Ultrasound is used in science and technology for a wide variety of applications. The physical principles of ultrasound are briefly described below.
When ultrasound from a frequency of 20 kHz and a sound intensity of 0.1 W/cm² is applied to liquid media, tiny cavitation bubbles are created due to the strong alternating stress. These finest cavities with low internal pressure are created due to the inertia of the medium and the induced mechanical vibrations. Due to the external pressure of the medium, the unstable bubbles implode after a short period of growth under high pressure and temperature peaks. This creates high shear forces at the boundary layer. This effect occurs especially at air bubbles or dirt particles, the so-called cavitation nuclei. Cavitation in water triggers the acoustically perceptible noise of high-power ultrasound devices.