VILLCHUR REVISITED - ANOTHER LOOK AT AUTOMATIC GAIN-CONTROL SIMULATION OF RECRUITING HEARING-LOSS

An algorithm to simulate the effects of sensorineural hearing impairme nt on speech reception was investigated. Like that described by Villch ur [J. Acoust. Sec. Am. 62, 665-674 (1977)], this simulation employs a utomatic gain control in independent frequency bands to reproduce the elevated audibility thresholds and loudness recruitment that are chara cteristic of this type of loss. In the present implementation, band ga ins are controlled in an effort to simulate loudness recruitment direc tly, using recruitment functions that depend only on the magnitude of hearing loss in the band. In a preliminary evaluation, two normal-hear ing subjects listened to the simulation matched to hearing losses stud ied 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 spe ech intelligibility tests was compared to that of normal-hearing subje cts listening to the output of the simulation. These tests included co nsonant-vowel syllable identification and sentence keyword identificat ion 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 tren d for the simulation to result in better intelligibility than observed for impaired listeners when high-frequency emphasis placed more of th e speech spectrum above threshold at higher frequencies. Also, the hea ring-impaired listener with the greatest loss showed the largest discr epancies with the simulation. (C) Acoustical Society of America.