SPEECH RECOGNITION IN AMPLITUDE-MODULATED NOISE OF LISTENERS WITH NORMAL AND LISTENERS WITH IMPAIRED HEARING

The effect of amplitude-modulated (AM) noise on speech recognition in listeners with normal and impaired hearing was investigated in two exp eriments. In the first experiment, nonsense syllables were presented i n high-pass steady-state or AM noise to determine whether the release from masking in AM noise relative to steady-state noise was significan tly different between normal-hearing and hearing-impaired subjects whe n the two groups listened under equivalent masker conditions. The norm al-hearing subjects were tested in the experimental noise under two co nditions: (a) in a spectrally shaped broadband noise that produced pur e tone thresholds equivalent to those of the hearing-impaired subjects , and (b) without the spectrally shaped broadband noise. The release f rom masking in AM noise was significantly greater for the normal-heari ng group than for either the hearing-impaired or masked normal-hearing groups. In the second experiment, normal-hearing and hearing-impaired subjects identified nonsense syllables in isolation and target words in sentences in steady-state or AM noise adjusted to approximate the s pectral shape and gain of a hearing aid prescription. The release from masking was significantly less for the subjects with impaired hearing . These data suggest that hearing-impaired listeners obtain less relea se from masking in AM noise than do normal-hearing listeners even when both the speech and noise are presented at levels that are above thre shold over much of the speech frequency range.