The influence of subglottal acoustics on laboratory models of phonation

The influence of vocal fold geometry and stiffness on phonation onset was experimentally investigated using a body-cover physical model of the vocal folds. Results showed that a lower phonation threshold pressure and phonation onset frequency can be achieved by reducing body-layer or cover-layer stiffness, reducing medial surface thickness, or increasing cover-layer depth. Increasing body-layer stiffness also restricted vocal fold motion to the cover layer and reduced prephonatory glottal opening. Excitation of anterior-posterior modes was also observed, particularly for large values of the body-cover stiffness ratio. The results of this study were also discussed in relation to previous theoretical and experimental studies.

“…The experimental setup is similar to that used in previous studies (Zhang et al, 2006. More details of the setup can be found in these previous studies.…”

Section: Methodsmentioning

confidence: 92%

Phonation threshold pressure and onset frequency in a two-layer physical model of the vocal folds

Mendelsohn

Zhang²

2011

“…The experimental setup is similar to that used in previous studies (Zhang et al, 2006;Zhang, 2010b;Mendelsohn and Zhang, 2011). More details of the setup can be found in these previous studies.…”

Section: Experimental Setup and Methodsmentioning

confidence: 92%

Asymmetric vibration in a two-layer vocal fold model with left-right stiffness asymmetry: Experiment and simulation

Zhang¹,

Luu²

2012

Self Cite

Vibration characteristics of a self-oscillating two-layer vocal fold model with left-right asymmetry in body-layer stiffness were experimentally and numerically investigated. Two regimes of distinct vibratory pattern were identified as a function of left-right stiffness mismatch. In the first regime with extremely large left-right stiffness mismatch, phonation onset resulted from an eigenmode synchronization process that involved only eigenmodes of the soft fold. Vocal fold vibration in this regime was dominated by a large-amplitude vibration of the soft fold, and phonation frequency was determined by the properties of the soft fold alone. The stiff fold was only enslaved to vibrate at a much reduced amplitude. In the second regime with small left-right stiffness mismatch, eigenmodes of both folds actively participated in the eigenmode synchronization process. The two folds vibrated with comparable amplitude, but the stiff fold consistently led the soft fold in phase for all conditions. A qualitatively good agreement was obtained between experiment and simulation, although the simulations generally underestimated phonation threshold pressure and onset frequency. The clinical implications of the results of this study are also discussed.

“…Some evidence of nonlinear source-filter coupling comes from earlier voice source analysis ͑Rothenberg, 1981; Fant, 1986͒, excised larynx experiments ͑Alipour et al, 2001͒, and physical model experiments ͑Chan and Titze, 2006Zhang et al, 2006͒. A more extensive discussion and bibliography is given in the companion paper ͑Titze, 2008͒.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear source–filter coupling in phonation: Vocal exercises

Titze

Riede

Popolo

2008

167

Nonlinear source-filter coupling has been demonstrated in computer simulations, in excised larynx experiments, and in physical models, but not in a consistent and unequivocal way in natural human phonations. Eighteen subjects ͑nine adult males and nine adult females͒ performed three vocal exercises that represented a combination of various fundamental frequency and formant glides. The goal of this study was to pinpoint the proportion of source instabilities that are due to nonlinear source-tract coupling. It was hypothesized that vocal fold vibration is maximally destabilized when F 0 crosses F 1 , where the acoustic load changes dramatically. A companion paper provides the theoretical underpinnings. Expected manifestations of a source-filter interaction were sudden frequency jumps, subharmonic generation, or chaotic vocal fold vibrations that coincide with F 0 -F 1 crossovers. Results indicated that the bifurcations occur more often in phonations with F 0 -F 1 crossovers, suggesting that nonlinear source-filter coupling is partly responsible for source instabilities. Furthermore it was observed that male subjects show more bifurcations in phonations with F 0 -F 1 crossovers, presumably because in normal speech they are less likely to encounter these crossovers as much as females and hence have less practice in suppressing unwanted instabilities.