Sonar is simply making use of an echo. When an animal or machine makes a noise, it sends sound waves into the environment around it. Those waves bounce off nearby objects, and some of them reflect back to the object that made the noise. It’s those reflected sound waves that you hear when your voice echoes back to you from a canyon. Whales and specialized machines can use reflected waves to locate distant objects and sense their shape and movement.
The range of low-frequency sonar is remarkable. Dolphins and whales can tell the difference between objects as small as a BB pellet from 50 feet (15 meters) away, and they use sonar much more than sight to find their food, families, and direction. The LFA sonar being tested by the military can travel thousands of miles, and could cover 80% of the earth’s oceans by broadcasting from only four points. The frequency that both whales and the military use falls between 100 and 500 Hz. Whales send signals out between 160 and 190 Db, the Navy has tested its sonar signals at levels up to 235 Db.
To detect, track and destroy enemy ships and submarines.
To detect and destroy enemy underwater mines.
To communicate using underwater sound as a medium.
To navigate under ice.
Safe navigation in shallow water.
Determining navigational location.
Measuring sound velocity.
Emergency location beacon.
Wreck location and salvage.
Animal location and tracking.
Machinery maintenance and repair.
- Detecting & tracking submarines, ships, etc. (Under-water combat)
- Mapping the ocean floor. (Navigation/Surveilance)
- Detecting under-water mines.
Passive Sonar (Hydrophones)
- Passive detection/tracking: Listening to the noise from enemy submarines, surface vessels, etc. over long ranges.
P.S. Many animals use echo-location (biological sonar) for hunting & navigation purposes.