SST's tend to do that. Undo the offending cable, housing and frame cable stops. Find some internal cable route sheathing and place it over maybe 80% of the length of the cable that is hidden inside the frame. Get some of those "doughnuts" you find on external routed toptube brake cables and place them at intervals along the length of the internal sheathing. Button everything back up and the noise should be greatly reduced/ nonexistent...


Or you can be lazy and live with it like I do.