The ultrasonic cavitation threshold is closely related to the ultrasonic frequency. The higher the frequency, the higher the cavitation valve. In other words, the lower the frequency, the easier cavitation is to produce, and the compression and sparsity of the liquid under the condition of low frequency has a longer time interval, so that the bubbles can grow to a larger size before the collapse, increasing the strength of high altitude, which is conducive to the cleaning effect.

Therefore, low-frequency ultrasonic cleaning is suitable for the surface of large parts or the surface of dirt and cleaning parts of the high degree of integration. However, it is easy to corrode the surface of cleaning parts, and it is not suitable to clean the parts with high surface finish, and the cavitation noise is large. At the frequency of about 40KHZ, the number of cavitation bubbles produced is more than that at the frequency of 20KHZ with the same sound intensity, and the penetration is stronger. It is suitable to clean the workpiece with complex surface shape or blind hole. The cavitation noise is small, but the cavitation intensity is low, and it is suitable for the occasions where the binding force between the dirt and the surface of the cleaned part is weak. High frequency ultrasonic cleaning is suitable for fine cleaning of computer and micro-electronic components; Megahertz ultrasonic cleaning is suitable for the cleaning of integrated circuit chips, silicon wafers and wave films. It can remove micron and submicron level dirt without any damage to the cleaning parts. Therefore, considering the cleaning effect and economy, the frequency is generally selected in the range of 20-130khz. Of course, it is very important to select the correct frequency, and the specific selection of appropriate working frequency needs to do some experiments to obtain.