FORMANT TRANSITION DURATION AND SPEECH RECOGNITION IN NORMAL AND HEARING-IMPAIRED LISTENERS

Listeners with sensorineural hearing loss often have difficulty discri minating stop consonants even when the speech signals are presented at high levels. One possible explanation for this deficit is that hearin g-impaired listeners cannot use the information contained in the rapid formant transitions as well as normal-hearing listeners. If this is t he case, then perhaps slowing the rate of frequency change in formant transitions might assist their ability to perceive these speech sounds . In the present study, sets of consonant plus vowel (CV) syllables we re synthesized corresponding to /ba, da, ga/ with formant transitions for each set ranging from 5 to 160 ms in duration. The listener's task was to identify the consonant in a three-alternative, closed-set resp onse task. The results for normal-hearing listeners showed nearly perf ect performance for transitions of 20 ms and longer, whereas the short est transitions yielded poorer performance. A group of eight hearing-i mpaired listeners pure-tone averages (PTAs) ranging from 30 to 62 dB H L) was also tested. The hearing-impaired listeners tended to show poor er performance than the normals for transitions of all durations; howe ver, the performance of a few hearing-impaired subjects was equal to t hat of normals for the shortest-duration transitions. A strong inverse relation was observed between degree of hearing loss and improvement in score as a function of transition duration. These results suggest t hat increasing the duration of formant transitions for listeners with more severe hearing losses may not provide a helpful solution to their speech recognition difficulties. (C) 1997 Acoustical Society of Ameri ca.