I wanted to let you guys know that Johnson Smith Company sells a small red siren for about 20 dollars that sort of operates like a fire truck siren, and outputs a loud continuous blast. It is electric and can be wired to lighting effects, or sensor pads, to activate when your props are activated. I bought one and have many ideas it. For being small, it has some good output. The only bad thing, is that you can't let small kids around it, because the protection housing doesn't offer enough protection and someone could easilly have a finger shredded. Personally, I enjoy terrorizing unsuspecting guest with it, but will later incorporate them into props.

Screamhaunt