Sonar (SOund Navigation And Ranging) is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water. It measures the time between the transmission of a pulse and the return of the echo.
There are two basic types of Sonar-
Active sonar –
where a sound is generated (or pinged) by a projector,and the sound waves generated travel through the sea to the target, and are returned as sonar echoes, to a hydrophone, which converts the sound into electricity.
Passive sonar –
Passive Sonar uses the sound radiated by the target. This is a one-way transmission and a hydrophone picks up the sound and converts this into electricity.
There is a complex signal processing system, which converts these sounds (electrical impulses) for use in a modern sonar system, that tracks the position of the target.