For many years, the United States operated a large set of passive sonar arrays at various points in the world's oceans, collectively called sound surveillance system (SOSUS) and later integrated undersea surveillance system (IUSS).
Durante moitos anos os Estados Unidos tivo operativo un gran conxunto de matrices de sonar pasivo en varios puntos dos océanos do mundo, chamado colectivamente SOSUS (Sound Surveillance System, sistema de vixilancia sonora) e máis tarde IUSS (Integrated Undersea Surveillance System, sistema integrado de vixilancia submarina).