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https://www.bbc.com/news/in-pictures-46348917?SThisFB&fbclid=IwAR3KjK4RwbucaG_2y-Eye6rzGmIg862NH7Ch2o4nBHP8VNaUop6_Kb00s6o

Fascinating stuff. At the Jodrell Bank visitor centre they have a pair of well separated accoustic mirrors facing each other allowing people, each speaking onto one of them, to converse in whispers despite the distance.

Olly

 

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I've been somewhere else where they have a pair of accoustic mirrors for people to try.  I had no idea the ones in the BBC article existed though.

James

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I went to school at Haileybury College, whose dining hall has/had a huge unsupported dome as its ceiling. With the hall full of 600 people sitting and talking, you could stand in one corner and have a perfectly audible quiet conversation with another person in the opposite corner.

Magnus

Edit: I should add, fascinating link, Thanks Olly!

Edited by Captain Magenta
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Tom Scott had made a video about these sound mirrors 5 months ago, I found it an interesting watch if anyone is intrigued.

If I remeber correctly, his team demonstrated by putting a microphone in the middle of the dish in Romney marsh, which picked up birds tweeting across the lake. They also flown a drone nearby (with permission from the local airport) to demonstrate what it would be like picking an aircraft miles off the coast back in the day.

 

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5 hours ago, ollypenrice said:

https://www.bbc.com/news/in-pictures-46348917?SThisFB&fbclid=IwAR3KjK4RwbucaG_2y-Eye6rzGmIg862NH7Ch2o4nBHP8VNaUop6_Kb00s6o

Fascinating stuff. At the Jodrell Bank visitor centre they have a pair of well separated accoustic mirrors facing each other allowing people, each speaking onto one of them, to converse in whispers despite the distance.

Olly

 

I thought there were some really big ones on the South coast. They were the subject of a tv programme I recall. They tried to replicate their operation by flying a plane towards them and seeing how far away they could detect.

I've been to the JB ones with the grandchildren, and they really are quite effective. It wouldn't surprise me if the Science Museum had them as well.

If this link works, have a look at the Youtube vid on the Denge mirrors. https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.youtube.com/watch%3Fv%3DpOFP_ouhA6M&ved=2ahUKEwifiYu4td7fAhU7TBUIHYpwAz4QwqsBMAt6BAgNEAU&usg=AOvVaw0Mt6Y_oIBOUwiwVpYoHsAu

Ian

Edited by The Admiral
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11 hours ago, JamesF said:

I've been somewhere else where they have a pair of accoustic mirrors for people to try.  I had no idea the ones in the BBC article existed though.

James

There are some acoustic mirrors or something similar at The Observatory Science Centre, Herstmonceux. Details near the bottom of this page here

I`ve tried them out for myself when I was there with the family.

Edited by Phil Fargaze
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This led me into reading about the Zeppelin attacks in WW1. Obviously a hydrogen lifted Zeppelin is a potential bomb but it turned out that only incendiary bullets actually set them alight and, even then, mainly when the pilots fired from below. I wonder why that was.

Olly

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9 hours ago, ollypenrice said:

This led me into reading about the Zeppelin attacks in WW1. Obviously a hydrogen lifted Zeppelin is a potential bomb but it turned out that only incendiary bullets actually set them alight and, even then, mainly when the pilots fired from below. I wonder why that was.

Olly

I'd assume that bullets fired from below would be slowed by the pull of gravity and spend more time in the envelope. I don't know a whole lot about ballistics though

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On 09/01/2019 at 23:31, Mognet said:

I'd assume that bullets fired from below would be slowed by the pull of gravity and spend more time in the envelope. I don't know a whole lot about ballistics though

That's a thought. In the end they found that you needed magazines loaded with alternate rounds of explosive and incendiary bullets, the explosive ones needed to tear the gasbags enough to proved sufficient oxygen for combustion. Lieutenant Robinson, the first to shoot down a Zeppelin, concentrated his fire into one place with his final magazine and that did the trick. Clearly oxygen was the key. Another remarkable fact is that the gas bags were made from cow's intestines at the rate of 250,000 cows per Zeppelin. During the war sausage making was temporarily banned to keep the Zeppelins in the air...

Olly

Edited by ollypenrice
Corrected 25,000 into 250,000. Apologies.
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