Echolocation

See:

Animal echolocation: animals emitting sound waves and listening to the echo in order to locate objects or navigate.
Sonar: (sound navigation and ranging) the use of sound to navigate or to locate other watercraft, usually by submarines.
Echo sounding: listening to the echo of sound pulses to measure the distance to the bottom of the sea, a special case of Sonar.
Medical ultrasonography: the use of ultrasound echos to look inside the body