A comparison between flexible disk transducer cavitation measurements and predictions

An investigation of the threshold of cavitation of flexible disk transducers used as underwater acoustic sources was conducted. The principal task was the estimation of the cavitation threshold in sound pressure level (SPL) of an individual transducer as a function of operating depth and the actual measurement of the cavitation threshold. The transducers under test were driven at a series of voltage levels, using CW pulse lengths of 50 and 100 ms. these drive voltages were increased in steps and the received signals were analyzed for total harmonic distortion (THD), transmitting voltage response (TVR), output SPL, and voltage-current phase angle, all as a function of depth. The onset of cavitation on the flex disk is well defined in terms of THD. Comparing the measured values for the onset of cavitation to those predicted by an expression recommended by Sherman and Butler, a value of the cavitation parameter, gamma, was determined to be about 0.36, consistent with, and bracketed by, their values, for a number of transducer shapes. predictions of cavitation threshold versus depth for the flexible disk transducer were within 1 to 2 dB of measured results.