What do we call sound waves with frequencies above 20,000 Hz?

Sound waves with frequencies above 20,000 Hz are known as ultrasound. This term is widely used in various applications, particularly in medical imaging, where high-frequency sound waves are utilized to create images of the inside of the body, such as in ultrasound scans.

Frequencies above 20 kHz are beyond the upper limit of human hearing, which typically ranges from about 20 Hz to 20 kHz. Hence, these high-frequency sound waves are not audible to humans, making the term relevant in contexts where distinguishing between what can be heard and what cannot is important.

In contrast, infrasound refers to sound waves with frequencies below 20 Hz, while audible sound encompasses the range of frequencies that can be detected by the human ear (20 Hz to 20 kHz). Subsonic pertains to speeds that are less than the speed of sound, which is a different concept altogether. Thus, ultrasound is the appropriate term for sound waves with frequencies greater than 20,000 Hz.