Cork as an acoustical ceiling block

Much of the sound travels through the structure (i.e. the joists). What you would like to do is separate the joists from the ceiling with a small air gap decoupled from the joists (we have designs just for this) and have a high mass ceiling attached to it of varying layers. You will lose about 3 inches of ceiling height doing this, but it is very effective. Cork isn't high mass enough. It will reduce mid band and high frequencies, but won't have much effect on the energy the subwoofer is delivering.

Whatever you use, MAKE SURE THAT IT'S FIRE-RETARDANT (or is treated with a fire retardant spray)! As the tragedy in Warwick, R.I. showed, some accoustic material can ignite and burn like napalm, while also spewing a variety of toxic fumes (phosgene which is similar to "Mustard Gas" of W.W.1, and cyanide). Enjoy, but be safe!

Thanks fellas. You've given me some greatideas.