Something to reflect on


To some they are a blot on the landscape. To others an interesting part of our history. But love them or hate them, what you can’t do is ignore them, especially the one that is 230 feet long. There are two others, one 30 feet and the smallest 20 feet long.

So, what are they? Situated on an island in a disused gravel pit, the Denge sound mirrors or listening ears are close to Greatstone, about three miles north of Dungeness. Built of concrete, the idea dates back to 1916, and was a response to severely damaging Zeppelin raids. Construction began in 1927. Development continued through to the 1930s. They were a forerunner of radar. The idea was that a microphone in front of the structures would pick up the sound of approaching enemy aircraft and even airships from up to 25 miles away. The shapes of the mirrors would concentrate the sound of the fairly slow aircraft of the times and the microphone would transmit the sound to the operators.

The microphones were the type known as hot wire, developed by Major William Sansome Tucker, who was also a doctor of science specialising in sound phenomena. They had originated during the first world war and a heated platinum wire, in a box, was, with other equipment, able to pick up the sounds of distant cannon fire. The major developed the idea further, publishing his paper on the subject in 1923. His microphones would give anti-aircraft artillery about 15 minutes warning, to allow them to get into position.

Obviously, they were developed to give early warning of air invasion by Germany. The concept was workable, but faster aircraft meant that they would be seen by the time that they were heard, so rather limiting the usefulness of the idea. Then the sound mirrors technology was overtaken by the development of radar during the 1930s, a more sophisticated method of tracking.

Now they stand like silent sentinels, relics of our military past, safe from vandals on their island. They still have a use, appearing on record sleeves and as a background for fashion shoots.

Image Credits: Heidi Foster .

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  1. This article stirred a memory, as I recall having the story related to me many years ago, although I think some of the ‘facts’ were fabricated in order to make it more interesting! However, this is a most informative and interesting article so many thanks for writing and publishing it. Our 20th century local history has so many stories to tell, but most of it never gets a public airing.

  2. Many thanks for your kind comment John. It has been said that 20th century history is easily overlooked because there is no history so distant as the recent past. MM


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