Light Touch
Britain's Acoustic Mirrors
Just as lenses reflect and concentrate light, dish-like structures called acoustic mirrors can amplify sound. These odd-looking devices have played a key role in the military history of Great Britain—and are now getting a second life as works of art.
Sound mirror in Denge, Kent, England.
Along the southern coast of England, there are several curious structures that seem almost alien in nature—large inverse hemispheres made of reinforced concrete. There are about a dozen of them, 10 or more meters in diameter each, and most are slowly crumbling. They look like giant clumsy satellite dishes. However, these lens-shaped structures, which were constructed between World War I and the early 1930s, were meant not as optical devices, but rather to concentrate sound. The British constructed these so-called acoustic mirrors for the practical purpose of detecting long-range aircraft during military conflicts.
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