John Sayers' Recording Studio Design Forum

Hello,

I'm new here:) I won't be original saing, I'm very impressed with this forum. You guys are doing great job!

I'm saing hallo from Poland, where I have my home film sound postproduction studio. I have just finished the acoustic treatment of my control room, which is still not perfect, but I will come back to it later.
Now it is very important for me to design and construct a treatment of my little voice over / adr / foley studio. If you would be so kind to take a look, here it is:





Forgive me my poor drawing skills, I did my best…

As you can see the room is almost rectangular (297 x 154) and almost square (295 x 297) - fortunatelly, one wall (wall C on the second drawing) is higher (331) and in fact it's trapezoid. This is what I have and I can NOT interfere in walls construction. What I can do, is most optimal treatment.
The goal is to make the room well isolated (foley recordings) and evenly sounding in the whole band. At the moment it is pretty noisy - I can clearly hear the street which is just around the corner. But I guess it's the ventilation hole (not treated yet… - see photo - right corner)



The walls are made of bricks and concrete (strange mix, build in early communist era - 1959), but thick (from what I know at least 50 cm).
The room is situated on the second (top) floor of my house. From one side (wall A on second drawing) there are neighbours - very quiet people. The rest walls border with my house (no kids, no dog - also quiet). Under the studio is my bathroom (no sounds from that).
That's it. And now time for questions:)

First, the layers - In general, I'm going to build the framing and fill it with rockwool (I know it should be around 50kg/m3). Than cover it with transparent cloth. As it is adr and voice over studio I suppose I do not cover the rockwool with drywall (??) - it is supposed to be rather dead than live.

On the side walls (A and B) I'm going to put 5 cm of rockwool - too little? (the room is very narrow anyway…)
On the A wall I'm going to put additionally 0,5 cm polyethylen or polyurethane isolationg boards first (than rockwool and others) - just in case my neighbours will change. Does it make any sense? Do these foams really work? Maybe you advise another material?

Wall C, D and the ceiling can be filled with 10 cm of rockwool (or more?). Here I can also use the air gaps - how thick the air gaps and rockwool layers? On D wall - bass traps (super chunk).

Carpet on the floor. Double door.

Last question:
Most of the studios I've seen on the web (and also on John's Sayers page) have irregular shapes. Mine is rectangular. Is it a good idea to build one wall (C) at a slant (proper english word?) - see drawing 2. I would make the framing so that it would be thiner closer to the door and thicker closer to the A wall.

I know I don't give you any specific details on how noisy my room actually is and how much isolation it needs.
I just hope you can share with me some general rules on the treatment of vo and adr spaces. Or maybe redirect me to some places where I can find that information.

I will be very grateful for your opinion!

Best,
Kate

Hi Kate, and welcome!

Foley studios need to be VERY quiet. EXTREMELY quiet. I'm not sure that you have enough space there to be able to build your isolation walls, put the treatment in, and stll have a usable space inside. The room is 154 cm wide. The isolation walls are going to take off at least 15cm each side, leaving the room just 124 wide. Then you'll probably need another 10 to 20 cm on each side for treatment: the final interior space is going to be less than one meter wide. That's very small. Do you have another, larger room that you could use?

Cloth will not help at all to isolate: You will need at least two layers of 16mm drywall on that framing. Then you can add the treatment inside, when those walls are finished.

You do both, actually! First you put up the drywall, to create your isolation system, then you put more rockwool on that drywall, probably in some type of simple frame. The drywall along with your existing walls creates your isolation system, and the rockwool adds the treatment.
I would use thicker: 10cm at least. You might not need to do the entire wall: you could do it in large sections, some with rockwoll, some without.

No, they do not work at all to isolate. The only way to stop sound is with mass: very large, heavy, solid materials, such as drywall, plywood, MDF; OSB, brick, concrete, glass, etc. Those foams are not much use at all in acoustics. They don't have enough mass to be useful for isolation, and most of them are closed cell, not open cell, so they are no use for treatment either!

No. Not a good idea. Especially for a Foley studio, where you will need your pits with sand, gravel, dirt, wood, metal, stone, etc. Much better to just leave your floor as bare concrete, then set up your pits on top of that. Treat the walls and ceiling, but leave the floor hard.

Definitely!

It would be nice to do that, but you don't have enough space to angle your walls: It needs to be at least 6° angle, and that would take up way too much space in your room. Just leave it rectangular, with lots of treatment to keep it fairly dead.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Dear Stuart,

Thank you very, very much for your response!! You made things much clearer to me.


Unfortunatelly, it's all I got at the moment. As you said, the room is too small to make the proper isolation and treatment. So I guess I should begin with isolating the ventilation hole and building solid isolated doors. This will allow me to evaluate the real need of isolation in this room. I hope the noise will significantly decrease (other rooms at the house are pretty quiet) and I will do just the treatment to make the room dead enough to play there voice overs and foleys.


If I decide on making just the treatment and put 10 cm of rock wool on every wall and ceiling, would it make my studio optimally dead? I'm afraid of loosing too much of high frequencies. On the other hand, at the moment (without any treatment) the room sounds awfully (many resonances to my ear, I didn't measure it in any way). What would be the best proportions between treated space and untreated? How to make this room sound even and at the same time get rid of those resonances?
How big the super chunks on D wall?


I wasn't precise in that matter. The main purpose of building this studio is having the possibility to make the voice over recordings. Having this done I will also record there some foleys that I often need in some smaller productions I work on (the one, that con not afford to hire professional foley studio). So clothes, some props, etc. But it's clear for me, that the room is too small to treat it as professional foley studio. I won't keep there any pits for recording footsteps. In that case, the carpet isn't bad idea I guess? It surely makes the room more dead.


For voice over job and little foleys it would be still enough space if I angled the C wall 6°. Even 10 seems fine (if it's better). But, as I understand it, it should be done like this:

It means a real lot of material = big costs. I would decide on this if it would really make my room sound much better. If the room dimensions are not so bad and lots of treatment, as you said, will be enough to make it sound even, I will leave it rectangular. (Still have to buy Neumann and some other gear...)

I also wander if it is possible to record ADR in there. Actually I have never seen such small ADR studio... I'm afraid that acoustic of such small space would be adverse for ADR recordings. Has anyone any experience in using small room or booth for ADR?

Stuart, thanks again, you've already helped a lot!

I wonder if someone could answer just two of my questions

First, I'm really bothered about the amount of treatment needed in voice over studio with my room's dimensions. I have been searching the net and all I see is that… there are many approaches to it. Some leave the naked spaces, some don't, some use acoustic foams, some use rockwool, and other use both. I wander if there is some generall rule on treating voice over studio. How to make it balanced? Even? Is it possible to make it too dead??

The second question is: to angle or not to angle? Taking into account my room dimensions, would it help a lot??
It is difficult for me to imagine the difference in sound. The only visible difference is in costs… But I really want to make it good. So, still wonder.

If anyone could drop a line... would be great!

Personally, I would not angle the wall too much, since you have so little space. I would also do it with slot walls, rather than additional solid walls, as that will accomplish pretty much the same thing for mids and highs. I would angle two adjacent walls, so that nothing is parallel, but since the room is so narrow, I think the best way to angle the long wall would be "out and back". In other words, have one half angling out into the room and the other half angling back again.

Each room is different, so approaches to treatment will be different too. But the general guideline is to put enough absorption in the room to get the RT-60 times under control and in accordance with ITU recommendations, and spread it around suitably. For a room with those dimensions, you need 188 Sabins of absorption, which is roughly 188 square feet of perfect absorber. The total surface area of your room (walls, floor and ceiling) is about 500 square feet, so you need to cover about 35% to 40% of that. You can't cover the floor, obviously, so that leaves the walls and ceiling, totaling 450 square feet. So you need to cover about 45% of that with absorption. The type of absorption isn't that important: mineral wool, fiberglass, and acoustic foam will all work... Provided that it really is acoustic foam! There are a few unscrupulous "foam by mail" companies that offer really cheap stuff that they call "acoustic foam", but that actually is useless, acoustically, so be careful where you buy if you want to use foam. There are many types of foam that look good, but are worthless for acoustics.

Can you make it too dead? Yes you can, but for a small vocal and Foley booth, it will need to be fairly dead. I would start by covering about 40% of the walls with absorption, in the form of large bass traps in some of the corners and thick panels spaced away from the walls, and "checker-boarded", plus something on the ceiling, then measure the room acoustically (with REW) to see how it is behaving, and use that to decide what else needs doing.

For example, you could do one long wall and one short wall as slot walls (angled, possibly), then cover most of the opposite walls with absorption, plus a thick cloud hung down from the ceiling: Measure how that works out with REW, and see where you still have problems, then decide how to deal with those.

That would be my approach.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart,

Thanks again for your time and help!

I had a brainstorm with a friend who is going to help me with the treatment. Standing there I clearly see, that the room is too narrow to put there "large bass traps" and "thick panels spaced away from the walls" as it should be done I guess I'm forced to decide on big compromise between the possibilities and… quality, which I hate and never do!

I will surely remember all your thoughts and advices. I would also like to build a slot walls, as you suggest. And here's my question… I've been searching the net and the forum, but couldn't find any precise instructions on how to build a slot wall.
There is a layer of rockwool under the slots, isn't it???
How to tune the slot wall properly? There surely are some rules. Where could I find them?

That's what I suspected. So just make it as good as you possibly can.

Yes, there is.

Slot walls are just a series of Helmholtz resonators, tuned to different frequencies, or different ranges of frequencies. You tune each slot by varying the dimensions of the gap and also the depth of the air cavity behind it.

You might find this useful:

http://johnlsayers.com/Recmanual/index.htm

You don't really need to worry too much about tuning: If you follow John's design, he already did the math and figured it all out, to make his slot walls broadband. So just follow his dimensions, and it will work fine.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hello, I'm back! But I have nothing to be proud of yet… Actually I didn't even start my job. There's been much to do with other things. But the time has come and I've came back to my little project.

I've spent some time in the room preparing it, planing the studs' placement, etc. and, to my horror, I began to hear my neighbours! The problem, that I underestimated at the beginning, is the main issue I have to overcome now.

So, I need to enlarge the isolation somehow. I know that isolation is mass and mass is space. As I don't have the last one (just to remind you, my room is very! small), making my studio well isolated is probably impossible. And here I need your help. Please, tell me if any of my solutions could work, and which is the best.
Instead of putting 10 cm rockwool on the adjoining neighbours wall I could construct one of the 3 following projects:



The first solution takes 15 cm of space – a lot. But it doesn't matter if it could be efficient. I would still have enough space for VO recordings.

If you could comment on these solutions, the thickness of each layer, I would be very grateful.

I read about 3 layers' dangers. All of these are 3 layers projects... How about that?

I could also put 2 cm of OSB on the floor and wall D (see the picture in my first post).
On the adjoining neighbours wall I could put 2 layers of 2,2 cm OSB, which would give me 4,4 cm thick layer. Would it make a big difference?

Christmas is coming but if you find some time to drop a line, would be awsome.

All the best,
Kate

How about a floating floor?? Under the room there is my bathroom - no noise from that. But the noises from my neighbours could "transfer" also through the floor not just the adjoining wall, am I right?

I could build something similar to the drawing on this site:
http://www.euroform.co.uk/versalayer_ap ... er_1.shtml

OSB instead of timber and some carpet on top. Makes sense or is it waste of money, time and sweat?

Hi Kate! My first question will be exactly from what part of Poland are you? (asking because I'm form PL too):):P

It would be helpful if you could measure the level and spectrum of existing noise, so that we knew with what we are dealing.



Floating floor would be a good idea if you want to build whole internal isolation shell. As you said it has to be somewhat of lightweight floating floor in order not to overload the building structure with great mass of additional floor and walls. Details to be discussed.


About the walls:

You could try to use a plasterboard-deadsheet-plasterboard sandwich, with 50mm high density mineral wool. Deadsheet could be 5kg/m2 rubber glued to the boards. It would be quite expensive solution (1m2 of 4mm thick rubber cost around 60PLN/m2 (15E))

It is only one thing to be remembered: The more isolation you get, the less sound escapes the room, the more stays inside and the more internal treatment will you need..

Merry Christmas Everyone!

Actually, floating floor would be a bad idea, and ESPECIALLY a "lightweight floating floor"! There is no such thing. Correctly floating a floor requires a large amount of mass. You might want to read this:
viewtopic.php?f=2&t=8173

Once again, that would be a bad idea, for many reasons. There is no point in using such high density rubber, since it will not decouple the layers of drywall effectively, and gluing it to the drywall would increase transmission, not reduce it. It would also prevent the rubber from doing what it does best: flexing in sheer. Gluing it would greatly harm the isolation around coincidence.

If you truly want to maximize isolation of low frequencies with proper constrained layer damping, then Green Glue is your best bet.

High density mineral wool is also a bad idea. Optimum density for mineral wool in an MSM system is 48 kg/m3. Any higher than that and you start to lose effectiveness for low frequencies, which is precisely what you need to deal with most. Any lower than that and you start to lose effectiveness due to the reduced mass, reduced average path length, reduced damping, and reduced absorption at the coincidence dip. MSM resonance rises, and transmission loss falls.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Hi Stuart, hi Cracow! I'm from Warsaw:) Thanks for your reply! I'm very glad you droped in, because my time gets short. On Thursday someone is coming to help me with construction. As I am weak woman and know nothing about nails and hammer I must depand on somebody's help.

As to floating floor:
I know that the drawing I pasted in my previous post doesn't show the real "floating floor". It is just construction that would probably give me better isolation.
At the moment there are just some wooden boards ("klepki" in polish;) put on a bare concrete. I thing about putting 10 cm of rockwool on that, than 22 mm OSB and a carpet (just to cover the OSB). What do you think?

Now walls...
To be honest I'm really upset with the noise floor in the room. I have no possibility to measure it in any way.
I can't hear clearly what my neighbours are saying (especially they speak vietnamese) but I can hear them walking up and down the interior wooden stairs, taking bath, laughing... Disaster!

I made 3 projects of wall isolation in my previous post (please see the drawing). On a bare wall I would put some rockwool (5? 10? cm) than 1 or 2 OSB (22 mm thick, 2 layers of OSB is better, isn't it?) and rockwool again (10 cm). I thought that thick OSB could stop the sound enough. Could you check if I don't make any mistakes in that and which of the 3 projects makes bigger sense? How about the 2 vs. 3 layers concept?

Of course you are right if we do need a high degree of isolation from high to low freqency range floating a floor correctly require use of a concrete slab.

But if the noise source is below the noise protected room and there is no possibility to build a heavy floor structure, then the only possibility is to build a floor which is lighter and uses a sandwich of materials like plasterboard, chipboard, plywood, deadsheet etc with thin (3-4 cm) high density foam (130-160kg/m3) as a base. And of course it would give you almost no isolation improvement in the lower frequency band but in the mid and high range it would increase the isolation.



You are absolutely right but in this solution rubber is used to add mass to the whole wall system, damp the resonances of plasterboard, not to decouple layers of plasterboard. If we decouple two layers of plasterboard it will give us a 3 leaf system. Green glue is not avaiable in Poland.

There are two more solutions:
1. Reconstituted polyurethane foam around 80kg/m3 glued to the structural wall and 2 layers of plasterboard glued to it.
2. Floated wall made of hollow concrete blocks filled with sand. It would have a low resonant frequency and provide a good absorption in a wide range of frequencies.


My bad, around 50kg/m3 as you said will be better.

No it is not a good idea. First od all 10cm of mineral wool (I assume that you mean Rockwool Rockton probably) has too low density and is too thick to create a floor not using a concrete slab. Secondly one layer of 22mm OSB is definitely too light for it.

If you really want to 'float' a floor you definitely need to calculate total mass of the floor itselt+equipment in the room, then you choose the lowest base 'spring' layer with proper characteristics. And of course the more mass=the better isolation.

But as it was said floating a floor needs a lot of mass, knowledge and structural engineer. Summing up it could be very problematical, expensive and useless if made improperly.

So my suggestion is that first take care about the walls and then decide if there is necessity to build 'floating' floor. Hope there's not. I wrote some solutions of wall treatment before and maybe someone with bigger experience will suggest which would be suitable for you:)

There are no magical combinations of materials that somehow increase isolation. All materials are subject to the laws of physics, which are rather well understood. For a structure such as you suggest, the governing principle would be mass law. That sandwich of "plasterboard, chipboard, plywood, deadsheet" will behave no differently than any other sandwich having the same total mass. For example, 3 layers of plywood, or three layers of chipboard, or three layers of plasterboard that had the same total mass as your "sandwich" would all provide the same level of isolation, which would be pretty low, actually. The slight benefit in the area of the coincidence dip from having dissimilar materials would not be worth the trouble.

Sorry, but that is way too dense. With such high density, it would provide very little isolation at all for low frequencies, and in fact would tend to create a flanking path. Low density is what you need for low frequency isolation, not high density.

Also, unless it were open-cell foam, it would be useless, acoustically, and open cell foam that dense is rather expensive...

Exactly. And since this is supposed to be a Foley room, low frequency isolation is what you need most!

Then it would be a waste of money, as I said before, since it would do neither. Using rubber to add mass is a very expensive way of adding mass! Sound waves do not care how much you pay for your mass: All they see is the total mass. They can't read price tags, so they won't be impressed by the very high cost of the rubber. And no, it won't damp resonance unless it is specifically designed for that purpose, and has the correct characteristics. Constrained layer damping has rather specific needs, and "5kg/m2 rubber" would not work. Besides, even if it DID work, gluing the rubber to the board would defeat the entire purpose, since it would prevent the two from working independently, sliding past each other in sheer.

If you disagree, then please post a link to some recognized research done in independent acoustic laboratories, showing that a sandwich of such as you propose, of "plasterboard, chipboard, plywood, 5kg/m2 rubber, and high density foam 130-160kg/m3", would be effective for isolating the floor of a Foley studio.

No it will not, when done with something like Green Glue, which acts as constrained layer damping, not decoupling.

Once again, a bad idea. Polyurethane foam is usually closed-cell, and therefore useless acoustically. Open cell polyurethane foam is expensive, to say the least, and unless it is applied carefully, can create flanking paths.

The coefficient of absorption for concrete is practically zero, across the entire spectrum.

http://www.sae.edu/reference_material/p ... 0Chart.htm

And floating such a wall would require heavy duty springs and careful calculation of the weight, deflection and loading. What springs would you suggest, what loading factor, and how much deflection?

The brand of mineral wool is irrelevant. There is not much difference in gas flow resistivity between the various brands, at the same density. So all brands would work roughly the same.

That's rather confusing! Conventional wisdom in acoustics says that using THICKER layers of isolation material DECREASES the MSM resonant frequency and thus IMPROVES isolation!

----


You could probably do something like Glenn's Drum Riser across the entire floor, as that really does work for isolating impact noise and low frequency sounds. It still will not get you the level you need for a seriously Foley room, and will not be the ideal surface for that, but it would help. So the basic idea would be a 10cm layer of OC-703, with two or even three layers of 22mm OSB or plywood. Cut the plywood just a bit smaller than the inner-leaf walls, just 2 or 3 mm, and fill the gap with backer rod, then high quality flexible acoustic caulk.

So you have to build the walls first, then do the floor at the end.

Forget carpet. Do not use carpet on the floor. Carpet has poor acoustic qualities.

The basic idea is correct, except that you have to build a frame to attach the OSB, and that frame cannot touch the existing walls or ceiling: it is a separate frame, that stands on the concrete floor only, and must have a ceiling built the same way.

Yes, two layers of OSB would be better than one layer, provided that they two layers are on top of each other, with no air gap between them. So you would put up your frame about 2cm away from the wall, fill the frame with mineral wool, nail or screw the first layer of OSB to the frame, then nail or screw the second layer of OSB directly over the first layer. Take care to seal all joints with acoustic caulk.

So the first option on your drawing is the best: you do need a large air gap between the concrete wall and the OSB, and the frame will provide that.

The final layer of mineral wool is part of your treatment, not part of your isolation. So you would not need to put that in until after the room is finished an tested. In other words, the finished surface of your room would be the second layer of OSB. After you test that, then you can see what type of acoustic treatment is needed.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.