The effect of three-dimensional glottal geometry on intraglottal quasi-steady flow distributions and their relationship with phonation

Abstract

Vocal fold geometry plays an important role in human phonation. The intraglottal quasi-steady pressure and velocity distributions depend upon the shape, size, and diameter of the glottis. This study reports the effects of the variation of glottal shapes on intraglottal pressures and velocities using a Plexiglas model with a glottis having nine symmetric glottal angles (uniform, as well as convergent and divergent 5 degrees, 10 degrees, 20 degrees and 40 degrees), while the minimal glottal diameter was held constant at 0.06 cm. The empirical data were supported by penalty finite element computational results. The results suggest that larger convergent glottal angles correspond to increased pressures and decreased velocities in the glottis upstream of the minimum glottal location, with a reversal of this pattern at the minimal glottal diameter location. The pressure dip near the glottal entrance for divergent glottal angles was greatest for the 10 degrees divergence angle condition, and was sequentially less for 5 degrees, 20 degrees, and 40 degrees. Flow resistance was greater for a convergent angle than a divergent angle of the same value, and least for the 10 degrees divergent condition. Pressure recovery in the glottis suggested that the optimal glottal diffuser angle was near 10 degrees. Results suggest that the glottal geometry has a critical relationship with phonation (especially for vocal efficiency), and therefore important significance to understanding artistic voice and clinical voice management.

Entrance loss coefficients and exit coefficients for a physical model of the glottis with convergent angles

“…This value was adopted in pioneering work on the two-mass model by Ishizaka and Matsudaira 2 and by Ishizaka and Flanagan. 3 Because of its importance in describing the relationship between the pressure at the glottal entrance and the glottal flow rate, a number of studies were done with different physical models of the glottis [4][5][6][7][8][9][10][11] to examine the distribution of pressures along the inferior glottal surface, within the glottis, and at the glottal exit and beyond. The model with the greatest sampling of pressure locations has been the physical model M5 (Refs.…”