LRAD, (Long Range Acoustic Device), VAncouver Police have it, just in time for the winter olympi
I stared down the LRAD every day in Pittsburgh. There are a few things to know about it:
1) It's essentially got a volume knob, and generally they won't turn the full force on civilian demonstrators. Though it can be used, at the far end of the spectrum, to inflict overwhelming pain on subjects, this is a crucial moment for the LRAD (which was, until PGH, never before used in civilian applications), and unnecessary use of force would draw unwanted attention.
2) The LRAD's cone of influence seems to me highly directional. Now, if you're outside of that cone, it will still be incredibly loud -- but if you can avoid getting the dish pointed directly at you, you can probably avoid the gurgly stomach-feeling Monkeywrench mentioned. Save your constitution for the tear gas.
3) Ear plugs may not work the way you hope they will -- you'll still hear the chief of Pittsburgh Police sharing a recorded message in both English and Spanish, for instance -- but they CAN reduce the damage your own personal set of ears receives. Remember, earplugs are a good idea; even if it seems like the noise level with them in is still uncomfortable, they might be the low-tech failsafe between you and lasting ear damage.
4) Other possible countermeasures: It's commonly known that sound waves bounce off solid surfaces and back to the originating point. The basic way to enact this principle is to engage the LRAD anywhere but out in the open, if you can choose your turf. I also have a vision of a concave panel being hoisted by protestors to bounce sound back to the LRAD operator, but the practical difficulties of deploying something like that at a rally seem to suggest finding a more effective countermeasure, such as:
5) EMP (ElectroMagnetic Pulse) LRAD runs on generators. Need I say more? Will cost thousands of dollars to buy or you can make your own. For legal reasons, I do not recommend trying this at home, or around friends with pacemakers.