This is a fantastic question. Maybe it would be helpful if some of the AVS members who have/are working with green chimed in. Most of them aren't finished with their rooms, i don't think. But a couple of gents from this forum have commented that it cleared up "echos" in their room (one of their words), etc. if they see this, perhaps they will comment.
I will answer this with what i know, as i know it.
it'll eliminate or at least grossly reduce the chance of the wall rattling. it will improve sound transmission, blah blah blah
My understanding of the impact of Green Glue on in-room absorption is somewhat different. I would anticipate that the absorption of a common wall would ahve two traits
1. it would be fairly narrow in band
2. it would ring (re-radiate some sound back inot the room after the music stopped)
Green glue would (this is my thoughts) flatten and broaden the absorption curve, and it will 110,000% wholly eliminate ringing. But i don't think it will raise the peak absorption of the wall.
anyone is welcome to chip in.
Now, i am not nearly as competent to discuss room acoustics as Noral Stewart who is a very noteworthy acoustics professional. see here: http://www.stewartacousticalconsultants.com/people.html
in this thraed: http://groups-beta.google.com/group/...mindspring.net
he enters this comment about damped walls in this regard: "In theory and concept it should provide some benefit as claimed. Light gypsum walls do vibrate and absorb some energy in doing so. In concept, the material improves this ability to absorb energy and reduces the chances of any of that energy being re-radiated."
so perhaps my understanding needs a tweaking.
another thing that is interesting to measure, although i don't know what it means for the sound in a room, is the tendency for walls, ceilings, etc. to vibrate (sometimes strongly) at their resonant frequencies even when no noise is being played at those frequencies.
in loudspeaker cabinets this is called "wolf-tone" behavior.
we did a study in one room, on the walls and ceiling, and found that this wolf-tone behavior spanned about one octave. The ceiling had a primary structural resonance at an average of 172hz.
noise between 100 and 250hz caused the ceiling to vibrate at 172hz (average, again). For about 1/2 octave, the ceiling vibrate dmore at 172 hz than at, say, 157hz or 198 hz.
interesting, and i don't know what any of this means.
whatever the case, this is something that we will study when time allows, and attemp tto offer predictions of absorption for Green walls of various configurations.