When ultrasonic waves are emitted into a liquid, bubbles called cavitation are generated, and when the bubbles burst, the shock waves generated can be used for cleaning. Similarly, when the capillary waves formed on the liquid surface break, aerosol is dispersed from the tip of the wave and is used in atomization devices. Cavitation size and aerosol particle size depend on the ultrasound frequency. When designing equipment, the frequency of the ultrasonic waves, or in other words the resonant frequency of the piezoelectric ceramics used, is important.