Further observations on speech preparatory activity of the jaw
Sandra L. Hamlet, M. Stone, B. Cullison, L. Schoner · The Journal of the Acoustical Society of America · 1978
In a previous paper [S. L. Hamlet and M. Stone, J. Acoust. Soc. Am. 59, S85(A) (1976)] preliminary observations were reported on the relationship between jaw openness prior to speech onset and jaw positions for vowels later in the sentence. Significant correlations between these measures were found. An additional study was undertaken to systematically examine prespeech jaw activity for single words and sentences in relation to jaw activity following acoustical speech onset. Recordings were made while subjects spoke with two different thicknesses of dental prostheses; an experimental procedure which acts to increase the variance in jaw displacements, and thus to better reveal correspondences between prespeech and later jaw positions. Physiological data were obtained using a strain gauge jaw motion transducer. Both jaw displacement and velocity were studied—velocity obtained by analog differentiation of the displacement signal. A prespeech plateau position of the jaw was identified by determining the last velocity zero before the jaw moved into the position for the initial sound. This point occurred on the order of 250 ms before acoustical speech onset. Maximum velocity in the approach to the first sound was also analyzed relative to closing and opening velocities found later in the utterances. Results are interpreted relative to the nature of anticipatory coarticulation and the extent of preplanning of an utterance. [Work supported by NIDR grant DE-03631.]