Effects of oscillation of a mechanical hemilarynx model on mean transglottal pressures and flows

This study introduces a mechanical model of the larynx for investigating dynamic aerodynamic effects of phonation. The model mimics the hemilarynx. The tracheal inlet section was rectangular (25-mm width, 20-mm height). The vocal fold was fabricated with precision machinery from hard plastic with an attached oscillating plunger. A speaker assembly and audio amplifier drove the plunger, mimicking one-dimensional vocal-fold motion toward a flat wall. The glottal shape was rectangular. The glottal diameter was well specified or dynamically followed with a laser system. The air was sucked through the channel using a vacuum with controlled speed. Frequency and amplitude of the glottis were varied. The mean pressure and mean flow data were recorded. For steady-flow conditions, the glottal gap ranged from 0.39 to 2.58 mm. The pressure coefficient for steady flow had a range of 3.1 to 1.3 for Reynolds numbers between 300 and 9000. For oscillation conditions (a) the frequency was varied from 75 to 150 Hz while the amplitude was held relatively constant, and (b) the amplitude was varied to 0.3 mm for a fixed frequency of 100 Hz. The results indicate that the hemilarynx model provides mean pressure-flow data similar in form to other models with two vocal folds. Furthermore, the dimensional and non-dimensional pressure coefficient is sensitive to variations in glottal gap and glottal amplitude, but relatively insensitive to the frequency of oscillation.