I have a couple of the JC whitney sirens. The pitch is too high at full voltage (12v I think). In my spare time I will be doing some more experiments like slowing down the motor to try and get the right pitch, then stagger the slots to get the dual pitches. I removed the air scoop on one of mine to trim it down. At about $30 each its worth playing with for the time being.
http://www.jcwhitney.com/MINI_MOTOR-...;0;2001354;0;0
Edwin
Almost forgot - Pete, Pete, Pete, what did you do to that Sig Sundancer.