Effects of spectral and temporal cues to Mandarin concurrent-vowels identification for normal-hearing and hearing-impaired listeners

In Mandarin Chinese, lexical Tones are inherently bonded with vowels, making both spectral and temporal cues available for speech perception. Temporal cues provided by Tone contrast have been shown facilitating segregation in Mandarin concurrent-vowels identification (MCVI). The present study investigated the effect of spectral cue measured by vowel contrast within the syllable-pair on MCVI, both for normal-hearing (NH) and hearing-impaired (HI) listeners. Acoustic cues of duration and mean F0 difference were carefully controlled. Results exhibited that facilitation from vowel contrast existed for NH listeners but was reduced for HI listeners. Identification score positively correlated with the spectral envelope contrast of different vowel-pairs for both groups, but the coefficient for HI listeners was lower. Further analyses based on a power function model revealed more weighting of temporal cues than spectral cues for NH listeners, while the contributions were equal for HI listeners. These results suggested that the spectral cue provided by vowel contrast could facilitate the MCVI, and auditory processing of temporal cues might be more susceptible to hearing loss than that of spectral cues. These findings have instructions for designing speech processing algorithms for Mandarin-speaking HI listeners.