what it is: highly concentrated audio beams to alter your intent
where i found it: don't exactly remember
Somehow I ended up reading about LRAD machines, these contraptions that send highly concentrated audio beams that can be used to torture, disperse crowds, "alter intent" or broadcast crystal clear messages for miles in any direction. Apparently the sound beams pass through walls and other solid material, so don't think you can just put in ear plugs. HERE's the link to the LRAD line of products, the descriptions of which would be good for a laugh if they didn't have such sinister possibilities. If you're still curious after that, HERE's a longer explanation of how these things work.