Pressure and velocity profiles in a static mechanical hemilarynx model

Abstract

This study examined pressure and velocity profiles in a hemilarynx mechanical model of phonation. The glottal section was fabricated from hard plastic. Twelve pressure taps were mounted in the vocal-fold surface and connected to a differential pressure transducer through a pressure switch. The glottal gap was measured with a filter gauge and the glottal angle was well specified by use of a laser system. Eight pressure transducers were placed in the flat Plexiglas wall opposite the vocal fold. Hot-wire anemometry was used to obtain velocity profiles upstream and downstream of the glottis. The results indicate that the pressures were asymmetric in the glottis: the pressure distribution on the vocal fold was consistent with pressure change along a parallel duct, whereas the pressures on the opposite flat wall typically were lower. The upstream velocity profiles were symmetric regardless of the constriction shape and size. The jet velocity downstream of the glottis was turbulent even for laminar upstream conditions. The narrower the glottis, the closer the jet stayed to the upper wall and traveled further before expanding. The turbulence ratio was greater on the skirt of the jet and reached as high as 25% of the maximum jet velocity.