ASA 127th Meeting M.I.T. 1994 June 6-10

5aPP13. Speech recognition of normal-hearing and hearing-impaired listeners in amplitude-modulated noise.

Laurie S. Eisenberg

Donald D. Dirks

Theodore S. Bell

Div. of Head & Neck Surgery, UCLA School of Medicine, 31-24 Rehab. Ctr., Los Angeles, CA 90024

Nonsense syllables were presented in high-pass, steady-state, and amplitude-modulated (AM) noise to determine whether the release from masking in AM noise was significantly different between normal-hearing and hearing-impaired subjects when the two groups listened under equivalent masker conditions. The normal-hearing subjects were tested in noise under two conditions: (1) in a spectrally shaped noise that produced 1/3-octave band thresholds equivalent to the hearing-impaired subjects; and (2) without the spectrally shaped noise. The release from masking in AM noise was significantly greater for the normal-hearing group than for either the hearing-impaired or masked normal groups. In a second experiment, normal-hearing and hearing-impaired subjects identified nonsense syllables and sentences in steady-state and AM noise at levels adjusted to approximate the spectral shape and gain of a hearing aid prescription. The release from masking was significantly less for the hearing-impaired subjects. These data suggest that hearing-impaired listeners are unable to benefit from the valleys in the amplitude envelope of a fluctuating masker even when both the speech and masker are presented at levels that are audible over much of the speech frequency range. [Work supported by NIDCD and VA R&D.]