If you were wondering what the biggest and loudest air raid siren of all time is, then wonder no more, because it's the American Chrysler Victory Siren, made in the 1950s. Well, I don't know for sure that it was -- I'd like to see what the Soviets had to offer -- but it was clearly a mighty impressive piece of hardware: 12 feet long; 3 tons in weight; and 138 decibels at a distance of 100 feet! (120 dB is the pain threshold.) These were dotted all over the United States -- 20 in Detroit alone.
You can hear one of the few remaining examples in action here. It certainly sends a chill down my spine, which is perhaps strange as nuclear drills were not a feature of my youth here in Australia, so I only know the sound of such sirens second-hand. But I can't help but imagine what would have been happening to the communities these sirens were meant to warn, as the missiles (or in the 1950s, the bombs) rained down. Which in turn leads one to marvel at the optimistic choice of the name Victory Siren ... though I suppose the Defeat Siren ("If you can hear this, you're already dead") might not have sold so well!1
Of course, nuclear war looked somewhat more winnable in the 1950s, and civil defence correspondingly less pointless, than was later the case. But still. ↩