The sounds of civil defense and air raid sirens like the Federal SD10, Thunderbolt 1000, Federal STH10, 2t22, and so on, both alert and attack modes? Any air raid siren enthusiasts out there?
Google didn’t turn up anything?
You posted on a forum filled with audiobook readers and people recording their guitar.
There are some civil defense sirens on Freesound … http://freesound.org/search/?q=+civil+defense