Not sure if anyone came across this, or if it had been posted in the past, but the NRC did a TON of tests back in 1995 on various interior wall construction methods and subsequent sound transmission.

Really quite impressive results and really helps to narrow down what makes a difference and what doesn't.

Sound Transmission Through Gypsum Board Walls:
Sound Transmission Results
By J.D. Quirt, A.C.C. Warnock, J.A. Birta
Internal Report IRC-IR-693
October 1995

http://archive.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir693/ir693.pdf

That is a cool document. I will admit that I just scrolled (quickly) down until I got past all of those "words" until I saw pictures. LOL

No, I always do that with long articles just to skim through to get an overview of what it contains. It lines up with what I read elsewhere about my soundproofing for my theater. It comes back with a STC of 57 for me, which is more than a rating of 50 which is considered good for home theaters with loud sound sequences, but not quite the 60 which is good for home theaters at full volume all of the time.

I got that from page 3 of the following document:
Soundproofing Home Theaters and Media Rooms

NOTE: My link above I just found when googling a few minutes ago. It seems like it kicks into high product advertisement mode just a few pages in, so don't take it as ideal advice or that I am even suggesting any of the methods there. The link in chesseroo (where I didn't see a lot of specific brand products mentioned at all, which is more unbias and what you want). Heck, I didn't even really read before or after the chart on page 3 of my link above.

Ours is probably about a STC of 40 for the walls and maybe 46-48 for the ceiling based on extrapolation of additional batting thickness on STC. We had considered the staggered studs method which would have added maybe 5 to 7 more STC but really, i doubt anyone would notice substantially in the upstairs rooms. No one cares much about sound immediately outside of the HT room itself and a 30dB drop in SPL has been measured just by closing the HT doors. In the meantime, we would have decreased the media room size which was a larger concern.

If we ever decided to do more in the future, adding a second gypsum layer would add 5 STC and not substantially change much else in the room, although the pain of going through more mudding and sanding wouldn't be worth it IMO especially considering we have ducting in the insulated walls which is likely the weakest link in the acoustics that escape the room.

Just in time! Thx chess.

Thank the NRC for doing such extensive research.
The work is a bit old now, but the materials they tested likely wouldn't have changed dramatically.