Geometry of the Vocal Tract and Properties of Phonation near Threshold: Calculations and Measurements

Abstract

In voice research, analytically-based models are efficient tools to investigate the basic physical mechanisms of phonation. Calculations based on lumped element models describe the effects of the air in the vocal tract upon threshold pressure (Pth) by its inertance. The latter depends on the geometrical boundary conditions prescribed by the vocal tract length (directly) and its cross-sectional area (inversely). Using Titze’s surface wave model (SWM) to account for the properties of the vocal folds, the influence of the vocal tract inertia is examined by two sets of calculations in combination with experiments that apply silicone-based vocal folds. In the first set, a vocal tract is constructed whose cross-sectional area is adjustable from 2.7 cm2 to 11.7 cm2. In the second set, the length of the vocal tract is varied from 4.0 cm to 59.0 cm. For both sets, the pressure and frequency data are collected and compared with calculations based on the SWM. In most cases, the measurements support the calculations; hence, the model is suited to describe and predict basic mechanisms of phonation and the inertial effects caused by a vocal tract.

Effect of Ligament Fibers on Dynamics of Synthetic, Self-Oscillating Vocal Folds in a Biomimetic Larynx Model

“…MLM1, however, lied in these ranges, which will be discussed in more detail in Section 3.5. These higher values of the P sub in synthetic models matched well with many previous studies [31,51,80]. When compared to ex vivo measurements [45][46][47][48]81], the P sub in our models is also higher.…”

An Investigation of Acoustic Back-Coupling in Human Phonation on a Synthetic Larynx Model

“…It can be seen that V stays roughly constant for L ≤ 340 mm and decreases monotonically for larger L. The same behavior can be observed in the transglottal pressure P trans = P sub − P supra , where P sub and P supra are the mean pressure values measured by the pressure probes in the sub-and supraglottal channel, respectively. The decrease in V with increasing L is similar to what Fulcher et al [41] found, where they used an analytical surface wave model in combination with validation experiments to predict the phonation threshold pressure as a function of the vocal tract length. They related the decreased threshold pressure to an increase in vocal tract inertance due to the increased length.…”