Microwave auditory effect

The microwave auditory effect was first reported by persons working in the vicinity of radar transponders.

It consists of audible clicks produced by microwave pulses and perceived directly by the recipient without the aid of any receiving equipment.

Initial research by NASA in the 1970s showed that this effect occurs as a result of thermal expansion of parts of the human ear around the cochlea.

It was studied for its possible use in communications but has not been developed due to the possible hazardous biological effects of microwave radiation.

References:

Lin, J.C., 1980, The microwave auditory phenomenon, Proceedings of the IEEE, 68:67-73. Navy-NSF-supported research.
Guy, A.W., C.K. Chou, J.C. Lin and D. Christensen, 1975, Microwave induced acoustic effects in mammalian auditory systems and physical materials, Annals of New York Academy of Sciences, 247:194-218

Some conspiracy theorists have supposed that this effect is used for mind control.