Ultrasonic transmission requires medium, which is usually water, so we usually add water in the tank of ultrasonic cleaning machine. The ultrasonic cleaning machine operates by the action of ultrasonic high-frequency oscillation on water molecules, and the energy is also absorbed by water, so it will not cause any damage to people. The reason for the sound is that it is not ultrasonic. People can't hear ultrasonic. This also needs to be explained by the principle of ultrasonic cleaning machine: when ultrasonic wave acts on the liquid, tens of thousands of bubbles will be generated in the liquid, which will burst all the time, resulting in a shock wave with great energy, which is equivalent to an instantaneous high temperature of hundreds of degrees and up to thousands of atmospheres. This phenomenon is called "cavitation", Ultrasonic cleaning machine uses the shock wave generated by bubble explosion in liquid to wash and clean the inner or outer surface of workpiece gap.

超声波会在液体中传播，使液体与机槽在超声频率下一起振荡，液体与清洗槽振动时都有各自的固有频率，所以人们在使用超声波机器时，会听到这种振荡中产生的“啧啧啧”的声音。刚开始可能会听不习惯，感觉不是很安心，但这是心理作用，实际上对人体并没有什么危害。

The ultrasonic wave will propagate in the liquid and make the liquid and the machine tank oscillate together at the ultrasonic frequency. When the liquid and the cleaning tank vibrate, they have their own natural frequencies. Therefore, when using the ultrasonic machine, people will hear the "tut tut" sound generated in this oscillation. At first, you may not be used to listening and feel at ease, but this is a psychological effect. In fact, it does no harm to the human body.

超声波在空气里传播的衰减率大，所以超声波对人体并不会有多大的影响。

The attenuation rate of ultrasonic wave propagation in the air is the largest, so ultrasonic wave will not have much impact on the human body.

如果非要说工业超声波清洗机对人体有伤害，那则是与人体的接触问题了。在清洗机工作的时间段中，要是不带着手套就直接去接触正在工作的超声水槽里的水，则会感受到微妙的变化，会有感觉不舒服。使用者应尽量避免直接把手放在正在工作的水槽里。如果一定要接触，为了起见应该带上手套。若还是不太放心的话，那建议在超声波清洗机工作时，不要长时间呆在机子旁边，也要尽量少接触清洗剂。

If the industrial ultrasonic cleaning machine is harmful to human body, it is a contact problem with human body. During the working period of the cleaning machine, if you directly contact the water in the working ultrasonic tank without gloves, you will feel subtle changes and feel uncomfortable. Users should try to avoid putting their hands directly in the working sink. If contact is necessary, gloves should be worn for safety. If you are still worried, it is recommended not to stay next to the ultrasonic cleaning machine for a long time and contact the cleaning agent as little as possible.

超声波清洗剂的选择普通能够从两个方面思索，一方面要从污物的性质来选择的清洗剂，另一方面则是要思索清洗剂外表张力、黏度以及高温后所产生的蒸汽压的上下。由于这些特性会影响到超声波空化强弱，高蒸汽压会降低超声波空化强度，清洗液体外表的张力大、粘滞度高则不容易产生空化。

The choice of ultrasonic cleaning agent can be considered from two aspects: on the one hand, the cleaning agent should be selected according to the nature of dirt; on the other hand, the surface tension, viscosity and steam pressure generated after high temperature should be considered. Because these characteristics will affect the intensity of ultrasonic cavitation, high vapor pressure will reduce the intensity of ultrasonic cavitation. If the surface tension and viscosity of cleaning liquid are large, cavitation is not easy to occur.