Articulatory correlates of stress clash rhythms

Linguistic characterizations of English stress patterns typically claim that when one stressed syllable is followed immediately by another and the rhythmic clash is not corrected by retracting the first stress to an earlier position, then the first vowel will be protracted, increasing the phonetic separation between the adjacent beats and thereby regularizing the rhythm. Acoustic studies, however, consistently show that the mean duration for the first vowel in such a stress clash is not substantially longer than that of its counterpart in an alternating stress pattern. Examination of articulatory correlates suggests an explanation for this discrepancy: Syllables in a stress clash may undergo a rhythmic reorganization of segmental gestures that can distance the first syllable's prosodic peak from the following stress without lengthening the vowel's measured duration. Displacements, durations, and peak velocities of jaw opening and closing gestures were measured for four speakers' productions of stress clash sequences Pop posed and alternating stress sequences Pop opposed. In general, the jaw opening gesture was relatively shorter and the closing gesture relatively longer in the stress clash context. If the degree of jaw opening is taken as an approximation to the sonority contour within the syllable, this result means that the prosodic peak occurred relatively earlier within the initial [pap] in Pop posed. [Work supported by the National Science Foundation under grants IRI-8617852 to Mary Beckman and IRI-8617873 to Jan Edwards.]