Buzzing noise

There is a noise coming from somewhere under my dash that sounds like a mini motor or like a line on the stereo has crossed with something and I am picking up reception. The buzzing/motor sound speeds up when I accelerate and idles when I do. I took it to my mechanic who is scratching his head, thought it might be a transmission thing and tried shifting the ?crankcase? on the floor from 2wheel to 4wheel to neutral no change...

After looking through some other posts I think this might be related to the bearings? How would I know? And what are the bearings?

SOMEBODY???? ANYBODY??? The noise is louder now and I would like to know if ignoring it is going to hurt me later