design for iso booth/part-time control room

[mwhetzel]

Hello all! I would like to build an iso booth from the ground up (I have been thinking about things like double framed walls with offset studs and a floating floor) and I also would like to stick with the sepmeyer/louden recommended ratios if possible. However, with the sepmeyer ratio of 1.00:1.28:1.54, my numbers work out to very uneven values.

I cannot go any higher than 8ft in interior height due to my existing structure with a 10ft ceiling, but the numbers work out to 10.24ft in width, and 12.32ft in length. I am worried about the logistics of building a space with such careful tolerances. I have considered simply rounding the numbers to 8ft x 10ft x 12ft, but I'm worried about modal resonances that this may cause.

Also, I would ideally design the space to be modular and able to be taken down, transported, and put back up with no hugely significant effort. This seems like a large aspiration, especially with my desire for true isolated double walls and a floating floor (floated wood floor filled with sand or other heavy medium, not a floating concrete slab). This raises issues when it comes to building the booth in modular sections that can be taken apart, due to the uneven length and width. I suppose I could build a series of identically sized panels, then a few odd sized end panels to finish out the sepmeyer ratio length.

My other issue is determining the room shape itself. I know the sepmeyer and louden ratios are supposed to ideally space out the modal resonances of rooms, but I'm not sure how to address non-rectangular room shapes. I'm sure there are some great acoustical room shapes that are not rectangular, but I don't know where to start when it comes to calculating the size ratios.

Sorry if this came across as rambling, as I'm trying to lay this all out for my own benefit as much as anyone else's. I would very much appreciate any sort of constructive feedback on my first design project though! I would like this to become a regular thing for me, and thanks to John Sayers for maintaining this community for us!

[mwhetzel]

I just had another thought...I will calculate out some other room ratio sizes based on other ratios provided by louden and sepmeyer. I'm sure some of them will work out neater than the 8ft ceiling does with the 1.00:1.28:1.54 ratio. Since I am limited to basically an 8ft ceiling, that is the dimension I will use to calculate my length and width according to published ratios.

My question still stands about non rectangular spaces, as I know I will end up having to treat parallel walls for flutter echo and standing waves to some degree, even if the shape works out very nicely in terms of modes. Please let me know if anyone has information regarding non-rectangular room design that is acoustically viable!

[mwhetzel]

Also, I thought it worth mentioning after double checking the "BEFORE YOU POST" sticky, that I am looking to build a space capable of isolating sounds of 70-80db relatively well. Ideally the goal is well-isolated recordings INSIDE the space, so this means keeping external noise OUT of the structure, but I also have neighbors to worry about, so I would like to minimize leakage out of the space. I have read the books by Gervais and Everest and I have been researching as many resources as I can find on the subject (so I'm decently well-versed on at least the basics of acoustical construction), but I'm always open to suggestions!

[Soundman2020]

Hi there "mwhetzel", and Welcome!

would like to stick with the sepmeyer/louden recommended ratios if possible.

For an iso booth, that isn't really necessary. As long as your dimensions are not direct multiples of each other (or within about 5% of that), that's all you really need to worry about. Good ratios are only really important for control rooms, or other critical listening rooms. For an iso booth, just try to make it as big as you can while staying away from the "multiple" issue I mentioned above.

I cannot go any higher than 8ft in interior height due to my existing structure with a 10ft ceiling,

Why not? Surely, if you have an existing ten foot ceiling then you should be able to get about 9' 8" or so inside the booth, if you design and build it correctly.... What is preventing you from going higher than 8'?

I am worried about the logistics of building a space with such careful tolerances.

You don't need to be too worried about such high precision. The wavelengths of the problematic frequencies are measured in tens of feet, so there's no need to be accurate down to fractions of an inch for an iso booth.

Also, I would ideally design the space to be modular

It can be done, as long as you don't need huge amounts of isolation. You could design it as sections that bolt together, and come up with a way of sealing the joints air-tight while still being possible to disassemble.

with my desire for true isolated double walls and a floating floor (floated wood floor filled with sand or other heavy medium, not a floating concrete slab).

Why do you need a floated floor? Have you read this thread: ? http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

My other issue is determining the room shape itself. I know the sepmeyer and louden ratios are supposed to ideally space out the modal resonances of rooms, but I'm not sure how to address non-rectangular room shapes.

If the room is non-rectangular, or has more than six sides, then all simple calculations are out the window, and the only way to predict the modal response is with a rather complex (and expensive) FEM/FEA process. Probably not what you had in mind! And not necessary at all, in any case. This is just an iso booth, not a control room or critical listening room, so there's no need to go to exotic lengths to predict behavior. Ratios only apply to rectangular or nearly-rectangular rooms. As soon as you angle one or more of the sides significantly, then ratios stop being applicable, since there is no longer a simple relationship between the room dimensions and sound wave-lengths.

That said, why do you want it to be non-rectangular?

I am looking to build a space capable of isolating sounds of 70-80db relatively well.

That's a nit ambiguous. Do you mean that there are sound levels of 80 dB either inside or outside the room, and you want that to be inaudible on the other side of the wall? Or do you mean that you want 80 dB of isolation? Those are very, very different things. If you just want to isolate 80 dB sounds, then that's not too much of a problem. But if you want 80 dB of isolation, then you are pretty much out of luck. Unless you have a LOT of money to spend....

- Stuart -