Abstract
Finite-element modeling of self-sustained vocal fold oscillations during voice production has mostly considered the air as incompressible, due to numerical complexity. This study overcomes this limitation and studies the influence of air compressibility on phonatory pressures, flow and vocal fold vibratory characteristics. A two-dimensional finite-element model is used, which incorporates layered vocal fold structure, vocal fold collisions, large deformations of the vocal fold tissue, morphing the fluid mesh according to the vocal fold motion by the arbitrary Lagrangian-Eulerian approach and vocal tract model of Czech vowel [i:] based on data from magnetic resonance images. Unsteady viscous compressible or incompressible airflow is described by the Navier-Stokes equations. An explicit coupling scheme with separated solvers for structure and fluid domain was used for modeling the fluid-structure-acoustic interaction. Results of the simulations show clear differences in the glottal flow and vocal fold vibration waveforms between the incompressible and compressible fluid flow. These results provide the evidence on the existence of the coupling between the vocal tract acoustics and the glottal flow (Level 1 interactions), as well as between the vocal tract acoustics and the vocal fold vibrations (Level 2 interactions).
Highlights
Understanding the physiology and biomechanics of human voice production is the basis of voice and speech sciences
To take into account the layered structure of the vocal folds (VFs) [72], four layers of the VF tissue were included in the model – epithelium, superficial layer of lamina propria (SLP), ligament and muscle [72, 73]
The higher Wgmax results from the more compliant environment of the compressible flow compared to incompressible flow and from the structure-acoustic interaction (SAI) below the first acoustic resonance in the vocal tract (VT)
Summary
Understanding the physiology and biomechanics of human voice production is the basis of voice and speech sciences. Voice is produced through self-sustained oscillations of the vocal folds (VFs) which are excited by air flowing from the lungs. The VF oscillations modulate the airflow and cause acoustic pressure oscillations; these propagate with the speed of sound through the cavities of the vocal tract (VT). The voice production mechanisms should, in principle, involve the forward and backward fluid-structure-acoustic interaction (FSAI). The current mathematical models, which can handle such complex interaction, are mostly based on partial differential equations (PDEs), P. Hajek et al / Applied and Computational Mechanics 15 (2021) 1–20 an extensive work has been done on the lumped-mass models mainly because of their understandability and low demands on hardware
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