Acoustic torpedo

An acoustic torpedo is a torpedo that aims itself by listening for characteristic sounds of its target or by searching for it using sonar (acoustic homing). Acoustic torpedoes are usually designed for medium-range use, and often fired from a submarine. The first passive acoustic torpedoes were developed nearly simultaneously by the United States Navy and the Germans during World War II. The Germans developed the G7e/T4 Falke, which was first deployed by the submarines , and in March 1943. Few of these torpedoes were actually used and quickly phased out of service in favor of the T4's successor, the G7es T5 Zaunkönig torpedo in August 1943. The T5 first saw widespread use in September 1943 against North Atlantic escort vessels and merchant ships in convoys. On the Allied side, the US Navy developed the Mark 24 mine, which was actually an aircraft launched, anti-submarine passive acoustic homing torpedo. The first production Mk. 24s were delivered to the U.S. Navy in March 1943, and it scored its first verified combat kills in May 1943. About 204 torpedoes were launched against submarine targets, with 37 Axis submarines being sunk and a further 18 damaged. Since its introduction, the acoustic torpedo has proven to be an effective weapon against surface ships as well as serving as an anti-submarine weapon. Today, acoustic torpedoes are mostly used against submarines. Acoustic homing torpedoes are equipped with a pattern of acoustic transducers on the nose of the weapon. By a process of phase delaying the signals from these transducers a series of "acoustic beams" (i.e. a variation of acoustic signal sensitivity dependent on the incident angle of the noise energy). In early homing torpedoes the "beam patterns" were fixed whereas in more modern weapons the patterns were modifiable under on-board computer control. These sensor systems are capable of either detecting sound originating from the target itself i.e. engine and machinery noise, propeller cavitation, etc.