OPTIMAL GLOTTAL CONFIGURATION FOR EASE OF PHONATION

Recent experimental studies have shown the existence of optimal values of the glottal width and convergence angle, at which the phonation th reshold pressure is minimum. These results indicate the existence of a n optimal glottal configuration for ease of phonation, not predicted b y the previous theory. In this paper, the origin of the optimal config uration is investigated using a low dimensional mathematical model of the vocal fold. Two phenomena of glottal aerodynamics are examined: pr essure losses due to air viscosity, and air flow separation from a div ergent glottis. The optimal glottal configuration seems to be a conseq uence of the combined effect of both factors. The results agree with t he experimental data, showing that the phonation threshold pressure is minimum when the vocal folds are slightly separated in a near rectang ular glottis.