Labial and Mandibular Dynamics during the Production of Bilabial Consonants: Preliminary Observations

Abstract

Simultaneous recordings of upper lip, lower lip, and jaw movements concomitant with intramuscular electromyography were obtained from five subjects during the production of VCV tokens where V = /i/, /ε/, and /æ/ and C = /p/, /b/, and /m/. The temporal sequencing of muscle activity from major elevators and depressors of the lips and jaw was determined and incorporated into a preliminary description of the motor control of the bilabial gesture. Magnitudes of articulator displacement and velocity and electromyographic data revealed a trend among the bilabial consonants so that the voiceless stop /p/ was produced with the highest level of preocclusion activity, and the nasal consonant /m/, with the highest level of postocclusion activity. Production of the three stop cognates involved a complementary contribution of aerodynamic and neuromuscular forces in the achievement of the necessary upper articulatory maneuvers. A left-to-right coarticulation effect for jaw depression whereby the EMG level related to V 2 was reduced as V 1 lowered was shown to span the medial stop consonant. A right-to-left coarticulation effect was observed in one speaker whereby jaw elevation was inversely related to the openness of V 2 . Such an anticipatory maneuver was contradictory to more immediate phonetic goals and necessitated neuromuscular compensatory adjustments of the lower lip.