Deliberate use of distortion in singing

Abstract

Singers are able to create aperiodic vibration of the vocal folds by either desynchronizing the primary oscillators (the vocal folds) or by engaging secondary sound sources (the false vocal folds, the aryepiglottic folds, or the velum). The desynchronization of the primary oscillators can be accomplished by creating a slight left-right asymmetry and then using the vocal tract (an acoustic oscillator) to entrain one vocal fold, leaving the other vocal fold to oscillate independently. Other aperiodicities can be created by driving the vocal folds at large amplitudes (with the critical parameter being A/L, the amplitude to length ratio of the vocal folds). In this mode of distortion, the highly nonlinear stress-strain characteristics of the vocal fold tissues are exploited. Infant cries, shouts, and groans are characteristic of this type of nonlinearity. Some videotaped examples and some computer simulations will be given to illustrate these phenomena.