Lip and jaw movements during altered speaking rates

Abstract

Previous research has shown that lip and jaw movements can vary dramatically with speaking rate. However, few studies have explored lip and jaw movements over a range of contrived speaking rates. The purpose of this investigation was to examine kinematically movement parameters associated with six different rates of speaking (1–6 s). The upper lip, lower lip, and jaw vertical amplitudes of a naive male speaker were transduced via a strain gauge system and recorded concurrent with the speaker's utterances. Consonant-vowel syllables composed of /m, p, k, w/ in combination with the vowels /i/ and /æ/ served as the speech sample. Desired rates of production were obtained by training the subject to synchronize his productions with an audiovisual timing device. The results demonstrated generally increased upper lip amplitudes and reduced jaw amplitudes as the rate of speaking increased. More importantly, lower lip velocity was observed to increase systematically from 1 to 3 s but decreased precipitously at 4 s, and thereafter increased in a pattern similar to that found for the slowest rates. This apparent reorganization at a consistent rate corresponded to voicing and movement variability also associated with an utterance rate of four syllables per second. Discussion will focus upon these variables.