The Sound Mirrors of Denge at Passing Strangeness. If a technology solves a problem that’s particularly desperate (or it solves one that’s less desperate but more profitable), it’s often prefigured by other, lesser technologies.
Archive for the ‘History’ Category
Denge and fighter control
Sunday, June 28th, 2009Holderness defences
Sunday, March 15th, 2009
The August 2006 issue of East Yorkshire local magazine The West In View looked at military defences in Holderness, including the Kilnsea sound mirror, and used some of my photos of the Cherry Cob Sands bombing decoy.
You can download a PDF of the magazine.
Dutch acoustic research in the 1920s and 30s
Sunday, January 4th, 2009
The Museum Waalsdorp near Den Haag reflects the history of TNO Defense, Security and Safety at location Waalsdorp (and its predecessors) since 1927
.
At the Waalsdorp site, Dutch scientist JL van Soest investigated the use of listening equipment for aircraft observation by the army, developing his own equipment. The Van Soest apparatus was a great success and has led to industrial production for the Army.
The museum’s website has an interesting short history of Dutch sound location. From the first world war until the 30’s air acoustics played an important role in the air defence. Air vehicles carrying a weapon could not be located from the ground e.g. at night time or under cloudy conditions. As radar was still to be discovered, vision had to be supplemented by hearing using the sound of the engines.
Kilnsea sound mirror on the BBC
Wednesday, October 15th, 2008
A huge concrete dish, pointing at the North Sea from an East Yorkshire field, was once a vital part of Britain’s defence system
says a BBC video about the Kilnsea acoustic mirror.
The interview with local historian Jan Crowther is part of the BBC Look North programme’s Abandoned series with Matt Richards.
Matt was recently in touch seeking information for a proposed broadcast about Drewton tunnel on the old Hull & Barnsley Railway.
Maghtab mirror pictures and a model
Sunday, October 5th, 2008“Norwichpaul” has posted some photographs of the 200ft long Sound Mirror at Maghtab in Malta on the Airfield Information Exchange forum.
Steven Vella of St Nicholas College in Malta has built a model of it.
A while ago I built a 4 mm/ft scale model of the somewhat smaller Tags: Malta
Posted in History, Sound mirrors | No Comments »
Would the sound mirrors have been much use?
Monday, June 16th, 2008
Probably not, concludes Brett Holman in a posting on his Airminded blog entitled The widening margin. It is an interesting analysis by someone doing a PhD at the University of Melbourne, examining the impact of airpower propaganda on the British people between 1908 and 1939
. The whole site looks worth a poke around.
Lastly, here’s a counterfactual which I’ve long wondered about. Between 1933 and 1935, the Air Ministry put a fair amount of effort into researching the feasibility of using acoustic mirrors as a comprehensive early warning system. The acoustic mirrors were, mostly, concrete hemispheric dishes for focusing sound, which had been used as early as 1916. The biggest ones, at Dungeness in Kent and Maghtab in Malta, were 200 feet long curved walls. Land was actually purchased along the Thames Estuary for the beginnings of a national acoustic mirror system, but work never started because radar came along. But if it hadn’t, then in 1940 Fighter Command might have relied upon a network of these acoustic mirrors all along the coast. How useful would they have been?
The experimental mirrors had a maximum detection range of 22 miles (on very windy days it was a lot less). I’ll be generous and call it 25 miles, which is then added to the 50 miles from the coast to London for a total distance of 75 miles. The Thames Estuary acoustic mirrors probably would have come online in 1936, and so again I’ll be generous, and assume that London at least would have a working early warning system from that year.
Taking all this into account, the results can be seen above [article has a graphic]. And sadly the acoustic mirrors wouldn’t have made much difference — a margin of only about 10 minutes, not much improved on the 5 minutes with no warning system. Of course, even a few minutes’ extra warning was worth having, but the Air Ministry was right to terminate development of the acoustic mirror network in order to concentrate on the far more promising radar.
Read Holman’s full article (and some warnings about the assumptions made).
Early electronic warfare
Wednesday, May 28th, 2008There is an interesting article about Electronic Warfare in WW1 on the Landships website, in which Robert Robinson describes a somewhat obscure aspect of the Great War.
There is a common misconception that electronic warfare began with the Second World War but, even if it was not so labelled, it played a significant part in the First World War at both a strategic and a tactical level.
Fans of sound mirrors might be interested in the tale of how the Eiffel Tower was used to confuse Zeppelins.
