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.

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.
Encyclopædia Britannica