It certainly is. I estimate an audible range of slightly under 20 miles maximum for a pure frequency of 440 Hz and and SPL of 138 dB at 100 feet. This is estimating an atmospheric absorption loss of 1 dB/1000 feet at 500 Hz plus the inverse square law loss of 6 dB/doubling the distance while assuming the most ideal quiet conditions at the point of measurement.
The thing is that the Chrysler siren produced a square wave, which means the pure tone component is around 3 dB less or around 135 dB at 100 feet.
For a pure frequency of 220 Hz with an initial SPL of 138 dB at 100 feet, however, you would get around 34 dB at 100,000 feet (18.94 miles). The Chrysler siren used a common blower/chopper, which lost considerable output as the shaft speed reduced. The output at 220 Hz would have been much less than that at 440 Hz, so the SPL at 100,000 feet would be well below 34 dB. The Big Bertha siren, however, used a separate blower and like a Thunderbolt or Hurricane was capable of high output during wind down. It might have actually achieved an SPL as high as 30 dB at 20 miles.
holler wrote:50 mile audible range, sounds like a slight overstatement to me.
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