Early warning sound mirrors

[Denge acoustic mirrors]

A forerunner of radar, acoustic mirrors were built on the south and northeast coasts of England between about 1916 and the 1930s. The ‘listening ears’ were intended to provide early warning of incoming enemy aeroplanes and airships about to attack coastal towns. With the development of faster aircraft the sound mirrors became less useful, as an aircraft would be within sight by the time it had been located, and radar finally rendered the mirrors obsolete.

The sound mirrors at Denge in Kent have become quite famous, but it is less well known that a number of other mirrors existed, built to a range of different designs. These webpages bring together photographs of the surviving mirrors, and some details of where they are if you are interested in visiting them.

During World War I sound mirrors were built along the northeast coast, at

Mirrors were also built on the south coast at various times and locations

One mirror was built overseas, at

A different style of aeroplane detection system was tried on Romney Marsh


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Modern mirrors working on similar principles have been built for art, education and entertainment. Some examples are

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Northern mirrors

Information about the northern (and Selsey) sound mirrors is sketchy to non-existent. Even the suggested dates for their construction is guesswork.

Do you know anything about them? Have you seen something published in a book, newspaper or magazine, did a relative tell you a story about them, have you found details in an archive? Why were the locations selected, and when were the mirrors built? Do you know of any other mirror locations?

If you can offer even a scrap of information, please drop me a message - any information at all would be useful!

I would be particularly interested in any photographs which I could add to this website, especially of the mirrors I haven't yet got pictures of. There is also a Flickr sound mirrors pool which you are welcome to add your photos to.

[Picture of the sea]

North Sea waves breaking on the sand at Spurn Head on a windy December afternoon.