Originally Posted by
Pharos
I disagree. If the sound is travelling through air, (compression and rarification of that air), it will be prevented from exiting the source room by sealing, and constraining that process from reaching and entering the receiving room.
If it is travelling through the subststrate, this substrate must either be restrained from movement, (bracing in the case of a cabinet), or more realistically, absorbed somehow from that substrate. In the case of speaker cabinets heavy absorbing layers are applied to the internal surfaces, but it is difficult to see how this could be done with a wall, a 6" thick rubber 'sheet' glued to the walls perhaps. :(