Many acoustic cues have been proposed as indicators and coordinators of upcoming turn-exchanges in conversational interactions, including syllable rhythm. Rhythmic coordination can help to explain close coordination of speech during these exchanges with intervals on the order of 250 ms or less, or with fluent and non-disruptive overlaps. While general questions surrounding speech rhythm remain unanswered, investigations of syllable alignment across partners in conversation can bypass such questions by assessing directly for patterns that align across vocal exchanges. We develop models of syllable rhythm for this purpose using hand-coded syllable durations from spontaneous conversations and from turn-taking responses elicited by recorded stimuli. Our approach builds on evidence that turn-takers begin planning their utterance approximately 0.5 s prior to turn endings. Syllable duration strings from appropriately identified frames are replaced by Gaussian curves to create oscillatory waveforms, and cross-correlation functions are applied to identify rhythmic continuities across exchanges. Patterns identified using this technique are explanatory of close coordination in the spontaneous exchanges, and supra-syllabic units such as the foot and phrase are identified as well. This syllable framework can be developed further by incorporating additional acoustic measures such as f;o and amplitude to build a multidimensional construct for interactional rhythm alignment.