Of course this does have some interesting implications. The US Govt has experimented with loud low frequencies for non-lethal crowd control. Apparently, if a human is subjected a 3-4 Hz sound wave at sufficient volume, the sphincter muscle of the rectum involuntarily relaxes. Your tax dollars at work.
Untrue. The experiment has been tried a few times (and probably by the government as well), but there isn't in fact a reproducable "brown note" effect. If there was, it really *would* be common equipment in crowd control gear - and of vast use in Iraq, among other places. The approach fails twice - first, no actual frequency affects people in this fashion; second, well, everyone here knows how fast SPL falls off with distance. Even if 4Hz @ 150db made someone lose control, how much energy would you have to pump in, to generate 150db @ 1m? At 10m? At the 50m+ you want, for crowd control? That's a lot of power, exceeding what large-venue rock concerts generate. You don't do that with highly portable gear. And imagine the effect on the operator of the equipment, who would be within a few meters of a source of 150db @ 50m. He'd be deaf in seconds.
This isn't to say that 8Hz can't upset the tummy - human flesh does have a resonant frequency, just like anything else, and 8Hz or so can tweak organs. That could inspire the occasional unlucky person to find a bathroom. Just not in general.
I have read, somewhere, that 16000Hz+16002Hz creates an extremely unpleasant pattern and that people exposed to it gain motivation to be elsewhere. But it's got the same SPL problem: you have to make it very loud to affect any large area, and that means you damage the hearing of people nearby.
Of course, maybe differential ultrasonics could be used to create this effect out of 4 tones - ultrasonics *are* very highly directional and aimable...
