The influence of speaking rate on the duration of jaw movements

• Published in: Journal of phonetics Vol. 15; no. 2; pp. 111 - 126
• Main Authors: Wieneke, G., Janssen, P., Belderbos, H.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.04.1987; Seminar Press
• DOI: 10.1016/S0095-4470(19)30547-9
• ISSN: 0095-4470

Slowing of speech is a therapeutic procedure for a number of speech disorders. It is not clear why it works. This study focussed on the question whether rate reduction may be beneficial because the articulatory movements become slower or because the periods of time between the movements lengthen. The durations of fast jaw movements were measured in four sentences spoken at four speaking rates by four different subjects. Three types of movement were distinguished: (1) movement associated with a transition between two adjacent phonemes, (2) movement which extended over a whole phoneme, and (3) movement which extended over a sequence of phonemes. Durations of movements of the first type increased much less than total sentence duration as speech was slowed. This effect was quantified by the regression coefficient of movement duration on the total sentence duration, controlled for amplitude changes of the movement. The regression analysis revealed that the increase of movement duration was only 29% of the increase expected on the basis of a proportional relationship with sentence duration. The main conclusion is that the beneficial effect of speaking rate reduction may be related to the lengthening of the periods of time between the movements and consequently may be due to a reduction of kinematic interaction and coarticulation or to increased preparation time.