Effects of tempo and context on jaw openings for vowel in vowel sequence words

Jaw movements were observed using a system which was composed of infrared light emitting diodes and an optical position sensitive detector. The jaw opening for each vowel was measured in the production of vowel sequences at slow and fast speaking rates. The influence of (1) the speaking rate and (2) the context on the jaw opening for each vowel were observed for open vowels; (1) the jaw opening for each vowel at the fast speaking rate was less than that at the slow rate, and (2) the jaw opening for the word-final vowel followed by /d/ in the carrier phrase /desu/ was less than that for the vowel in any other word-internal position. The mechanism of these variations in jaw openings were investigated in terms of the duration and the target of the jaw opening for each vowel. The results suggest that the variations in the jaw opening for the same vowel were caused not only by the under-shoot due to the shortness of the duration, but also by the variation in the target of the jaw opening.