Modeling viscous dissipation during vocal fold contact: the influence of tissue viscosity and thickness with implications for hydration
The mechanics of vocal fold contact during phonation is known to play a crucial role in both normal and pathological speech production, though the underlying physics is not well understood. Herein, a viscoelastic model of the stresses during vocal fold contact is developed. This model assumes the cover to be a poroelastic structure wherein interstitial fluid translocates in response to mechanical squeezing. The maximum interstitial fluid pressure is found to generally increase with decreasing viscous dissipation and/or decreasing tissue elasticity. A global minimum in the total contact stress, comprising interstitial fluid pressure and elastic stress in the tissue, is observed over the studied dimensionless parameter range. Interestingly, physiologically reasonable estimates for the governing parameters fall within this global minimum region. The model is validated against prior experimental and computational work, wherein the predicted contact stress magnitude and impact duration agree well with published results. Lastly, observations of the potential relationship between vocal fold hydration and increased risk of tissue damage are discussed based upon model predictions of stress as functions of cover layer thickness and viscosity.
KeywordsViscoelasticity Contact stress Viscous dissipation Vocal fold hydration Voiced speech modeling
This work was funded in part by the Ontario Ministry of Research and Innovation through the Early Researcher Award program Grant ER13-09-269, the Natural Sciences and Engineering Research Council through Grant 386282-2010, and the Chilean CONICYT through Grants FONDECYT 1151077 and BASAL FB0008.
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