Effect of relative amplitude, presentation level, and vowel duration on perception of voiceless stop consonants by normal and hearing-impaired listeners

Previous work on the influence of relative amplitude and presentation level in listeners with normal hearing and those with sensorineural hearing loss was extended to include (1) a comparison of relative amplitude manipulation in the presence of neutral formant transitions versus manipulation of both formant transition and relative amplitude and (2) the additional variable of vowel duration. Synthetic consonant-vowel (CV) stimuli were used, and the amplitude of the burst relative to the vowel in the F4-F5 frequency range was varied across a 20-dB range using a /p-t/ contrast. In experiment I, some stimuli had neutral formant transition values and relative amplitude manipulations; other stimuli had both formant transition and relative amplitude manipulations. For stimuli in experiment II, neutral formant transition values were used, relative amplitude was manipulated, and vowel duration ranged from 14 to 200 ms. Results from experiment I showed no significant difference between listener groups when only relative amplitude information was manipulated, but significant differences when both relative amplitude and formant transition information was present. These results suggest that the listeners with normal hearing weighted the two acoustic cues differently from listeners with sensorineural hearing loss. Results from experiment II indicated that increasing vowel duration generally increased the number of labial responses from listeners with normal hearing, but did not always increase the number of labial responses from listeners with sensorineural hearing loss. (C) 1996 Acoustical Society of America.