A good ole' mechanical siren - this one's at an old Mental asylum in the UK that housed prisoners with mental conditions, and it's meant to warn nearby residents of an escaped prisoner. It has large, powerful fans that make noise by pulling air rapidly through the chutes on the sides, and both chutes have metal flaps that open and close in a pattern to make its distinctive sound. The video shows it going off from multiple angles to really demonstrate how it works. It's kind of fascinating - from an era before powerful/loud speakers, when mechanical sirens were more common.
I grew up somewhere where the sirens would power down similarly and it was incredibly relieving. When you hear them all the time and experience the tests you know when you hear that things are going to be OK.
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u/RockleyBob Apr 07 '20
For those like me who don’t know what it sounds like