original template by Ray Lam, Fall 97

revised template by Rachel Shorey and Steve Bergen 2/9/98

Sonar

Sonar is a machine that detects depth of oceans by sending sound waves. It can also detect schools of fish or reefs. There are two types of sonar: active sonar and passive sonar. The active sonar sends a sound which is like a ping, when it hits an object; it is sent back up to the boat to tell how deep the water is. This is called echo ranging. Passive sonar listens for sounds given off targets. This system cannot detect the distance, but it can find the direction of an object. When passive sonar listens, it does not give off a sound; therefore, other sonar cannot detect it. Submarines usually would have both types of sonar so they are prepared in any circumstance. The British scientists developed sonar after World War I. They realized the threat that German submarines had posed during the war, so they developed a way to seek them out. The first system was set in operation in 1921. It was known as ASDIC after the Allied Submarine Detection Investigation Committee. The US started to use sonar in 1927. During WWII the US used sonar to surprise the Germans, but in those days it was operated manually. After WW II , sonar was developed that could automatically rotate and that could travel up to ten miles. They also developed sonar which didnŐt get affected by low water temperature . Aircraft can also use sonar by dropping devices into the water which would signal by radio the information it picked up. Also ships can use sonar to find old ship wrecks and to find the treasures under the sea. Sonar has been an extremely useful discovery. It has improved our naval fighting strategies over the last seventy years. It will continue to improve as the technology is discovered.

Sonar I am a helper to many seamen, I serve to protect them from rocks and debris that could cause a hazard. At the same time, helping them with their jobs. From locating fish to catch, all the way to protecting the armed services around the world. I enable the people of the world to get to know all the depths of the oceans .