Different cleaning requirements require different ultrasonic frequencies. Lower ultrasonic frequencies indicate greater cavitation bubbles and more intense cavitation internal rupture. Cavitation bubbles are much smaller at higher frequencies and although cavitation breaks less intensely. The lower the ultrasonic frequency is, the more powerful the cavitation produced in the liquid is, the stronger the force is, and it is suitable for coarse and dirty initial washing of workpieces. At high frequencies, the ultrasonic directionality is strong enough for fine object cleaning. Ultrasonic working frequency is low, the working noise is louder, and the noise is significantly reduced with the increase of working frequency. The industrial common frequency is 16, 18, 20, 25, 28, 40 kHz. The choice of frequency needs to be determined based on practical experience and process tests. Selection errors can cause a lot of trouble. For example, silicon wafers that are cleaned with a frequency of 28 kHz are often shattered, and ferrite permanent magnets with 40 kHz cleaning are often not effective.