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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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Physical Model of the Vocal Folds
Kryštůfek, Jan ; Bula, Vítězslav ; Horáček, Jaromír
Assuming symmetry of self-oscillations, a half physical model of the vocal folds was made. Working principle of the model is based on self-induced oscillations occurring when a critical air flow rate is crossed. Air flow rate of 0,6 l/s was used for generation of flow-induced oscillations of elastic part of the model with fundamental frequency 117 Hz. Used elastic element made of polyurethane rubber was designed and manufactured by Thomson from Purdue University (Indiana) [1], [2]. The introductory measurements were performed by using a high speed digital camera. We propose to use the model as a source of acoustic pressure for excitation of physical models of the human vocal tract.
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Computational and Experimental analysis of Effect of Tonillectomy on Production of Czech Vowels
Švancara, P. ; Vokřál, J. ; Horáček, Jaromír
The effect of tonsillectomy on production of Czech vowels is numerically and experimentally examined. Experimental results show statistically significant shift down to lower frequencies of 3rd formant frequency for vowels /a/, /e/ and /o/. The finite element (FE) models of the acoustic spaces corresponding to the human vocal tracts and acoustic space around the human head are used in numerical simulations of phonation. Computed results show that tonsillectomy causes frequency shifts of some formant frequencies mostly down to lower frequencies. The frequency shifts of the formants are significantly dependent on position and size of th tonsils. Experimental and computational results are consistent.
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Computational modelling of efect of tonsillectomy on production of czech vowels
Švancara, P. ; Horáček, Jaromír
Effects of tonsillectomy on production of Czech vowels are numerically examined. The finite element (FE) models of the acoustic spaces corresponding to the vocal tracts and acoustic space around the human head are used in numerical simulations of phonation. Models for vowels /a/,/e/,/i/,/o/ and /u/ are analyzed. The acoustic resonant characteristics of the FE models are studied using modal and transient analyses (excitation by a short pulse). The production of vowels is simulated in time domain using transient analysis of the FE models excited by Liljencrants-Fantś (LF) glottal signal. Calculated results show that tonsillectomy causes frequency shifts of some formant frequencies mostly down to lower frequencies. Biggest shifts were obtained for 2nd and 3rd formants for vowel /o/-300Hz down to lower frequencies and for 2nd (-450Hz) and 3rd(-150 Hz) formants for vowel /u/ down too. The frequency shifts of the formants are significantly dependent on position and size of the tonsils.
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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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Influence of tonsillectomy on voice and 3D mathematical models
Vokřál, J. ; Černý, L. ; Lavička, L. ; Švancara, Pavel ; Horáček, Jaromír
After the phoniatric examination the tape-recording of voice was carried out on 14 patients (6male, 8 female, age from 16 to 39 years) in a studio. The second recording was performed appproximately 1 month after tonsillectomy. Patients phonated five Czech vowels /a:/, /e:/, /i:/, /o:/, /u:/. The acoustic analysis was performed by Multi-Dimensional Voice Program and the position of the first four formants was evaluated. The finite element (FE) models of the acoustic spaces corresponding to the human vocal tract for the Czech vowels /a:/ and /i:/ were used in the mathematical modelling. The acoustic resonant characteristics of the FE models were studied by modal and transient analyses. The acoustic analyses were realised by the software code SYSNOISE.
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