On 2/10/2014 11:01 PM, -MIKE- wrote:

I've done that type of wall in studios and they perform very poorly.
Are they better than a standard stud wall? Yes, for ordinary
residential use.
But they would never work for a studio.

Never say never.

They do for some practical applications in the studio. Depends upon the
location, distance from, and frequency that you wish to mitigate.

Installed correctly, double stud walls will mitigate sound transmission
_by decoupling_, for _practical_ isolation in areas like vocal booths,
not so effectively in areas like drum and amp booths.

But a double stud wall room/booth, a few feet away from a separate
double stud wall/booth, will often get you close enough for practical
purposes.

RWAR is fairly effective for decoupling, not so practical, and what you
make on the bananas you lose on the grapes ... IME, ventilation in RWAR
becomes a problem that brings with it its own sound transmission problems.

Good thing as a practical matter, most of the time it is not necessary
to totally "soundproof" a studio, or an area within a studio, just
attenuate the transmission of unwanted frequencies/sound in those areas
to an amplitude that doesn't interfere with the recording process.

The problem is quite a bit more involved mathematically/physically than
what is said here, but the practical application basically boils down
to, and roughly speaking, the necessity for effective sound absorption
techniques to require a dimension equal to the length of the absorbed
sound wave to be effective.

A 20Hz sound wave (@sea level) is approximately 56', not taking into
account properties of the material it is passing though, like mass, etc,
making soundproofing with material impractical in most situations ...
although at some frequencies it can be done with noise cancellation
techniques. (Example: sometimes running a monitor system 180 degrees out
of phase with the source will attenuate the sound picked up by a mic to
an acceptable level for both recording, and to prevent feedback on a
sound stage).

As far as residential application, when I build a house I generally
specify double/alternating stud walls in rooms next to the utility
rooms. In my own house, my bed is less than five feet from a washer and
dryer in the utility room next to the master bedroom, and for all
purposes it doesn't exist as a sound problem. I do have to watch the
framers, plumbers, electricians and drywall crew very closely during
construction to insure that they don't couple the walls with pipes, etc.

--
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