Phonation Threshold Flow Research Articles

The phonation critical condition in rectangular glottis with wide prephonatory gaps

The effect of the pressure recovery at glottal exit is introduced to modify the one-mass model. Using the modified one-mass model, the phonation critical condition, including phonation threshold pressure and phonation threshold flow, is analyzed by using the small-amplitude oscillation theory. It is found that the phonation threshold pressure is not sensitive to the change of the prephonatory glottal width at a wide glottal gap. This result agrees with previous experimental observations and suggests that the low slope of dependence of phonation threshold pressure on prephonatory gap found by Chan and Titze [J. Acoust. Soc. Am. 119, 2351-2362 (2006)] could be a consequence of the pressure recovery effect at the glottal exit. In addition, it is predicted that the phonation threshold flow is always significantly increased with the prephonatory gap even at a wide prephonatory glottal gap. Therefore, the phonation threshold flow has an advantage in assessing the phonatory system at a wide prephonatory gap in comparison with the phonation threshold pressure. The phonation threshold flow can be a useful aerodynamic parameter for pathological conditions in which the incomplete glottal gap is often seen.

Comparing Phonation Threshold Flow and Pressure by Abducting Excised Larynges

This experiment studied a new aerodynamic parameter, phonation threshold flow, along with phonation threshold pressure, by varying prephonatory glottal width in canine larynges ex vivo. Goals were to examine phonation threshold flow as a measurable parameter sensitive to physiologic changes in the vocal folds and compare the relative sensitivities of phonation threshold flow and phonation threshold pressure. Ten excised canine larynges were tested on a bench apparatus for subglottal pressure and airflow at phonation onset. Metal shims simulated abduction levels ranging from 0.0 to 4.0 mm. For each glottal configuration, airflow through the larynx was increased until the vocal folds began vibrating, and onset airflow and pressures were recorded. One-way analysis of variance (ANOVA) found significant differences in the aggregate phonation threshold flow means over the latter portion of the width domain (1.0-4.0 mm). Phonation threshold flow increased as posterior glottal width increased and was modeled linearly. One-way ANOVA of phonation threshold pressure means was insignificant, with a P value of .941. Results showed phonation threshold flow to be more sensitive to posterior glottal width changes than phonation threshold pressure. Therefore, phonation threshold flow could be a more effective indicator than phonation threshold pressure for those vocal diseases related to abduction.

The minimum glottal airflow to initiate vocal fold oscillation

Phonation threshold flow (PTF) is proposed as a new aerodynamic parameter of the speech production system in this study. PTF is defined as the minimum airflow that can initiate stable vocal fold vibration. Because the glottal airflow can be noninvasively measured, it is suggested that the aerodynamic parameter PTF may be more practical for clinical vocal disease assessment. In order to investigate the relationship between PTF and phonatory system properties, the stability of the body-cover vocal fold model was analyzed. The study has theoretically shown that PTF is a sensitive aerodynamic parameter dependent on tissue properties, glottal configuration, and vocal tract loading. It was predicted that PTF can be reduced by decreasing tissue viscosity, decreasing mucosal wave velocity, increasing vocal fold thickness, or decreasing prephonatory glottal area. Furthermore, it was predicted that a divergent glottis or low vocal tract resistance lead to a reduced PTF. Also discussed is the potential significance of PTF in investigating the energy distribution in a vocal fold vibration system and related clinical applications.

A new aerodynamic critical parameter of the speech production: Phonation threshold flow

In this paper, the implications of phonation threshold flow (PTF) as an addition to the aerodynamic parameters of speech production system are studied. PTF, the minimum airflow volume velocity able to sustain stable vocal-fold vibration, could have utility in clinical vocal disease assessment just like phonation threshold pressure (PTP) [I. R. Titze, J. Acoust. Soc. Am. 83, 1536–1552 (1988)]. Furthermore, because glottal airflow can be more easily measured noninvasively than subglottal pressure, PTF could be more suitable for routine clinical assessment than PTP. Theoretical studies indicate that PTF is a sensitive aerodynamic parameter dependent on tissue properties, glottal configuration, and vocal-tract loading. Accordingly, this theory suggests that PTF is reduced by the following: decreasing tissue viscosity, decreasing mucosal wave velocity, increasing vocal-fold thickness, or decreasing prephonatory glottal area. A divergent glottis and low vocal-tract resistance also reduce phonation threshold flow. Finally, the significance of PTF for investigation of the distribution of energy in a vocal-fold vibration system and the potential for application of the PTF parameter are assessed. [Work supported by NIH.]