Numerical Analysis of Effects of Transglottal Pressure Change on Fundamental Frequency of Phonation

Abstract

Objectives: In humans, a decrease in transglottal pressure ( Pt) causes an increase in the fundamental frequency of phonation ( F0) only at a specific voice pitch within the modal register, the mechanism of which remains unclear. Methods: In the present study, numerical analyses were performed to investigate the mechanism of the voice pitch-dependent positive change of F0 due to Pt decrease. The airflow and the airway, including the vocal folds, were modeled in terms of mechanics of fluid and structure. Results: Simulations of phonation using the numerical model indicated that Pt affects both the average position and the average amplitude magnitude of vocal fold self-excited oscillation in a non-monotonous manner. This effect results in voice pitch-dependent responses of F0 to Ft decreases, including the positive response of F0 as actually observed in humans. Conclusions: The findings of the present study highlight the importance of considering self-excited oscillation of the vocal folds in elucidation of the phonation mechanism.