Acoustic communication systems are Sonar devices where there is both a sound wave projector and receiver on both sides of the signal path. By 1918, both Britain and the U.S had built active systems, in active Sonar signals are both sent out and then received back. The first Sonar devices were passive listening devices - no signals were sent out. He was too late to help very much with the war effort however, Langévin's work heavily influenced future sonar designs.

In 1915, Paul Langévin invented the first sonar type device for detecting submarines called an 'echo location to detect submarines' using the piezoelectric properties of the quartz.

Interest in Sonar was increased during World War I when there was a need to be able to detect submarines. Lewis Nixon invented the very first Sonar type listening device in 1906, as a way of detecting icebergs. This early research led to the invention of dedicated sonar devices by other inventors. The Sonar device will send out a subsurface sound wave and then listens for returning echoes, the sound data is relayed to the human operators by a loudspeaker or by being displayed on a monitor.Īs early as 1822, Daniel Colloden used an underwater bell to calculate the speed of sound underwater in Lake Geneva, Switzerland. It has been used for submarine and mine detection, depth detection, commercial fishing, diving safety and communication at sea. Sonar is a system that uses transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distances underwater.

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