Greetings!

Actually, my personal preference (for emergency audio) would probably be the old US Emergency Broadcast System tone. It is a duotone, composed of an 853Hz sine wave and a 960Hz sine wave. Any (older? US) person walking by would recognize that tone... "This has been a test of the Emergency Broadcast System."

Seriously, I think there are laws against booby traps that can cause bodily harm. But if you were going to do this, you might be better off with a cheap air horn - very loud in a car and you don't have to worry about your empeg, amp or speakers! All you would need it a trip mechanism.

Paul G.
SN# 090000587 (40GB Green)