I use a heavy bag spring between the bag and the ceiling hanger (I use the same ceiling hanger, screwed into the ceiling studs with lag bolts). The spring doesn't eliminate the noise, but it's certainly easier on the studs. Note: you may have to get a different spring, since your heavy bag is 70 pounds and the one I linked to is specifically for 150 pound bags.

EDIT: Here are a variety of springs for different weight bags.