I have a friend from Pittsburgh (Rick) who is a firefighter and a siren lover like me (also a lurker on this board), he sent me a recording today of the neighboring fire department's siren (easily my favorite in existence) and I had to share it with all of you. If you listen closely, you can hear the harmonics of that thing bouncing off the hills around it (and making it sound like 2 sirens). See if you can figure out what we are listening to!
Dave
http://www.zshare.net/audio/67574361539c6f/