Intrinsic factors of releasing motions in an articulator: On assuming segmental input in speech-production models

Abstract

Prominent models of speech production use serial input that is assumed to be commensurate with linguistic segments. The view is that such units underlie a serial activation of aperture motions such as closing and opening motions of the lips in articulating a bilabial stop. This is incompatible with conventional EMG observations showing a single burst of activity of labial adductors at the onset of a close-open cycle. The present study examines the spring-like effects of bilabial compression and pressure on labial opening (release) following a relaxation of the orbicularis oris muscle. Using reiterative series [papapapa] produced at increasing intensities, the range and velocity of opening motions of the lower-lip were correlated with lip compression and oral-pressure. The results for three speakers show that pressure and compression are correlated and that these factors account for 45% to 66% of the variance in velocity of lower-lip opening, and for 47% to 73% of the variance in the range of lower-lip opening. These results complement earlier findings of Abbs and Eilenberg (1976) showing the intrinsic effects of muscle elasticity on opening motions of the lips. Close-open cycles in articulators may not reflect segment-by-segment serial activation.