# Acoustic Mirrors for Aircraft Detection



## Matt308 (Oct 11, 2010)

Acoustic ears and mirrors used for detection of airborne invasion were spawned from the idea of stereoscopic sound locating devices to provide location/distance information to defensive forces. These family of devices were used to detect anything from artillery rounds in WWI to aircraft in WWII. Modern day versions are now used to detect acoustic signatures for determination of sniper locations. Some interesting pics and wiki link to the listening ears used to protect England in WWII.

Acoustic mirror - Wikipedia, the free encyclopedia

Acoustic Radar.


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## Matt308 (Oct 11, 2010)

I found this interesting...
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"Britain never publicly admitted it was using radar until well into the war, and instead publicity was given to acoustic location, as in the USA. It has been suggested that the Germans remained wary of the possibility of acoustic location. and this is why the engines of their heavy bombers were run unsynchronised, instead of synchronised as was the usual practice, in the hope that this would make detection more difficult. "


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## RabidAlien (Oct 11, 2010)

Actually, it is! Thanks for posting that, Matt!


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## BombTaxi (Oct 12, 2010)

I _think_ the third pic down is somewhere in the UK (big concrete reflectors), and I know I've seen an excellent article of a recent site visit somewhere on t'internet, with a good explanation of the building process and the rationale of creating those massive concrete structures, which I will post when I find it. Matt, do you know the location of that shot?


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## fastmongrel (Oct 12, 2010)

The sound mirrors in the 3rd pic are the ones at Denge in Kent near Dungeness. Well worth a visit if your in the area but you need to book in advance, the largest one is huge and must have been a formidable engineering task in the 1930s. Heres a useful link
Denge sound mirrors Sound mirrors


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## Matt308 (Oct 12, 2010)

Mongrel is right. I have also been told that there was a UK documentary on this site. Anyone know where we might download that?


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## fastmongrel (Oct 12, 2010)

The BBC series Coast did a section on the sound mirrors. I think it was the 1st series possibly the 2nd but not the 3rd series. Also Channel 5 and the National Geographic channel did a series called Great Railway adventures that had a section on the Denge mirrors.

War Heroes Photos - Great Railway Adventures with Dan Cruickshank - National Geographic Channel - UK


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## RabidAlien (Oct 12, 2010)

That second photo, is that WW1 era?


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## vikingBerserker (Oct 12, 2010)

Very intersting!


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## tail end charlie (Oct 13, 2010)

I suppose what did for these systems was the simple laws of physics. Even if they had worked perfectly you only find out where the bomber was several minutes ago.


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## CharlesBronson (Oct 20, 2010)

> I suppose what did for these systems was the simple laws of physics. Even if they had worked perfectly you only find out where the bomber was several minutes ago.



Exactly, the speed of sound ( in good weather) is 321 meter per second....compared with the 299,998 km/ per second of the radar waves... no contest. 8)


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