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Computer modeling of effects of vocal exercising with a tube on vocal tract sound power transfer
Horáček, Jaromír ; Vampola, T. ; Laukkanen, A. M. ; Švec, J. G.
Two 3D finite element (FE) models were constructed, based on CT measurements of a subject phonating on [a:] before and after phonation into a tube. Acoustic analysis was performed exciting the models by acoustic flow velocity at the vocal folds. The generated acoustic pressure of the response was computed in front of the mouth and inside the vocal tract for both FE models. Average amplitudes of the pressure oscillations inside the vocal tract and in front of the mouth were compared to display a cost-efficiency of sound energy transfer at different formant frequencies. Comparison of the pressure oscillation inside and outside the vocal tract showed that formants differ in their efficiency, F4 (at about 3.5 kHz, i.e. at the speaker’s or singer’s formant region) being the most effective. The results suggest that exercising on semi-occlusions help in improving the vocal economy.
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FE model of the human vocal folds considering fluid-structure interaction
Švancara, P. ; Horáček, Jaromír ; Hrůza, V.
The study presents three-dimensional finite element (FE) model of flow induced oscillations of the human vocal folds in interaction with acoustic processes in the simplified vocal tract model. The FE model includes vocal folds pretension before phonation, large deformations of the vocal fold tissue, vocal folds contact, fluid-structure interaction, morphing the fluid mesh according the vocal folds motion, unsteady viscous compressible airflow and airflow separation during the glottis closure. Fluid-structure interaction is solved using partitioned approach, where the results of solution for the flow are transferred as loads on the vocal folds surface, then the vocal folds motion is computed and then again the equations for the flow are solved. Numerical results confirmed that the developed model can be used for simulation of the vocal folds self-oscillations, and especially for numerical simulations of quantities that are difficult to measure in clinical research.
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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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Pěvecký formant: Předběžné výsledky vyhodnocení snímků z magnetické rezonance a akustických záznamů při fonaci zpěváků
Švec, J. ; Herbst, C. ; Havlík, R. ; Horáček, Jaromír ; Krupa, P. ; Lejska, M. ; Miller, D.G.
Singerś formant is a desirable quality in operatic singing. This study investigates the strategies of two male operatic singers used for achieving the singerś formant. The subjects were asked to produce voice both in naïve and operatic singing quality at the same fundamental frequency for two different vowels [a] and [e]. Changes in the shape of the vocal tract were investigated using magnetic resonance imaging (MRI), and differences in acoustic voice quality were analyzed using sound spectrography. In operatic voice quality the MR images revealed a) lowered larynx, b) raised soft palate, c) flattened tongue and d)straightened spine. Clustering and lowering the formant frequencies was seen in the spectrograms but the strategy was different for the two vowels and the two singers. The data suggest that different anatomical dispositions in singers lead to different strategies for optimizing the voice quality.
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PROBLEMS OF SINGER’S FORMANT MATHEMATICAL MODELING
Radolf, Vojtěch
Theme of the paper belongs into the field of acoustics in biomechanics. In co-operation with foniatric departments in Czech Republic the spatial and then simplified geometric models of acoustic human vocal cavities were created. Using various mathematical models the dynamic characteristics of the models were finding out. One of the objectives of the project is to investigate singer's formant cluster. The mathematical models are designed to find such configuration of acoustic cavities, respecting real physiological limits, which leads to excitation of predefined acoustic resonances. It is so called formant tuning. Using these models the appropriate geometry for the singer's formant cluster formation were searching for.
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