. Certain acoustic cues for segregation are recombined in order to clarify the description. Four series of experiments study the auditory mechanisms responsible for the segregation of stimuli within which these cues are present. The first two series investigate the auditory mechanism underlying the use of the cue incoherent frequency modulation. The next two series are concerned with interactions among four cues. The first series of experiments showed that the detection of auditory beats is not solely responsible for the segregation of a study sound played simultaneously with a sound whose fundamental frequency is either diferent or modulated in frequency. The second series of experiments verified that there exists a mechanism which can compare the outputs of different auditory frequency channels and detect whether their frequency modulations are incoherent. If the number of frequency regions contaiging the incoherence is greater, the detection is easier. The auditory system can also combine the information from neighboring frequency channels that have coherent responses. The third series of experimented focussed on the mutually reinforcing interactions among four segregation cues for concurrent sound sources: onset asynchrony, amplitude modulation incoherence, frequency modulation incoherence, and polyperiodicity (or the presence of compenent signals whose periods are different and not integer multiples of one another). The presence of several segregation cues results in an improvement over the performance obtained with a single cue. A predominance of one cue over another is not generally observed, with the exception of amplitude modulation which seems to be a less important cue than the others. The last series of experiments showed that the frequency modulation coherence cue succeeds in reducing the effect of the polyperiodicity cue, but does no have an influence on an intensity difference cue
Abstract FR:
Ce travail recherche quels sont les macanismes auditifs a l'origine de la separation des sources sonores simultanees. Un regroupement de certains indices acoustiques de separation est fait pour en clarifier la description. Puis quatre series d'exeriences cherchent a connaitre les mecanismes auditis responsables de la scision de stimulti dans lesquels ces indices sont presents. Les deux premieres recherchent le mecanisme auditif a l'origine incoherence des modulations de frequence. Les deux suivantes s'interessent aux interactions de quatre indices. La premiere serie d'experiences montre que la detection de battements auditifs n'est pas seule responsable de la separation d'un son fixe joue simultanement a un son dont la frequence fondamentale est differente. La deuxieme serie d'experiences verifie qu'il existe un mecanisme qui peut comparer les sorties des differents canaux frequentiels, et detecter si leurs modulations en frequence sont incohenrentes. Plus le nombre de regions frequentiels, et detecter si leurs modulations en frequence sont detection est aisee. Le systeme auditif peut aussi regrouper les informations de canaux frequentiels voisins ayant des reponses coherentes. La troisieme serie d'experiences porte sur les interactions de quatre indices de separation des sources sonores simultanees: l'asynchronisme, l'incoherence de la modulation d'amplitude, l'incoherence de la modulation de frequence et la polyperiodicite (presence de signaux ayant des periodes differentes qui ne sont pas multiples entiers). La presence de plusieurs indices de separation permet d'ameliorer la performance obtenue avec un seul indice. On ne constate pas la predominance d'un indice sur l'autre, mais la modulation d'amplitude est un indice moins important que les autres. La derniere serie d'experiences montre que la coherence de la modulation de frequence reussit a empecher l'indice de separation polyperiodicite d'operer, mais elle n'a pas d'influence sur l'indice differente d'intensite.