Regulation of glottal closure and airflow in a three-dimensional phonation model: Implications for vocal intensity control

Abstract

Maintaining a small glottal opening across a large range of voice conditions is critical to normal voice production. This study investigated the effectiveness of vocal fold approximation and stiffening in regulating glottal opening and airflow during phonation, using a three-dimensional numerical model of phonation. The results showed that with increasing subglottal pressure the vocal folds were gradually pushed open, leading to increased mean glottal opening and flow rate. A small glottal opening and a mean glottal flow rate typical of human phonation can be maintained against increasing subglottal pressure by proportionally increasing the degree of vocal fold approximation for low to medium subglottal pressures and vocal fold stiffening at high subglottal pressures. Although sound intensity was primarily determined by the subglottal pressure, the results suggest that, to maintain small glottal opening as the sound intensity increases, one has to simultaneously tighten vocal fold approximation and/or stiffen the vocal folds, resulting in increased glottal resistance, vocal efficiency, and fundamental frequency.

Cause-effect relationship between vocal fold physiology and voice production in a three-dimensional phonation model

“…The reader is referred to the Zhang (2015) paper for details of the model. The Zhang (2015) model is computationally efficient due to the following three major simplifications. First, linear elasticity is assumed for vocal fold mechanics, neglecting both material and geometric nonlinearities.…”

“…Downstream of the flow separation point the pressure is assumed equal to atmospheric pressure. Finally, the use of vocal fold eigenmodes as basis functions in Zhang (2015) significantly reduces the degrees of freedom of the system governing equations. The eigenmodes can be pre-computed prior to phonation simulations instead of at every single time step, which further improves computational efficiency.…”

“…Considering the large number of conditions to be investigated, the reducedorder three-dimensional phonation model described in Zhang (2015) is used. The reader is referred to the Zhang (2015) paper for details of the model.…”

“…In this study, the effects of vocal fold properties on vocal fold vibration and the resulting acoustics are investigated using a three-dimensional reduced-order continuum model of phonation (Zhang, 2015). To facilitate linking vocal fold biomechanics to the acoustics of the produced voice, this study focuses on the glottal closure pattern and various voice spectral measures and how they can be regulated by changes in vocal fold stiffness and medial surface thickness, the resting glottal opening, and the subglottal pressure.…”

“…For example, although many studies have shown that various laryngeal adjustments have only a slight effect on vocal intensity (Tanaka and Gould, 1983;Titze, 1988;Tanaka and Tanabe, 1986;Zhang, 2015), human subjects experiments show that as vocal intensity increases, the increasing subglottal pressure is often accompanied by a proportional increase in the glottal resistance, particularly at low pitch voice production (Isshiki, 1964;Hirano et al, 1969;Tanaka and Tanabe, 1986;Holmberg et al, 1988;Stathopoulos and Sapienza, 1993). It has been hypothesized that the observed increase in the glottal resistance accompanying vocal intensity increase is due to laryngeal adjustments required to maintain sufficient glottal closure and certain acoustic goals (Isshiki, 1964;Zhang, 2011).…”