Electrophonic hearing is the direct stimulation of the auditory nerves by external electromagnetic fields. In 1962 Allan H Frey carried out a series of experiments which proved that microwaves can produce the sound even in those who are deaf. The theory is unable to explain why only the sense of hearing is affected - though there are rare reports of people noting odd smells accompanying an aurora display. See also the discussion of the Electrophonic effect/Microwave auditory effect which covers various mechanisms in detail.