How Does Sonar Work?

Sonar (Sound Navigation And Ranging) works on the same principle as echolocation used by bats and dolphins. Active sonar emits a pulse of sound (a "ping") from a transducer and then listens for the echo reflected off objects. By measuring the time delay between the ping and the return echo, and knowing the speed of sound in water (about 1,500 m/s), the system calculates the distance to the object. The echo direction reveals the object bearing, and the frequency shift (Doppler effect) can indicate whether it is moving toward or away. Passive sonar, by contrast, simply listens for sounds made by ships, submarines, or marine life without emitting any signal.