Introduction:
The human voice exhibits a wide range of expressions, primarily produced through the regular oscillatory motion of the vocal folds. However, other structures within the vocal tract can also vibrate, as seen in various singing techniques, supraglottic voice production, and functional voice disorders.
Material and Methods:
To explore the range of irregular phonation types during vocal effects in non-classical singing a heavy metal singer was asked to perform ten vocal effects such distortion, grunt, growl, rattle, vocal fry, etc. after normal phonation. The tasks were recorded using trans-nasal high-speed digital imaging with a frame rate of 20.000fps in combination with electroglottography and acoustic recordings. After segmentation the glottal area function and the supraglottic area function were calculated.
Results:
Some of the vocal qualities exhibited nearly periodic or period-doubling oscillatory patterns, which differed in their interrelationships, behavior during glissando, and the structures involved in oscillation. Increased irregularity was associated with both reduced glottal adduction and heightened glottal and supraglottic compression. Moreover, supraglottic oscillations were found to coexist with different glottal oscillation mechanisms. Based on the data, we identified several categories of nonlinear phenomena, including synchronized oscillations with defined frequency ratios, bifurcations, biphonation, and chaotic oscillations.
Conclusions:
The data show that trained singers can consciously control and synchronize supraglottic and glottal oscillators, producing both periodic and aperiodic vibration patterns. These findings provide new insights into the mechanisms of supraglottic vibration and may support future applications in therapeutic voice training and advanced vocal performance.