1st ETRW on Speech Production Modeling: From Control Strategies to Acoustics 4th Speech Production Seminar: Models and Data Autrans, France May 20-24, 1996

Bifurcations in 2-Mass Models of the Vocal Folds - The Role of the Vocal Tract

Patrick Mergell (1), Hanspeter Herzel (2)

(1) ENT Clinics, University Erlangen/Nürnberg, Erlangen, Germany
(2) Institute of Theoretical Physics, Technical University Berlin, Germany

Instabilities of the human voice source appear in normal voices under certain conditions (newborn cries, vocal fry, creaky voice) and are symptomatic of voice pathologies. Vocal instabilities are intimately related to bifurcations of the underlying nonlinear dynamical system. We analyze in this paper bifurcations in 2-mass models of the vocal folds and study, in particular, how the incorporation of the vocal tract effects bifurcation diagrams. A comparison of a simplified model [1] with an extended version including vocal tract resonances [2] reveals that essential features of the bifurcation diagrams (as e.g. the period-doubling for increasing left-right asymmetry) are found in both model versions. However, vocal instabilities appear in the extended model at lower subglottal pressures. Moreover, the waveforms of both models are quite different.

Full Paper

Bibliographic reference.  Mergell, Patrick / Herzel, Hanspeter (1996): "Bifurcations in 2-mass models of the vocal folds - the role of the vocal tract", In SPM-1996, 189-192.