Several main parameters of ultrasound

Wavelength: In the air at 20℃, λ≤2cm (because the effect is similar in practical applications, usually λ≤3.4cm, that is, the mechanical wave with f≥10KHz is also called ultrasonic wave)

Wave speed: in the air at 20℃, v=343m/s, the speed is faster in the liquid, and the fastest in the solid

Power density: The defined formula is p=transmitting power (W)/transmitting area (cm²), usually p≥0.3W/cm². The ultrasonic wave propagating in the liquid can clean the dirt on the surface of the object. The principle can be explained by the phenomenon of "cavitation": when the pressure caused by the mechanical wave of the ultrasonic wave in the liquid reaches one atmospheric pressure, its power density is 0.35W/cm², At this time, the peak of the ultrasonic wave can reach vacuum or negative pressure, but in fact there is no negative pressure, so a large pressure is generated in the liquid, which pulls the liquid molecules into cavitation nuclei. This cavity is very close to a vacuum. It ruptures when the reverse of the ultrasonic wave reaches its maximum, and the strong impact caused by the rupture knocks down the dirt on the surface of the object. This shock wave phenomenon caused by the bursting of countless tiny cavitation bubbles is called "cavitation" phenomenon. Too small sound intensity cannot produce cavitation effect.