Wall design using a propietary polymer layer . .

I guess after reading all the issues concerning 3 leaves I began to think ohhhh nooo . . but I have a differant approach here with a very secret layer that I can only talk about to a limited degree . . but I will say that after looking at Quiet solutions and having a keyboard player that is a polymer chemist, we came up with a pretty cool idea . . any thoughts here . . BTW you guys seriously rock out there with all your work, focus and dedication to this science . . I am having a blast reading your posts.

You are still triple leafing. You would get about a 10 point better STC by putting all the gypsum etc in the middle leaf on the inside leaf. Have a look at the bottom of this link at the various constructions and sound isolation. Rw is similar to STC. http://www.domesticsoundproofing.co.uk/tloss.htm Andre

Thanks Andre for the reply . . so you are telling me to forget all together the inner most studs, and just put two layers of my "sandwiched panels" on the middle wall? I was going to float the floor and have that inner stud wall on the floor. But it sounds like you are suggesting to eliminate that all together? Cheers, Mark

Hi Mark, Is your "exterior fibreboard wall" sealed or can air (and sound) pass through it? If they can (not sealed), you can leave your plans as they are.If they can't (sealed), then Andre is right in what he's told you. :) In the second case, I would add some more mass to the outer wall, as it "looks" less dense and massive. :) cheers

HI Sen, The outer wall is pretty flimsey fiber board and I would say that air and sound get through for sure. Here is a photo right before I started putting up the studs, I had to raise the building to replace the concrete wall as it had fallen in. I will take another tomorrow and show more detail. Thanks so much for responding, I am most appreciative. Cheers . . .

Is your "exterior fibreboard wall" sealed or can air (and sound) pass through it? If they can (not sealed), you can leave your plans as they are

Regardless of how "sealed" the outer wall is, it will act as a membrane at low frequencies. The only difference is that if it is not sealed, the wall will act as a Helmholtz resonator instead od a panel resonator, in addition to letting sound through. If it isn't sealed, then the first step is to seal it! Andre

Excuse me for butting in here.....Hey mark!!! Long time... Love the CD...Check your PM.. Doug M

I never thought I'd find a thread where it fits so well, but here it is. Thanks to Z60611 who created the "soundproofing coat of arms". Caulk (seal) everything. No triple leaf.

AVare wrote:

Regardless of how "sealed" the outer wall is, it will act as a membrane at low frequencies. Andre

Hello, I'm not sure that two sealed and one unsealed leaves of mass would provide WORSE isolation than two sealed leaves.That's basically what you're saying.If Mark sealed the outter wall, by all means GET RID OF THE MIDDLE WALL. But in case of his outter wall which is...

The outer wall is pretty flimsey fiber board and I would say that air and sound get through for sure.

I don't think it will ruin much isolation that the other two walls will provide. I don't think panel absorbers and Helmholtz resonators have anything to do with this either.But of course, this is just my newby opinion, and please don't quote me on this.I'm certainly still learning and will gladly take any corrections anyone may have for me. :) cheers

I'm certainly still learning and will gladly take any corrections anyone may have for me.

Well, start with this. http://forum.studiotips.com/viewtopic.php?t=1198 Membrane effect just HELD close to the door! Andre

yeah, if you read that post you linked to, you will see that I just talked about this thread and was puzzled with Paul's experiment, which brought me back to what I wrote here. And sorry to Frustrate you Andre, as you said in your post here, http://forum.studiotips.com/viewtopic.php?t=1199. I did admit I was only learning about this stuff, so I didn't feel you should be frustrated.I'm pretty sure you're still learning too, and that there are some areas you're not an expert in.Have a nice day, and sorry to have frustrated you.

edenorchestra: Green Glue is a relatively new commercially available viscoelastic (from http://www.audioalloy.com/ ) It's viscoelastic, and cheaper than previous things.

My super secret viscoelastic material is free . . I have 115, 5 gallon buckets of it.

edenorchestra: free is good !

Soooooo . . what's the conclusion if any . . can I get away with the current construction? The darker studs are the existing building with the fiber board facing the outside. I was planning to put the sandwiched-viscoelastic drywall on the inner studs and then float another wall inside this on the floating floor. I had planned to fill the area in this photo with insulation (most likely blown in cellulose) for heat as all walls are exposed the outside air. This is a stand alone building. regards,

Soooooo . . what's the conclusion if any . . can I get away with the current construction?

You can get away with anything you want. For the most sound isolation possible with the materials you have planned to use, here it is in more detail. Seal the outer wall if it isn't air tight already. Forget one of the inner walls that you are planning to build. Sorry, but in terms of isolation the middle one that you have already framed is the preferred one to forget. Place all the wall material you were going to put on the two new walls on the one remaining wall. If you want to do something to increase the mass of the outer wall, then put additional material against the fiberboard between the studs. Regardless of which wall you decide to keep, fill the space with sound absorbing insulation. Andre

Hey Mark you're getting some good tips around here :lol: . If I may just add: If you do decide to keep the outter wall and increase the mass of it, it would probably be easier to attach a new layer from the outside (over the fibreboard) instead of between the studs. that way you have something to screw the new layer into (ie. your studs).So are you leaving just the two walls you have now (outter and the built frame) or...??Is that inner frame (pictured) floating or...? If it's not you could still keep it and use the RC on it!? :?

I just did some quick calculations. With the fiberboard and vinyl on the ouside, 10" airgap, and 4 layers of gypsum on the inside, the STC is 59 with TL 23dB@50Hz. Assuming that the compound shifts the resonance frequency down half an octave, the STC will be in the mid 60s. Changing the airgap to 15" doesn't affect the STC significantly but it does increase the LF TL by 3dB. Numerically; Andre

Andre . . tis very kind of you to check this out for me. What are you using to run the calculations? Are you putting the 4 drywall layers on the studs in my last photo? thanks for your help . . I appreciate it.

What are you using to run the calculations?

I ran them on INSUL using the Knightfly modification on the first leaf to make the density close to fiberboard and vinyl siding. Guesstimating the effect of the damping material to be reducing the resonance, the red line shows my guess at performance.

Are you putting the 4 drywall layers on the studs in my last photo?

Without knowing the exact dimensions, I guessed that the space for the studs is 10" airgap. Here is a screen shot (I can do that now! I am still high on that.)

Andre . . I guess I could do that . . I am considering putting drywall between the outside studs first. Possibly putting Homasote 440 and then Drywall between the studs. I guess that's the only alternative. Sounds like I blew it on the studs. The thing is . . what do people normally do with a separate building that already has external wall coverings (ie. siding and fiberboard). I feel like I am stuck to some degree. sigh . . . thanks for your help and interest . . . cheers . . .

edenorchestra wrote:

Andre . . I guess I could do that . . I am considering putting drywall between the outside studs first. Possibly putting Homasote 440 and then Drywall between the studs. I guess that's the only alternative. Sounds like I blew it on the studs.

Why the homasote? It is not as dense as gypsum. Put an extra layer of gypsum.

The thing is . . what do people normally do with a separate building that already has external wall coverings (ie. siding and fiberboard). I feel like I am stuck to some degree. sigh . .

Either a new exterior or exactly what we are writing about. Andre

Ok cool . . well for shits and giggles, if I was to take down the vinyl siding, which ultimately I wil be doing for aestethics, what can be put on the outside? Drywall would not be tolerant of the weather even if covering with an additional barrier such as plastic and then ???? you've been most helpful . . I am grateful

Also if I do put the drywall between the studs as you suggested, will I need to caulk that tightly between. And can I glue that to the fiberboard, or possibly tightly fit it and put some coarse thread screw through the drywall into the fiberboard? Best Regards,

Yes to your second post. For ideas on wall construction that are sound tested have a look at NRCC-44764. http://irc.nrc-cnrc.gc.ca/irc/fulltext/nrcc44764/nrcc44764.pdf Andre