Warbird Information Exchange

Modern anti-submarine warfare grew from the WWII convoy and battle group movement through hostile waters. It was imperative that submarines be detected and neutralized long before the task group came within range of an attack. Aircraft-based submarine detection was the obvious solution. The maturity of radio communication and sonar technology made it possible to combine a sonar transducer, batteries, a radio transmitter and whip antenna, within a self-contained air-deployed floating (sono)buoy.

Early sonobuoys had limited range, limited battery life and were overwhelmed by the noise of the ocean. They first appeared towards the end of WWII where they were first used in July 1942 by RAF Coastal Command under the code name 'High Tea', the first squadron to use them operationally being No. 210 Squadron RAF, operating Sunderlands. They were also limited by the use of human ears to discriminate man-made noises from the oceanic background. However, they demonstrated that the technology was viable. With the development of better hydrophones, the transistor and miniaturization, and the realisation that very low frequency sound was important, more effective acoustic sensors followed. The sonobuoy went from being an imposing six feet tall, two feet diameter sensor to the compact suite of electronics it is today.

The commander of its Composite Squadron 69 (VC-69), Lt. Cdr. Jesse Taylor, immediately took off in his TBF in pursuit of the Japanese sub. As Taylor patrolled in the darkness, his radarman, Chief Ed Whitlock, picked up a blip. They went after it and dropped flares, lighting up the 350-foot long cargo sub. Taylor closed in, dropping two depth bombs. I-52 dived and the TBF dropped a sonobuoy into the water. The newly-developed sonobuoys picked up long-carrying underwater noises and transmitted these back to the carrier. Following the sonobuoy's signal, Taylor dropped a Mark 24 "Fido" acoustic torpedo.

Use of Sonobuoys in WWII
(See Japanese submarine I-52 (1943) )

According to the article, the submarine was traced and later sunk thanks to sonobouys from TBF Avengers from the USS Bogue.

That article also provides some interesting details (albeit unreferenced) which aren't mentioned in this article:

"Taylor dropped a purple sonobuoy, a newly-developed device that floated, picked up underwater noise, and transmitted it back. A searching aircraft usually dropped these in packs of five, named purple, orange, blue, red and yellow (POBRY); the operator was able to monitor each buoy in turn to listen for sounds emitted by its target."