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.
Sonobuoys are expendable acoustic sensors dropped from maritime patrol aircraft and helicopters to detect and track submarines. Once they hit the water, a sonobuoy deploys a hydrophone to a preset depth on a wire, listens for submarine sounds, and transmits the acoustic data back to the aircraft via a UHF radio link. Passive sonobuoys simply listen for submarine-generated noise, while active sonobuoys emit a sonar ping and listen for echoes from the submarine's hull.
Maritime patrol aircraft like the P-8 Poseidon can carry dozens of sonobuoys and deploy them in patterns designed to detect submarines in a given area. Common patterns include barriers (lines of buoys across a chokepoint), screens (grids covering a search area), and localization patterns (clusters designed to pinpoint a contact detected by other sensors). The aircraft's onboard acoustic processing systems analyze the sonobuoy data in real time to detect, classify, and track submarine contacts.
Sonobuoys have been a primary anti-submarine warfare tool since the 1950s and continue to be refined with improved hydrophones, longer battery life, deeper operating depths, and GPS positioning. The growing quietness of modern submarines has driven the development of multistatic sonobuoy operations, where the ping from one active buoy is received by multiple passive buoys, dramatically improving detection probability against low-noise targets.
Related Terms
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.
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.
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.
Related Articles
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.