An algorithm to simulate the effects of sensorineural hearing impairment on speech reception was investigated. Like that described by Villchur [J. Acoust. Sec. Am. 62, 665-674 (1977)], this simulation employs automatic gain control in independent frequency bands to reproduce the elevated audibility thresholds and loudness recruitment that are characteristic of this type of loss. In the present implementation, band gains are controlled in an effort to simulate loudness recruitment directly, using recruitment functions that depend only on the magnitude of hearing loss in the band. In a preliminary evaluation, two normal-hearing subjects listened to the simulation matched to hearing losses studied previously [Zurek and Delhorne, J. Acoust. Sec. Am. 82, 1548-1559 (1987)] with noise-masking simulations. This evaluation indicated that the present automatic gain control simulation yielded scores roughly similar to those of both the hearing-impaired listeners and the masked-normal listeners. in the more-detailed evaluation, the performance of three listeners with severe sensorineural hearing loss on several speech intelligibility tests was compared to that of normal-hearing subjects listening to the output of the simulation. These tests included consonant-vowel syllable identification and sentence keyword identification for several combinations of speech-to-noise ratio, frequency-gain characteristic, and overall level. Generally, the simulation algorithm reproduced speech intelligibility well, though there was a clear trend for the simulation to result in better intelligibility than observed for impaired listeners when high-frequency emphasis placed more of the speech spectrum above threshold at higher frequencies. Also, the hearing-impaired listener with the greatest loss showed the largest discrepancies with the simulation. (C) Acoustical Society of America.
