Voices in the Head.

Voices in the Head
Washington Post on Electronic Harassment Technologies

"An academic paper written for the Air Force in the mid-1990s mentions the idea of a weapon that would use sound waves to send words into a person's head. "The signal can be a 'message from God' that can warn the enemy of impending doom, or encourage the enemy to surrender." In 2002, the Air Force Research Laboratory patented precisely such a technology: using microwaves to send words into someone's head. The patent was based on human experimentation in October 1994 at the Air Force lab, where scientists were able to transmit phrases into the heads of human subjects..."
  -- Washington Post article on electronic harassment and voices in the head, 1/14/07