SONAR

SONAR, which stands for SOund Navigation And Ranging, is a sensor system used by marine ships and submarines to detect other vessels and navigational hazards while operating on and under the water.

Modes

SONAR has two main modes of operation: passive and active.

Passive

Passive SONAR is typically employed by ships and especially submarines to detect and identify enemy vessels without giving away their own position. The basic operation of passive SONAR is to have an operator listening very carefully to several acoustic hydrophones positioned on the outside of the hull of the ship. A good SONAR operator can tell by carefully listening to the sounds received what other vessels are nearby. Most modern SONAR systems make use of computers with databases of known undersea sounds to assist in the identification of sound sources in the water.

Active

Active SONAR uses a sound emitted by the vessel, often referred to as a "ping", to gain precise information on a potential target. Like all forms of active sensors, it has the disadvantage of alerting any other vessels nearby that are listening. While passive SONAR is able to identify the general location of a potential target, active SONAR is required to gain the precise distance, vector, and bearing of that target. The use of acoustic homing torpedoes usually means that active SONAR is not required to lock weapons and fire at a target.