Fluid-structure energy exchange during phonation: investigation of dissipated collision energy by direct measurement of internal tissue velocity

The vocal fold (VF) oscillation kinematics during phonation arise due to the balance between the energy provided by the airflow and that dissipated by the VF tissue, with most of the energy dissipated during the collision phase. Elucidating the mechanics of energy dissipation within the tissue is, therefore, paramount to gaining insight into the dynamics of VF oscillations. Assessing the dissipated collision energy requires computing the kinetic energy of the VF immediately preceding contact, which is a function of the  VF tissue velocity. This study aims to quantify the distribution of the tissue velocity inside a synthetic VF model to calculate the associated dissipated collision energy. Measurements were performed with a multi-layer, self-oscillating silicone VF model in a hemilaryngeal flow facility. Fluorescent particles were mixed and cured within the different silicone layers during fabrication, and then illuminated by a laser sheet during self-oscillation. Digital image correlation was performed with an sCMOS camera to compute the interior VF tissue velocity and calculate the dissipated energy. Results revealed that the velocity magnitude decays quickly as a function of distance from the medial surface, and the VF kinetic energy is mainly limited to the cover layer.