I imagine many have already seen this, but for those who haven't, here's a one-page article my father found in an old issue (January 1943) of Popular Science talking about the Chrysler siren. Sorry for the poor image quality, I currently don't have a working scanner.
If you can't read it, here's what the article says:
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(PHOTO CAPTION) Testing the machine, engineers have to hold their ears as the siren blasts out its mighty roar over New York
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New York Air-Raid Siren Nears Top Limit on Noise
Scientists have estimated that the loudest sound that could be produced would not reach more than 190 decibels. New York's super air-raid siren atop the RCA Building, when operating at full throttle, reaches a horn volume of 170 decibels, and can be heard over 50 miles away. The revolving mammoth "howler" comprising the siren proper, a blower to supply compressed air, and a 140-hp. engine to drive both, creates an ear-shattering roar by a high-frequency air disturbance. A "chopper," 25 inches in diameter, revolves behind six "throats" leading to the horn. As compressed air is sent into the throats at the rate of 2,500 cubic feet a minute, it is sliced off by the blades of the chopper, which revolves at a rate of 4,400 r.p.m.