In vivo insights into irregular voice production as a complex nonlinear system-a case study

Area of Science:

• Biomechanics of speech and voice
• Nonlinear dynamics in biological systems
• Acoustic phonetics

Background:

• The human voice relies on vocal fold oscillations for sound production.
• Vocal tract structures beyond the vocal folds can also oscillate, influencing voice quality.
• Understanding irregular phonation types requires a nonlinear systems approach.

Purpose of the Study:

• To investigate the spectrum of irregular phonation types from a nonlinear systems perspective.
• To analyze oscillatory mechanisms in diverse voice qualities produced by a professional metal singer.
• To identify nonlinear phenomena associated with irregular voice production.

Main Methods:

• In vivo investigations using transnasal high-speed digital imaging.
• Simultaneous electroglottography and acoustic data acquisition.
• Analysis of 10 distinct voice qualities from a professional metal singer.

Main Results:

• Identified nearly periodic oscillatory patterns in voice qualities, differing in glottal/supraglottic oscillation ratios and behavior during glissando.
• Reduced glottal adduction and increased compression contribute to voice irregularity.
• Supraglottic oscillations can coexist with various glottal oscillation mechanisms, leading to nonlinear phenomena like synchronized oscillations, bifurcations, biphonations, and chaos.

Conclusions:

• Irregular phonation involves complex interactions between glottal and supraglottic oscillatory mechanisms.
• Nonlinear dynamics play a crucial role in generating diverse and complex voice qualities.
• The study provides insights into the biomechanical and acoustic underpinnings of extreme vocal techniques and voice disorders.