"I suspect the noisy gif phenomenon is closely related to what we call the Visually-Evoked Auditory Response, or vEAR for short," explained Fassnidge.
"This is the ability of some people to hear moving objects even though they don't make a sound, which may be a subtle form of synaesthesia - the triggering of one sense by another.
"We are constantly surrounded by movements that make a sound, whether they are footsteps as people walk, lip movements while they talk, a ball bouncing in the playground, or the crash as we drop a glass. There is some evidence to suggest that synaesthetic pairings are, to some extent, learnt during infancy.
"I might assume I am hearing the footsteps of a person walking on the other side of the street, when really the sound exists only in my mind.
http://www.bbc.com/news/science-environment-42237092
