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.

超聲波會在液體中傳播，使液體（tǐ）與機槽在超聲（shēng）頻率下一起振蕩，液體與清洗槽振（zhèn）動（dòng）時都有各自的固有頻率，所以人們在使用超聲波機器時，會（huì）聽到這種振蕩中產生的“嘖嘖嘖”的聲音。剛開始可能會聽不習慣，感覺不是很安心，但這是心理作用，實際上對人體並沒有什麽危（wēi）害（hài）。

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.

超聲波在空氣裏傳播的衰減率（lǜ）大，所以超聲波對人體並不會有多大的影響（xiǎng）。

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.

如果非要說工業超聲波清洗機對人體（tǐ）有（yǒu）傷害，那則是與人體的接觸問（wèn）題了。在清洗機工作的時間段中，要是不帶著手套就直接去接觸正在工作的超聲水槽裏的水（shuǐ），則會感受到微妙的變化（huà），會有感覺不（bú）舒服。使用者應盡量避（bì）免直接把手放在正在工作的水槽裏。如果一定要接觸，為了安全起（qǐ）見應該帶上手套。若還（hái）是不太放心的話，那建議在超聲（shēng）波清洗機（jī）工（gōng）作時，不要長時間呆（dāi）在機子旁邊（biān），也要盡（jìn）量少接觸清洗劑。

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.

超聲波清洗劑（jì）的選擇普通能夠從兩個方麵思索，一方麵要從汙物的性質來選擇的清洗劑，另一方麵則是要（yào）思索清洗劑外表張力、黏度以及高溫後所產生的蒸（zhēng）汽壓的上下。由於這些特性會影響（xiǎng）到超聲波空化強弱，高蒸汽壓會降（jiàng）低（dī）超聲波空化強度，清（qīng）洗液體外表的張力大、粘滯度高則不容易產生空化。

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.