Sequential auditory scene analysis for hearing impaired subjects

Sounds that rapidly follow each other in time tend to be organized into perceptual streams by the auditory system, based on similarity criteria like frequency proximity. Previous studies have shown that spectral differences between temporally-adjacent sounds, if resolved by the peripheral auditory system, strongly promote stream segregation. This may explain why hearing-impaired listeners, whose peripheral frequency resolution is reduced by cochlear damage, display reduced stream segregation "abilities". This, in turn, may account for some of the difficulties that these listeners experience in cocktail-party situations. Recent studies indicate that in the absence of spectral cues, normal-hearing listeners can exploit temporal cues in order to segregate successive sounds. In particular, differences in fundamental frequency between harmonic complexes whose components are unresolved, as well as differences in amplitude-modulation rate between broadband noise bursts, can induce stream segregation. In this study the ability of hearing-impaired subjects to exploit fast temporal envelope cues in order to segregate sounds into streams is investigated. The results of the individual hearing-impaired subjects show better than normal performance in the ability to use temporal envelope cues for streaming. Part of the results were, however, invalidated and further testing is required to decrypt this complex pattern of results.