The ‘alert’ tone is just a steady tone that plays at a constant pitch......that's all.....I have heard it before...It doesn't sound like what you are hoping it sounds like rather just an early 60's electronic siren found in use in Police Cars , Ambulances, etc. It has absolutely nothing to do with Civil Defense or mimicking the sound produced by a Thunderbolt as an example
. I'm sure that if you do some looking that you might stumble across an audio sample of either the Federal PA 15 or PA 20 alert tone.
I petition that everyone who joins the board should have to put there age or year of birth in thier signature...32 here
....54 for another year