Here is a couple of videos of Federal's new "Rumbler" siren. The Rumbler is basically a 80w police siren subwoofer. It takes the output of a normal siren, reduces the tone by 75%, and amplifies it. There was something posted about it on this board not to long ago. Anyway, here are the vids, the second vid has the Rumbler cutting in and out to help demonstrate the difference. Be aware that a video camera cannot capture the all of the harmonics produced by the Rumbler.
http://media.putfile.com/FedSig-Rumbler-Clip
http://media.putfile.com/Rumbler-vs-reg ... ren-sounds