During the Cold War, the United States deployed a classified undersea listening system so advanced it could detect Soviet submarines from hundreds of miles away — without firing a single shot. This is the story of SOSUS (Sound Surveillance System), a secret network of ocean-floor hydrophones designed to track Soviet nuclear submarines as they moved through key Atlantic and Pacific routes. Built as a major breakthrough in military engineering and war technology, SOSUS became one of the most important tools of American signal intelligence and anti-submarine warfare. In this military history documentary, we explain how SOSUS worked using deep-ocean acoustic physics, low-frequency sound propagation, seabed cable arrays, and classified analysis stations that could identify submarines by their unique noise signatures. It was silent surveillance — a hidden war fought through sound. This system

Source: How SOSUS Secretly Heard Soviet Submarines During the Cold War