Divergent or convergent glottal angles: Which give greater flow?

Abstract

During phonation, the glottis alters between convergent and divergent angles. For the same angle value, diameter, and transglottal pressure, which angle, divergent or convergent, results in greater flow? The symmetric glottal angles of the physical static model M5 were used. Characteristics (life-size) of the model were: axial glottal length 0.30 cm; angles of 5, 10, 20, and 40 degrees; diameters of 0.005, 0.01, 0.02, 0.04, 0.08, 0.16, and 0.32 cm; transglottal pressures from 1 to 25 cm H2O; resulting in flows from 2.7 to 1536 cc/s and Reynolds number from 29.4 to 13,058. Results: (1) For diameters of 0.04, 0.08 and 0.16 cm, the divergent angle always gave more flow than the convergent angle (about 5–25%); (2) for the smallest (0.005 cm) and largest diameter (0.32 cm), the divergent angles always gave less flow (10–30%); (3) for diameters of 0.01 and 0.02 cm, flow was greater for divergent 5 and 10 degrees, and less for divergent 20 and 40 degrees. These results suggest that the divergent glottal angle will increase the glottal flow for midrange glottal diameters (skewing the glottal flow further “to the right”?), and create less flow at very small diameters (increasing energy in the higher harmonics?).