The stop-glide distinction: acoustic analysis and perceptual effect of variation in syllable amplitude envelope for initial /b/ and /w/.

Amplitude change at consonantal release has been proposed as an invariant acoustic property distinguishing between the classes of stops and glides [Mack and Blumstein, J. Acoust. Soc. Am. 73, 1739-1750 (1983)]. Following procedures of Mack and Blumstein, we measured the amplitude change in the vicinity of the consonantal release for two speakers. The results for one speaker matched those of Mack and Blumstein, while those for the second speaker showed some differences. In a subsequent experiment, we tested the hypothesis that a difference in amplitude change serves as an invariant perceptual cue for distinguishing between continuants and noncontinuants, and more specifically, as a critical cue for identifying stops and glides [Shinn and Blumstein, J. Acoust. Soc. Am. 75, 1243-1252 (1984)]. Interchanging the amplitude envelopes of natural /bV/ and /wV/ syllables containing the same vowel had little effect on perception: 97% of all syllables were identified as originally produced. Thus, although amplitude change in the vicinity of consonantal release may distinguish acoustically between stops and glides with some consistency, the change is not fully invariant, and certainly does not seem to be a critical perceptual cue in natural speech.