How does sonar work?
Sonar (SOund NAvigation and Ranging) gives our submarines virtual “eyes” underwater. Sonar is used primarily to detect ships and submarines. There are two types of sonar: active and passive. When using active sonar, a submarine transmits a pulse of sound into the water and listens for how long it takes to bounce off another object such as a ship or submarine and return. This gives information about that ship or submarine’s direction and distance away. Unfortunately, if a submarine uses active sonar, all the other sonar-capable ships and submarines in the area would know that the submarine is there. Since the primary advantage that submarines enjoy is stealth (other ships don’t know where they are), most submarines rarely use active sonar. Passive sonar listens for the sounds coming from other ships and submarines. When a submarine uses passive sonar, it is able to obtain information about other ships and submarines without revealing its own position.
Bats do it, whales do it, even subs at sea do it. They all find out about their surroundings with reflected sound waves. Dolphins are so good at it that they can tell the difference between balls two inches in diameter and others only an eighth inch larger. The common name for the process is SONAR, which is an acronym for Sound Navigation and Ranging. The process of underwater sonic detection began in World War I and continued through World War II to combat the German submarines trying to destroy the maritime trade which kept Great Britain alive. The British developed a system know as ASDIC, which was put on destroyers to help find submarines. As this system was improved, it was also deployed on both sides. Sonar has two modes, passive and active. In the passive mode, you listen to hear what is going on. Different kinds of ships make different kinds of sounds and so it is possible to tell what kind of ship is going by and in what direction it is just by listening. In the active mode, t
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 te
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. Much more detail at the site http://www.exploratorium.edu/theworld/sonar/sonar.
