More in Floors
Put a 1" foam spacer against the wall, much like a baseboard, to keep the floor from touching the side walls (Image 1). Don't allow for the floor and walls to touch -- it helps absorb sound and lets the floor move up and down just like the ceiling.
The flooring is covered with specialized sound insulation (Image 2), which is specifically engineered to add sound absorption to concrete floors.
Note: The floating floor system is made up of small low-density fiberglass isolation pads (Image 3) spaced 12" apart that support the plywood, and they're also designed to support other weight such as furniture and floor traffic.
Once the fiberglass is in place, it's time to install "two" layers of plywood on the floor--again using the same methods that was utilized on the walls and ceiling to make sure the seams on the second layer don't match the first (Image 1).
With this particular installation the two layers will be glued and screwed together to avoid any creaking. Using two layers of plywood on the floor in addition to the fiberglass base will help increase the sound absorption.
For this DIY project specialty sound products are being utilized, but there are less expensive ways to create floating floors to enhance the acoustics of a home theater. One way is to buy vibration-insulation pads at a supply store. They are normally used for HVAC systems. Lay them out in 16" spacing grids. Take 2x4's and lay them across in rows. Now you have a space in between the 2x4's that you fill with standard batt insulation (Image 2). And when laying the plywood, make sure to glue and screw the plywood together to prevent any creaking sounds when walking across the floor.