The importance of medial surface vertical thickness to the control of voice production

Abstract

While vocal fold vibration is often studied from a superior view, the vertical thickness of the vocal fold medial surface (or the portion that forms the glottal constriction) has long been hypothesized to play an important role in the control of voice production. This importance of the vertical thickness is confirmed in our recent computational studies, which showed that the vertical thickness, not the degree of vocal fold approximation, has a dominant effect on the vocal fold contact pattern and the spectral shape of the produced voice. Specifically, thicker folds often vibrate with a larger closed quotient, a lower H1-H2 value, and stronger excitation of higher-order harmonics. Thicker folds are also more likely to exhibit irregular vibration. These studies also showed an important effect of the transverse stiffness of the vocal fold in the coronal plane on the resulting voice quality, but a relatively small effect of the longitudinal tension on voice quality except around phonation onset. These results suggest that in addition to the superior view, more attention should be given to vocal fold shape along the vertical dimension and its control. [Work supported by NIH grant R01DC011299.]