10 An Investigation into the Dynamic Response of Vocal Folds

In phonation process, the vocal folds collision during glottal closure is considered to be a risk factor for pathological development. This research is aimed at designing a dependable finite element (FE) model of the vocal folds for frequency and dynamics analysis and for calculating the impact stress on the vocal folds during glottal closure. A three-dimensional model with irregular geometry and a layered structure has been designed. The measured viscoelastic properties of the vocal-fold mucosa and the transverse isotropic elastic properties of the vocal fold muscle are applied in the model. The frequency and dynamic characters are presented using Abaqus™ software. The FE model is validated by both experimental modal analysis (EMA) model results and in vivo experimental results from the literature. The model's results indicate that

1. The closure process is independent of the subglottal pressure.

2. The glottal opening amplitude and closing velocity vary approximately linear with the subglottal pressure.

3. The maximum impact stress occurs on the mid-area of the inferior surfaces.

4. The impact stress is approximately linear with the subglottal pressure.

5. The impact stress will cause vocal-fold tissue damage when the subglottal pressure is over 800 Pa. The model would help to identify voice disorders such as vocal-fold paralysis and vocal-fold nodules.