Abstract:

This study examined the perceptual grouping of the rapid sinusoidal tone sequence ABA--ABA for normal and hearing-impaired listeners. Tone A was fixed at 250, 500, 1000, or 2000 Hz. Tone B started with a frequency well above or below that of tone A, and its frequency was swept toward that of tone A. Listeners had to indicate when they could no longer hear two separate streams (fission boundary). For 12 normally hearing listeners, the fission boundary was roughly independent of the frequency of tone A when expressed as the difference in number of ERBs (delta E) between A and B, consistent with a recent model of stream segregation [M. W. Beauvois and R. Meddis, J. Acoust. Soc. Am. 99, 2270--2280 (1996)]. For four unilaterally hearing-impaired listeners, there was no consistent difference in the delta E magnitudes across ears, even though the auditory filters were broader in the impaired ears. This is not consistent with the theory of Beauvois and Meddis. The ten bilaterally hearing-impaired listeners showed fission boundaries ranging from normal to well above normal. The results are discussed in terms of the factors that might influence perceptual stream formation in hearing-impaired listeners. [Work supported by the Hearing Research Trust.]