If you screw or nail the sill to the floor, a bridge is created wall->studs->sill->screw->joist->rest of the house through which sound can propagate to other parts, whether you use rubber between the sill and the floor or not, if I have understood it correctly - so partly what is the function of the rubber and how should you attach the sill instead? Or is the rubber more intended to seal gaps than vibrations?
