sound mirrors .pdf

8/14/2019 sound mirrors .pdf

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Sound MirrorsBritains First Early

Warning system


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After the First World War, people realised

that the next war would be fought in a

different way.


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Instead of men standing in trenches

shooting at each other across no-mans

land, armies would use machines such asaircraft and tanks to fight their battles.


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The Government asked Scientists and the armedforces to come up with ideas to detect enemyaircraft before they crossed the coast-line

on their way to attack targets in Britain.


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The scientists looked at the way that peoplehear sounds and decided that a possiblemethod of detecting enemy aircraft would be

to erect giant listening ears or SoundMirrors to collect the sound - copying theway that our ears collect sounds beforesending them to our brains.


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Sound Mirrors were built in various placesaround the coast of Britain however, thelargest Sound Mirrors were built on the South

Coast at a place called Denge near Dungeness.

These Sound Mirrors were built between 1928and 1930.


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The Sound Mirrors were made of concrete andpositioned facing France.

Three different sizes of Sound Mirror werebuilt at Denge - the first was the 20 footmirror.


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In 1930 another larger, 30 foot mirror wasbuilt.

The Sound Mirror in 1930 The Sound Mirror today


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In this design the listener sat in a chamberbeneath the sound collecting bowl.


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Because aircraft engines emit long wavesounds (they can be heard a long way away)the scientists realised that they needed a

large detecting surface so they built amassive concrete wall - this is known as the200 foot mirror because it is 200 feet or 60meters long - that is half a football pitch

long! It was so big that the Romney, Hytheand Dymchurch miniature railway was extendedso that supplies could be delivered duringits construction.


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This huge mirror is a actually a segment of asphere and is 60 meters long and 8 metershigh.


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This is what the 200 foot mirror looked likewhen it was built.


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And this is what the 200 foot mirror lookslike today.


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During the early 1930s the Sound Mirrorswere used in experiments to detect aircraft -the results being passed to RAF Uxbridge

which was the home of the Royal ObserverCorps - the group of people responsible forspotting and identifying aircraft crossinginto the country.


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The Sound Mirrors did work, and were able topick up the sound of an approaching aircraftbut it was difficult to tell from which

direction the aircraft were coming.

Sadly, the use of Sound Mirrors came to anend once RADAR or R dio etection And Rangingwas invented - RADAR could pick up aircraftfurther away and with more accuracy.


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After the Second World War, the area of landaround where the Sound Mirrors were built wasturned into gravel pits and excavated. The

deep pits left behind were then flooded.

In recent years the mirrors have beenvandalized so, to protect them, a channel wasdug leaving the mirrors on their own island.


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A swing bridge was built so that only thewarden can open the bridge and allow peopleto walk across.

Today, the only way to visit the SoundMirrors is to go on one of the guided walksrun by the Romney Marsh Countryside Projectwhich take place about three times a year.They are very popular - at the open day thisyear over 400 people went to have a look atthe mirrors.


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