Ing. Pavel Švancara, Ph.D.
E-mail:   svancara@fme.vutbr.cz  Dept.:   Institute of Solid Mechanics, Mechatronics and Biomechanics Dept. of Biomechanics Position:   Assistant Professor Room:   A2/605

Supervised courses:

• Bioacoustics (9BIA)
• Biomechanics IV - Bioacoustics (RBK)
• Dynamics of Machine Tools (GDV)
• Dynamics of Machine Tools (GDV-K)
• Vibrations and Noise (9VAH)

Publications:

• Švancara, P., Horáček, J., Hrůza V.:
  FE modelling of the fluid-structure-acoustic interaction for the vocal folds self-oscillation,
  Vibration Problems ICOVP 2011, pp.801-807, ISBN 978-94-007-2068-8, (2011), Springer
  conference paper
  akce: The 10th International Conference on Vibration Problems - ICOVP 2011, Praha, 05.09.2011-08.09.2011
• MIŠUN, V.; ŠVANCARA, P.; VAŠEK, M.:
  Experimental Analysis of the Characteristics of Artificial Vocal Folds, Journal of Voice
  journal article in Web of Science
• ŠVANCARA, P., HORÁČEK, J.:
  Numerical Modelling of Effect of Tonsillectomy on Production of Czech Vowels, S. Hirzel Verlag
  journal article in Web of Science
• ŠVANCARA, P., HORÁČEK, J., VOKŘÁL, J., ČERNÝ, L.:
  Computational modelling of effect of tonsillectomy on voice production,
  Logopedics Phoniatrics Vocology, Vol.31, (2006), No.3, pp.117-125, ISSN 1401-5439, Taylor & Francis
  journal article - other
• ŠVANCARA, P.; HORÁČEK, J.:
  FE modelling of effect of tonsillectomy on production of Czech vowels,
  Inženýrská mechanika - Engineering Mechanics, Vol.12, (2005), No.5, pp.347-354, ISSN 1210-2717
  journal article - other

List of publications at Portal BUT

Abstracts of most important papers:

• Švancara, P., Horáček, J., Hrůza V.:
  FE modelling of the fluid-structure-acoustic interaction for the vocal folds self-oscillation,
  Vibration Problems ICOVP 2011, pp.801-807, ISBN 978-94-007-2068-8, (2011), Springer
  conference paper
  akce: The 10th International Conference on Vibration Problems - ICOVP 2011, Praha, 05.09.2011-08.09.2011
  The flow induced self/oscillation of the human vocal folds in interaction with acoustic processes on the simplified vocal tract model was explored by 3D FE model. Developed FE model includes vocal folds pretension before phonation, large deformations of the vocal tissue, vocal folds contact, fluid-structure interaction, morphing the fluid mesh according the vocal folds motion (ALE approach), unsteady viscous compressible airflow described by the Navier-Stokes equations and airflow separation during the glottis closure. Iterative partitioned approach is used for modelling the fluid-structure interaction. Computed results prove that the developed model can be used for simulation of the vocal folds self-oscillation and resulting acoustic waves. The developed model enables to numerically simulate an influence of some pathological changes in the vocal fold tissue on the voice production.
• MIŠUN, V.; ŠVANCARA, P.; VAŠEK, M.:
  Experimental Analysis of the Characteristics of Artificial Vocal Folds, Journal of Voice
  journal article in Web of Science
  The article focuses on the constructional definition of artificial vocal folds and their experimental analysis. The analysis is conducted for voiced source voice phonation and for the changing mean value of the subglottal pressure. The article further deals with the analysis of the pressure of the airflow through the vocal folds, which is cut (separated) into individual pulses by the vibrating vocal folds. The analysis results show that air pulse characteristics are relevant to voice generation, as they are produced by the flowing air and vibrating vocal folds.
• LAUKANNEN, A. M., HORÁČEK, J., ŠVANCARA, P., LEHTINEN, E.:
  Effects of FE Modelled Consequences of Tonillectomy on Perceptual Evaluation of Voice,
  INTERSPEECH 2007: 8TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION, pp.1182-1185, ISBN 978-1-60560-316-2, (2007), ISCA-INST SPEECH COMMUNICATION ASSOC,
  conference paper
  akce: INTERSPEECH 2007: 8TH ANNUAL CONFERENCE OF THE INTERNATIONAL SPEECH COMMUNICATION ASSOCIATION, Antwerp, Belgium, 27.08.2007-31.08.2007
  This study aimed to investigate the effects of a tonsillectomy on the perceived overall voice quality and timbre. Computer simulations of five Czech vowels were made, including both the calculated resonance effects of large tonsils (size 1.6 cm3) and the resonances without tonsils. The simulations were made using a finite element model of the vocal tract, based on magnetic resonance images. The size and shape of the tonsils were ascertained from clinical data. The generated pressure outputs were transformed into sound records presented to 10 trained listeners. Formant frequencies of the simulated samples were measured. The samples with and without tonsils did not differ significantly from each other in voice quality. F3 was significantly lower and the timbre was darker without tonsils. Thus, the effects of tonsillectomy on voice may be perceptible, at least in the case of large tonsils. The effect, however, may disappear in time due to changes in the tissue and due to compensatory changes in articulation.
• ŠVANCARA, P., HORÁČEK, J.:
  Numerical Modelling of Effect of Tonsillectomy on Production of Czech Vowels, S. Hirzel Verlag
  journal article in Web of Science
  Aim of the study is to numerically examine the effect of tonsillectomy on production of Czech vowels. Similar experimental studies on living subjects are not easily realisable. 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. Models for Czech 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-Fants (LF) glottal signal model. Calculated results show that tonsillectomy causes frequency shifts of some formant frequencies mostly down to lower frequencies. Biggest shifts were obtained for 3rd and 4th formants for vowel /o/ ~300Hz down to lower frequencies, for 3rd (~450Hz) and 4th (~150Hz) formants for vowel /u/ and for 4th (~200Hz) formant of vowel /e/ down too. The frequency shifts of the formants are significantly dependent on position and size of the tonsils.
• ŠVANCARA, P., HORÁČEK, J., VOKŘÁL, J., ČERNÝ, L.:
  Computational modelling of effect of tonsillectomy on voice production,
  Logopedics Phoniatrics Vocology, Vol.31, (2006), No.3, pp.117-125, ISSN 1401-5439, Taylor & Francis
  journal article - other
  The aim of this study is to develop mathematical 3D finite element (FE) models for numerical simulations of vibroacoustic properties of the human vocal tract after a tonsillectomy. Similar experimental studies are not easily realisable on living subjects. The FE models of the acoustic spaces corresponding to the human vocal tract for the Czech vowels /A/ and /I/ and the acoustic space around the human head were used in numerical simulations of phonation. The acoustic resonant characteristics of the FE models were studied using modal and transient analyses (excitation by a short pulse). Calculated results show that a tonsillectomy causes a frequency shift of the 3rd (~180Hz) and 4th (~120Hz) formants down to the lower frequencies for the vowel /A/ and similarly for the 2nd, 4th and 5th formants for the vowel /I/ (all ~100Hz). Similar effects and results can be found in experimental studies in literature. The formant changes are dependent on the size of additional acoustic spaces that occur after a tonsillectomy. The verification of the model was performed on the recordings of patients before and after the tonsillectomy operation. Multi-Dimensional Voice Program (MDVP Advanced, KAY Elemetrics) was used for the comparing of the formant center frequencies. Very small differences in the results of subjective evaluation of the voice before and after tonsillectomy were found.