Infrasound
Wikipedia has a pretty good article on the subject, so I'll recommend you look that up.

The Brown Noise is fantasy- it's based on hitting the resonant frequency of the abdominal cavity to make your intestines vibrate, thereby inducing intense shitting episodes. As no two abdomens are the same, the effectiveness of this is marginal at best.

What I have in mind is to make a half-wave rectifier (basically a large diode and a capacitor and a resistor), hook it up to a transformer to get some current at a low voltage, then run it through a large power transistor hooked up to an oscillator (basically a resistor and a capacitor), with a variable resistor (aka dimmer switch) to vary the frequency. I want to hit about 19Hz, ideally.

My plan is to make a fuck-off big electromagnet to run it through, and position it behind a nice big iron washer mounted to a sheet of rubber on an open cylinder (like a drum made from a piece of inner tube). I want to make very large amplitude waves with this.

Why?

So at Halloween time I can put it outside and scare the piss out of all the little kids on the street at once, without them knowing why they got scared.

Yes, I'm serious.
( The Resident Loon Not a demographic. Do not measure., Tue 29 Apr 2008, 16:54, Reply)