Mechanisms for tongue-tip trills

Abstract

Possible mechanisms for the production of tongue-tip trills are discussed. It is necessary that energy be transferred from the airstream to the tongue tip to enable it to vibrate. A two-mass model, similar to that of the vocal folds, is one possible model for tongue trills, but there are others that allow the tongue one-degree-of-freedom motion. It is possible that the boundary-layer separation point is affected by the acceleration of air, which is not accounted for in the quasistatic approximation. An argument will be given that the acceleration term produces a favorable energy transfer during trills. Also, the capacitive loading of the vocal tract behind the tongue constriction can provide necessary phase shifts between constriction volume velocity and intraoral pressure for favorable energy transfer. A numerical simulation of the latter model is presented with parameters derived from measurements of oral-nasal volume velocity and intraoral pressure during sustained trills. Some of the features of the trills are reproduced with this simulation.