Hi John!
-> I ran across something a couple weeks ago that might interest some of
-> the harder core among us. While talking with a contractor I spotted
-> a new product for home construction. It is a weather sealed 3/4 inch
-> chip board sandwich with six inches of extremely heavy density
-> polyurethane foam middle, formed at high pressure into panels. They
-> are used for freestanding (read: no studs or framing) wall and roof
-> construction. They have a Plus R40 insulating factor for walls and
-> ceilings and are the closest thing to soundproof I ha seen. In a
-> house constructed of these and with good double pane wi unable to
-> here a big D9 Cat bulldozer less than 50 feet away, le side yard !!!
I have seen some of that material, and you are right, it is an excellent
material for sound isolation.  A couple of additional comments on that
thought. As long as the "bread" of the sandwich, the plywood or wood
surfaces are not coupled to each other by a stud or something even
like a nail, and the filler is all solid polystyrene or whatever they
are using for the filler, it should work quite well.
An old acoustic saying is "air is the best isolation", the only thing
better than that material, is to build a shell of it within the existing
room (loosing a few inches along each wall of floor space) using air
between the walls for further isolation,
One studio I know uses 40" of concrete between the control room and
studio walls! Now that's an extreme, but then Steve Lawson at Bad
Animals Seattle tends to want the best available in his studios. I think
a much cheaper solution to a similar problem would be tiltup concrete
for one wall, a little air space and then something like what you
mentioned for the interior wall, if you really don't want to bother your
neighbors, or have them bothering you while you try to capture the
maiting sounds of the tsetse fly or something equally demanding on noise
floor requirements.
Bonnie *:>
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