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.
The Sound Surveillance System (SOSUS) is a network of fixed passive sonar arrays installed on the ocean floor at strategic chokepoints and across ocean basins. Originally deployed in the 1950s and expanded throughout the Cold War, SOSUS was designed to detect and track Soviet submarines as they transited from their home ports into the open Atlantic and Pacific oceans. The system exploits deep sound channels in the ocean that allow low-frequency sounds to propagate over thousands of kilometers.
During the Cold War, SOSUS was one of the most closely guarded secrets in the U.S. military. The system proved remarkably effective at detecting and tracking Soviet submarines, providing early warning of submarine deployments and cueing mobile anti-submarine warfare assets to investigate contacts. Its existence was not officially acknowledged until the early 1990s, when its declassified capabilities were made available for oceanographic research.
While the original SOSUS arrays remain operational, they have been supplemented by more modern systems including the Integrated Undersea Surveillance System (IUSS) and deployable autonomous sensors. The growing quietness of modern submarines, particularly Russian Yasen-class and Chinese Type 095 boats, has reduced the effectiveness of fixed acoustic arrays, driving investment in advanced signal processing and new sensor technologies to maintain undersea awareness.
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.
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.
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.
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Why Submarines Listen Instead of Look, and How Sound Bends Underwater to Help Them
A submarine's most important weapon isn't a torpedo. It's listening. Passive sonar, towed arrays, thermoclines, and the SOFAR channel form the invisible architecture of undersea warfare. Here's how it all works, and why the ocean itself is the biggest variable in every engagement.