Viscous effects in a static physical model of the uniform glottis.

The classic work on laryngeal flow resistance by van den Berg et al. [J. Acoust. Soc. Am. 29, 626-631 (1957)] is revisited. These authors used a formula to summarize their measurements, and thus they separated the effects of entrance loss and pressure recovery from those of viscosity within the glottis. Analysis of intraglottal pressure distributions obtained from the physical model M5 [R. Scherer et al., J. Acoust. Soc. Am. 109, 1616-1630 (2001)] reveals substantial regions within the glottis where the pressure gradient is almost constant for glottal diameters from 0.005 to 0.16 cm, as expected when viscous effects dominate the flow resistance of a narrow channel. For this set of glottal diameters, the part of the pressure gradient that has a linear dependence on the glottal volume velocity is isolated. The inverse cube diameter of the Poiseuille expression for glottal flows is examined with the data set provided by the M5 intraglottal pressure distributions. The Poiseuille effect is found to give a reasonable account of viscous effects in the diameter interval from 0.0075 to 0.02 cm, but an inverse 2.59 power law gives a closer fit across all diameters.