Acoustic mirrors

https://www.bbc.co.uk/news/in-pictures-46348917

Once the cutting edge of technology, but now crumbling and forgotten, overtaken by the development of radar. Interestingly, although the mirrors themselves were overtaken by radar as a means of detection, the experience gained in using a network - linking and plotting individual sightings - to give a more precise fix than a single receiver did translate to radar stations, such that in the early part of the war, the British radar system was more effective that that of the Germans, even though German radar devices were individually more sophisticated.

Tom

 

They were the subject of one of the episodes of the TV programme 'Abandoned Engineering'.

 

At Jodrell Bank they have two smaller ‘whispering dishes’ facing one another to demonstrate how well a dish can pick up and reflect sound waves. You can have a conversation in a normal voice with someone standing at the other dish 25 metres away.

 

I read that article yesterday. Have seen the ones near the RH&DR but didn’t realise others existed elsewhere nor that some date back to WW1.

 

The ones at Fan Bay are immediately outside the Fan Bay Shelter now owned by the National Trust and opened for guided tours. In WW2 they were the location for the latrines for these shelters.

 

Its a fascinating story. Its an interesting example of how an attempt was made to solve a problem before modern technology - in this case Radar

 

There were a pair of "whispering mirrors" at the Snibston discovery museum (Now sadly closed). I did not know that so many of the originals still existed.

 

Apparently the council tried to demolish the ones at Fan Bay about 50 years ago but could not break them up so they cover them with soil. They have now been uncovered again. They a are at differnt angles, perhaps one to detect aircraft and the other ships.

I did hear a story that one of those on Romney Marsh was not much good at deteccting aircraft but could "hear" a train leaving Calais Maritime Station.

A branch line was built from the RHDR to serve the mirrors built on Romney Marsh near Greatstone

 

Thanks- that made me wonder what kind of servicing they needed. One of the links said there was a microphone in front of the dish. And presumably operators, perhaps in a little hut with amplifiers and headphones (or some sort of recording device?) interpreting the incoming sounds and communicating with those who needed to know.

 

https://www.google.co.uk/maps/searc...090309,-1.4125141,626320m/data=!3m1!1e3?hl=en

 

I really wish that it had been designed as an enourmous concrete ear.

 

Definitely "old tech" but certainly works ...