Soundproof room in a condominium

Hello! :D After reading this forum for months, I finally decided to ask a question about my soundproof booth I want to build. The current situation is the following: I live on a second floor of a 3 store building. The floors and ceilings are 6'' concrete slabs, and my condo is a corner unit, which means that I don't have any neighbors on the sides. I plan to record a drum set in that room. The dimensions I planned for it are: 9'L X 9'W X 7'6''H. The main problem seems to be the kick drum with almost 98db around 55-60Hz. It doesn't bother to hear a bit of drumming on the outside of the room as long as it doesn't reach the below neighbors (impact sound mostly). I did quite a bit of research, I found no testimonials about situations similar to mine... Everybody building a soundproof room seems to have a house, a rented industrial space or a separate garage. I have neighbors below and on top of me... I've been discussing lately with Doug Johnson of Kinetic, who helped me a lot, so on my little plan I base my calculations upon Kinetic products (http://www.kineticsnoise.com/arch/rim/wood.aspx, http://www.kineticsnoise.com/arch/isomax/index.aspx). I have a rough budget of 3'000$ but if I need to spend a bit more in order to achieve a superior results, it is quite feasible. So my questions are: 1) With a STC 71 for the floor structure (with TL of around 32db around 50-60hz) what can I do to improve further the transmission loss of low frequencies? 2) Can I invert the inner wall (interior > 2X4 > isomax clips with resilient channel > 5/8'' + 5/8'' drywall > airspace > next wall) in order to benefit from deadening of exposed Roxuls batts (covered with fabric for aesthetics)? 3) May the resilient channel with 5/8'' + 5/8'' drywall on top of it considered as a Third Leaf? 4) Will the Green Glue be of any help in my situation (floors and walls)? Thank you very much in advance! A.

Three things that I would change are your measurements that are the same (9'L X 9'W) since square is never good, but as small as this booth is with drums inside, may have to be treated down all over, anyway. Second is removing the clip/channel off the wall facing the exterior. This is actually shrinking your air space not to mention it is a cost that is not required at that specific part of the panel. Third and last is to get on the ground floor, like mostly everyone else that builds. When you place a lot of weight on a structure that is elevated(even concrete) you still have weight load considerations that only the people involved in that buildings construction can get you a proper answer on.

Thank you for the reply xSpace! Since for the next 5 years or so it will be impossible for me to move to a ground floor ( :( ) I will try to get an evaluation from a constructor/engineer to know if the current structure will support 5000lb booth... Anyway I wasn't planning to start building anything before making sure that I'm not throwing my money away. But besides from the weight problem, do you think that the construction of the booth itself is adequate for intended purpose?

I am pretty certain that a square room is never good, as I said, and that the clips and hat track on the outside of the inner wall shrinks the air space and this product is not being used correctly, as I also said.

Consider those two factors removed: new dimensions of the room might be 10'L X 8'W X 7'6''H, which are closer to a recommended ratio of 1 : 1.14 : 1.39. Also there will be no more isomax clips on the inner walls (unless I cannot make the wall inverted). But it is there any problem of inverting the wall? Could it be detrimental to the transmission loss? Because that solution will spare me buying roughly another 12 packages of Roxul!.. :) Thank you for your time again!

By inverting you are saying "inside out wall" which is John Sayers baby. "...isomax clips on the inner walls (unless I cannot make the wall inverted)" Doesn't matter what the interior wall is it does not need clips. The only reason you would use these is to decouple the framing. Take a look at your ceiling, that is a proper use of these decoupling products. Your room-in-a-room already has decoupled walls, so there is no requirement for these clips any longer. Anything else shows that you need to spend more time getting educated so as to spend less time on speculation. Well, it doesn't rhyme very well, but you get the point :)

That's what I'm here for: education! :wink: Thanks again xSpace! Those clips were recommended to me by Kinetic engineers... and I have a costly tendency to overdo things "just to make sure" :) Do you recommend the usage of Green Glue on any of the surfaces (especially on the floor, to augment the transmission loss of lower frequencies)?

But it is there any problem of inverting the wall? Could it be detrimental to the transmission loss? Because that solution will spare me buying roughly another 12 packages of Roxul!.. :)

There is no problem with "inverting" the wall (I assume that you mean "building it inside-out"). An inside-out build is a good way of saving space, if you don't have much. But I can't see how building inside-out will save you any insulation: you will most likely still need the same total amount of insulation, no matter which way you build.

Do you recommend the usage of Green Glue on any of the surfaces (especially on the floor, to augment the transmission loss of lower frequencies)?

Yup! If you can afford it, then definitely use GG between all your layers of drywall. It will help with low frequency transmission loss. - Stuart -

The idea of the economy of the 12 packs of Roxul is based on fact that I need to render that booth completely dead and that requires a lot of Roxul, but since the "inside-out-wall" has almost 99% of exposed rockwool (that I can cover with fabric) the room is already dead :D Basically the same rockwool serves as insulation and acoustic "killer". As for the Green Glue, I will wait until I can afford some, because if I pay 3000$, I might as well pay 3500$ but get it done right! Thank you for your input! Any more suggestions? :D

The idea of the economy of the 12 packs of Roxul is based on fact that I need to render that booth completely dead and that requires a lot of Roxul, but since the "inside-out-wall" has almost 99% of exposed rockwool (that I can cover with fabric) the room is already dead :D Basically the same rockwool serves as insulation and acoustic "killer".

To me, it sounds like you are planning to NOT put insulation in your air gap (the space between the inner leaf and outer leaf. If you do not put insulation in there, you will lose big time on isolation. Perhaps as much as 10 dB, or even 16 dB, will be sacrificed. Plus, the MSM resonant frequency of the wall will be much higher than it would have been if you used insulation correctly, which will compromise your isolation in the low frequency end of the spectrum. Building a wall inside-out does not mean that you can forget about putting insulation in the air gap. You still need to do that if you want good isolation. The only advantage from building inside out is that you can use the stud space (which is now inside your room) for acoustic treatment. But you still have to construct the MSM system correctly.

I need to render that booth completely dead

Probably not a good idea! completely dead sounds like, .... welll ... ummm... very VERY DEAD! = unpleasant. Even a vocal booth needs a bit of life to it, to sound good.

1) With a STC 71 for the floor structure (with TL of around 32db around 50-60hz) what can I do to improve further the transmission loss of low frequencies?

How did you determine that you have STC-71 for your floor, and that your TL is 32 dB at 50 Hz?

3) May the resilient channel with 5/8'' + 5/8'' drywall on top of it considered as a Third Leaf?

That depends: What else is there behind that? How is the existing wall built?

(interior > 2X4 > isomax clips with resilient channel > 5/8'' + 5/8'' drywall > airspace > next wall)

If you are building a new stud frame that will be decoupled from the existing wall, which is what it sounds like, the forget the isomax clips: You do NOT need them! You will just be wasting your money there. Since your new frame will be decoupled already, it makes no sense at all to decouple it again with clips. Those clips only make sense when you do not have a decoupled frame.

Any more suggestions?

If you want to save a lot of money, then build your own treatment instead of buying commercial treatment. It can be just as effective, acoustically, and is much cheaper. It is hard to see from your simple sketch what your existing structure is, and what your proposed new structure is. Maybe you could highlight the different parts, to make it clear. You really should do your drawings in SketchUp. Much, much better! - Stuart -

Arhythmic wrote:

That's what I'm here for: education! :wink: Thanks again xSpace! Those clips were recommended to me by Kinetic engineers... and I have a costly tendency to overdo things "just to make sure" :) Do you recommend the usage of Green Glue on any of the surfaces (especially on the floor, to augment the transmission loss of lower frequencies)?

The people here that do recommend this product, that have used it (which I have not) it reads like they suggest that if it is going to be used, then do so in the most offending parts of the room. Since you have a booth...all parts of it would be the offending part, so to speak :) So if you use it in one place, like the floor, it does little good to not use it in all other parts of the build/booth. As I understand it,

Thank you for such a detailed reply Stuart! Apparently I had a misconception of inside-out-wall, but after looking carefully at Mr. Sayers' Left Out Studios build, I see how it really should be built! Following your suggestion, I will leave the floor reflective and the rest of the acoustical treatments will be done after the room is built :D Concerning the STC 71 factor, I found all of the information on the Kinetic site (the tests were made by independent organization, National Research Counsil of Canada in this case). The test results can be found here: http://www.kineticsnoise.com/arch/tests/pdf/A15-b.pdf. On pages 6 and 7 you can see that the TL is decreasing as the frequencies gets lower (the test only goes to 80Hz, but following the plot tendencies you can approximate the 50Hz's TL at around 32-34). My rudimental plan only shows the new structure I'm building, the existing structure was left out since my booth will only contact the floor through RIM (or equivalent). The existing structure consists of: 6'' concrete floor, 6'' ceiling (with 1'' of airspace between my booth ceiling and the concrete one), and 3 concrete walls (and the 4th regular sheetrock wall is my other room) with about 4-6'' of airspace between new structure and existent. Since the room in which I'm going to build my booth is a corner unit, with no neighbors on the sides. I will gladly use a non-commercial equivalent of Kinetic products as soon as I find some! :D It is very true that they products are pricey (2'' RIM subfloor, 48'' X 25' is 1000$), but it is also true that the data they provide seem accurate. Don't get me wrong, I'm all about DIY (I did the furniture for my studio, the guitar cabs, a few guitars, etc.) but I just don't want to invest 500$ (instead of 1000$ of commercial products) in DIY products and then starting over if the results are not satisfactory. I will use the Green Glue in between layers of sheetrock, but that stuff is still quite expensive... :D Thank you very much again! :D

I have another little question: after reading Mr. Gervais' excellent book, and especially the chapter on floating floors, I was wondering if a sand filled floor of roughly 2.5" thick would be advisable in my situation? Kinetic tell me that they can adopt their floating floors to that extra weight. As I understand it more weight is better right? :) The weight of the floor is around 1660lbs (sand filled) against 600lbs for my previous floor solution... Will this gain in mass be profitable acoustically? This weight will be included for my structural analysis with an engineer next week :D Thank you again for your comments and suggestions!

I have to let Rod speak about his work in reference to his book, but let me say this. If you have the skills to build a container that will be used as a base/floor and it can completely contain the sand with no leakage, why would you need the kinetics rim floor? Sand is the best natural material in respect to being flexible, damping ability and mass, pretty much nothing else is going to improve on that fact.

Since I would like to achieve maximum attenuation, I was thinking of of sand filled floor as the Mass, of the Kinetic RIM subfloor as the Spring and of the existing concrete floor as the other Mass. Am I wrong again? :(