Weird noise-mechanical question

Bought a 96 Jetta that I am fixing up, and I had a question. I have a interesting noise, coming from the rear I believe. You can hear it alot more in the backseat. Its a humming/vibration sound/echo, that I would normally equate with someone having a window down and hearing that weird noise, but I know its nothing to do with air leak in windows or anything, sound like its lower like a echo in the wheel wells or something. Its just annoying and want to know if anyone has had that problem and knows what to do, my mechanic kinda thought i was crazy...i know it sounds weird but i hear it happens to some jettas when they get older. Any help would be appreciated...?

humming vibration noise is usually a wheel bearing.