Impact of subglottal resonances on bifurcations and register changes in laboratory models of phonation

Abstract

Many laboratory studies of phonation have failed to fully specify the subglottal system employed during research. Many of these same studies have reported a variety of nonlinear phenomena, such as bifurcations and vocal register changes. While such phenomena are often presumed to result from changes in the biomechanical properties of the larynx, such phenomena may also be a manifestation of coupling between the voice source and the subglottal tract. Using laboratory models of phonation, a variety of examples will be given of nonlinear phenomena induced by both laryngeal and subglottal mechanisms. Moreover, using tracheal tube lengths commonly reported in the literature, it will be shown that most of the nonlinear phenomena commonly reported in voice production may be replicated solely on the acoustical resonances of the subglottal system. Finally, recommendations will be given regarding the experimental design of laboratory experiments which may allow laryngeally induced bifurcations to be distinguished from subglottally induced bifurcations.