A sonar machine

Sonar is a machine that uses underwater sound waves to find other objects in the sea. A sonar can work by sending out sound and listening for echoes (active sonar), like a radar, or by listening for sound made by the object it is trying to find (passive sonar).

The basic parts of an active sonar are:

• the transmitter creates the sound waves.
• the hydrophone or hydrophone array converts the sound waves into electricity.