http://www.federalwarningsystems.com/sites/default/files/downloads/AlternateWail.wav http://www.federalwarningsystems.com/sites/default/files/dow... It's Feder

http://www.federalwarningsystems.com/sites/default/files/downloads/AlternateWail.wav http://www.federalwarningsystems.com/sites/default/files/dow... It's Federal Signals' "Alternate Wail" setting for their outdoor warning products. Multiple overlapping arrays making this sound is (as you can tell) very effective at making people take shelter.