Interaction effects in laryngeal and respiratory control of the voice source and vocal fold contact pressure.

Previous studies of laryngeal and respiratory control of the voice source often focus on main effects of individual control parameters but not their interactions. The goal of this study is to systematically identify important interaction effects in laryngeal and respiratory control of the voice source and vocal fold contact pressure in a three-dimensional voice production model. Computational simulations were performed with parametric variations in vocal fold geometry, stiffness, prephonatory glottal gap, and subglottal pressure. The results showed that, while the glottal closure pattern and source spectral shape were dominantly controlled by vocal fold vertical thickness, the prephonatory glottal gap had important effects in thick vocal folds or near phonation onset. Coordinated adjustments in both the prephonatory glottal gap and thickness were required to produce a long duration of the closed phase and strong high-frequency harmonic production. Interaction between subglottal pressure and transverse stiffness was observed in the control of the peak vocal fold contact pressure. The contact pressure was highest in vocal folds with low transverse stiffness when exposed to high subglottal pressure, indicating the importance of maintaining a balance between subglottal pressure and transverse stiffness to minimizing vocal fold injury.