LWWAA fiber-optic passive hull-mounted sensor array. [Northrop Grumman]
For more than a century, the U.S. Navy has been interested in techniques to acoustically listen for targets at sea. But while the Navy’s early experimentation with submarine-mounted acoustic arrays and surface-vessel/ submarine-towed acoustic arrays dates back to 1917, it was only after World War II, and during the ensuing Cold War, that development began on large acoustic arrays—hull mounted, towed, or mounted on the seafloor—specifically designed for anti-submarine warfare.