Physiological process for locating distant or invisible objects (such as prey) by emitting sound waves that are reflected back to the emitter by the objects. Echolocation is used by an animal to orient itself, avoid obstacles, find food, and interact socially. Most bats employ echolocation, as do most, if not all, toothed whales (but apparently no baleen whales), a few shrews, and two kinds of birds (oilbirds and certain cave swiftlets). Echolocation pulses consist of short bursts of sound at frequencies ranging from about 1,000 Hz in birds to at least 200,000 Hz in whales. Bats use frequencies from about 30,000 to about 120,000 Hz.