Influence of vocal fold cover layer thickness on its vibratory dynamics during voice production

Abstract

The influence of vocal fold cover layer thickness on the flow-induced vibration and voice production was studied by using a continuum-mechanics based computational model. The cover-body thickness ratio of a three-layer vocal fold was systematically varied. The effect on the vocal fold stiffness, eigenfrequencies and eigenmodes, fundamental frequencies, glottal flow rate, vocal fold vibratory dynamics, and synchronization of the eigenmodes were analyzed by using the structure eigen analysis and flowstructure interaction simulations. It was found that the cover-body layer thickness ratio significantly affected the strength and synchronization of the eigenmodes during flow-structure interactions, and ultimately affected the fundamental frequency and vibration pattern. With the increasing cover-body thickness ratio, the strength of the wave-type higher-eigenfrequency modes increased, and that resulted in a nonlinear bifurcation of the system in which the system evolved from a regular periodic vibration to a periodic doubling vibration and then back to a regular periodic vibration with increased fundamental frequencies. During the transition, the system vibrated chaotically. Because of the increased strength of the wave-type modes, the maximum divergent angle of the glottis was also increased with the increasing cover-body thickness ratio. V

Normative data for certain vocal fold biomarkers among young normophonic adults using ultrasonography

“…This measurement has been proposed as an alternative to assess vocal fold stiffness, which is essential for the generation of mucosal waves [ 13 – 15 ]. The VFL, which is used to study vocal fold behavior [ 16 ], is typically calculated by measuring the length of the vocal fold from the anterior commissure of the arytenoid cartilage to the edge of the vocal process [ 17 ]. Although ultrasonography (USG) has demonstrated great effectiveness in clinical practice for laryngeal examination, there are currently no established norms for laryngeal examination.…”

Impact of Instructed Laryngeal Manipulation on Acoustic Measures of Voice–Preliminary Results

“…29 The cover-body layer thickness ratio significantly affects flow-tissue interactions influencing both fundamental frequency (F0) and vibration pattern. 30 Increased vocal fold thickness (thick TVFM) was believed to result in greater vertical phase difference and longer glottal closure time, leading to stronger harmonic structures. 31 Currently, there is a lack of human-based experiments that have succeeded in simulating the changes in TVFM that take part in phonation.…”