Lip and Jaw Coarticulation for the Phoneme /æ/

Abstract

The timing and coarticulation of jaw lowering and lip retraction was investigated. Meaningful sentences containing sequences of up to four consonants preceding the vowel /æ/ were constructed, and high speed cinefluorographic films were made of four subjects speaking all sequences at normal production rates and effort levels. Curve fitting indicated that the lips and jaw do not behave as second-order mechanical systems responding to a step-function of muscle driving force. Lip retraction was a poor estimate of lip spreading, being small in amount, and variable in starting points. The jaw never achieved target values, and a majority of lip targets were undershot. Articulator target positions based on sustained, isolated phoneme productions are probably not realistic. Jaw displacement and less consistently, lip retraction, extended over two and, in several cases, three consonants preceding /æ/. This result might have been extended had the /s/ phone not been contradictory to one or both gestures. Extensive incoordination of lips and jaw in achieving target positions simultaneously and in starting at like time points was observed. The data were related to several models of articulation.