Which term describes sound frequencies above 20 kHz?

The term that describes sound frequencies above 20 kHz is ultrasound. Ultrasound refers specifically to sound waves that are at frequencies higher than what the human ear can detect, which is generally considered to be 20 kHz. This range of sound is widely utilized in various applications, particularly in medical imaging and diagnostics, where ultrasound waves can create images of internal body structures.

In medical contexts, ultrasound is commonly used to visualize organs and tissues, as well as to monitor fetal development during pregnancy. The high frequency allows for better resolution and more detailed imaging compared to lower frequencies.

Other types of sound, such as infrasound (which refers to sound frequencies below 20 Hz), audible sound (which falls within the 20 Hz to 20 kHz range), and infrared sound (which does not actually refer to sound but rather to electromagnetic radiation wavelengths in the infrared range), do not pertain to frequencies above 20 kHz.