A theoretical model of the pressure field arising from asymmetric intraglottal flows applied to a two-mass model of the vocal folds

Abstract

A theoretical flow solution is presented for predicting the pressure distribution along the vocal fold walls arising from asymmetric flow that forms during the closing phases of speech. The resultant wall jet was analyzed using boundary layer methods in a non-inertial reference frame attached to the moving wall. A solution for the near-wall velocity profiles on the flow wall was developed based on a Falkner-Skan similarity solution and it was demonstrated that the pressure distribution along the flow wall is imposed by the velocity in the inviscid core of the wall jet. The method was validated with experimental velocity data from 7.5 times life-size vocal fold models, acquired for varying flow rates and glottal divergence angles. The solution for the asymmetric pressures was incorporated into a widely used two-mass model of vocal fold oscillation with a coupled acoustical model of sound propagation. Asymmetric pressure loading was found to facilitate glottal closure, which yielded only slightly higher values of maximum flow declination rate and radiated sound, and a small decrease in the slope of the spectral tilt. While the impact on symmetrically tensioned vocal folds was small, results indicate the effect becomes more significant for asymmetrically tensioned vocal folds.

Comments on “A theoretical model of the pressure field arising from asymmetric intraglottal flows applied to a two-mass model of the vocal folds” [J. Acoust. Soc. Am. 130, 389–403 (2011)]

“…An alternative model is proposed, which avoids these problems and predicts that there is a minimum glottal opening below which the walljet does not separate from the wall at the glottal exit. This is in agreement with the experimental results provided by Erath et In a series of recent papers Erath et al [1][2][3] consider the interesting problem of the asymmetry of the flow in the downstream part of the glottis during the closing phase of the vocal fold oscillation cycle. The glottis is then a slit shaped converging-diverging channel with a neck (width a min ) at the upstream side of the glottis.…”

“…It is one of the merits of Erath et al cycle. Once this fact was established, Erath et al 2 made an attempt to estimate the impact of such an asymmetry on the motion of the vocal folds and the sound production. They have developed a semi-empirical model, which they call Boundary Layer Estimation of Asymmetric Pressure (BLEAP) aiming at calculating the transversal force on the wall on which the jet is attached.…”

“…They have developed a semi-empirical model, which they call Boundary Layer Estimation of Asymmetric Pressure (BLEAP) aiming at calculating the transversal force on the wall on which the jet is attached. 2 Combining this with a simplified two-mass lumped element model for the dynamics of the vocal folds, they estimate the influence of the asymmetry on the movement of the folds. 2 Mittal et al 3 place this work in a broader context and provide a review of literature on the subject.…”

Corrected contact dynamics for the Steinecke and Herzel asymmetric two-mass model of the vocal folds

“…We have shown that employing the corrected contact force model causes potentially significant changes in the dynamics for a given subglottal pressure and asymmetry factor. The recent developments of asymmetric fluid loading models 6 and interest in utilizing chaos as a potential diagnostic technique 7 make it critical that the governing equations of the simplified model be correct.…”

Investigating acoustic correlates of human vocal fold vibratory phase asymmetry through modeling and laryngeal high-speed videoendoscopy

“…10). Future model modifications may take into account this observation, especially as it relates to subjects with vocal pathologies, and ongoing work is beginning to look at alternative implementations of asymmetric intraglottal flow (Erath et al, 2011). In addition, the model assumption of a uniform rectangular glottis is violated in many of the subjects with voice disorders (exemplified in Fig.…”