[adamzk]

I think depending on the size and shape of the region of constructive interference it's possible to apply force selectively to somebody's head. In my old apartment, one of the cabinet doors in the kitchen would rattle when the music in the living room played a certain note. Putting my hand in that area I could feel the force of it and it had fairly discreet boundaries in all 3 dimensions. I can imagine it would cause quite a headache if that were suddenly applied directly to my brain. And that's just from my stereo. Work a moving source with broader range, it's theoretically possible to"sweep" an area for susceptible targets. When the source is outside the audible range it would could be largely unnoticeable. Selectively applying pressure to certain parts of the brain can cause a range of symptoms. Like if all of a sudden somebody squeezed your pituitary gland how would you feel?