I filmed an ambiance of this siren in July. I said at the time that I'd re-record it in a better spot to try to eliminate the traffic noise. I succeeded at that, but I had a few other problems this time. It's still good enough to post in my opinion, though.
You can find more details in the video description.
Enjoy. And stay tuned - a university near me is testing on Tuesday...
https://www.youtube.com/watch?v=mmxPnWnJGVQ