E. William Yund Thomas R. Crain
VA Med. Ctr., 150 Muir Rd., Martinez, CA 94553
The effect of full-range multichannel compression (MCC) on vowel discrimination was studied in hearing-impaired and normal-hearing subjects. For normal-hearing subjects MCC was fit to four hypothetical flat losses, with thresholds ranging from 60 to 90 dB SPL, and one hypothetical sloped loss, with thresholds normal at 500 Hz and 90 dB SPL at 4 kHz. Each hearing-impaired subject was tested with the flat MCC systems as well as one fit to the subject's own hearing loss profile. Compression ratios varied from 1.75 to 7.00, in the flat MCC, and the number of channels varied from 2 to 31. Robinson--Huntington compression [C. E. Robinson and D. A. Huntington, J. Acoust. Soc. Am. 54, 314 (1973)] had a 10-ms time window in all channels. Unprocessed stimuli and frequency-equalized linear amplification were control conditions. The expected deleterious effects of MCC on vowel discrimination are clear for the most severe compression systems, but preliminary results indicate that they fall off rapidly as the number of channels and compression ratios decrease. Complete results and their implications for the application of MCC in hearing aids will be discussed. [Work supported by Department of Veterans Affairs.]