Vertical hyoid bone displacement and fundamental frequency of phonation.

Vertical displacement of the hyoid bone as well as its effects on F0 were studied using five excised human larynges. Cranial force introduced to the hyoid bone caused a widening of the vestibule of the larynx, enlargement of the laryngeal ventricles, abduction of the ventricular folds, heightening of the epiglottis and slight abduction of the vocal folds. The displacement (X +/- SD) of the anterior part (corpus) of the bone was 8.0 +/- 5.2 mm and of the posterior part, 22.2 +/- 6.1 mm with a 10 N force. The difference was statistically significant and was found to depend mainly on the tight middle hyothyroid ligament. The cranial force displacing the hyoid bone invariably showed a positive relationship with F0. The F0 changes were statistically significant but relatively small (X +/- SD): 8 +/- 8.4 Hz (about 10%) with an intact hyothyroid ligament. When the subglottal pressure was low, a change in the vibratory pattern of the vocal folds was found in several specimens. The F0 changes found in the present study are too small to explain alone the differences in the so-called intrinsic F0 of vowels. However, they are believed to contribute to this phenomenon.