Computational modeling of phonatory dynamics in a tubular three-dimensional model of the human larynx

Although vocal folds are known to be anisotropic, the influence of material anisotropy on vocal fold vibration remains largely unknown. Using a linear stability analysis, phonation onset characteristics were investigated in a three-dimensional anisotropic vocal fold model. The results showed that isotropic models had a tendency to vibrate in a swing-like motion, with vibration primarily along the superior-inferior direction. Anterior-posterior (AP) out-of-phase motion was also observed and large vocal fold vibration was confined to the middle third region along the AP length. In contrast, increasing anisotropy or increasing AP-transverse stiffness ratio suppressed this swing-like motion and allowed the vocal fold to vibrate in a more wave-like motion with strong medial-lateral motion over the entire medial surface. Increasing anisotropy also suppressed the AP out-of-phase motion, allowing the vocal fold to vibrate in phase along the entire AP length. Results also showed that such improvement in vibration pattern was the most effective with large anisotropy in the cover layer alone. These numerical predictions were consistent with previous experimental observations using self-oscillating physical models. It was further hypothesized that these differences may facilitate complete glottal closure in finite-amplitude vibration of anisotropic models as observed in recent experiments.

Section: Introductionmentioning

confidence: 99%

The influence of material anisotropy on vibration at onset in a three-dimensional vocal fold model

Zhang¹

2014

“…(6) Potential age and gender influences and vocal tract influences were not investigated. (7) An unavoidable limitation is that left-right asymmetric conditions (as investigated in numerical [58][59][60] and full larynx 57 models), realistic vocal fold collision, and realistic subglottal and supraglottal loading could not be simulated using the hemilarynx methodology.…”

Section: A Limitationsmentioning

confidence: 99%

Dynamic vocal fold parameters with changing adduction in ex-vivo hemilarynx experiments

Döllinger

Berry

Kniesburges

2016

Ex-vivo hemilarynx experiments allow the visualization and quantification of three-dimensional dynamics of the medial vocal fold surface. For three excised human male larynges, the vibrational output, the glottal flow resistance, and the sound pressure during sustained phonation were analyzed as a function of vocal fold adduction for varying subglottal pressure. Empirical eigenfunctions, displacements, and velocities were investigated along the vocal fold surface. For two larynges, an increase of adduction level resulted in an increase of the glottal flow resistance at equal subglottal pressures. This caused an increase of lateral and vertical oscillation amplitudes and velocity indicating an improved energy transfer from the airflow to the vocal folds. In contrast, the third larynx exhibited an amplitude decrease for rising adduction accompanying reduction of the flow resistance. By evaluating the empirical eigenfunctions, this reduced flow resistance was assigned to an unbalanced oscillation pattern with predominantly lateral amplitudes. The results suggest that adduction facilitates the phonatory process by increasing the glottal flow resistance and enhancing the vibrational amplitudes. However, this interrelation only holds for a maintained balanced ratio between vertical and lateral displacements. Indeed, a balanced vertical-lateral oscillation pattern may be more beneficial to phonation than strong periodicity with predominantly lateral vibrations.

“…Clearly, some laryngeal adjustments of vocal fold properties (stiffness, tension, geometry, and position) are required in order to restrain the vocal folds from being pushed apart by airflow. Despite many previous studies on the effect of laryngeal adjustments on phonation, both in humans (e.g., Isshiki, 1964Isshiki, , 1969Hirano et al, 1969;Gay et al, 1972;Choi et al, 1993) and three-dimensional simulations (Titze and Talkin, 1979;Alipour et al, 2000;Zheng et al, 2011;Xue et al, 2012;Sidlof et al, 2013), the interaction between the subglottal pressure and laryngeal adjustments of vocal fold properties in regulating glottal closure and airflow has not been systematically investigated.…”

Section: Introductionmentioning

confidence: 99%

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

Zhang¹

2015

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.