Variation in anticipatory coarticulation with changes in clarity and rate

This study tests the hypothesis that the relative timing, or coarticulation , of articulatory movements at VC and CV boundaries is influenced by both t he listener's requirement for clarity and the speaker's strategy to economi ze effort. Movement and acoustic data were collected from 7 subjects who sp oke in three conditions: normal, clear, and fast. it was predicted that fas t speech would show more coarticulation and clear speech would show less co articulation than normal speech. The speech materials were designed to inve stigate coarticulation in the movements of the upper lip and tongue. They c onsisted of repetitions of [iC(n)U] utterances embedded in carrier phrases, where the number of consonants, n, ranged from 1 to 3. Analyses focused on kinematic measures and the amount of coarticulation (overlap) of the /i-u/ transition movement with the acoustic interval of the /i/. The consonant-s tring duration was longest in the clear speaking condition and shortest in the fast condition. Compared to the normal condition, peak velocities were higher in the fast and clear speaking conditions, indicating increased effo rt. The influences of speaking condition on coarticulation and on the forma nts of the /i/ were small. Thus, even though there was evidence of increase d effort in the clear and fast conditions, the hypothesized effects of a tr ade-off between clarity and economy of effort were minimally evident in for mant values for /i/ and measures of coarticulation.