Air raid siren

The Second World War brought a new kind of attack to Europe - the air raid. The Luftwaffe and the RAF took the battle to the skies, bombing strategic and industrial targets with the intention of weakening the enemy.

The problem for both sides was that industrial sites were frequently located very near to, or even in the midst of, residential areas, which meant that homes and civilian lives were at risk. Minimising the human loss meant that the population took to their shelters to preserve their lives, and warning was given as early as possible by the ARP wardens, most frequently using the 'Moaning Minnie' siren.

This device consisted of a fan, which blew air across a number of pipes, producing a multi-tone wailing. The sound ranged across a range of freqencies designed to be heard both at a distance, and was capable of penetrating buildings. The siren was freqently powered by electricity, but were most often hand-powered, driven by a crank. Pity the poor warden, who would stand behind or beside the beast, pumping away at the handle, driven to distraction by the noise, despite ear protection.

The rising wail was the signal for civilian, military, emergency services and Home Guard action. The civilians would take to their shelters, the military and other services took up positions of readiness to tackle fires and casualties. For many who had already lost loved ones, the siren brought back dread memories, and carried with it the question "Who is next?" - never welcome feelings of fear, uncertainty and doubt.

Long after the Battle of Britain, the Blitz over and peace restored, people still lived and worked in fear of the siren. Post-traumatic stress was not just limited to the military. My parents told me a story once of a neighbour of theirs who could not bear to hear the trumpet or any wind instrument, and who would run out into the street if he heard one.

In peacetime, a similar pattern of siren is used in many cases where warning is required: in tornado areas, close to some chemical works, mines or industrial areas where leaks, accidents or warnings may still need to be given.

Now, it is peaceful in Europe, yet the sound still engenders feelings, as though some deep-rooted racial memory were at work. Perhaps it is the current fear of terrorism, the knowledge that somewhere else in the world, people live in fear of their own dread 'Moaning Minnie'. I hope that we never need to dust off our own sirens, ever again. Currently, a .wav file is available, at the second url below, should you wish to listen and share the feeling.

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The German director Erwin Piscator was famed for his use of odd machinery and sound effects, and controversially, often used the old sirens in his productions.

http://news.bbc.co.uk/hi/english/special_report/1999/08/99/world_war_ii/newsid_430000/430152.stm
http://usmilitary.about.com/library/milinfo/milsounds/blairraid.htm
Encyclopædia Britannica

Air raid sirens were used during World War II to alert the public of an imminent air raid so that people could take shelter.

Mechanical sirens (either electrically powered or operated via a hand crank) operate as follows: a motor or crank turns either one or two (for single and dual tone sirens, respectively)fans or impellers. (In the case of a dual tone siren, the two impellers would have different numbers of blades, often 5 and 6 or 10 and 12, equally spaced). The impeller(s) would be placed inside a housing with slots that corresponded to the number of blades. As the impeller turned, it would draw air in and force it out the slots, creating a tone. As the speed increased, so did the frequency of the note produced. In the case of a dual tone siren, the ratio of the number of blades was equal to the ratio of the note frequencies; a 5:6 ratio would produce a minor third (the most common type), a 4:5 ratio would produce a major third, a 2:3 ratio would produce a major fifth, and a 1:2 ratio would produce an octave.

The siren would be used to inform the public of impending doom. In the case of an air raid, a "red alert" would be sounded. A red alert consisted of an oscillating tone, or slow rising and falling wail. This oscillation was achieved by turning the siren on, letting it rise to the highest note, and then turning the siren off, allowing the blades to slow and the pitch of the note to drop. The siren was then restarted and the process repeated.

When the danger passed, the all clear, or "white alert" would sound. A white alert consisted of the siren being turned on, and letting it stay on the high note for an extended length of time.

During the Cold War, sirens came back into use. There was, however, an added degree of complexity: the danger of radioactive fallout. In order to warn the public of possible fallout (usually within the hour), a "grey alert" was sounded. A grey alert was produced by having the siren hold the high note for 2 ¹/₂ minutes, while opening and closing a shutter at the front of the siren. This would cause an intermittent high note. On hand-operated sirens, the shutter was to be open for five turns and closed for five turns. If there was an immediate danger of fallout, a "black alert" was sounded. Instead of the evenly spaced high notes of the grey alert, a black alert would sound the Morse code "D", or long short short. Another variation of the black alert would involve three short notes instead of the Morse code D.

Electronic sirens produce the same types of sounds that mechanical sirens could, but they do it using speakers as opposed to impellers. Electronic sirens have the added advantage of (depending on the model) being able to double as PA systems.

Now that there is no danger (supposedly) of air raids or fallout, alert sirens are often used to warn of natural disasters (such as tornadoes, earthquakes, hurricanes, fires, etc.), chemical spills, terrorist attacks, or in such enlightened places as Chicago's suburbs, they warn of snowplows being deployed on the streets (because, of course, snowplows present a grave threat to the public safety).

Credit to: http://freespace.virgin.net/roy.smith5/sirens.htm, http://www.cityofchicago.org/Emergency911/Tornado.html
Suburbs that use sirens to warn of snowplows: Skokie (http://www.skokie.org/public/snow.html)

In the small Australian town called Ballarat, in the early 1970s, a nuclear family of three is at home on a Sunday morning. They live on a street near the local fire station, which has on its roof a siren. For one reason or another, on that morning those inside the fire station decide to test the siren, and its infantile wail is heard across town. When they hear it, the two parents are immediately stricken with absolute, immobilising terror; the blood seems to drain from the mother's face, sweat appears on the father's forehead, and both of them look utterly without hope.

The reason for their fear is that the siren is an old, repurposed air raid siren from World War II. It is of that same rotary design that was once found in Berlin and Kyoto, the cities from which the parents in that nuclear family immigrated two decades earlier, where as children they had heard those sirens and been just as terrified as on this day.

More than thirty years later Kerry Müller, the woman who was the young teenager in that nuclear family, remembers that morning, and says, "Christ, they nearly shat themselves. I think that's the kind of thing that people need, though, and it's the kind of thing that stays with you. The way a sound like that can give someone such a physical reaction, and affect them at such a subconscious level, that's the kind of thing that really makes you a pacifist."

For BrevityQuest10, 250 words.