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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 combination with records of oral air pressure and force of labial contact. The results of this experiment suggested that the lips were moving at a high velocity when the oral closure occurred. They also indicated mechanical interactions between the lips during the closure, including tissue compression and the lower lip moving the upper lip upward. The second experiment studied patterns of upper and lower lip interactions, movement variability within and across speakers, and the effects on lip and jaw kinematics of stop consonant voicing and vowel context. Again, the results showed that the lips were moving at a high velocity at the onset of the oral closure. No consistent influences of stop consonant voicing were observed on lip and jaw kinematics in five subjects, nor on a derived measure of lip aperture. The overall results are compatible with the hypothesis that one target for the lips in bilabial stop production is a region of negative lip aperture. A negative lip aperture implies that to reach their virtual target, the lips would have to move beyond each other. Such a control strategy would ensure that the lips will form an air light seal irrespective of any contextual variability in the onset positions of their closing movements.
Löfqvist et al. (Fri,) studied this question.