The propagation laws of ultrasound in media, such as reflection, refraction, diffraction, and scattering, are not fundamentally different from those of audible sound waves. But the wavelength of ultrasound is very short, only a few centimeters, even a few thousandths of a millimeter. Compared with audible sound waves, ultrasound has many peculiar characteristics: propagation characteristics - the wavelength of ultrasound is very short, and the size of typical obstacles is many times larger than that of ultrasound, so the diffraction ability of ultrasound is poor. It can propagate in a straight direction in a uniform medium, and the shorter the wavelength of ultrasound, the more significant this characteristic is. Power characteristics - when sound propagates in the air, it drives particles in the air to vibrate back and forth, doing work on the particles. Sound wave power is a physical quantity that represents the speed at which sound waves do work. At the same intensity, the higher the frequency of sound waves, the greater their power.

Due to the high frequency of ultrasound, its power is very high compared to general sound waves. Cavitation effect - When ultrasound propagates in a liquid, small cavities are generated inside the liquid due to the violent vibration of liquid particles. These small voids rapidly expand and close, causing violent collisions between liquid particles, resulting in pressures of several thousand to tens of thousands of atmospheres. The intense interaction between particles can cause a sudden increase in the temperature of the liquid, which plays a good stirring role, causing two immiscible liquids (such as water and oil) to emulsify and accelerate the dissolution of solutes, accelerating chemical reactions. The various effects caused by the action of ultrasound in liquids are called the cavitation effect of ultrasound.