Effects of left‐right asymmetry in vocal fold geometry and stiffness on phonation onset in a physical model.

Abstract

Vocal fold paralysis or paresis often leads to left‐right asymmetry in vocal fold geometry and stiffness. An improved understanding of the influence of such left‐right asymmetry on phonation would allow clinicians to better diagnose and treat these voice disorders. In this study, the effects of such left‐right asymmetry on phonation were investigated using a two‐layer physical vocal fold model. Specific vocal fold parameters investigated included body layer stiffness, cover layer stiffness, cover layer thickness, and cover layer depth. Results showed that a unilateral decrease in vocal fold body layer or cover layer stiffness reduced the phonation threshold pressure and onset frequency to a value that was closer to that of the less stiff fold in symmetric conditions. Unilateral thinning of the cover layer depth caused an increase in phonation threshold pressure and onset frequency, whereas unilateral shortening of cover layer thickness led to a threshold pressure close to the averaged threshold pressures of the two unique geometries in symmetric conditions. The clinical implications of the results were also discussed. [Work supported by the NIH.]