Cavitation is a phenomenon in which the static pressure of a liquid is reduced below the vapor pressure of the liquid, resulting in the formation of small vapor-filled bubbles in the liquid. When exposed to higher pressures, these cavities, called “bubbles” or “cavities,” collapse and can generate shock waves that can damage machinery. These shock waves are strong when they are very close to the imploded bubble, but weaken rapidly as they propagate away from the implosion. Cavitation normally generates random and high-frequency broadband energy that is superimposed on the blade passage frequency (VP) and sometimes its harmonics