construction

the forgotten sound mirrors

by deputydog ⋅ 29 / 12 / 2007 ⋅ post a comment


photo credit: csstudios

from 1915 onwards these huge eerie concrete structures started popping up along the uk coast, all built with one purpose: to provide the military with an early warning system in relation to incoming aircraft. their construction was pretty much limited to the uk and arrived just before radar technology as we know it became widespread.


photo credit: get down

the majority of sound mirrors actually built were large concrete parabolic or hemispherical dishes tilted at a slight angle towards the sky, manned by an operator either behind or underneath the dish in a special chamber. the dish would reflect the incoming engine sounds onto a large movable microphone placed at the focus of the mirror and enable the operator to judge the distance and direction of the approaching aircraft.


photo credit: feersumendjinn

in 1930 the military also decided to build a massive 200ft long sound mirror wall at denge, a then raf base in kent. obviously its size resulted in greater accuracy and range with an unaided ear able to detect aircraft from 6.5 miles on a clear day. that coupled with the use of the microphones gave the operator a range of over 20 miles.

here’s the direct google maps link to the old air base where you can still see the mirror wall and 2 other more common sound mirror dishes. the original plan was to place the mirror walls along the entire coast, every 25 miles or so, with a couple of smaller dishes in between each one. in the 1930s radar reared its head and aircraft became too fast to make this method of detection advantageous so the military dropped the idea and left the mirrors intact. many of them remain to this day, scattered along the south east coast.

for more info about sound mirrors…

1, 2, 3, 4

discussion

33 comments for “the forgotten sound mirrors”

  1. Random, off topic comment. But you have an amazing blog that is always filled with compelling, interesting content.

    A shining example of what a niche blog can and should be.

    Thanks for your hard work.

    posted by Chris | 29th of December, 2007, 11:11 am

  2. Very Cool !

    Thanks for sharing these.

    Ken

    posted by Ken | 29th of December, 2007, 1:59 pm

  3. agree with ken here …
    wonder where you guys get all these interesting news … and the pictures to go with ‘em …
    hehe …
    sound mirrors eh … ? these military guys sure fund a lot of starnge stuff …

    posted by subcorpus | 29th of December, 2007, 2:42 pm

  4. Maybe Stonehenge was the original “sound mirror”???

    posted by vince | 29th of December, 2007, 4:40 pm

  5. yes but the big question is

    DO THEY WORK?

    Could you for example place your ear on the focal point an hear things hundreds of miles away?

    posted by klip | 30th of December, 2007, 12:59 am

  6. 100 years from now beings will marvel.
    “Stonedenge……

    posted by Pete Dooley | 30th of December, 2007, 3:56 am

  7. @klip - no, they don’t. signal/noise ratio is way too high for them to produce anything useful.

    British artist Tacita Dean has used the sound mirrors in one of her films. I’ve always wanted to visit them but have never pulled my thumb out of my arse and actually gone and done it.

    posted by wikiphile | 30th of December, 2007, 4:29 am

  8. @klip: they do work. They were tested in the BBC series Coast. You can probably find a torrent somewhere online.
    I’m guessing that if I try and post a link it’ll be stripped out, but a Google for “coast sound mirrors crane” gets a link to the BBC web page at number one.

    @wikiphile: they were also used in a film by Derek Jarman’s film. I *think* it was ‘The Garden’. He had a house and garden at Dungeness which is near the sound mirrors.

    As far as I know they exist only in one other place in the world, Malta. I’ve been to Malta several times, but I’ve never seen them there. I think they are somewhere near the football stadium.

    posted by Bryan | 30th of December, 2007, 5:29 am

  9. Thank you for maintaining ones faith and interest in the net.

    posted by Andrew Ziminski | 30th of December, 2007, 3:36 pm

  10. As kids, we actually used to play in one of these. It was built on the side of a cliff about 1/2 mile from our house on the Kent Coast. Still there as far as I know. Impressive structures……

    posted by LittleInsect | 1st of January, 2008, 3:34 am

  11. Love them.

    Check these sound mirror sculptures. They were inspired by a visit in dungeness.

    It works amazingly well.

    http://www.troika.uk.com/wattyler.htm

    posted by sebastien noel | 2nd of January, 2008, 3:49 pm

  12. Do they work? I know on a smaller scale that these work on the campus of NC State University in Raleigh, North Carolina. You can hold a normal conversation even though the two disks are a good 50 yards apart.

    http://rduwtf.com/blog1/2007/09/26/seven-wonders-of-central-raleigh-number-three/

    posted by Clarksa | 3rd of January, 2008, 9:22 am

  13. Talk about walls having ears!
    You did it better than me ;)

    posted by Norman Blogster | 3rd of January, 2008, 2:51 pm

  14. we have a few of these in Malta too, in the british forts from the colonial days…but they’re more horizontal…they used to be great fun to slide down!

    posted by James | 4th of January, 2008, 3:03 pm

  15. a more recent project:
    http://www.soundmirrors.org/

    posted by gavin starks | 7th of January, 2008, 5:56 pm

  16. Here is a page with a bunch of pics

    posted by Ruben | 8th of January, 2008, 9:57 am

  17. looks like a long lost skate spot

    posted by sir jorge | 18th of January, 2008, 8:18 pm

  18. Yes they do work - there is a program on BBC at the moment call ‘Coast’ in one of the episodes they tested them (the ones in the pic) - and they worked fine…

    posted by Andy | 22nd of January, 2008, 5:11 am

  19. In Thomas Pynchon’s “Gravity’s Rainbow” there is a scene in Germany which occurs in a field filled with concrete “mirrors”, only they were faced down for percussive explosives to be used on infantry. I don’t know if Pynchon actually saw these things, perhaps he was inspired?

    posted by Cameron | 2nd of February, 2008, 11:54 am

  20. they’re also featured pretty predominately in a video by Blank & Jones… i’d wondered what they were.

    http://www.youtube.com/watch?v=lYVYagz3jsU

    posted by robert | 10th of March, 2008, 7:43 am


post a comment