In simple terms, Sonar refers to a system used to transmit sound waves underwater. It also receives the reflections of sound waves and uses that information to detect underwater depths or the existence of and/or the locations of the submerged objects. Sonar is an acronym for Sound Navigation and Ranging.
A Sonar device sends out sound waves at a steady frequency and then listens to the waves that return to the source. The data from the reflected sound waves is then relayed to operators through a display on a monitor or a loudspeaker.
Invented by Lewis Nixon in 1906, the importance of the technology grew as it came in handy for the detection of submarines during the First World War. Nixon is credited with inventing the first device to detect sound waves underwater, but the first device capable of detecting submarines was invented by Paul Langevin in 1915.
Initially, sonar systems relied on listening to sounds underwater without any sounds being sent out. Active sonar systems that send and receive sounds came forth by 1918 in both the U.S. and Britain. The need for detecting submarines created the perfect opportunity for further development of the technology, but it never came into use for the First World War.
During the Second World War, active sonar systems came into use, and it was also when the term Sonar was initially coined.
Primarily, there are two types of active sonar systems. Short-range active sonar systems emit pings or pulses of constantly changing frequency. The receiver of such sonar systems relies on differentiating between the sound emitted and sound received to process the gain and derive the information about the detection of distances.
Long-term active sonar systems rely on low-frequency pulses instead. They measure the time elapsed between the transmission and the detection of the low-frequency sound waves under water.
Passive sonar systems do not send out sounds, but they listen. Typically used for military applications, these sonar systems rely on a massive sonar database to accurately detect different classes of ships and maneuvers, based on the sound their movement makes.
While sonar systems are mainly used for military purposes, they have several other uses as well. Depth detection, diving safety, communications at sea and even commercial fishing nowadays rely on the technology due to its effectiveness in underwater detection.
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