Zargon You need to buy the Roxul brand Fire and Sound insulation.It is greenish brown in color and you cut it easy with the help of a bread knive.If you use regular Olfa knive it will dull the blades fast.Don't use R19 Dow Corning Pink ,that's good for thermal only ,although I believe pink brand makes their own version of acoustical insulation.My local Home Depot here in Toronto only stock Roxul.
George
George