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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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