Towed Array Sonar
A long cable containing hydrophones towed behind a submarine or surface ship, providing passive acoustic detection of other submarines and ships at ranges far exceeding hull-mounted sonar.
Towed array sonar is a passive acoustic sensor consisting of a cable hundreds of meters long embedded with sensitive hydrophones, towed behind a submarine or surface ship at a distance that isolates it from the towing vessel's own noise. By placing the hydrophones far from the ship's machinery, propeller, and flow noise, the towed array achieves detection ranges that can be ten times greater than hull-mounted sonar systems.
The physics of underwater sound propagation make towed arrays extremely effective. Low-frequency sounds can travel hundreds of kilometers through the ocean, and the long baseline of a towed array provides the angular resolution needed to determine the bearing to a distant sound source. By analyzing the frequency and characteristics of detected sounds, sonar operators can classify contacts as specific submarine types, surface ships, or marine life.
Both submarines and surface combatants deploy towed arrays. The U.S. Navy's TB-29A thin-line towed array is carried by submarines, while the SQR-19 and its successors are deployed by surface ships. The primary limitation of towed arrays is that they can only be used at relatively low speeds, high speed creates too much flow noise over the hydrophones, and they reduce the ship's maneuverability since the cable must not become entangled with the ship or other objects.
Related Terms
Sonobuoy
A small expendable sensor dropped from aircraft into the water that listens for submarine sounds and transmits the acoustic data back to the aircraft via radio.
SOSUS(Sound Surveillance System)
Sound Surveillance System is a network of underwater listening arrays on the ocean floor, originally designed to detect Soviet submarines by their acoustic signatures during the Cold War.
MAD(Magnetic Anomaly Detector)
Magnetic Anomaly Detector is an airborne sensor that detects subtle distortions in the Earth's magnetic field caused by the large metal hull of a submerged submarine.
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