Phonovibratory Influences from Offset to Onset in Repeated Phonation

Phonation onset and offset are important aspects of singing and speech. Their execution requires control of timing and coordination of complex vocal fold kinematics, glottal configuration, laryngeal muscular adjustments, and respiration. The purpose of this study was to examine effects of timing and coordination of vocal fold adductory and abductory movements on vocal fold vibratory behavior from offset to onset in a series of repeated phonation gestures, using high-speed digital imaging. Of particular interest were differences in vocal fold adductory positioning for slower and faster tempi; patterns of oscillation during onset and offset for the different tempi, and effects of onset and offset timing events on subsequent vibratory patterns. Method: 11 subjects, all classically trained, experienced professional singers, were videoendoscopically recorded singing a series of repeated notes at two different tempi, using high-speed digital imaging. Vocal fold adductory positioning was measured in terms of relative glottal width during onset in slower and faster tempi. Vocal fold vibratory behavior was measured in timing of offset and onset “events,” number, spacing, and timing of PPOs and pSSOs. Results: Relative glottal widths were significantly smaller for the faster tempo, supporting a hypothesis that vocal agility requires closer vocal fold approximation before onset. Significant differences were found in offset vs. onset timings and numbers of prephonatory and post-steady-state oscillations, supporting a theory of oscillation hysteresis.