Welcome to our new beta design! Click here to go back to the old Newschoolers.
It sounds like it probably is the bearings. You know how winter tires sound on dry pavement? When bearings go bad it sounds like that, but WAY worse; like a lot louder.
If you get it done at a shop it'll probably cost between $400 and $500 but you can do it yourself for like $100 or less (Depending on the brand of bearing you get) and it's pretty easy to do. You can get away without doing anything about it for awhile though.