Just because you hear voices in your head doesn't mean you're crazy. Witness the Army's Microwave Beam Gun.

[You probably are crazy, but you know... still.]

US Army toyed with telepathic ray gun - tech - 21 March 2008 - New Scientist Tech:

"...Other ideas, like a microwave gun to 'beam' words directly into people's ears, have been tested. It is claimed that the so-called 'Frey Effect' – using close-range microwaves to produce audible sounds in a person's ears – has been used to project the spoken numbers 1 to 10 across a lab to volunteers'.

In 2004 the US Navy funded research into using the Frey effect to project sound that caused 'discomfort' into the ears of crowds."