Animal echolocation
Echolocation, also called bio sonar, is a biological active sonar used by several animal groups, both in the air and underwater. Echolocating animals emit calls and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocation is used for navigation, foraging, and hunting prey. Echolocation calls can be frequency modulated (FM, varying in pitch during the call) or constant frequency (CF).