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An acoustic receiver and radio transmitter mounted in a buoy that can be dropped from an aircraft by parachute to pick up underwater sounds of a submarine and transmit them to the aircraft; to track a submarine, several buoys are dropped in a pattern that includes the known or suspected location of the submarine, with each buoy transmitting an identifiable signal; an electronic computer then determines the location of the submarine by comparison of the received signals and triangulation of the resulting time-delay data. Also known as radio sonobuoy.



a marine buoy equipped with electronic equipment, designed to detect and locate submerged submarines and to investigate marine noises and acoustic propagation conditions in the ocean. Sonobuoys classified as passive types are used to pick up the acoustic vibrations produced by submarines; those classified as active types emit ultrasonic signals and pick up the signals reflected from submarines. Both passive and active sonobuoys detect a submarine and determine its direction (bearing); in addition, active sonobuoys determine the distance to the detected submarine.

Sonobuoys are dropped into position from airplanes, helicopters, and antisubmarine vessels in groups of several units; they form barrier lines or enclosures in the directions in which the submarines can move, or in their suspected positions. Sonobuoys equipped with anchors are moored in the area where they are dropped; those without anchoring devices drift after placement as a result of the action of the wind, waves, and ocean currents. Sonobuoys may operate continuously or according to a prescribed program; some of the latter type are equipped with a radar beacon (a transponder) and light-signaling device that facilitate the approach of an airplane, helicopter, or ship to the buoy.

The first sonobuoys appeared after World War II and have since become widely used, particularly with the development of atomic submarines armed with missiles having nuclear warheads. Automated systems based on the sonobuoy have been created abroad; they are designed to detect submarines and warn and guide antisubmarine forces, whose search potential is thus increased. The detection range of a sonobuoy depends on the type of hydroacoustic equipment on the buoy, the sea conditions, and the characteristics of the target submarine; it varies from several hundred meters to several kilometers. The effective distance of the radio link between a sonobuoy and an airplane can reach several tens of kilometers. The weight and size of a sonobuoy depend on its purpose and on the type of carrier.


Karlov, L. B., and E. I. Shoshkov. Gidroakustika v voennom dele. Moscow, 1963.
Khorbenko, I. G. Zvuki v morskikh glubinakh. Moscow, 1962.


References in periodicals archive ?
He joined the RAF as part of his National Service, and spoke endlessly of flying in Lancaster bombers and researching the use of sonar buoys to locate submarines after the war.
"They take the pack up kit and put some sonar buoys in the ocean that are instrumented," said Mohler.