I need sound absorption now! I have a serious echo/hard slap in my HT room. I have been looking for a board type material to absorb the sound but I have not found anything I want to use. I am just going to use furling strips and batting. How do I determine what type of batting to purchase. Thickness (ounce?) and quality (poly - cotton)? Where is a good place to purchase this material? Should I do the walls from top to bottom or just the 1st 40 to 44"?