sonar science definition

1. Short for sound navigation and ranging. A method of detecting, locating, and determining the speed of objects through the use of reflected sound waves. A sound signal is produced, and the time it takes for the signal to reach an object and for its echo to return is used to calculate the object's distance. The Doppler effect  can also be used to determine the object's relative velocity. Electronic sonar systems are used for submarine navigation and for detecting schools of fish. Some mammals, especially bats, use biological sonar to navigate and detect prey in dark conditions, commonly called echolocation.
2. The equipment or physiology used in doing this. See also Doppler effect, lidar, radar.

sonar

An electrical impulse is converted into sound waves that are transmitted underwater. The sound waves are reflected off objects in their paths, creating echoes that return to the vessel and are picked up by the sonar equipment.