Release-from-masking effects provided by a hearing aid digital signal processor

Abstract

Release-from-masking effects provided by a digital hearing aid signal processor utilizing multiple-microphone inputs were evaluated with three measures of speech recognition. Speech recognition measures were monosyllabic word recognition score, reaction time, and subjective rating of the intelligibility of selected passages of continuous discourse. Microphones, placed on KEMAR, recorded speech stimuli embedded in cafeteria noise yielding S/N ratios of 0 and 8 dB SPL. Half of the speech-in-noise stimuli were processed through the hearing aid digital signal processor while half remained unprocessed. The hearing aid processor utilizes a technology similar to adaptive-beamforming to reduce the masking effects of background noise on speech recognition. Unprocessed and processed speech-in-noise stimuli were presented to 10 normally hearing subjects, 10 hearing-impaired subjects, and 10 hearing-impaired individuals fit with linear amplification. Comparison of word recognition scores, reaction times, and intelligibility ratings for the two S/N ratios between unprocessed and processed speech-in-noise stimuli suggest that the hearing aid processing scheme provides significant release-from-masking effects which may improve the recognition of speech in noise for normally hearing and hearing-impaired listeners.