At the time the only way to detect submarines was by listening for them (passive sonar), or visually by chance when they were on the surface recharging their battery banks.

In 1931, the Coast and Geodetic Survey proposed the replacement of crewed station ships with "radio-sonobuoys", and placed the new buoys in service beginning in July 1936.

Sonar was installed on a number of ships along with radar and high-frequency direction finding ("Huff-Duff") to detect surfaced submarines.

Modern anti-submarine warfare methods evolved from the techniques devised for the movement of convoys and battle groups through hostile waters during World War II.

With the development of better hydrophones, the transistor and miniaturization, and the realization that very low frequency sound was important, more effective acoustic sensors followed.

The advancement in sonobuoy technology aided the development of aircraft such as the P-2 Neptune, S-2 Tracker, S-3B Viking and P-3 Orion for anti-submarine warfare.

Multiple aircraft or ships monitor the pattern either passively listening or actively transmitting to drive the submarine into the sonar net.

Sometimes the pattern takes the shape of a grid or other array formation and complex beamforming signal processing is used to transcend the capabilities of single, or limited numbers of, hydrophones.