Phase relations of jaw and tongue tip movements in the production of VCV utterances

Abstract

A previous study by Nittrouer et al. [J. Acoust. Soc. Am. 84, 1653-1661 (1988)] found that the spatiotemporal relations between jaw and upper lip movements for speech were affected not only by the segmental structure of the utterance, but by stress pattern and rate of production, as well. Specifically, the angle on the vowel-to-vowel jaw cycle phase plane at which the upper lip began moving toward closure for an intervocalic consonant varied systematically and discretely with changes in vowel-cycle duration. The development of the X-ray microbeam has permitted the observation of these effects for gestures involving articulators other than the lips and jaw. In the present study, the onset of tongue tip movement for an intervocalic consonant was represented as an angle on the jaw cycle phase plane for vowel-consonant-vowel utterances. Although the tongue tip exhibited greater variability in its movement onset than the upper lip had, the relative phasing of tongue tip movement onset was also found to vary with jaw vowel-cycle duration: Any manipulation that shortened the jaw vowel cycle also served to reduce the phase angle at which the tongue tip began movement. This relation was not found to be continuous in nature, but rather a main effect of phonetic and nonphonetic factors.