Abbot’s Cliff Acoustic Mirror
|Date||10 February 2013|
|Location||Abbot’s Cliff, Folkestone, Kent||TR 27188 38605; 51.10170°N, 1.24369°E|
Before the advent of radar, there was an experimental programme during the 1920s and 30s in which a number of concrete sound reflectors, in a variety of shapes, were built at coastal locations in order to provide early warning of approaching enemy aircraft. A microphone, placed at a focal point, was used to detect the sound waves arriving at and concentrated by the acoustic mirror. These concrete structures were in fixed positions and were spherical, rather than paraboloidal, reflectors. This meant that direction finding could be achieved by altering the position of the microphone rather than moving the mirror.
The acoustic mirror at Abbot’s Cliff is located on the cliff top almost midway between Folkestone and Dover.