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1D modeling of the influence of velopharyngeal insufficiency on phonation of vowels
Radolf, Vojtěch ; Vampola, T.
Velopharyngeal insufficiency is modeled in frequency domain by the transfer matrix method in connection with conical acoustical elements. The vocal tract is considered as a branched system with two nasal ducts. The influence of viscous losses and radiation impedance both at the level of the lips and at the level of the nostrils are considered. Configuration of the vocal tract corresponds to the vowel /a:/. The modal analysis is performed and the results are compared with those gained from 3D FEM models.
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Napěťová analýza lidských hlasivek
Vampola, T. ; Horáček, Jaromír
A three-dimensional (3D) finite element (FE) fully parametric model of the human larynx was developed and used for numerical simulation of stresses during vibrating vocal folds the collisions. The complex model consists of the vocal folds, arytenoids, thyroid and cricoid cartilages. The vocal fold tissue is modelled as a three layered orthotropic material. The results of numerical simulation of the vocal folds oscillations excited by a prescribed intraglottal aerodynamic pressure are presented. The FE contact elements are used modelling the vocal folds collisions and the principal and shear stresses are computed in time domain on the surface and inside the vocal fold tissue. The results show significant dynamic stresses in all there directions and comparable maxima of Von Mises stresses were obtained for closed and open phases of the vocal folds motion.
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Modelování vibračních vlastností lidských hlasivek
Vampola, T. ; Horáček, Jaromír ; Klepáček, I.
A 3D finite element model of the human larynx including the vocal folds was developed. The model enables to take into account phonation position (tinsion and adduction) of the vocal folds by positioning of the arythenoid and thyroid cartilages. Anisotropic properties of the three layers of the vocal fold living tissue (epitel, ligament and muscle) are modelled respecting the material nonlinearities with increasing prolongation of the tissue in longitudinal direction. The motion of the vocal folds is numerically simulated for a prescribed subglottal pressure loading the vocal folds by a periodic function in the time domain. the generated motion of the vocal folds seems to be qualitatively similar to a vibration mode known from clinical measurements.
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Možnosti ladění a optimalizace akustických rezonančních vlastností vokálního traktu člověka
Radolf, Vojtěch ; Vampola, T.
The paper deals with optimization process finding such geometrical form of acoustical cavities of the human supraglottal spaces which leads to excitation of predefined acousic resonance, especially between a domain of the third and the fifth formant. The problem is solved by the transfer matrix method using conic acoustic elements for the vocal tract modelling and numerical method of searching a minimum of a goal function of several variables. The results should help to obtain a physical background for voice rehabilitation, for teaching of opera singers at musical facuoties and for better understanding of biomechanics of voice production.
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Influence of velopharyngeal insufficiency on phonation of Czech vowels
Vampola, T. ; Horáček, Jaromír
The effects of velopharyngeal insufficiency on acoustic frequency-modal characteristics of human supraglottal spaces are investigated. The finite element model was developed from magnetic resonance images (MRI) of the subject during phonation. The influence of the velopharyngeal insufficiency on phonation of the Czech vowels /A,I,U/ is numerically simulated in time domain. The Liljecrants-Fantś pulse is used for excitation of the acoustic system.
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1D model of the human vocal and nasal tract
Radolf, Vojtěch ; Vampola, T. ; Horáček, Jaromír
The paper deals with use of the transfer matrix method to determine acoustic characteristics of the human vocal tract connected with the nasal tract. The system models the influence of velopharyngeal insufficiency on production of Czech vowel /a/. The advantage of this method is significant shortening of the computing time compared to computations with 3D FE method. The model of the acoustical spaces is created by cylindrical elements. The calculation is carried out for periodic "L-F" signal applied at the position of glottis. Time dependent acoustic pressure and air flow volume velocity at the position of the lips and nose are computed. The resulting frequency response functions of the tract are compared with computations realized by 3D FE model.
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