MUSEUM "WAALSDORP"

The Mk 1 Sound Locator was manufactured by A.W. Gamage Ltd. in Britain during the first World War. In the early days of the First World War, anti-aircraft defence was a totally new field. The detection of unseen incoming aircraft was a major problem. The only possible solution with the technology available at the time was sound detectors, which could provide a rough idea of an aircraft's direction and height based upon the sound of its engine. Tubes connected the bases of two horizontally mounted gramophone-style horns to a pair of stethoscope earpieces. An operator moved the detector until the sound was heard equally in each ear, at which point (theoretically) it would be pointed in the direction of the aircraft. A second operator used the vertically mounted horns to estimate height. The system was rudimentary at best, however, as the location of the aircraft could only be established for the time that the sound was recorded. After a sound contact was made, laborious calculations were then required to properly aim an anti-aircraft gun, and any deviation in the aircraft's flight path rendered the system useless. It was, however, the only system available for detecting the approach of unseen aircraft until the development of radar in the 1930s.

(Page content by courtesy of the Canadian War Museum, Ottawa, Canada)