Just remember, you can instantly calculate the speed of any siren simply by knowing its pitch and the number of ports. For example, there is a Sentry siren near me that I have recorded, and when I analyzed the sound with a spectrograph, I found its pitch to be 473.1 Hz. I believe it's a 3V8-H, 7V8, ...

I'm probably alone on this, but I'm actually disappointed that Sentry caved and jumped on the electronic bandwagon. I think mechanical sirens are superior, and I've always respected Sentry for taking a stand on that. I guess that wasn't enough to keep up with the competition, so they finally said &q...

One of my very first (and favorite) siren experiences happened while driving my pickup truck to an evening class I was taking at a local community college. It was Spring or Summer 1995, and I was living in Clinton County, Iowa at the time. I had the windows open because it was very warm for that tim...

Without a doubt, the greatest siren ever manufactured. Excellent job with the videos, too.

I thought that yelp tones only applied to electronic police sirens, not to outdoor civil defense sirens. But I could be wrong. You can download a police yelp tone here:
https://www.sosgate.com/files/file/1-yelp-mp3/

An electric motor draws the most current (hence it produces the most heat) when the rotor is accelerating from rest (or from a slow speed). Once it reaches it's steady-state running speed, the current draw is MUCH less. When the manufacturer specifies a certain duty cycle, he's assuming that the mot...

That's actually an excellent question. I would love to know the answer, too.

This one is brand-new:

http://www.wral.com/shearon-harris-nucl ... /17274101/

Another couple of new-ish clips:

https://youtu.be/zQJW709M824

https://youtu.be/U9CBWLrhUIE

Not very old, but has some sirens:

https://youtu.be/siIxQZi8LRg