navigation during flight by the use of high frequency sound (sonar) pulses, the echo from which is detected by the ears and interpreted by the brain (acoustic orientation).

Echolocation calls are vocalizations that are produced in the larynx. Calls are emitted through the mouth or the nostrils. Bats that emit calls through the nostrils, such as Rhinolophidae and Hipposideridae, often have complex folds and/or flaps surrounding the nostrils, which may affect the signal.
A few megachiropterans also use echolocation (e.g., some species of Rousettus ), but these bats produce sound by clicking their tongues rather than by vocalization.

Examples of echolocation calls:
Nyctalus noctula (detector set to 25kHz)
Rhinolophus (Rhinolophus hipposideros, detector set to 105kHz)

Recordings used courtesy of:
-The Bat Conservation Trust, London.

Alternative forms for echolocation : biosonar, echolocate.