Kinematics of compensatory vowel shortening: Intra and interarticulatory timing

Abstract

The acoustic shortening of vowels has been demonstrated to occur across a variety of contextual variations. The current study examined the kinematic adjustments involved in vowel shortening, as a function of speaking rate and coda composition (singleton consonants versus consonant clusters). Five normal speakers repeated the syllables /paep/, /paeps/, and /paepst/, embedded in a carrier phrase, across three distinct speaking rates (slow, normal, and fast). Changes in the timing of the jaw-closing gesture for post-vocalic bilabial production, and in the upper lip–jaw timing relationship (measured via phase angles), were examined. The onset of the jaw-closing gesture typically shifted earlier in the cycle of jaw movement for consonant cluster productions, across all speaking rates. Subject-specific modifications of interarticulator timing were observed, with some speakers adjusting upper lip movement in order to maintain constant timing with the jaw, while others tended to dissociate the upper lip and jaw. Both coda composition and speaking-rate manipulations resulted in substantial intersubject variability in the lip–jaw timing relationship. These findings suggest that, in order to achieve the intended acoustic-perceptual goals, articulatory coordination may not be absolutely invariant, but rather, systematically and individually organized across task manipulations. [Work supported by CRDF-University of Pittsburgh and NSERC.]