3D-FV-FE Aeroacoustic Larynx Model for Investigation of Functional Based Voice Disorders.

Sebastian Falk,Stefan Schoder,Paul Maurerlehner,Bernhard Jakubaß,Michael Döllinger,Manfred Kaltenbacher,Matthias Echternach,Stefan Kniesburges

doi:10.3389/fphys.2021.616985

Abstract

For the clinical analysis of underlying mechanisms of voice disorders, we developed a numerical aeroacoustic larynx model, called simVoice, that mimics commonly observed functional laryngeal disorders as glottal insufficiency and vibrational left-right asymmetries. The model is a combination of the Finite Volume (FV) CFD solver Star-CCM+ and the Finite Element (FE) aeroacoustic solver CFS++. simVoice models turbulence using Large Eddy Simulations (LES) and the acoustic wave propagation with the perturbed convective wave equation (PCWE). Its geometry corresponds to a simplified larynx and a vocal tract model representing the vowel /a/. The oscillations of the vocal folds are externally driven. In total, 10 configurations with different degrees of functional-based disorders were simulated and analyzed. The energy transfer between the glottal airflow and the vocal folds decreases with an increasing glottal insufficiency and potentially reflects the higher effort during speech for patients being concerned. This loss of energy transfer may also have an essential influence on the quality of the sound signal as expressed by decreasing sound pressure level (SPL), Cepstral Peak Prominence (CPP), and Vocal Efficiency (VE). Asymmetry in the vocal fold oscillations also reduces the quality of the sound signal. However, simVoice confirmed previous clinical and experimental observations that a high level of glottal insufficiency worsens the acoustic signal quality more than oscillatory left-right asymmetry. Both symptoms in combination will further reduce the quality of the sound signal. In summary, simVoice allows for detailed analysis of the origins of disordered voice production and hence fosters the further understanding of laryngeal physiology, including occurring dependencies. A current walltime of 10 h/cycle is, with a prospective increase in computing power, auspicious for a future clinical use of simVoice.

Highlights

The human voice as a prerequisite for speech production is our most important tool to communicate with other people
The 3D aeroacoustic numeric larynx model simVoice is a combination of the Finite Volume (FV) computational fluid dynamic (CFD) solver Star-CCM+ and the Finite Element (FE) solver CFS++ (Kaltenbacher, 2015)
Numerical Methods The aeroacoustic sound generation and acoustic wave propagation is described by the perturbed convective wave equation (PCWE) (Kaltenbacher et al, 2016), which is solved via the finite element solver CFS++ (Schoder et al, 2020)

Summary

Introduction

The human voice as a prerequisite for speech production is our most important tool to communicate with other people. The phonatory process, the prerequisite for human speech, describes the production of the human voice and depends on various factors as age, gender, training, and health status (Titze, 2000; Aronson and Bless, 2009). The human voice results from a periodic oscillation of the vocal folds (VF) in the larynx, see Figure 1. The oscillations are caused by a complex fluid-structure interaction between the tracheal airflow and the elastic tissue of the vocal folds. Thereby, the airflow is the main sound generating source, that is subsequently modulated by the vocal tract consisting of the upper airway structures and is emitted from the lips as an audible signal

Methods

Discussion

Conclusion