Ultrasound is sound waves with frequency higher than 20 kHz that human cannot hear it. There is no difference between ultrasound with 'normal' (audible) sound in its physical properties. Normally, higher the frequency, shorter the wavelength. Therefore, when the frequency of the ultrasonic waves is higher enough, the wavelength can be smaller than the macroscopic size in the heterogeneous media, which can cause the ‘wave scattering’. Ultrasonic is an adjective related to ultrasound. For example: ultrasonic instrumentation, ultrasonic transducer, ultrasonic CODA waves, ultrasonic pulse velocity test (UPV test) etc.
Contributor: Xin Wang (ESR1)