VO booth design

Hi y'all, I've spent a while foraging and scrounging for some ideas and methods on building a VO isolation booth and I've come up with a basic design. Considering the investment it would take I wanted to post it here so hopefully you good folks could help me catch any major design flaws. In this post I'm just focusing on the main structure and walls, there are of course many additional elements such as ventilation, lighting, equipment connections etc or any internal absorbtion materials that aren't in the diagrams. The materials I plan to use: 15mm Gyproc Soundbloc - 2 layers on the outer surface of both stud walls and 1 on the inner surface of both. 100mm thick Rockwool RW5 100 x 50mm stud timbers 19mm OSB on floor with a layer of 19mm quiet board Auralex SheetBlok Sound Isolation Barrier )or similar - between floor boards and between outer plaster board. U-boats on the booth floor joists. Green glue or similar and/or joist tape for around the studs and where they butt together. 2 x 45mm thick standard firedoors Total upper budget: £5k About the location: Unfortunately in my home I'm plagued with flybys from a near by airbase and large trucks so I feel a lot of isolation is required. The booth would be located in my house which has a concrete floor, I believe it's a thick pad but don't know for sure. The room height is 2.38m. The overall structure is basically a booth within a booth using two stud walls separated with a 50mm airgap. Two outer layers of plasterboard, 1 inner and a rubber mat isolation barrier per stud wall and the ceilings. Rockwool to fill the walls. The floor has 100mm joists using the U-boats and rockwool between the joists and capped with plasterboard also between the joists. On top of that two 19mm OSBs sandwiches a Quietboard and 1 or more layers of the rubber mat isolation barrier. There would also be something used on top of that internal to the booth but I'm not sure which of the many options to choose at the moment. I hope I've sufficiently shown the intention and I hope there are no major issues, please do let me know if you believe this would achieve the goal and any improvements or corrections that would help. Thanks for your time and consideration. Regards.

Hi "Hydra". Please read the forum rules for posting (click here). You seem to be missing a couple of things! :)

15mm Gyproc Soundbloc - 2 layers on the outer surface of both stud walls and 1 on the inner surface of both...

That would be a four leaf wall, which is even worse than a three-leaf wall in low frequencies, and the three-leaf is already worse than the two leaf, all other things being equal. This is not intuitive, because it involves the principle of resonance, which most people don't think about very much in their daily lives! People think that if one leaf is bad, and two leaves is good, then three must be even better and four must be fantastic! But that is not the case. Here's an image that illustrates what really happens: The one on the left is a typical house wall with no insulation, and the one just next to that is the same thing but WITH insulation. The very next one shows what you propose: a pair of walls with a total of four leaves. As you can see by the STC rating, even though the wall is now more than twice as thick, and has double the mass, the isolation only increase by 4 points! Not expected at all. The next image shows what happens if you have the exact same situation, but leave out one of the leaves: so it is a 3-leaf system. Surprisingly, the isolation jumps by a whopping ten points! That wall actually has 25% LESS mass than the one to its left, but it is twice as good (subjectively) at isolating sound. The second last image shows what happens if you take out ANOTHER one of those leaves inside the wall: Once again, you get a whopping jump in isolation. This is nowa simple two-leaf wall, and even though it has 50% less mass than that four-leaf wall, it is 17 points more effective at isolating sound! Very much unexpected. The last image on the right shows what would happen if you took those to sheets of drywall (or MDF) that you pulled out the middle, and instead just nailed it as a second layer on each of the leaves: Yet another very useful six-point jump. So, a properly built 2-leaf wall is a ginormous 23 points better at isolating than the wall you propose, using the exact same mass and total thickness of the wall. That's the power of resonance in action. Not intuitive at all, but very true, and very useful. Many aspects of acoustics are not intuitive. Sound does not actually behave the way people think it should behave!

19mm OSB on floor with a layer of 19mm quiet board

What is the existing floor made of?

SheetBlok Sound Isolation Barrier )or similar - between floor boards and between outer plaster board.

MLV is very, very expensive mass. That's not a good choice for isolation in your walls. Mass is mass, and sound waves don't carey how much you paid for it...

U-boats on the booth floor joists.

Bad idea. That's a cheap and ill-advised attempt to float your floor. Here's why it is a bad idea: viewtopic.php?f=2&t=8173

Green glue or similar and/or joist tape for around the studs and where they butt together.

That's not what Green Glue is for! Green Glue is a constrained layer damping compound, that you apply in between layers of mass in your isolation leaf. It is not an adhesive (despite the name).

l a lot of isolation is required.

How much is "a lot"? How many decibels of isolation do you need?

and a rubber mat isolation barrier per stud wall and the ceilings

You did not mention that rubber mat in the sequence of materials. What type of rubber, and where in the sequence did you plan to install that?

please do let me know if you believe this would achieve the goal and any improvements or corrections that would help.

Take a look at the image and explanation I posted at above, to see why you should NOT be building a 4-leaf system, and instead SHOULD be building only a 2-leaf system. Also take a close look at that thread on floating floors, to understand why you should NOT attempt to do that. - Stuart -

Hi Stuart, Thanks so much for your reply it is deeply appreciated. I will absolutely employ a two leaf system as indicated, at first it seems totally counter-intuitive but considering resonance and transmission it's slowly making more sense. Also after reading the linked article about floating floors and the U-boats I will abandon that idea. I'd like to answer you questions here:

19mm OSB on floor with a layer of 19mm quiet board What is the existing floor made of?

It's a concrete floor

SheetBlok Sound Isolation Barrier )or similar - between floor boards and between outer plaster board. MLV is very, very expensive mass. That's not a good choice for isolation in your walls. Mass is mass, and sound waves don't carey how much you paid for it...

I've just seen this in several diagrams, do you reckons it's redundant or would you recommend a substitution?

U-boats on the booth floor joists. Bad idea. That's a cheap and ill-advised attempt to float your floor. Here's why it is a bad idea: viewtopic.php?f=2&t=8173

Considering this it's been abandoned.

Green glue or similar and/or joist tape for around the studs and where they butt together. That's not what Green Glue is for! Green Glue is a constrained layer damping compound, that you apply in between layers of mass in your isolation leaf. It is not an adhesive (despite the name).

I was planning on using Green Glue or Quiet Glue where the studs meet the floor, where any frame work butts together, where the plasterboard is attached to the studwork and inbetween the plasterboard. I would be grateful for a recommendation how to fix the plasterboard together and to the stud work. Also any advice on adhesives to affix the insulation would be great.

l a lot of isolation is required. How much is "a lot"? How many decibels of isolation do you need?

Looking at info in gathered from a smartphone app dB meter the jets where registering between High 50s to high 60s.

and a rubber mat isolation barrier per stud wall and the ceilings You did not mention that rubber mat in the sequence of materials. What type of rubber, and where in the sequence did you plan to install that?

Sorry for the lack of clarity here I was referring to the Auralex SheetBlok Sound Isolation Barrier, but like that is there a better option, losing the U-Boats gives me back about 20mm so another layer on the floor?

please do let me know if you believe this would achieve the goal and any improvements or corrections that would help. Take a look at the image and explanation I posted at above, to see why you should NOT be building a 4-leaf system, and instead SHOULD be building only a 2-leaf system. Also take a close look at that thread on floating floors, to understand why you should NOT attempt to do that.

Yeah absolutely, I cannot thank you enough for your input. Regards Will

It's a concrete floor

Perfect! Then you have the best possible floor for your studio already. If it is in good condition, you could just polish it, or stain it, for a very nice effect. If it's not in good condition (cracked, flaky, unsightly, etc.) or if you just don't like the idea of bare concrete under your feet, then you could lay something like laminate flooring (on a suitable underlay, of course), or maybe ceramic. Great looks, still a good floor, acoustically.

I've just seen this in several diagrams, do you reckons it's redundant or would you recommend a substitution?

MLV works, no doubt about it. But when sandwiched between layers of drywall, it works just like any other mass. And since it costs about fifteen times as much per unit area as compared to drywall or MDF, there's no justification for it. The equations for calculating the isolation provided by a wall, floor or ceiling take into account mostly mass. There's no variable where you can plug in "this is MLV mass, not drywall mass", because mass is mass. 10 kg is 10 kg, regardless of how much you paid for it. Sound waves cannot read price tags, and won't be more impressed if you paid a very high price for your mass. They just don't care: they merely react to the mass in the wall. So it makes sense to get the lowest cost high density material you can find in your area. In most places around the world, that is usually plain old drywall (plasterboard, gypsum board, sheetrock, ...). Yes, MLV does have it's uses: it is great when you have to isolate a highly curved surface, such as a pipe or duct, and need flexible mass to form into the right shape. It is great for membrane traps, that are tuned to a certain range of frequencies. I often use it in speaker soffits, because it is higher density than wood, so I an make the baffle thinner and still keep plenty of mass in it. Etc. But when you stick large flat sheets of it inside your walls, all that you accomplish is to spend a lot more money than you needed to! Do the math: How much does a square meter of MLV cost that weighs 11 kg? ANd how much does a square meter of drywall cost, that weighs 11 kg? Compare... (I use 11kg to make it simple, because that's roughly the weight per square meter of 16mm drywall....)

I was planning on using Green Glue or Quiet Glue where the studs meet the floor, where any frame work butts together, where the plasterboard is attached to the studwork and inbetween the plasterboard. I would be grateful for a recommendation how to fix the plasterboard together and to the stud work. Also any advice on adhesives to affix the insulation would be great.

Despite the name, Green Glue is not actually glue. Confusing! They just call it that for a catchy, marketable name, but it is not an adhesive at all. What it is, is a visco-elastic polymer that never hardens. It acts as something called "constrained layer damping" when it is used correctly between two layers or a wall, floor or ceiling. It provides a resilient layer that damps certain types of resonance in the wall, this improving isolation, especially in low frequencies. It is great stuff when used correctly, but it is not glue, and cannot be used to stick things together. You use it by squirting three entire tubes of it onto the back face of the SECOND layer of drywall, just before you put it up and nail it in place on top of the first layer. It never hardens, and stays viscous, even after it is fully cured. But it is not glue. Regarding your actual question, the stud framing for your new inner-leaf walls is attached to the floor in the normal way: bolted through. You should lay a couple of beads of caulk under the sole plate, to ensure that you get an air-tight seal there, but apart from that, there's nothing special. Just build the frame and bolt it to the floor in the correct location. The inner-leaf walls are attached to each other in the normal way: nailed. Once again, you might want to put some caulk in between the faces that but up against each other, but that's it. And the new inner-leaf ceiling framing sits in top of the new inner-leaf wall framing in the same manner: nailed in place, with caulk for sealing.

Looking at info in gathered from a smartphone app dB meter the jets where registering between High 50s to high 60s.

How did you measure that? "A" weighting or "C" weighting? Slow or fast response? Smartphone apps are not very accurate, for many reasons, but assuming it really is roughly 60 dB, it should be possible to deal with that just fine with normal two-leaf construction.

Sorry for the lack of clarity here I was referring to the Auralex SheetBlok Sound Isolation Barrier,

OK, that's MLV, not rubber. It looks like rubber, but it isn't. It is vinyl, basically.

losing the U-Boats gives me back about 20mm so another layer on the floor?

Nope! No floor at all! You do not need any additional floor. The concrete is the best you can get. Anything you do to that will make it worse, and also rob you of room height. You want that hard, solid, rigid, massive, reflective surface down there. It's your best option. Don't waste it! Worst case, lay laminate flooring (which is thin: maybe 15mm total, including the underlay) or ceramic tiles, or something similar. But nothing that has air cavities in it. - Stuart -