Towed-Array Sonar

A towed-array sonar is a long line of hydrophones streamed on a cable astern of a surface ship or submarine, well behind the platform’s own machinery noise and propeller wake, to listen passively for low-frequency tonals from a distant submarine. The length sets the low-frequency aperture and detection range, so arrays run hundreds to over a thousand meters. The towed array complements a submarine’s hull and flank arrays and gives a frigate its longest-range ASW sensor; pairing it with a low-frequency active source (variable-depth sonar) counters quiet AIP boats in the littoral.