Physical modeling of buzzing artificial lips: The effect of acoustical feedback

The influence of the up- and downstream acoustics on the buzzing behavior of artificial lips has been studied. In the presence of a long downstream pipe, the oscillation frequency is well predicted by means of a model assuming a single mechanical degree of freedom for the lips. A minimum of the threshold pressure for buzzing is observed when the lips are just closed at rest. The magnitude of this threshold pressure is underestimated by the model. In order to fit experiments the quality factor of the lip resonance has to be reduced by a factor two compared to the measured quality factor. In the absence of downstream pipe the threshold pressure increases by a factor three and a jump in oscillation frequency from one mechanical lip-mode to another one is observed as the lung pressure is increased. An attempt to describe this behavior by means of a 2-mass-model fails.