There's a humming noise when going down the road... any ideas?

Hello, Does the noise increase with speed? Or change a bit while turning? That humming might be a failing wheel bearing/hub. You'll need to get it to a shop for proper diagnosis! http://repairpal.com/volvo-within-10-miles-of-brooklyn-connecticut-06234

Likely a failing wheel bearing...fairly common on these. Figuring out which one can be a bit tricky, so have a shop check to verify to be sure.