This article clipping courtesy of Harry Barry.

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 its 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.