Bifurcations in an asymmetric vocal-fold model

Area of Science:

• Nonlinear Dynamics
• Voice Biomechanics
• Acoustic Science

Background:

• Vocal fold vibrations are complex and can lead to voice disorders.
• Understanding the dynamics of vocal fold vibration is crucial for diagnosing and treating voice pathologies.
• Previous models have simplified vocal fold mechanics, potentially missing key dynamic behaviors.

Purpose of the Study:

• To analyze a two-mass model of vocal fold vibrations using nonlinear dynamics.
• To investigate the impact of physiological parameters on vocal fold vibration stability.
• To explore the onset of complex vibrational patterns, including chaos, due to vocal fold asymmetry.

Main Methods:

• Analysis of a two-mass model of vocal fold vibrations.
• Application of nonlinear dynamics techniques to locate bifurcations in physiological parameter planes.
• Characterization of attractors using phase portraits, spectra, and next-maximum maps.

Main Results:

• Bifurcations were identified in parameter planes related to subglottal pressure and vocal fold stiffness.
• A significant tension imbalance between the left and right vocal folds was shown to induce bifurcations.
• Complex dynamics including subharmonic regimes, toroidal oscillations, and chaos were observed.

Conclusions:

• Vocal fold tension asymmetry is a critical factor leading to complex and potentially pathological vibration patterns.
• The simulated chaotic dynamics offer a model for understanding voice disorders like laryngeal paralysis.
• Nonlinear dynamics provide valuable tools for elucidating the mechanisms underlying voice production and dysfunction.