Investigating an Acoustic Measure of Perceived Isochrony in Conversation: Preliminary Notes on the Role of Rhythm in Turn Transitions

In a preliminary investigation of isochrony, the rhythmic integration of talk, we evaluated rhythmic phenomena previously theorized to coordinate turn-transitions for correlates in the acoustic signal. Rhythmic sequencing is one of many elaborate contextualization cues regarded as facilitating a successful turn-transition. Previous studies of rhythm in conversation have attended only to its perceptual and interactional facets. In addressing this gap, our study finds quantitative justification for such claims of rhythmic turn-taking. We selected for acoustic analysis the twelve non-task-based, dyadic conversations of the Santa Barbara Corpus of Spoken American English (SBCSAE). Following Marcus’s (1981) assertion that the onset of the vowel is the closest acoustically-measurable location to the perceptual center of the syllable where the rhythmic downbeat occurs, duration was measured between vowel onsets to create prosodic syllables. Not all prosodic syllables can contain a rhythmic beat, and those that can are characterized as “prominent ” in nature (Couper-Kuhlen 1993). Out of 42,807 prosodic syllables measured, our methods yielded 15,972 prominent prosodic syllables. The units of duration between prominent syllables, hereafter intervals, were judged to form an isochronous sequence when the durations between at least three consecutive intervals varied by less than the conservative measure of the perceptual threshold for tolerance of isochrony, up to a 30 % variance (Couper-Kuhlen 1993)