Originally Posted by panino
I've already posted this in my theater thread, but decided to repost the question here so I can get a broader expert opinion on this soundproofing issue.
I'm about to build my screenwall. Since the stage is essentially sitting free from the walls to isolate any sound transmission, should I also decouple it from the ceiling when I build the screen wall? I would think the answer is yes, but I don't think I've seen any build on here that has done that. Everyone seems to just run posts from the stage floor straight up to the ceiling with no decoupling brackets. I would imagine there would be some transmittal of sound, especially low frequencies, into the ceiling this way, but maybe it is negligible?
There is a huge difference between the stage and the screenwall, though, and it has everything to do without how much surface area is in contact with the decoupled shell (walls and ceiling). A stage will have a pretty massive footprint pressed against the walls, if there is no gap, and this will result in a lot of energy being transferred to the walls. A screenwall, on the other hand, has a pretty negligible footprint on the ceiling resulting in pretty big drop in how much energy will be transferred.
I wish I had some numbers, but I can't find any anywhere.
That said, I was asking earlier about "through" door jambs versus disconnected ones especially since in one very specialized case, something as simple as a broom handle bridging outer and inner walls resulted in a staggering drop in soundproofing effectiveness. BasementBob gave a very good answer for that but, never being satisfied leaving well enough alone, I asked Rod Gervais directly. His response is excellent
: Rod Gervais Answer
Seriously, I'd recommend that everybody read that, since even his anecdotes are golden.
Anyway, the very very simplified answer (very simplified. very!) is that while the true reason is that the specific details matter a lot, there is a big element related to how much surface contact we are talking about. A through door jamb is touching the two walls in only a small footprint, compared to how much contact a non-decoupled wall would have between the layers of drywall or even the amount of contact that a concrete slab has on both decoupled walls.
That principle applies to the decoupled screenwall question, I think.