| Summary: | The vocal folds in the larynx experience a self-excited oscillation with a wavelike motion during speech owing to interaction with respiratory airflow. The mechanism of the onset of the oscillation remains elusive partly because of compound effects of laryngeal muscles, although its better understanding has clinical significance in determining the ease with which phonation can be achieved. Approaches to the mechanism using a mechanical vocal fold model are useful because it allows investigating the roles of interested parameters in isolation. Here, we designed a mechanical vocal fold model made of a pair of rubber sheets. A key feature of the experimental setup is that it enables observations of high-speed deformation of the oscillating vocal fold model, together with pressure evaluations while changing separately isolated parameters associated with the laryngeal muscle functions. The observations of the oscillation onset demonstrated a gradually developed wavelike oscillation that spreads out over the rubber sheets. The magnitude of the motion is restricted by either increase in rubber restoring force or reduction in flow path width, each of the effects mimics the actual laryngeal muscle functions and reduces, in the experimental results, the threshold upstream pressure that induces the onset of the self-excitation. Thus, the present study highlights close association between degrees of oscillation, flow-tissue interaction, and threshold pressure required for the onset.
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