xyz wrote:

I'd appreciate an explanation on what he meant also.

Materials like fiberglass or acoustic foam will _absorb_ only certain
frequencies. Which frequencies absorbed depends on the thickness. For
example, two inch acoustic foam will absorb some mids and highs, but
any low frequencies will still pass through. These materials are used
to stop the sound reflections from bouncing around your room
(eliminating echo and creating a "deader" environment), but they wont
soundproof your room.

Sound _proofing_ materials are designed to stop all sound frequencies
from passing through. This is mostly done by mass. Thick concrete or
floating rooms (a room built in a room) come to mind.

There is lots of great information on this he

http://www.auralex.com/

Michael Nickolas