Most probable is broken piston rings. Depends on the sound. Broken piston skirt can cause a knock and oil consumption. A hole in the top of the piston can cause oil consumption and a rough running engine. Depends on the size of the hole how bad it might sound and run. In either case the crankcase blowby would be pretty good. pull the oil filler cap off while it is running and see if you get any vapor coming out. Vapor coming out is really bad. not coming out doesnt mean there isn't excess blowby as the engine trys to burn it. Of course these are extremes and it could be more subtle then that. depends on how much oil is consumbed and how serious the sound change is. I wouldnt take any long trips in it at this point.