Electronic Portable Air Conditioner

What can be causing a humming noise in my bedroom? I have a severe hearing loss and my wife cannot hear it but sometime it drives me to the ragged edge. There are no electronic equipment except for a air conditioner in that room and the sound cannot be recorded on a portable tape recorder.Does anyone anywhere have any idea what could be causing it or has anyone ever heard of such happening? No possibility of air vent being the problem, thanks anyway Combatboots. I can't rule out tinnitus entirely but surely it would bother me in other rooms of the house if that was it. however it is a possibility as I have a severe hearing loss to the point where I can hardly engage in conversations! I can't rule out tinnitus entirely but surely it would bother me in other rooms of the house if that was it. however it is a possibility as I have a severe hearing loss to the point where I can hardly engage in conversations!