actually, the whelen's "gas" tone is only used in other countries, such as if you search for Denmark siren, that 1st video is actually attack, and the 2nd video posted here by holler is Wail
If you go to www.safetycom.com they have all of the sounds Whelens can make. Manhattan, KS uses the "Gas Proof Protection Tone" to warn of an earthquake strong enough to make a dam protecting the city fail. I am hoping to one of these days get a video of it.