Britain's vast cement "listening ears" designated a national landmark

Salim sez, "In the 1920s the British military used these vast concrete parabolic 'sound-mirrors' to detect approaching aircraft. The 'Listening Ears' at Denge have recently been designated as a historical preservation site by English Heritage, the government quango in charge of protecting national landmarks. From Wikipedia:"

Acoustic mirrors did work, and could effectively be used to detect slow moving enemy aircraft before they came into sight. They worked by concentrating sound waves towards a central point, where a microphone would have been located. However, their use was limited as aircraft became faster. Operators also found it difficult to distinguish between aircraft and seagoing vessels. In any case, they quickly became obsolete due to the invention of radar in 1932. The experiment was abandoned, and the mirrors left to decay. The gravel extraction works caused some undermining of at least one of the structures.
Denge sound mirrors (Thanks, Salim!)


  1. Sadly you can’t visit the sound mirror at Dungeness without a guided tour :(
    I love this photo of it.

    Incidentally, Dungeness is an otherworldly place. There’s 2 nuclear power stations there, a wildlife reserve, and some of the weirdest scenery in the UK. Check out the flickr group.

    Next time I go, I’m going to see “the boil”

  2. And Ive always wondered what a sound mirror was when I was listening to Clock DVA.

    Thanks Boing Boing for making me “that much smarter”. :)

  3. I sense some Stonehenge in the making. If there are still people around in the year 4000, they will probably wonder what this was used for – a weird cult with human sacrifices? All country audio equipment?

  4. The civil liberties of those aircraft are being grossly violated by these police state surveillance devices. Tear them down!

  5. Yes, but what are the implications of hooking you kindle to ’em and beaming TTS speech to France? (ducks, runs away…)

  6. WGMLeslie, Concrete is not ugly. (And I’d definitely argue with the 1920’s being “from WWII.”)

  7. I disagree strongly with #3. We should preserve what evidence we have of our collective history. And leaving as many examples up as possible increases accessibility, and provides redundancy in the event of some event destroying a singular example.

  8. concrete not cement

    cement is a powder you make concrete with


    but they are rather nice.

  9. i’ve sat in smaller scaled versions of these things and its amazing how well they work. i was a few hundred feet away from someone and we could hear each other at conversation levels.

  10. I have an irresponsible plan in my head…I’m still foggy on the details, but it involves motorcycles and racquetball…

  11. The artist Joe Banks (AKA Disinformation) made a fantastic installation piece called Blackout using sound recordings and images from these sites along with recordings of military burst transmissions back in the late 90s. He’s just put a version of this up on youtube:

  12. Re: “the government quango”

    As quango is an abbreviation of quasi-autonomous non-governmental organisation”, #12’s suggestion may well suit better!

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