Cavitation induced by asymmetric, distorted pulses of ultrasound: a biological test.

Prediction of the response of gaseous microbubbles to ultrasonic waves is complicated by the finite-amplitude distortion associated with large amplitude acoustic fields. Typical finite-amplitude pulses in medical applications consist of a sharp positive spike followed by a smaller, slowly varying negative pressure. In previous theoretical studies it was found that: (a) the peak-positive pressure is a very poor index of bubble response; (b) the peak-negative pressure typically underestimates the bubble response; (c) a better predictor of bubble response is the pressure amplitude of the fundamental in a Fourier series expansion of the distorted pulse. It is reported here that the killing of Drosophila larvae exposed to pulsed, symmetric, sinusoidal fields and to pulsed, asymmetric, distorted fields is consistent with these predictions.