An experimental analysis of the pressures and flows within a driven mechanical model of phonation.

The production of voice is related to the flow of air through the glottis, whose time-dependent shape is defined by the motion of the vocal folds and the translaryngeal pressure. A scaled dynamically similar experimental apparatus that mimics the motion of the vocal folds was designed and built, such that both the glottal diameter and glottal angle change during a motion cycle. This motion is more realistic than in other reported dynamic models. The motion of the folds can be driven at different frequencies. The glottal flow takes place at a constant inlet pressure, mimicking the lung pressure. The transglottal pressure difference and flow rate were measured over the motion cycle. Satisfactory agreement was obtained for identical cases by numerically solving the two-dimensional, incompressible Navier-Stokes equations. Both experimental and numerical data showed that the glottal flow rate and transglottal pressure were affected by the oscillation frequency of the vocal folds. Flow visualization showed that the glottal flow patterns, which are a potential source of aero-acoustic sound, are influenced by the oscillation frequency. However, glottal flow resistance depended to a lesser extent on vocal fold oscillation frequency for the portion of the cycle when the glottis was divergent.