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The Sound Mirrors: A History of the Future of War Noises

Publié le 1 juillet, 2008 | Pas de commentaires

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In an effort to detect oncoming enemy aircraft by means of acoustic amplification of the propellers’ drone, Britain built a series of concrete Sound Mirrors between 1915-1935. Primitive, massive and accidentally sculptural, the Sound Mirrors represent a lost link in the transformation of modern warfare. Although now obsolete, the mysterious structures still loom over the English coast, mute witnesses to an obscure historical moment, in which military architecture ran parallel to the desires of the avant-garde.

Sound Mirror at Abbot's Cliff, Capel-Le-Fern
Ithamar Silver, Sound Mirror at Abbot’s Cliff,
, 2006
(with permission of the artist), all rights reserved©

In his studies of railway architecture he said […] he could never quite shake off thoughts of the agony of leave-taking and the fear of foreign places, although such ideas were not part of architectural history proper. Yet, he said, it is often our mightiest projects that most obviously betray the degree of our insecurity. The construction of fortifications, for instance
W.G. Sebald.*

Although “not part of architectural history proper,” a series of moss and graffiti covered ruins along England’s southeastern coast belies one of the more grandly misguided displays of national insecurity to be produced by the tumult of the twentieth century. The remains are as imposing and impenetrable as any fortress—yet these were not traditional fortifications meant to withstand an enemy onslaught, a fact that renders their solidity largely palliative.

They were, essentially, ears.

Ruins are all that remain of the Sound Mirrors, built by the Air Defence Experimental Establishment between 1915 and 1934 in an attempt to detect oncoming enemy aircraft.

That Britain’s response was to erect a Stonehenge of band shells reveals much about the psychological need of the island nation to construct an architecture of reassurance. Other world powers experimented with acoustic location in a more portable manner—dishes of human-scale that could be easily mounted on a car, for example. No doubt, the constant threat of invasion from the continental Other had led to a status quo of tenuous uncertainty (does anyone else hear the half-hearted self-reassurance in “There’ll Always Be An England”?), and the permanence of fortification may have provided a modicum of comfort. In Walter Benjamin’s view, the calmative was in vain: “Now and then one hears of something ‘reassuring’ such as the invention of a sensitive listening device that registers the whir of propellers at great distances. And a few months later a soundless airplane is invented.1

The first Mirrors were successfully employed towards the end of World War I; they detected a handful of enemy raids and gave English artillery several minutes advance warning to intercept German bombers. But it was only after the war that the experimentation began in earnest. The Center for Acoustical Research was established in Hythe, on a hilly promontory known as “The Roughs.” Then nascent, the Royal Air Force was hesitant to furnish test planes for the project, and from the vantage point afforded by the hillside, the Mirrors were able to listen to the sounds of commercial air traffic. In 1927, Dr. William S. Tucker, Director of Acoustical Research and the man most responsible for the physical form the Sound Mirror, proposed the construction of a series of Mirrors along the coast. Though only two were built, a telephone-relay network was established and aircraft bearings were called in to a room in a London post office.

The principle behind this technology will be familiar to anyone who has visited a cathedral with a vaulted ceiling. Stand at the focal point of the concavity, and you can hear faint whispers made on the other side of the building as though the source of the sound were just beside your ear. In their earliest incarnation, the Sound Mirrors were equipped with a pivoting sound collector mounted on a pedestal. These were the days prior to electrically aided amplification; the sound collector was nothing more than a listening horn with stethoscope tubing emanating from the other end. The first Mirrors were hemispheric concavities carved into the faces of chalk cliffs and overlaid with grid marks 2. This system permitted a listener to perceive the directionality of a sound and track the lateral movement of an airplane through space.

All of the Mirrors built after 1930 integrated hot-wire microphones of Tucker’s own design. Instead of standing on a tall pedestal and rotating a large horn by hand, the operator sat in a booth and listened through headphones. Even so, distinguishing the faint rumble of distant engines was so taxing that listeners were rotated in 40-minute shifts. These 30-foot diameter Mirrors were more accurate than their predecessors, but Tucker was not satisfied: « Whereas the thirty-foot mirrors are very efficient for (sound) waves up to three feet or so […] the sounds we wish to deal with have waves of fifteen to eighteen feet […] This involves extension of the mirror surface to about ten times that hitherto employed. » To meet these requirements, a 200-foot long curved wall was built beside the 30-foot mirror in Romney Marsh, near Dungeness. A forecourt equipped with 20 microphones stretched out into the marshland before the wall; a listening booth was positioned behind the wall at its center.

The 200-foot wall at Dungeness represents the culmination of nearly twenty years of experimental building and technical innovation. The scale of its construction was such that a dedicated railway extension was built to carry it out. That the Dungeness Mirror was built at all is remarkable, given that the entire Sound Mirror project had been beset by fundamental flaws during every stage of its development. Unfavourable weather, operator fatigue, human error, and large variances in the hearing capabilities of listeners were unavoidable drawbacks. However, more critically, the Sound Mirrors amplified everything. Although apparently apocryphal, stories of the Mirrors picking up the sounds of trains leaving a nearby station nonetheless capture the fallibility of the technology. Though the Mirrors were built in remote locations, the encroaching drone of modernity began to threaten the silence. A holiday resort sprung up within range of the 200-foot Mirror, making passersby and picnickers a minor nuisance; an inspection by a high-ranking officer was apparently ruined by the rattle of a passing milk truck. Ultimately, the newly developed radar technology would render the Sound Mirrors obsolete. By 1937, the Sound Mirrors had been abandoned and their telephone-relay network usurped by the new technology.

The Sound Mirrors may seem laughably naive—a misguided, stone-age radar out of The Flintstones—yet this primitive technology was actually an imaginative and moderately successful response to the unfamiliar threat of the warplane. Swiss architect Le Corbusier, who wrote Aircraft in 1935, was still awed by “the bomb-carrying airplane” 3. The novelty of the bird’s eye view (Le Corbusier first flew in 1928, when commercial airlines were still scarce) is still fresh, and the visionary architect surveys the cities below with an utopist’s fevered ambition. Only from his new perch does Le Corbusier see the greedy, inhuman city for what it is, whence: “The airplane indicts the city.” For Le Corbusier, the airplane is a tool for imaging—a machine more in line with the camera or microscope than the locomotive. “The eye of the airplane is pitiless. This time we have the actual record of reality.4

Futurist poet, essayist, and noise artist F.T. Marinetti was present at the first use of airplanes in warfare, and claimed that the roar of the propeller on the battlefield “taught” him the mangled syntax and onomatopoetic ejaculations of Futurist poetry 5. If Le Corbusier was thrilled by the new vision afforded by flight, the Italian Futurists found their muse in the sonic possibilities of the modern battlefield. Lusting after the future in all its mechanized swiftness, the Futurist movement seized upon the noises of the battlefield “because they were the newest noises and required new artistic means for their expression.6” Luigi Russolo, in the Futurist manifesto The Art of Noises, declares: “In modern warfare, mechanical and metallic, the element of sight is almost zero. The sense, the significance and the expressiveness of noises, however, are infinite.7” Russolo goes on to describe how an experienced soldier is capable of discerning the different calibers of enemy munitions, as well as the size and direction of enemy patrols–by listening alone. Proto-Fascist, machine-obsessed and thrilled by the destructive din of war, the Futurists staged demonstrations petitioning Italy to enter The Great War so that they might have the privilege of enlisting and partaking in an actual version of their Dance of the Shrapnel 8. Floating high above the unwitting Futurist orchestra of agony below, Le Corbusier’s camera-aircraft itself emits the telltale hum of mechanized modernity, easy prey for an ear discerning enough to hear the music of the battlefield.

The Sound Mirrors were spared demolition by the outbreak of World War II and many remain more-or-less intact, though neglected. When I set out to visit the remains of the Kent Sound Mirrors in January of 2007, I was surprised to find that most were unguarded and easily accessible. The exceptions being one in Boulby that had somehow been transformed into a private residence, and the three Mirrors near Dungeness. The Dungeness Mirrors are the only structures of this sort protected under UK law and include a 20-foot dish, a 30-foot dish, and the 200-foot wall. The Kentish shingle they occupy has been sold to Cemex, a gravel excavation company. Unable to demolish the Sound Mirrors owing to their heritage status, but requiring a deterrent to the local teens who were climbing and graffiti-ing the Mirrors, Cemex hit upon a somewhat medieval solution: digging a manmade moat around the Sound Mirrors. The Internet led me to Owen Layshon, who holds the key to the 20-foot swing-bridge that pivots across the moat to permit access. Owen leads two tours every summer and politely denied my repeated requests to film the Sound Mirrors on one of these excursions. In his time as key holder, Owen recalls the one exception to his rule being a photo shoot that featured German supermodel, Claudia Schiffer. Undaunted, I made my pilgrimage; obtained a small, inflatable dinghy, and rowed across to the artificial island.


* W. G. Sebald Austerlitz. Trans. Anthea Bell.(New York: Alfred A. Knopf, 2001) 14.
1. Douglas Kahn. Noise, Water, Meat: A History of Sound in the Arts. (Cambridge, Mass.: The MIT Press, 1999) 66.
2. The exact location of the first Sound Mirror in unknown—many of these early mirrors were apparently filled in by the government in the 1980s and their whereabouts forgotten over time; a worthy puzzle for archeologists of the recent past.
3. Le Corbusier, Aircraft. (London: The Studio, Ltd., 1935) 12. It is perhaps difficult to recall that WWI saw the first large-scale deployment of aircraft as war machines. Indeed, in the early stages of the war, pilots on opposing sides reportedly waved at one another as they flew past. Gun-turrets came later and their synchronization out-of-phase with the rotation of the propeller, later still, a fact attested by the countless Swiss-cheese propellers.
4. Le Corbusier 102.
5. Kahn 61.
6. Kahn 59.
7. Kahn 67.
8. It should seriously be noted that a number of the Futurists were either killed, maimed or seriously injured on the battlefield. Both Marinetti and Russolo sustained major injuries that left lingering effects.

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