How to find planes without radar

Acoustic mirrors: how to find planes without radar, by Al Williams at Hackaday (“entertainment for engineers and engineering enthusiasts”):

While today the acoustic mirror is a museum curiosity, before World War II, it was a method of detecting aircraft. The mirror could focus the sound from an aircraft engine allowing early detection. There are several of these stations still on the coast of Britain and one in Malta. A microphone picked up the sound and the construction wasn’t actually parabolic, they were spherical mirrors. The reason is that a parabolic mirror has to move to determine direction, while a spherical mirror could detect direction by moving the microphone.

2017 Denge sound mirror open day date

This year’s annual open day at the Denge sound mirrors is scheduled for 10:00 to 15:00 on Saturday 15 July 2017. Open days are the ONLY WAY to access the Denge listening ears.

Denge sound mirror open day 2016

There will be a cash-only charge of £4 per adult, £2 per child or £3 per student, with a family discount of one free child per family. Under 5s, carers and RSPB members are also free.

More details on the Romney Marsh website

(Please note that has no connection to the open day, the RSPB or anything else! Please check the details with the RSPB before visiting)

Stuck at Dover? See a sound mirror!

Accot's Cliff Sound mirror

The Guardian article How to amuse yourself in a 14-hour queue at Dover suggests: “The A20 between Folkestone and Dover can be an area of breathtaking beauty, with sea views and endless greenery to distract you from your hellish conditions. Get stranded in the right place and you could go and explore the Abbot’s Cliff sound mirror, or the Samphire Hoe nature reserve.”

Covenant names new single Sound Mirrors

Covenant single Sound Mirrors

Swedish band Covenant has announced that its new single to be released on 26 August 2016 will be called ‘Sound Mirrors’. Music publisher Dependent says:

Covenant’s new single ‚Sound Mirrors’ gives us a first impression of their forthcoming album “The Blinding Dark”. For the first time ever, the Swedes address distinctly topical events in world politics: the refugee crisis with its accompanying hysteria and the anxiety about the future of a European continent that looks forward into uncertainty.

Sound Mirrors were acoustic mirrors that looked like giant stone ears, placed along the Englisch coast between 1916 and 1930 in order warn of approaching planes or war ships. Their elliptical shape bundled acoustic signals, and they were considered to be both technological and constructional masterpieces. Faster planes and especially the invention of radar made sound mirrors obsolete later on, so today, they are merely stone witnesses of bygone times along the southern and north-eastern coasts of England. The reference tot he refugee crisis and creeping radicalisation of Europe becomes particularly obvious when hearing Covenant’s lyrics for the corresponding song.

Musically, the band does not miss out on anything, delivering a club smasher that harks back to single classics such as ‚Stalker’ or ‚Last Dance’. While unusual splashes of colour enhance the overall picture, ‚Sound Mirrors’ is bound to become an enduring earworm that will soon set dancefloors aflame.

Band member Joakim Montelius wrote on the band’s Facebook page on 25 June 2016:

I was reading an article about this British pre-WWII project for early warning from attacks across the Channel, called Sound Mirrors. They were designed to amplify incoming sound from enemy aircraft enough to allow the defence to take them out before they could pose a serious threat. It was an elaborate and ingenious design, expensive as well, and it was rendered obsolete by the advent of radar.

My reading coincided with the refugee situation in Europe. The fact that we all knew about the reasons for it since years, without doing anything to help, made me think of this pattern. How we, humans in general, do everything in our power to try and predict future threats. That ability to anticipate possible scenarios is of course key to our survival, from an evolutionary point of view. [More…]

“Obscure functionalism melting into majestic land art”

The mirrors’ fruitlessness may be forgiven if only because of the uncanny impression one gets that they were built for a future not yet seen or understood. Indeed, its second life as a monument and relic has been more enduring than its first.

Christo Hall visits the sound mirrors on the Kent coast with photographer Stuart Leech and “finds an obscure functionalism melting into majestic land art”, in The Second Life Of Concrete: Brutalism’s Renaissance, published by The Quietus on 10 July 2016.

2016 Denge sound mirror open day

Denge sound mirror guided walk

The RSPB – which now owns the site – is holding an open day at the Denge sound mirrors on Saturday 23 July 2016, from 10:00 to 15:00. Open days are the ONLY WAY to access the Denge listening ears.

Saturday 23 July
Drop in any time between 10am and 3pm
Price: Free. Donations are welcome.

On this day only, RSPB Dungeness will open up the reserve for free! Come and see what this fantastic place has to offer and get up close to our recently acquired, historical Sound Mirrors (or Listening Ears)! Come along for the day where we open them up for everybody to have a wander around the site and talk to our staff and volunteers about what we are doing to give nature a home here. So why not spend the day surrounded in nature and history and afterwards head to the visitor centre for a cup of tea or an ice cream to round the day off nicely.


Please note that I have absolutely no connection with the RSPB or the open days. Make you sure that you confirm the details of the open day with the RSPB before going – do not rely on this Sound Mirrors website.

‘Remembering 1916’ exhibition in Croydon

Remembering 1916 exhibition

The Remembering 1916 – Life on the Western Front exhibition about the First World War in the year 1916 is being held at the Whitgift Exhibition Centre in south Croydon from 12 March to 31 August 2016. It is well worth seeing.

Remembering 1916 exhibition

The exhibition covers many aspects of the war, from Gallipoli to Jutland to the home front to conscientious objectors, with extensive displays of uniforms, documents, photographs, art, memorabilia, weapons and other exhibits from Britain, France and Germany.

Remembering 1916 exhibition

Remembering 1916 exhibition

Full-size mock-ups using real objects portray rooms in a 1916 house, a horse-drawn wagon, a trench on the first day of the Somme, a fort at Verdun and a German machine gun position.

Remembering 1916 exhibition Remembering 1916 exhibition

While there is nothing about sound mirrors there (as far as I could see), there is a display about Zeppelins.

Remembering 1916 exhibition Remembering 1916 exhibition
Remembering 1916 exhibition Remembering 1916 exhibition

Also of aviation interest is the display about an old boy of the school who was shot down (fatally) by the Red Baron.

The exhibition explicitly avoids getting bogged down in the politics and debates about who started the war or “lions led by donkeys”. In a refreshingly different approach, it attempts to give a 1916-eye view, and not simply see things through the lens of modern ideas about politics, class and gender – or a late-1980s TV sitcom.

Remembering 1916 exhibition

The exhibition is not far from central Croydon: plenty of buses stop nearby.


Remembering 1916 exhibition

Huw Morgan’s Sound Mirrors

Huw Morgan is a composer, organist and conductor is “drawn to the power of ancient, haunted landscapes and their lost inhabitants; fascinated by impermanence, space, and time.” This is the first perfomance of his new piece Sound Mirrors for organ and fixed media electronics, inspired by the Denge listening ears: “alien structures haunting the coastal landscape, still listening to the skies…”.

It was given by the composer as part of an Automatronic concert in the JAM-on-the-Marsh 2015 festival. Field recordings were made at St-Mary-on-the-Marsh and elsewhere on Romney Marsh.