Simulation of Multiple Source Vocalization in the Larynx: How True Folds, False Folds, and Aryepiglottic Folds May Interact
Ingo R. Titze- Speech and Hearing
- Linguistics and Language
- Language and Linguistics
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 aryepiglottic 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 supports oscillation with acoustic inertance.