LIP AND JAW KINEMATICS IN BILABIAL STOP CONSONANT PRODUCTION

This paper reports two experiments, each designed to clarify different aspects of bilabial stop consonant production. The first one examined events during the labial closure using kinematic recordings in combin ation with records of oral air pressure and force of labial contact. T he results of this experiment suggested that the lips were moving at a high velocity when the oral closure occurred. They also indicated mec hanical interactions between the lips during the closure, including ti ssue compression and the lower lip moving the upper lip upward. The se cond experiment studied patterns of upper and lower lip interactions, movement variability within and across speakers, and the effects on li p and law kinematics of stop consonant voicing and vowel context. Agai n, the results showed that the lips were moving at a high velocity at the onset of the oral closure. No consistent influences of stop conson ant voicing were observed on lip and law kinematics in five subjects, nor on a derived measure of lip aperture. The overall results are comp atible with the hypothesis that one target for the lips in bilabial st op production is a region of negative lip aperture. A negative lip ape rture implies that to reach their virtual target, the lips would have to move beyond each other. Such a control strategy would ensure that t he lips will form an air tight seal irrespective of any contextual var iability in the onset positions of their closing movements.