Echoes from the Sky: Acoustic Detection of Aircraft Paperback – 1 May 2017

Bought as a present, so I've not read it through, but it's a good summary of what Britain had for early warning before radar.

Although the idea of sound mirrors was poor the system resulted in the brilliant chain radar arrays.

This book contains a lot of very specialist knowledge and research. It would however have benefitted from editorial help when it was compiled. But if you’re interested in the UK's 'sound mirrors' (the major examples still stand just outside Dungeness), this is virtually the only book on the subject and we should thank the author for his efforts.

This is a unique view of one of the forks in the road of technology development that led to a dead end. The use of acoustic technology for providing early warning and fire control in anti-aircraft defenses was explored between World Wars 1 and 2 by several nations but typically in terms of mobile battlefield locators normally use four receiving horns or cones arranged in a cross to give height and bearing information. However, in the UK this technology was pushed into the use of large concrete spherical reflectors mounted at fixed positions to form a barrier. At some considerable effort, at least in terms of available resources, experimental installations were in place in the early 1930s that gave some some hope of bettering the results of visual observation. However by the mid 1930s radar development began to bear fruit and the difference in propagation speed of sound and electromagnetic radiation was so vast that as soon as radar detection ranges exceeded the 30 mile best case limit of the fixed acoustic installation and aircraft speed began to exceed 200 mph, there was no justification for continuing the acoustic development and the experimental activities were ended and the sites abandoned to become part of 21st century industrial archaeology. However, it should additionally be mentioned that the communications network planned to integrate a large scale acoustic array warning system did lay the groundwork for that actually adopted by the RAF to support the radar based system.So how well is this story told in this book? It bears all the strength and weaknesses of an "enthusiast" publication rather than one done by a professional publishing house. On the plus side is the clear passion and energy in archival and physical research displayed. The number and quality of the photographs is exceptional and very helpful in supporting the text. The numerous quotations from contemporary documents, especially communications about actual operations, are quite helpful in picturing the circumstances of the time. The author is quite well aware and appreciative of the context of the this technology project in the scope of the air defense of Great Britain and the construction of the radar based Integrated Air Defense System (IADS) that was completed in 1940.On the negative side we have the obvious lack of professional editorship leading to a disjointed and obscure narrative based on the authors decision to talk first about the different types of detectors and only later to pick up the way the constructed systems were tested and evaluated and then finally the historical- contextual issues. The lack of professional editing is also clear in the text body where quotations are visually run on into the text.It is also this case that, although the author clearly understood the principles of acoustic detection the chance is missed to include an Appendix that gives some of the basic mathematical treatment of the subject that any professional acoustic engineer could have provided. But then, that is a pet peeve of mine for many books about technology.I gave this book four stars, in spite of the issues mentioned above, because I really doubt this story is told anywhere else and sometimes we do need to remember the roads not followed to understand the road we are on.