Irregular vocal-fold vibration - High-speed observation and modeling

Direct observations of nonstationary asymmetric vocal-fold oscillations are reported. Complex time series of the left and the right vocal-fold vibrati ons are extracted from digital high-speed image sequences separately. The d ynamics of the corresponding high-speed glottograms reveals transitions bet ween low-dimensional attractors such as subharmonic and quasiperiodic oscil lations. The spectral components of either oscillation are given by positiv e linear combinations of two fundamental frequencies. Their ratio is determ ined from the high-speed sequences and is used as a parameter of laryngeal asymmetry in model calculations. The parameters of a simplified asymmetric two-mass model of the larynx are preset by using experimental data. Its bif urcation structure is explored in order to fit simulations to the observed time series. Appropriate parameter settings allow the reproduction of time series and differentiated amplitude contours with quantitative agreement. I n particular, several phase-locked episodes ranging from 4:5 to 2:3 rhythms are generated realistically with the model. (C) 2000 Acoustical Society of America. [S0001-4966(00)02711-9].