The first part of this paper reports an experimental investigation of some parameters that
control the occurrence of biologically effective cavitation‐type phenomena in the frequency
region 0.25 4 MHz. The experimental criterion by which “cavitation” is recognized here is the
simultaneous occurrence of degradation of DNA in aqueous solution, liberation of free I 2
from KI solution, and generation of half‐order subharmonic. The intensity threshold for
cavitation rises with frequency from 0.14 to 17.5 W cm− 2 (spatial peak) in the above …

Biological change consequent on ultrasonic exposure may arise through three distinct
modes: thermal, cavitational (including stable bubble), and “other.” The thermal mechanism
is quite well defined and predictable. Wide divergencies occur between different authors on
values of cavitation thresholds, but these may be due, in part, to differences in criteria used.
Our results are reported for dependence of “stable cavitation” on intensity, frequency,
pulsing parameters, ambient pressure, and nature of the medium (liquid, gel, or organized …