Most (all?) RCA dryers are made by GE. On that brand common places for noises are from the rear drum bearing being worn (best replaced in a kit like tomh said which comes with the drum shaft), the front drum glides (no rollers on GE built dryers) or a worn idler pulley.
My guess is the rear bearing and/or front drum slides are the most likely worn and causing the noise. Both are usually fairly inexpensive so replacing them both while the dryer is apart is often a good idea.
I also agree with Jennifer that you should discontinue use until corrected or other damage may be done to the dryer that will likely increase repair costs, possibly to the point of being uneconomical to repair.