Wall thickness ...

Hello, I'm planning the construction of my new studio here in south france ... all the details about what i want to achieve are in this thread at the first post : viewtopic.php?f=2&t=11707&p=85217#p85217 But i can say it must be a semi- pro recording studio build from scratch into a non residentiel area but with some neighbours around... The building will be concrete blocks filled w/ concrete and receive 2 box in the box inside, maybe onto steel framing and several layers of GB. All is on separates concrete floating floors for the CR and tracking room. the goal is to achieve the best iso to record rock bands with real acoustic drums ... I have a question regarding the thickness of the studio wall facing the wall of the CR. If I'm not very clear enough, look at the small sketchup file attached, it's pretty rough, and just for the principle not drawed to scale, dimensions are not real .... just to visualize what I want to explain ....!!! So in this file the brown room will be the C.R., and the orange one the tracking room ( the Studio ) So, the orange wall with the studio-window is the concerned. My question : since all the walls for the two boxes will be made from 3 layers if G.B., 13mm / 15 mm / 13 mm, is it a good idea to make this wall more thick, using for exemple : 3 GB layers 13 mm / 18 mm / 13 mm , in order to 1) achieve better iso from the wall exposed to louder SPLs... 2) Avoid coincident resonnant frequencies betwenn the 2 walls facing ? thanks for your advices, this place is awesome, Fabrice,

Fabrice, I suggest you do some searches on this forum for MSM, and double stud walls. There should be some helpful stickies on this, which should help you to gain a better understanding for what you need. :D Ian

My question : since all the walls for the two boxes will be made from 3 layers if G.B., 13mm / 15 mm / 13 mm, is it a good idea to make this wall more thick, using for exemple : 3 GB layers 13 mm / 18 mm / 13 mm , in order to 1) achieve better iso from the wall exposed to louder SPLs... 2) Avoid coincident resonnant frequencies betwenn the 2 walls facing ? ---- I m not an expert, but in my point of view ,yes it s better to have the rec studio wall thicker (or different) so you ll avoid the same resonnant frequencies on the 2 walls. I m also building a new studio ( see topic new studio), ive made my walls with 3X13mm but I plan to add a new layer on the rec studio wall with wood to solve the problem. Good luck

:) Hello, thank you for the answers.... I'll be waiting for other answers from experts, why not ?... and I plan to do that.... Fabrice, :jammin:

To be honest, I'm not convinced that using layers of different thickness GB helps all that much. I've seen arguments both ways, and I understand that theory behind using different thicknesses to avoid duplicate resonance, and help with refraction paths, etc., but I can't recall ever finding any papers or real laboratory tests that show a noticeable difference in isolation. On the other hand, more mass will always give you better isolation, all other factors being equal, so in your case I think I'd be inclined to go with three layers of 18 mm GB, which gives you more than 30% extra mass, beyond your original plan, and that alone is worth nearly 2 dB of extra isolation (if my calculations are right!) across the spectrum. I very much doubt that varying the thickness of the panels will gain you 2 dB. Now, if you add a layer of Green Glue as well, then you gain much more, especially in the low end. As far as I recall, the independent lab tests on Green Glue were all done using 5/8" GB, with no variation in thickness, so I think I'd go with what they have already tried and tested. Perhaps there would be a difference using GG and different thickness GB, but unless you can find real figures for that, then I think I'd just go with what has been proven to work well. So, to summarize, I think I'd use the thickest GB you can get, plus GG in between. (But that's just my non-expert opinion.) - Stuart -

Don't be fooled by Stuart's modesty, he knows his stuff! :D

Hello all, :) Thanks for reply, Stuart, I appreciate ... So,

Don't be fooled by Stuart's modesty, he knows his stuff! :D

Of course !! I have read many posts from Stuart, and I think his knowledge is huge and reliable.

To be honest, I'm not convinced that using layers of different thickness GB helps all that much. I've seen arguments both ways, and I understand that theory behind using different thicknesses to avoid duplicate resonance, and help with refraction paths, etc., but I can't recall ever finding any papers or real laboratory tests that show a noticeable difference in isolation.

In fact, my question is rather on using two different thickness for the 2 mass into the MAM system for the wall, than using different thickness of same material into the same partition. But to speak about that a little, several experts tell this :

3 layers of GB act differently rather one layer of the same total thickness. The critical frequency is related to the material and it thickness. When putting differents layers, we minimize the coicidences for this frequency. .... This precaution is not always useful, it depends of the project....

Fc for GB 13mm : 3077 Hz Fc for GB 15mm : 2660 Hz Fc for GB 13mm X 3 : 1026 Hz Fc for GB 13 mm + GB 15mm + GB 13MM : 976 Hz So the insulation is more efficient when using 2 different layers with 3 layers because the critical frequencies are not centered on a only one but on two different frequencies ..... And the partition is a little more heavier but it's rather unsignificant for the iso... You must double the mass of the partition to gain 4 dB of iso. ............

here is a link for a Canadian website BUT it's in french !!!! So if somebody can read it .... it explains severals things about composition and nature of walls in sound transmission loss... http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd239_f.html

On the other hand, more mass will always give you better isolation, all other factors being equal, so in your case I think I'd be inclined to go with three layers of 18 mm GB, which gives you more than 30% extra mass, beyond your original plan, and that alone is worth nearly 2 dB of extra isolation (if my calculations are right!) across the spectrum. I very much doubt that varying the thickness of the panels will gain you 2 dB.

Yes you're right, according to above, the gain of Iso is not interesting ... I just want to know in fact, is if it's recommended to make the 2 partitions into a MAM wall with different thickness, in order to overcome unwanted resonnances ... OR if you prefer is there are some drawbacks in using same thickness for the two partitions ...

o, to summarize, I think I'd use the thickest GB you can get, plus GG in between.

Yes of course, GG is a very good trick, But ... very hard to find in FRANCE, only at import from UK or US ... Some times ago STUDIOSPARES had GG, but no more now :( And I want real GG since their results are tested and proven ... So, Thanks, (and excuse for my english and the translations for the references ....) PS: Excuse me thor this rather log post ! :oops:

In the case of differing thicknesses of drywall on a wall assembly - don't waste your time. Put on the thickest you can afford - as many times as you can (or 2 layers at least with GG) and understand that the gain in mass more than makes up for the slight dip you get around the critical frequency. When you start talking about a 10 dB dip in iso from TL values of around 80 down to 70 - you realize that these are not your problem areas to begin with. HOWEVER - a doubling of mass will gain you 6dB (that's right - 6) in the area where you need it the most - low frequencies....... Rod

Hello Rod, very honored to have been contacted by you! :) Thank you for your answer, I'll consider it : concentrate on most possible mass and forget for the light change for Fc... Fabrice,

[quote="Fabrice"] here is a link for a Canadian website BUT it's in french !!!! So if somebody can read it .... it explains severals things about composition and nature of walls in sound transmission loss... http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd239_f.html [quote] The English version: http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd239_e.html

But to speak about that a little, several experts tell this : "...And the partition is a little more heavier but it's rather unsignificant for the iso... You must double the mass of the partition to gain 4 dB of iso. ............"

I don't think I'd be too inclined to trust an "expert" such as that! As Rod already pointed out, doubling the mass gains you 6 dB of isolation, not 4. Simple physics. ( And thanks for the accolades, Fabrice and NativeLuv17, but really, I ain't no expert! I'm, just a good "sponge": I absorb the stuff that I read from the REAL experts here and other places (such as MHoA), and when I get squeezed, then I can spit out that information again! That's about it. I guess I understand the basic principles, and I can quote folks like Rod and John and Ethan and Andre on some other stuff, but if it gets outside what I already learned, then don't ask me for the answer! I'm still on the learning curve, like most of the rest of you guys, just maybe a bit higher up. But my point is, please don't take my comments as gospel truth, carved in stone! Take Rod's comments like that, for sure, as well as Andre's, John's, Ethan's, Ro's, etc. But not mine. That said, the good thing about this forum is that if I do screw up and say something wrong, I'm sure the real experts will waste no time in promptly shooting me down in spectacular technicolor flames, and correcting my ignorance! For which I am very grateful, of course. ) - Stuart -

Stuart, we understand your still learning like the rest of us, but it's that "sponge" ability that allows you to retain and spit out valued information from which you have learned is what we value. I am sure if you didn't know the answer, you would admit it, but do to Rod, John, Ethan, Ro, and Andre (where did he go??) most likely not able to respond so often, we rely on you and Brien to steer us in the right direction from what you guys have learned. -Ian

hello, Thanks xspace for the link ...

I don't think I'd be too inclined to trust an "expert" such as that! As Rod already pointed out, doubling the mass gains you 6 dB of isolation, not 4. Simple physics.

Stuart, I must apologize, i have done a Shortcut , the quotation was out of context ..., I think this guy do not talk about a comparison between one thickness and the double of it, in this case of course you're right, physics tell us + 6 dB !! BUT I think the subject was to put 2 layers of the same material, with same thickness, it double mass, but the kind of fixations between them can decrease the iso by few dB, I think ...... However, I must clarify, the guy in question is reliable, this guy have worked with Tom Hidley , and has built several pros studios here in France, like : http://www.studiodelagrandearmee.com http://www.guillaumetell.com/ http://www.davout.com and have also work for PLUS XXX studio (Paris France) And if I use this forum, it is not for doubt the experts here, but as I learn permanently, just to understand... And again, I thank everybody here, for the different advice, experts or " not expert who always learn", sponges (or newbs as me:wink:) this place is stunning!!! :love: :thu: Fabrice,