On 2/11/14, 8:47 AM, Swingman wrote:
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.
Well, I am a drummer, right? :-p
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.
Now you're just making my point for me.
If one works, why are you now building two? :-)
As I said in my other post, a room-within-a-room: two walls with an air
gap between. For best results, they would have difference resonant
frequencies, or in other words, built from different materials. On
block, one wood. One wood stud and sheetrock, one metal stud and brick
or double rock. etc, etc. Which is what you talk about here...
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.
I would specify cement block. :-)
Having done some alternating stud walls, I'm left to wonder if it isn't
easier and more effective to simply build two walls, close to one
another for those purposes.
--
-MIKE-
"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com
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