Speech recognition in continuous and fluctuating maskers by listeners with normal and impaired hearing: Effects of presentation level

Abstract

Listeners with normal hearing show better speech recognition in the presence of fluctuating background sounds, such as a single competing voice, than in unmodulated noise at the same overall level. These performance differences are greatly reduced in listeners with hearing impairment who generally show little benefit from fluctuations in masker envelopes. If this lack of benefit is entirely due to elevated quiet thresholds and the resulting inaudibility of low-amplitude portions of signal+masker, hearing-impaired listeners should show an increasing benefit from masker fluctuations as the presentation levels increase. Normally hearing and hearing-impaired listeners were tested for sentence recognition at moderate and high presentation levels in a competing speech-shaped noise, in competing speech by a single talker, and in competing time-reversed speech by the same talker. Normal-hearing listeners showed more accurate recognition in the fluctuating maskers than in unmodulated noise with some evidence that modulated:unmodulated performance differences may decrease at high presentation levels. Hearing-impaired listeners showed more similar performance across maskers and presentation levels. The results suggest that audibility does not completely account for the group differences in performance with fluctuating maskers: supra-threshold processing differences between groups may also contribute to the disparity in performance. [Work supported by NIH.]