Simulation of multiple source vocalization in the larynx: How true folds, false folds, and aryepiglottic folds may interact

Abstract

Purpose: This study was a modest beginning to determine dominance and entrainment between three soft tissues in the larynx that can be set into flow-induced oscillation and act as sound sources. The hypothesis was that they interact as coupled oscillators with observable bifurcations as energy is exchanged between them. Methodology: The true vocal folds, the ventricular (false) folds, and the aryepi-glottic folds were part of a soft-walled airway that produced airflow for sound production. The methodology was computational, based on a simplified Navier- Stokes solution of convective and compressible airflow in a variable-geometry airway. Results: Three serially connected sources could all produce flow-induced self-oscillation with soft wall tissue and small cross-sectional area. When the glottal cross-sectional areas were similar, bifurcations such as subharmonics, delayed voice onset, and aphonia occurred in the coupled oscillations. Conclusions: Closely spaced sound sources in the larynx are highly interactive. They appear to entrain to the source that has the combined advantage of small cross-sectional glottal area and proximity to a downstream vocal tract that sup-ports oscillation with acoustic inertance.