Vocal tract adjustments to minimize vocal fold contact pressure during phonation.

This computational study aims to identify vocal tract adjustments that minimize the peak vocal fold contact pressure during phonation and thus should be targeted in voice therapy treating phonotraumatic vocal hyperfunction. The results showed that for a given subglottal pressure, the effect of vocal tract adjustments on the peak vocal fold contact pressure was generally small except when such adjustments caused noticeable changes in the glottal flow amplitude. In this study, this occurred mainly when the lip opening was reduced and at conditions of large initial glottal angles or high subglottal pressures, which decreased the peak contact pressure but also significantly reduced the output sound pressure level (SPL). On the other hand, increasing lip opening significantly increased sound radiation efficiency from the mouth and reduced the subglottal pressure required to produce a target SPL. Because of the large effect of the subglottal pressure on the peak contact pressure, increasing lip opening thus was able to significantly reduce the peak contact pressure in voice tasks targeting a specific SPL. In contrast, the effect of pharyngeal expansion alone had only a small effect on the peak contact pressure, whether controlling for the subglottal pressure or targeting a specific SPL.