A comparison of the 1941 watercolour painting “Bombing the Channel Ports” by war artist Eric Ravilious, and the same view of the Abbott’s Cliff sound mirror on 13 August 2017.
Bombing the Channel Ports © IWM (Art.IWM ART LD 1588)
The painting is described by the Imperial War Museum as showing “a deserted coastal road that leads past an ‘acoustic mirror’ early warning device. In the top right of the composition there are searchlights beaming up into the sky, and a large circular glow of light to one side.”
Black and white photos of the sound mirrors by Joe Pettet-Smith on the BBC News website.
More than 100 years ago acoustic mirrors along the coast of England were used to detect the sound of approaching German zeppelins.
Joe Pettet-Smith set out to photograph all the remaining structures following a conversation with his father, who told him about these large concrete structures dotted along the coastline between Brighton and Dover.
Source: The concrete blocks that once protected Britain, BBC News, 7 January 2019
There will be two open days at the Denge sound mirrors this year. The open days are scheduled for 10:00 to 15:00 on Saturday 7 July 2018 and Saturday 1 September 2018.
There will be a cash-only charge of £5 per adult, £2.50 per child (RSPB members free).
There are more details on the Romney Marsh website events listings for July 2018 and September 2018.
The open days are generally the only way for the public to access the Denge listening ears close up, although there have also been some photography days, so it might be worth keeping an eye out, if you are seriously interested.
(Please note that andrewgrantham.co.uk has no connection to the open day, the RSPB or anything else! Please check the details with the RSPB before visiting)
A pair of Richter Spielgeräte concrete sound mirrors in a small park on the banks of the River Thames at Kew in west London. Photographs taken on 11 March 2018.
Another visit to the Abbot’s Cliff sound mirror, while walking the North Downs Way long distance footpath.
Acoustic mirrors: how to find planes without radar, by Al Williams at Hackaday (“entertainment for engineers and engineering enthusiasts”):
While today the acoustic mirror is a museum curiosity, before World War II, it was a method of detecting aircraft. The mirror could focus the sound from an aircraft engine allowing early detection. There are several of these stations still on the coast of Britain and one in Malta. A microphone picked up the sound and the construction wasn’t actually parabolic, they were spherical mirrors. The reason is that a parabolic mirror has to move to determine direction, while a spherical mirror could detect direction by moving the microphone.