Cavitation Effects at Megahertz Frequencies

Abstract

This experimental programme, using plane travelling-wave ultrasound with the sample liquid in the first axial maximum of the acoustic far-field,, has the following objectives:-

• 1. To find threshold intensities for the onset and extinction of subhar-monic oscillation as the acoustic intensity is raised and lowered in the sample.

• 2. To find the equivalent thresholds for sonoluminescence in the sample, and compare these with I.

• 3. To study the effect of sample gas content on I and 2.

• 4. To investigate driving the transducer in an A.C. bridge, using the off-balance voltage of this bridge as an indication of changes in the motional impedance of the transducer, and compare these values with the R.F. voltage of the drive amplifier when coupled directly to the transducer.

• 5. To measure the sound velocity in the sample liquid by pulse-echo technique, looking for changes in bulk modulus at the subharmonic threshold.

• 6. To find the acoustic threshold for release of molecular iodine from KI/CCℓ4 samples which have varying gas content, and compare these thresholds with I and 2.

• 7. Compare a recently measured biological end-point with the above thresholds.