Natural Science Forum / Physics / Acoustics / November 2005

Not very well. Though the diconnect occurs, the air gap , typically an
inch or so, is still relatively rigid. That air gap must be made quite
wide, say 4", and preferably more. When that gap is made, RC has no
place to latch onto.

A separate stud wall is required to support the drywall, ergo a separate
stud wall it is, which is what I have advocated for decades (well, 25
years, anyway).

The added separate drywall stud wall should do well. Place fiberglass
batt, R13, or R19, in the entire gap for added damping.

Angelo Campanella

You are on the right track, but RC by itself does not provide a large enough
gap.  Any time you introduce an air space you create a resonance.  Isolation
is improved at frequencies above that resonance, but is actually decreased
at the resonance.  With just the half inch air space you get with the RC,
the resonance will be in the range of much common sound.  A larger air space
reduces the resonant frequency.  Consider using 25 gauge studs for furring
or more ideally stand them slightly out of contact with the concrete.  You
could consider 1.5 inch studs, but 2.5 or 3.5 inch studs would give a lower
resonance frequency.  Batts in the cavity are helpful.

Before doing all this, check carefully to make sure you do not have cracks
around the perimeter of the wall somewhere, and if so seal them.