Hi "Darth Edgelord", and Welcome!
(Glad to see that you corrected the issues with your previous post...
)
For the last couple of weeks I've been planning on building a rehearsal room for my band (rock band, Drums, bass, guitar, piano). After reading dozens of threads on soundproofing, I came up with a design.
So this is still in the design stage, correct? Nothing has been built yet? From some of the things you say, that isn't clear.
I need to insulate it at least as much that my neighbours won't hear any sound inside their houses, and if possible a minimum of sound inside my own house.
You'll need to put a number to that, in terms of decibels: How many decibels of isolation do you need? It isn't possible to design isolation based on a subjective feeling: An elderly neighbor who can't hear very well might tell you one thing about what is "acceptable", while a young person with very sensitive hearing might tell the exact opposite. The only way to be sure, is by defining how much isolation you need in terms of decibels: How loud will you be inside? How quiet does that have to be outside, according to the legal regulations of your area, all measured in decibels?
It's build on a rubber mat topped with a wooden construction filled with rockwool.
So you are trying to float your floor and walls? Here's why that is a bad idea.... :
http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173
In other words: don't even try. You don't need it, and would probably make it worse, not better.
Gypsum board | 2.75" Rockwool | 1.33" empty space | 2.75" Rockwool | Gypsum board.
That's the wall you plan to build? Inside the existing garage, which already has a wall? If that's the plan, then you have a big problem: That would create a three-leaf system, which will potentially give you WORSE isolation for low frequencies, then if you just built a standard 2-leaf system.
Also, why those dimensions? That makes your wall 6.83" thick, which is 17.35 cm.... I'm not aware of any lumber that would give you that thickness. Why do you want the "1.33 inch" gap, which is 33.78mm? Why such a precise and unusual dimension?
1: I have about 0.2" to spare, would it be better for me to put that space in the wall described above, or between the outer wall and the box-in-a-box?
OK; we have a problem. You are misunderstanding the "box in a box" principle. Yes, you do need to build like that: You do need to build a new "box" or "room" inside another "box" or "room", but you are missing the point: You
already have the outer box! It is your garage. That's the first "box". So you only need to build one more "box", and that is the single-leaf structure that is your final, inner-room. You only need to make one single stud frame, and then put drywall (gypsum board) on just ONE side of that frame. That's all you need.
2: Would it be better against resonances to keep the empty space between the walls consistent throughout the construction?
It's not necessary to do that. As long as the resonant frequency at the narrowest point (highest frequency) is still at least one octave below the lowest frequency that you need to isolate, that's fine. And you can always add extra mass if you need to get the frequency down at one point, due to a smaller gap.
3: Is it in my case necessary or wise to use a double door as shown in the 1st attachment?
Always, yes. But you cannot join the two frames, as you seem to show in that diagram. The inner-leaf frame is entirely separate and self-supporting, with no mechanical connection at all to the rest of the building.
4: Outside of the garage, I've measured about 65dB's of low frequencies while playing bass (I turned up the volume above my rehearsal volume to compensate for the absent drummer) If I build this room flawless and according to my current plans, how much of the sound will I be able to terminate?
You are going about this backwards! You are starting with a design, and then asking if it will fit your isolation needs, but in reality you should start out by defining your isolation needs, then designing the studio such that it meets those needs.
You need to first start out by measuring how loud you are in a typical session, but for the entire band: it's no good at all if the drummer is not there! The drum kit is, by far, the loudest of all, and it is percussive. It is much louder than the bass, and consists of a series of impact sounds at extremely high levels, that then decay at various different rates and frequencies. The bass, on the other hand, produces a series of fairly constant sound, smooth, sine-wave based tones with very little in the way of transients or high attack levels. You cannot compensate for the lack of one instrument by substituting another instrument that is entirely different, and produces sounds that are nowhere near the same.
So you need get the entire band together, and measure how loud they are inside the garage, using a good quality hand-held sound level meter (not an app on your iPhone!). Then you need to measure the level outside the garage (while they play the same song over and over), in many places around your property, including at the points that are closest to your neighbor's houses, and to your own house. Then you need to tell the band to stop playing, pack up, and go home. Then you make more measurements in the exact same locations, and measure how quite it is, with just the normal ambient sound of your neighborhood. You can use that information to determine how much isolation you have already, and how much isolation you need in total.
Thank you for your time! The folks at Gearslutz told me you guys would know more
Please tell them "Thank you very much for the vote of confidence!"
I'm also looking at your diagrams on paper, and thinking how much easier and better it would be if you did that in SketchUp. If you need to modify something on paper, you have to start on a blank sheet and draw it all over again, completely..... And if you need to do that several hundred times (as you typically do, when designing a studio), that's going to use up a lot of paper, a lot of pencils, and a lot of time!
There's a problem with the way you are doing your framing, for example, that can be fixed easily.
You also seem to be using 70mm studs, which is probably not enough for handling the weight of the ceiling. I would go with standard 90mm studs. 70mm is for light framing.
In addition, you show 13mm drywall (gypsum-board), but you'd be much better off with 16mm drywall. The extra mass gives you better isolation.
One other: you mentioned "Rockwool" insulation, but did not say which one. Rockwool is a brand name, and they make many different types of insulation. You need to choose one that has suitable acoustical characteristics for this specific application (damping in 2-leaf MSM isolation wall).
- Stuart -
PS: Edited to add: It is OK to give all your dimensions in Metric measurements! We are bilingual here!
