symptoms are pretty sketchy and buzz or rattles can result from a wide variety of problems. Just a few: Bridge too low allowing tail piece to touch. something loose ranging from bracing to resonator parts; such as the spider or resonator cone not seating properly. also cover could be not seating properly as mentioned earlier. to the other extreme bridge saddle could be high causing string to hit cover. Best possible solution is to examine the instrument carefully and try and determine exactly where the buzz is originating. You can usally find this by applying pressure with your fingers to different points of the guitar and seeing if you can eliminate the buzz. You can then determine what has to be done to fix it. Hope this helps