Adjustment of the Vocal Tract Shape via Biofeedback: A Case Study

Area of Science:

• Acoustics
• Speech Science
• Biofeedback

Background:

• Vocal tract shape influences voice production by modifying sound frequencies (formants).
• Biofeedback is used in voice training to help individuals self-regulate physiological processes.

Purpose of the Study:

• To investigate vocal tract shape adjustments using external sound waves as biofeedback.
• To explore the relationship between vocal tract resonance, amplification, and acoustic properties.

Main Methods:

• Subjects adjusted vocal tract shape to optimize amplification of external sound waves (1st and 2nd formant frequencies).
• Sound waves from a loudspeaker were amplified by the vocal tract, serving as biofeedback.
• Vocal tract resonance, bandwidth, and damping were analyzed.

Main Results:

• Vocal tract resonance amplification follows forced oscillation principles, with the vocal tract acting as a resonator.
• Increased amplification correlated with smaller bandwidths and lower damping.
• Tuned resonance frequencies persisted during exhalation and phonation.

Conclusions:

• External sound waves can serve as effective biofeedback for non-phonatory vocal tract adjustments.
• This non-phonatory biofeedback technique shows potential for enhancing standard voice training protocols.