The M3W as supplied has a screw on 'guard' on the rear sprocket, on the outboard side. This was a continual source of noise as the belt tracked side to side trying to align itself. A number of owners ( including myself) removed this and it reduced the belt noise a tad. Many other sources of belt noise are available, including dust, grit etc.
The only long term cure I have found is to go chain drive, courtesy of Mr Bleazey. Not sure if the Super rear hub is compatible, but worth checking if you are serious.
