BT - a sound designer friend, Brian Tibbetts, thinks this could explain synesthesia:

"but imagine some freaky experiments/research where they manipulated this protein and subsequent ion flooding with non sonic related methodology..

like through drug therapy. like squirting a fluid into the ear, vibrational/magnetic/EM manipulation, or even, like, a scent, a piece of food, a drink or something..

*This would cause people to hear things when there was no actual source of physical sound. And what would they hear? Could it be tweaked? How far?? ;)

Perhaps research in this vein will help explain the bizarre phenomenon of synesthesia where people�s neurological sensory processing systems are strangely wired.. causing them to, for instance, see sounds, hear colors, etc. Wild!"