Contents I. Introduction
Aconsiderable body of technical literature has built up over the last 50 years related to the physical processes and applications of acoustic cavitation [1]–[4]. Despite the prolonged and growing technological importance of high power ultrasound in applications such as ultrasonic cleaning, the development of standardized methods for quantifying the degree of acoustic cavitation occurring within such a system remains elusive, although valuable reviews of the contemporary measurement state-of-the-art have been published [5], [6]. This situation undoubtedly partly arises due to the complexity of the range of processes collectively known by the umbrella term cavitation, although a somewhat artificially precise distinction is commonly made between bubbles undergoing noninertial (stable) cavitation or inertial (transient) cavitation [4]. Whereas it is recognized that noninertial cavitation may be relevant in some applications of high-power ultrasound [7], inertial cavitation is the more technologically important phenomena, and it is the violent collapse of short-lived cavities or bubbles that provide the conditions responsible for the range of observed effects. A further factor cited as inhibiting the development of high-power measurement methods is the lack of suitable measurement sensors for determining cavitation [8], [9].
