the paper mentioned above is now located in another thread, forward on this board.
some clarifications are in order, and i'm back to make simpler a copule of points after a note from a friend that i got a little long-winded above. Brevity in type is a work-in-progress for this guy... :)
first, gluing rigid members between the two leaves of a wall does not represent damping. Damping is the rate of energy dissipation in a system - literally, that is the definition - and gluing the two sides of a double leaf wall together should be considered stiffening, not damping.
second, in data published by the NRC, stud spacing as close as 12" on center had a very significant change in the location of the MSM resonance, but no effect on the coincidence location at all.
third, adding insulation to a cavity will generally have no effect to a slight RAISING of the coincidence location (refer to IR-761 for a handful of examples where this slight or no effect is illustrated). The resonance above shifts down considerably when insulation is added.
fourth, adding insulation to the cavity has a menial effect on TL below the 600-1000hz dips, and had a notable impact on performance above the dip. this is classic behavior of a double leaf wall. It behaves approximately lke a single panel below the resonance, then de-couples (and insulation has an effect) above it.
fith, coincidence is a wave phenomenon, and increasing stud spacing is associated with an increase in the dpeth of the coincidence dip in many cases, as is making more resilient the wall (the bending waves can travel, being built-up by the waves in air, farther before they are interfered with by the studs). the faint dip at 2000hz may represent a coincidence dip, or it may be off the screen in this case, i haven't a clue, if the data went higher we could be more certain of where the dip lies.
finally, and a bit off topic, note that the minima around the MSM of these systems was the same for both the 5" deep cavity and the 1" deep cavity.
if we apply mass-air-mass resonance theory, it should have moved down by more than one ocatave. why this does not shift should be explained as well. i refer to curve 1 in the top graph and both curves in the second (Staggered stud) example.
finally^2, it is interesting to note that the staggered stud construction - very much deeper, more decoupled, and with far more insulating material - exhibits poorer transmission loss than the thin sample. more to think about, and more questions
this seems to be, perhaps, the largets misunderstanding among people - what damping is. it's energy being removed from a system, that's it, and that's all. stiffening is something else.
