Summary
An experimental study of the pressure distributions in an asymmetric larynx, hereafter
referred to as a hemilarynx, was carried out at a glottal diameter of 0.04 cm and transglottal pressures of 3, 5, 10, 20, and 40 cm H2O. In each case, the glottal wall “on the left” was chosen to have an angle of 0°
with the midline, and the angle of the glottal wall “on the right” was varied through
converging angles of 5°, 10°, and 20° and diverging angles of 5°, 10°, and 20°. The
case of two parallel glottal walls, or the uniform glottis, was also examined. With
the exception of the 20° convergent case, the pressure distributions for most angles
and pressures were bistable; that is, a stable flow situation persisted when the glottal
exit flow jet was directed downstream either to the right or to the left in the rectangular
“pharynx” tunnel. Bistability also occurred for the uniform glottis. Pressure differences
arising from the different directions of the flow jet were often found to be small;
however, differences for the diverging 10° case were as large as 7% or 8%, and for
the 20° divergent case, 12%. Calculations with FLUENT, a computational package, gave
excellent agreement with observed pressures. Implications of the pressure distribution
data for the functional similarity of normal and hemilaryngeal phonation, hypothesized
by Jiang and Titze, are discussed. In particular, the intraglottal pressures for converging
and diverging angles for the hemilarynx were found to be quite similar to those of
the full larynx with the same diameter and included angle or twice the diameter and
twice the included angle, suggesting that the same mechanism of energy transfer operates
in the two cases. Nondimensionalizing the pressure distributions with the transglottal
pressures suggests that the shapes of the distributions at P=3, 5, 10, 20, and 40 cm H2O for a given geometry are similar. The pressure average of these dimensionless distributions
may be interpreted as a template at that geometry, a description referred to as successful
pressure scaling. When the entire data set is considered, variations from consistent
pressure scaling averaged 1.4%, although these variations tend to be somewhat larger
near the glottal entrance and for diverging angles of 10° and 20°. Some possible implications
of the observed pressures for phonosurgery are discussed.
Key Words
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Article info
Publication history
Published online: June 09, 2008
Accepted:
February 25,
2008
Identification
Copyright
© 2010 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
