Bats (order Chiroptera) have the most acute hearing of any non-aquatic animal, due to their ultrasonic echolocation. Most species use frequencies in the 20-80 kHz range, although some can hear frequencies as high as 120-250 kHz, compared with almost 20 kHz for the human limit and 280 kHz for the common dolphin (Delphinus delphis).

Echolocation is a method of sensory perception by which bats orient themselves to their surroundings, detect obstacles, communicate with others, and find food. Bats send out sound waves using their mouth or nose and when the sound hits an object an echo comes back.  The bat can then identify an object by the sound of the echo. In fact, the echolocation system is so accurate that bats can detect insects the size of gnats and objects as fine as a human hair.