Michalakis A. Averkiou
Lawrence A. Crum
Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98105
Mark F. Hamilton
Univ. of Texas at Austin, Austin, TX 78712-1063
Measurements of finite-amplitude acoustic pulses radiated by a focused
piston source in water are reported. Pulses with center frequency of 2.25 MHz,
durations ranging from two to ten cycles, and peak sound pressures up to 3 MPa
were measured with a wideband (1--20 MHz) membrane hydrophone. The combined
effects of focusing, diffraction, and finite-amplitude distortion on short
pulses are demonstrated. Propagation curves for the peak positive and peak
negative pressure along the axis of the source are shown. The peak negative
pressure, which is an important factor in cavitation dynamics, is maximized in
the prefocal region and shifts closer to the source with increasing source
amplitude, as predicted earlier [Averkiou et al.,