Time-variation in Mandarin Voiceless Sibilant Spectra

The three Mandarin sibilant fricatives, [s], [sh], and [ç], were studied using a combination of time averaging and ensemble averaging as described by Xu and Wilde [J. Acoust. Soc. Am. 96, 3230 (A) (1994)]. Ten native speakers of Beijing Mandarin (5 male and 5 female) produced these fricatives followed by both unrounded and rounded high vowels. Time- averaged spectra were obtained by averaging 13 consecutive 8-ms FFT windows over 20-ms intervals. Token-ensemble-averaged spectra were then obtained by averaging over the time-averaged spectra of 10 repetitions of each sentence produced by each speaker at time-normalized locations in the utterances. Further ensemble-averaging was also performed over the male and female speakers separately to obtain group-ensemble- averaged spectra. Preliminary examination of both token-ensemble- averaged and group-ensemble-averaged spectra reveals that (a) Mandarin sibilants have substantial time variation in their noise spectra, indicating continuous articulatory movement throughout the production of the frication; and (b) all three sibilants manifest substantial spectral variation due to anticipatory coarticulation with the following vowel. This kind of variation is evident from the very beginning of the frication noise, indicating that the extent of the anticipatory coarticulation may go beyond the beginning of the frication. [Work supported by NIH.]

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