Class A design flaw-flanking noise

We just closed up our "dead air space" and hung our heads in shame. Here's the problem. When we decided to make the basement into a separate live room and control room instead of a open space project studio, we build our left dividing walls up against the existing sheetrock with a 1/4 inch caulked gap. Well, of course the sound is now traveling to the back of the rock in the drum room between the rock and 2" rigid insulation and straight into the control room! When we sealed the windows and had a drummer play the only sound we could hear was leaking into the left wall. The isolation from the ceiling was better than expected and there was none through the right wall, due to a decoupled room container the oil burner. We cut the top sill 2x4 and footer on both sides of the wall and the vibration was knocked down considerably but one piece of 4 x 8 rock, the one we are carrying in the picture below, is bridging one room into the other. Very dumb! Anyway, If we cut the rock up to the electrical box where the natural seam is, remove the rigid insulation with rockwool and stop it with some mass, leaving a 1/4' gap before the dead air space, that should do it I hope. The dividing walls are 2 layers of 5/8 rock with green glue and the dead air space is staggered studs filled with rock wool and finished with sonex. The ceiling is floating on hat channel and iso clips. We were actually very pleased with isolation we got everywhere but the left wall. We not only failed at stopping the sound from the left wall but invited it in. I hope cutting the rock will work. Any suggestions? Thanks.

I doubt your going to get a response. It's hard to understand what your talking about even with the great pictures. Can you draw a diagram (birds eye). Or explain better what -"dead air space" -our left dividing walls -traveling to the back of the rock....means Or at least re-read what you wrote out loud. :D i'd like to help

Or better yet keep all your question in one thread so we know the process you have taken from the beginning without having to search through old threads.

Thanks for responding. I'll have to download and learn a drawing program. Sorry I don't know all the jargon. :oops:

I've been doing mine in paint lately, so anything will do. From your last thread you cut back the top plates....but had a gap above the hat channel?? Which again I don't understand. Then your next thread you were discussing windows and caulk..... What's has happened since then. You see my point as to sticking to one thread. :D

Rock=plasterboard? Aahhh I see. Sorry :oops:

StellaDat, Please read the forum RULES (stickies) that can be found at this link: viewforum.php?f=17 Please correct your initial post to conform with these rules and guidelines. Many here will not only NOT help while waiting in respect for owners and other better qualified persons to proceed, but will simply ignore these type of posts completely. You may want to immediately ask "what is it that I have missed". Most often it is as simple as including your geographical location in your profile. Trust me in that the more you know the better others can help you and that the answer to that question is in the forum rules linked page. Until then, good luck, Brien

:oops: I do not have time this week to make up the drawings but I'm looking forward to learning the program. I might just have my dad draw it, he's retired and loves a challenge! I've added a few pics of the wall before we put the "Plasterboard" on. We call it sheetrock we're I live, or "rock" for short. I guess it's a location thing. You can see clearly in Pic #1 that we stupidly built our dividing walls, the walls between the control room and the live room, (double leaf?) with the last stud ending at the existing sheetrock. We left a 1/4" space between the last stud and the greenboard and filled the entire gap with silenseal caulk. But, now that I've put double sheetrock with green glue between on the outsides of both of these dividing walls, the sound problems are only coming through the sheetrock that is joining the two rooms. What we should have done was build these two dividing walls up against the concrete foundation. When the glass was placed in the frames, the noise coming through the sheetrock was equal in volume from the top to the bottom. So I think what needs to be done is cut the sheetrock close to the dividing walls and somehow stop it from traveling through to the other side. We also need to extend these two parallel walls to the concrete foundation. Anyway,it's off to work now and I will make up a proper drawing with all the room dimensions next week. I'm not looking for total isolation because this is just a home project studio. The design is extremely flawed and I can live with that as long as I can stop this one problem area. Thanks!

stelladat wrote:

we build our left dividing walls up against the existing sheetrock with a 1/4 inch caulked gap.

Could you explain this please?

stelladat wrote:

Thanks for responding. I'll have to download and learn a drawing program.

I've been using The Gimp http://www.gimp.org/ to illustrate points. That's only because I'm using Linux though. There's MSPaint in windows too. Wtf's the Mac's freebie? Anything?

Sketch up free works on MAC. Heaps better materials in the mac version :D

I tried Sketchup using Wine. No go. I do like it though. I'm actually kind of surprised that google won't port it.

Thanks for the response. In the bottom picture, the 2x4 studs farthest to the left were caulked into place, not screwed, into the green board you see surrounding the basement. We should have cut the green board and ended those two walls at the concrete foundation. Today, I severed the green board and took out a 2 foot section up to the next tape line. I also removed a sheet of 2" rigid insulation that was up against the foundation. I'll send pics tomorrow. There is no physical connection now between the two rooms. I just have to figure out how to add mass to the space that's to the left of those walls which would be 3.5" where the framing is up against the concrete foundation. Bedtime. Thanks again!

The issue with your room is that you have established a two leaf( double wall) in the middle of a room that has hard connections. Basically the two leaf is being jumped over, under, thru and around by all these connections. You can cut up the sheetrock or what have you but this is going to have minimum impact. The path of least resistance has to be terminated and that requires decoupling...not running over. "There is no physical connection now between the two rooms." I am afraid there is. The connection is as much with the ceiling as it is with the walls. Even cutting the sheetrock that seems like a good idea isn't helping as much as you might think. The vibration is running to the outermost side of the framing/wall and back into the existing framing wall on the opposite side room.

Hi Xspace. Because the basement is so small, it would have been extremely confining if we built a "room within a room". I knew I would have issues. We did hang both ceilings on each sie of the double leaf on hat channel in rubber isolation clips so there is decoupling there. We left a quarter in gap around the parameter of the ceiling and caulked all the gaps. The floor is concrete so I didn't think it would transmit much sound. On the right side of the two leaf wall there is another separate decoupled wall and we are getting very little sound through there. Given the space we are working in, I'm pretty happy with the isolation we've achieved. All is not lost and I can live with it. The only annoying point is the wall to the left of the two leaf with the shared piece of sheetrock. That is where I severed the sill, footer and the sheetrock and I'm down to the foundation on the drum room side of he two leaf about 24" wide and 8' up to the ceiling. I'm still trying to wrap my brain around what to do here to limit the midrange bleed Im hearing through the left wall. If I could knock down the leakage even just a little more I'd except it and move on. I'm going to try some experimentation tomorrow and see what happens. Thank again for your time!

I wasn't drunk when I posted the above but I was so tired, I could only keep one eye open. Apparently, depth of field affects spelling. :lol:

stelladat wrote:

Hi Xspace. Because the basement is so small, it would have been extremely confining if we built a "room within a room". !

If you have decoupled the ceilings AND the walls...this is essentially a room within a room, even if it may be short in the LF area due to the methods you used. I guess I AM drunk because I am not understanding what it is you are saying you did versus what it is that you actually did. Make sense?

I guess I must be drunk too, and I didn't even drink today! I'm just as confused as Brien is: you say you could not build a "room in a room", but what you describe sounds like you did exactly that! It is really hard to tell from the photos. I'd suggest that you carefully and accurately model what you did in SketchUp and post the file here. That would make it much easier to understand what you did, and suggest what you can do to fix your problem. - Stuart -