The relation between identification and discrimination of vowels in young and elderly listeners

This study examined both the identification and discrimination of vowels by three listener groups: elderly hearing-impaired, elderly normal-hearing, and young normal-hearing. Each hearing-impaired listener had a longstanding symmetrical, sloping, mild-to-moderate sensorineural hearing loss. Two signal levels [70 and 95 dB sound-pressure level (SPL)] were selected to assess the effects of audibility on both tasks. The stimuli were four vowels, /I,e, epsilon, ae/, synthesized for a female talker. Difference limens (DLs) were estimated for both F1 and F2 formants using adaptive tracking. Discrimination DLs for F1 formants were the same across groups and levels. Discrimination DLs for F2 showed that the best formant resolution was for the young normal-hearing group, the poorest was for the elderly normal-hearing group, and resolution for the elderly hearing-impaired group fell in between the other two at both signal levels. Only the elderly hearing-impaired group had DLs that were significantly poorer than those of the young listeners at the lower, 70 dB, level. In the identification task at both levels, young normal-hearing listeners demonstrated near-perfect performance (M = 95%), while both elderly groups were similar to one another and demonstrated lower performance (M = 71%). The results were examined using correlational analysis of the performance of the hearing-impaired subjects relative to that of the normal-hearing groups. The results suggest that both age and hearing impairment contribute to decreased vowel perception performance in elderly hearing-impaired persons.