Burst and transition cues to voicing perception for spoken initial stops by impaired- and normal-hearing listeners

The use of cues to voicing perception of initial stop consonants in multiple spoken syllables was studied for moderately/severely hearing-impaired (n = 43) and normal-hearing listeners (n = 12). The test stimuli were ten utterances each of the syllables/baed, gaed, daed, paed, kaed, taed/. The utterances were analyzed acoustically to confirm the presence of certain cues to initial-stop voicing, namely, differences in voice onset time (VOT), aspiration, and vowel-onset values of the first formant and of fundamental frequency (fo). Test conditions were prepared in which different portions of the syllable onsets were either deleted or interchanged for voicing-cognate syllables. Also the fo contour was flattened for syllable pairs via analysis/synthesis using linear predictor code (LPC) processing. The results confirmed that VOT was a strong voicing cue for both the hearing-impaired and normal-hearing listeners. When the aspirations of the voiceless stops were inserted between the release and the vowel of the voiced-stop syllables, the normal-hearing listeners perceived voiceless stops predominantly. The transition portions of the vowel onsets in burstless /baed, gaed, daed/ contained strong cues for voicing perception of /b,g,d/. The hearing-impaired listeners seemed less sensitive than the normal-hearing listeners to the aspiration-presence and the vowel-onset cues. The fo difference at vowel onset appeared to have no cue value for either group of listeners.