Eric Vatikiotis-Bateson,
David J. Ostry
An analysis of the dimensionality of jaw motion in speech
Abstract:The human jaw moves in three spatial dimensions, and its motion is fully specified by three orientation angles and three positions. Using OPTOTRAK, we characterize the basic motions in these six degrees of freedom and their interrelations during speech. As has been reported previously, the principle components of jaw motion fall primarily within the midsagittal plane, where the jaw rotates downward and translates forward during opening movements and follows a similar path during closing. In general, the relation between sagittal plane rotation and horizontal translation (protrusion) is linear. However, speakers display phoneme-specific differences in the slope of this relation and its position within the rotation-translation space. Furthermore, instances of pure rotation and pure translation are observed. These findings provide direct support for the claim that jaw rotation and translation are independently controlled (Flanagan, Ostry, & Feldman, 1990). Rotations out of the midsagittal plane are also observed. Yaw about the longitudinal body axis is approximately 3 degrees and roll usually less than 2 degrees. The remaining non-sagittal component, lateral translation, is small in magnitude and uncorrelated with other motions.