Now that's what I'm talking about!
As many times as I've held a cockroach up to my ear, I've never once been able to coax it to emit a single peep. I've had equally bad luck trying a twisted pair.
I think you have recreated the essence of cockroach speech quite nicely. My only suggestion would be to crank it up another octave to get that really spooky ultrasonic sizzle.
(Shouldn't this be in Bugs and Suggestions?)