Dept. of OAE, IEMN, Valenciennes Univ., BP 311 Le Mont-Houy, 59304 Valenciennes, France
Over the last 20 years, a large number of studies have been devoted to acoustic cavitation in liquids. High power transducers are needed to generate cavitation. A transducer working at 500 kHz will be presented. This transducer has been electrically matched using a stainless steel layer welded to a piezoelectric element. Optimal thickness of the matching layer, which is considered as a transmission line, has been found using a Mason's circuit. The transducer conversion efficiency is experimentally evaluated to determine the acoustic pressure amplitude needed to generate cavitation in a liquid. The cavitation noise recorded with a hydrophone is used to characterize the cavitation state in the fluid. The energy of this noise is correlated to the acoustic pressure amplitude. Then the correlation between cavitation noise energy and chemical reactivity in homogeneous chemistry is also made. The bio-effect of cavitation on E. Coli cells is presented as a function of cavitation noise energy. It is evidenced that cavitation noise energy is an efficient tool to characterize a cavitation state in a fluid and to predict its chemical and bacteriological effects.