Denge Marsh

The Sound Mirrors - Denge Marsh - most at 6am and some with Dad when I persuaded him to walk down the gravel path with me which was no mean feat for him!

Royal Air Force Denge or more simply RAF Denge is a former Royal Air Force site near Dungeness, in Kent, England. It is best known for the early experimental acoustic mirrors which remain there.

The RAF had begun research into acoustic mirrors during World War I.

The Denge acoustic mirrors, known colloquially as ’listening ears’, are located between Greatstone-on-Sea and Lydd Airport, on the banks of a now disused gravel pit. The mirrors were built in the late 1920s and early 1930s as an experimental early warning system for incoming aircraft, developed by William Sansome Tucker. Several were built along the south and east coasts, but the complex at Denge is the best preserved, and are protected as scheduled monuments.[2]

Denge complex There are three acoustic mirrors in the complex, each consisting of a single concrete hemispherical reflector.

The 200 foot mirror is a near vertical, curved wall, 200 feet (60m) long. It is one of only two similar acoustic mirrors in the world, the other being in Magħtab, Malta.

200 ft Acoustic mirror at Denge The 30 foot mirror is a circular dish, similar to a deeply curved satellite dish, 9 m (30 ft) across, supported on concrete buttresses. This mirror still retains the metal microphone pole at its centre.

The 20 foot mirror is similar to the 30 foot mirror, with a smaller, shallower dish 6 m (20 ft) across. The design is close to that of an acoustic mirror in Kilnsea, East Riding of Yorkshire.