Vocal wow in an adapted reflex resonance model.

Area of Science:

• Voice production and control
• Biophysics of phonation
• Sensorimotor integration

Background:

• Vocal wow and tremor are slow voice modulations linked to auditory and somatosensory feedback.
• Understanding their mechanisms is crucial for diagnosing neurological voice disorders.
• Existing models (e.g., reflex resonance model) primarily focus on somatosensory feedback.

Purpose of the Study:

• To expand the reflex resonance model by incorporating auditory feedback.
• To investigate the emergence of vocal wow and tremor under combined feedback conditions.
• To develop methods for analyzing vocal feedback parameters from acoustic signals.

Main Methods:

• Mathematical modeling of laryngeal muscle activation with integrated auditory and somatosensory feedback loops.
• Analysis of Hopf bifurcations to identify critical feedback parameters.
• Derivation of parametric formulas to estimate feedback parameters from voice signals.
• Illustration of model predictions with clinical data from subjects with voice disorders.

Main Results:

• Auditory feedback, when incorporated, can lead to vocal wow via Hopf bifurcation.
• Vocal wow period is sensitive to feedback delay, especially for delays exceeding 200 ms.
• Interactions between auditory and somatosensory feedback significantly alter vocal modulations.
• The model provides a framework for understanding phonatory instabilities in sensorimotor voice control.

Conclusions:

• The integrated model successfully predicts the emergence of vocal wow and tremor.
• Phonatory instabilities offer valuable insights into normal and pathological voice sensorimotor control.
• The findings have implications for understanding and potentially treating neurological voice disorders.