The Sound Mirrors, also known as Acoustic Mirrors, Concrete Dishes or Listening Ears, are large concrete structures designed as an early warning system for Britain to detect enemy aircraft.
There were three designs of mirrors and all three can be seen in Greatstone, located in the north east side of the Dungeness Nature Reserve. These three concrete " listening ears" range in size from 20 to 200 feet in size.
Built between 1928-30, the sound mirrors were part of Britain's national defence
strategy. They were designed to pick up the sound of approaching enemy aircraft.
Sound waves were caught in the belly of the mirror and relayed back through
microphones and a stethoscope to an operator who raised the alarm. Anti-aircraft
defences were then deployed. The mirrors effectively gave Britain a
fifteen-minute warning of an impending attack.
The 20 feet(diameter) mirror was the first to be built in 1928. It was precast as one huge slab of curved concrete. Lessons were quickly learnt and a 30 feet(diameter) mirror, set at a different angle and providing greater accuracy, was built in early 1930 alongside the 20 foot mirror. The third mirror was 200 feet in length and 26 feet high, and was built in 1930 alongside the other two smaller sound mirrors. Microphones were attached
to the curved surfaces and in favourable conditions could pick up the sounds of aircraft up to 24 miles away.
The mirrors did work, and could effectively be used to detect slow moving
enemy aircraft before they came into sight. They worked by concentrating sound
waves towards a central point, where the microphone would have been located. (note the microphone in the pictures of the 30 foot mirror).
However, their use was limited as aircraft became faster. Operators also found
it difficult to distinguish between aircraft and seagoing vessels. In any case,
they quickly became obsolete due to the invention of radar in 1935.
The sound mirrors are now a scheduled ancient monument (Number 462809). Please see National Monuments Record for more information.
How to See the Mirrors
The mirrors are situated on an island in Greatstone Lakes in the nature reserve. They are private and only accessible close up on poen days and guided walks. However they can be seen quite clearly from the east side of the south lake.
To see the mirrors, take one of the roads running west off Leonard Road eg Coleville Crescent, Hull Road and walk almost due west across the shingle and cross the style onto the footpath (what used to be the railway track) (see the Greatstone Map). From here, walking north will take you past the larger lake where you
can see the mirrors.
Alternatively, you can park in the car park in The Parade just past Hull Road, walk westwards down Taylor Road and then follow the signs for The Mirrors.
To see them close up, however, you need to go on one of the guided walks organised by The Romney Marsh Countryside Project and Dr Richard Scarth during the summer months.
For details of the open days and guided walks, please contact Owen Leyshon, Romney Marsh Countryside Project 01797 367934 or firstname.lastname@example.org.