ASC T-121 | Alert | Brookfield, WI | Waukesha Co. Siren Test | Oct 9, 2024

After paying homage to the Hurricane, Devin and I went and visited this shiny new T-121 in Brookfield
You may be wondering what in the hell is up with this camera angle. Well, poking over the top of the building in the background is a T-128 belonging to the City of Waukesha. I had janktastically used a fully extended selfie stick mounted to the top of an already flimsy tripod to get my camera high enough to get both sirens in frame in the unlikely event that the T-128 would also activate for the test. News flash, it did not. The background T-128 is tested by the City of Waukesha every Friday at 9:30 AM from the beginning of April through to the first Friday in October.
Fun Facts:
Siren: American Signal Corporation Tempest-121
Signal(s): Alert
Location: Hillcrest Elementary School
Local Municipality: Brookfield
County: Waukesha County, Wisconsin
Date Recorded: Oct 9, 2024
Testing Time(s): Brookfield's American Signal sirens are tested with Waukesha County's test every Wednesday at 2:00 PM from April through August, and the 2nd Wednesday of every month at 2:00 PM from September through March, weather permitting
Time of Activation: 2:00 PM
Distance from Pole: ~250 feet
Maximum Recorded SPL (@ ~250ft): 104.4 dBA (~108 dBC @ 472Hz)
Main Shot Video & Audio: iPhone 11 Pro
Other Sirens Heard: N/A
Enthusiasts Present: Devin (‪@WasherBoy2016‬)
(in)FAQ:
Q: Why did I measure sound pressure level in dBA?
A: I measured the SPL of this siren using A-weighted decibels because, although dBA is more representative of human hearing, and the purpose of a siren is to be heard by humans, at the time of recording, I did not know that C-weighted decibels are actually the more appropriate unit of measure to measure peak volume levels of very loud sounds (that and dBC appears to be the industry standard for sirens anyway).
Q: How did I convert dBA to dBC?
A: Step 1: Perform a spectrum analysis on the recorded audio to determine the prominent frequencies. Step 1.5: If it's a dual tone siren, take the average of the two frequencies. Step 2: Plug that frequency into a weighting filter differentiator (by Sengpielaudio) to calculate the difference between dBA and dBC at that frequency. Step 3: Add the difference to the original measurement in dBA to get a rough estimate in dBC. For simplicity's sake, and more importantly, my sanity, any prominent harmonics and/or overtones were ignored for this process. This is by no stretch of the imagination a scientific process, but it should produce conversions that are "close enough".
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