A computational study of the effects of vocal fold stiffness parameters on voice production.

A three-dimensional flow-structure interaction model of voice production is used to investigate the effect of the stiffness parameters of vocal fold layers on voice production. The vocal fold is modeled as a three-layer structure consisting of the cover, ligament, and body layers. All the three layers are modeled as transversely isotropic materials for which the stiffness parameters include the transverse elastic modulus and longitudinal elastic modulus. The results show that, in addition to the obvious monotonic effects on the fundamental frequency, flow rate and glottis opening, the stiffness parameters also have significant and nonmonotonic effects on the divergent angle, open quotient, and closing velocity. It is further found that the longitudinal stiffness parameters generally have more significant impacts on glottal flows and vocal fold vibrations than the transverse stiffness parameters. The sensitivity analysis shows that, among all the stiffness parameters, the transverse and longitudinal stiffness of the ligament layer have the most dominant effect on most output measures.