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Numerical investigation of acoustic characteristics of 3D human vocal tract model with nasal cavities
Vampola, T. ; Štorkán, J. ; Horáček, Jaromír ; Radolf, Vojtěch
Acoustic resonance characteristics of 3D human vocal tract model without and with nasal and\nparanasal cavities were computed. Nasal cavities (NC) form the side branches of the human vocal tract and exhibit antiresonance and resonance properties which influence the produced voice quality. Developed FE models of acoustic spaces of nasal and vocal tract for vowel /a:/ are used to study the influence of (NC) on phonation. Acoustics frequency-modal characteristics are studied by modal analysis and numerical simulation of acoustic signals in time domain is performed by transient analysis of the FE models.
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Experimental modelling of phonation using artificial models of human vocal folds and vocal tracts
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Košina, Jan
The study provides information on experimental research on a complete 1:1 scaled model of human phonation. The model includes human lungs, the trachea, the laryngeal part with artificial vocal folds and the vocal tracts designed for different vowels. The measurement set up enables modelling the time signals not easily measured in humans during phonation as for example fluctuations of the subglottic, laryngeal and oral pressures measured simultaneously with the glottis opening and the glottis area registered by a high-speed camera. The simulation of phonation is performed in the ranges of the airflow rate and the subglottic pressure typical for a normal humans' physiology.
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Interaction of flow and an elastic body
Kosík, Adam
In the submitted work we are concerned with the numerical simulation of fluid flow and elastic body interaction. This is a coupled problem of the equations of two kinds, equations describing the flow and equations describing dynamical behaviour of the elas- tic body, which is partly surrounded by the fluid. These systems are coupled by suitable transmission conditions. The fluid flow is described by the Navier-Stokes equations, which are reformulated by the ALE method because of the deformation of the computational domain caused by the body movement. The deformation of the elastic body is described by the linear elasticity system with the generalized Hooke's law. We solve the problem by the finite element method. The developed methods are tested on the physical model of human vocal folds. 1
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Numerical simulation of the effect of stiffness of lamina propria on the self-sustained oscillation of the vocal folds
Hájek, P. ; Švancara, P. ; Horáček, Jaromír ; Švec, J. G.
A two-dimensional (2D) finite element (FE) model of the fluid-structure-acoustic interaction during selfsustained oscillation of the human vocal folds (VF) is presented in this paper. The aim is to analyze the effect of stiffness of lamina propria on VF vibrations. Such stiffness change can be caused by some VF pathologies. The developed FE model consists of the FE models of the VF, trachea and a simplified human vocal tract. The vocal tract model shaped for simulation of phonation of Czech vowel [a:] was created by converting data from the magnetic resonance images (MRI). The developed FE model includes VF contact, large deformations of the VF tissue, fluid-structure interaction (FSI), moving boundary of the fluid mesh (Arbitrary Lagrangian-Eulerian (ALE) approach), airflow separation during the glottis closure and solution of unsteady viscous compressible airflow described by the Navier-Stokes equations. The numerical simulations showed that higher values of lamina propria Young's modulus (stiffer lamina propria) result in a decrease of the maximum glottis opening. Stiffer lamina propria also requires the use of higher subglottal pressure to initiate self-sustained vibration of the VF.
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Dynamic characteristics obtained from solution of simple vocal folds models
Kubíček, Radek ; Švancara, Pavel (referee) ; Hájek, Petr (advisor)
Bachelor’s thesis concerns the biomechanics of voice and its aim is to obtain dynamic characteristics of simple analytical and numerical vocal folds models. Thesis includes main theories of voice production and thorough analysis of the widest used computational models. Essential is an anatomical and physiological introduction including basic pathologies. Behaviour of computational models mentioned in the bibliographic research is demonstrated by the dynamics characteristics gained by modal analysis and by the solid mechanics equation solution. Eigenfrequencies come under range from literature. The aim of thesis is comparison of analytical and numerical solution and particular computational models.
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Acoustic resonance characteristics of the human vocal tract with respect to a soft tissue
Radolf, Vojtěch ; Horáček, Jaromír
A mathematical model, which can help to clarify physical background of an influence of the soft tissue of vocal cavities on the formant frequencies, has been extended. Strong acoustic-structural interaction is demonstrated on the vocal tract cavity for vowel /u:/ prolonged by a tube that is used for voice training and therapy purposes. The glottis is closed by a yielding wall, considering a mass, compliance and structural damping. Viscous losses of the acoustic cavities and radiation impedance at the output are assumed. Significant change in the first acoustic resonance frequency caused by the compliance of the soft tissue at the glottis corresponds to the data found experimentally in earlier study.
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Acoustic-structural interaction in human vocal tract prolonged by a tube
Radolf, Vojtěch ; Horáček, Jaromír
Phonation into tubes is often used for voice training and therapy. This paper introduces a mathematical model, which can help to clarify physical background of an influence of the soft tissues of vocal cavities on the acoustic resonances (formant frequencies). Substantial change in the first formant frequency caused by the soft tissues in the human vocal tract is in principle in the acoustic-structural interaction of the acoustic cavity semiocluded by the tube, with the yielding wall created for example by the soft tissues in the larynx.
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