This study takes place within the theoretical framework of Gestalt theory. The aim of this work is to determine the way the prosodic scene reorganises itself according to the variation of speech rate. In other words: how do the forms constituted by stressed syllables interact with the ground of unstressed syllables?

We present a study of the temporal structure of a one thousand word speech corpus. The corpus was produced at three different rates (normal, fast and slow) by one speaker with two repetitions. The goal is to constrain the rhythmical structure of speech in order to observe how rhythmic patterns depend on the variation of speech rate.

Results show that rhythm is not elastic: temporal structuring produced at a slow rate is not the consequence of a linear decrease. When speech rate changes, syllabic duration does not vary in the same way for stressed and for unstressed syllables. Unstressed syllables have very little elasticity compared with stressed syllables. This last result supports the hypothesis that the unstressed syllable is an anchor point in the rhythmic structure of French.