Studio layout, design and construction

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 1:01 am

Why is a 3 leave system not good (in a few words plaese)

It REDUCES the isolation at lower frequencies. So all your bass frequencies will pass through your wall BETTER than if you only have two leaves. And roughly the same as if you only had ONE leaf.

See the graph below.

Three leaf is better for high frequencies, but high frequencies are not a problem anyway: LOW frequencies are where the problems are for us, and blocking low frequencies is ALREADY hard enough due to the laws of physics, without making it even harder by adding a third leaf.

So, if you only ever plan to play / record / mix piccolos in your room, then you'll be fine with a three lead. But if you might ever need to play / record / mix music that has things like drums, bass guitar and keyboards in it, then you have a problem. Three-leaf increases the transmission through the walls, as compared with two-leaf.

I'd suggest that you really need to figure out a way to get the inner gypsum board off that existing wall before you put up the inner wall. You might also need to beef up the outer layer of gypsum board on that outer wall, but you actually can do that from inside the wall, by adding extra gypsum board between the studs. The good news is that you can do it without ever touching the outside of that wall at all (the far left side on your drawing.)

The only other possibility is to make your inner wall extremely massive, such as several inches of reinforced concrete, or many multiple layers of gypsum board. That's the only other way to increase transmission loss: increase mass. However, you need LOTS of mass there to make up for the reduction that you are getting due to the third leaf. Don't forget that mass law says that, theoretically, you get an extra 6 dB of isolation each time you DOUBLE the mass. So going from 2 layers of gypsum board to eight layers of gypsum board will buy you an extra 12 dB of isolation. And going to sixteen layers will get you another 6 dB. And if you need yet another 6 dB of isolation, then you need thirty-two layers of gypsum board.... etc.

With a two-leaf wall, mass law does not kick in until you get down to very low frequencies, but with a three-leaf wall, it kicks in at much higher frequencies.

And that's without even considering the resonance and coincidence dip frequencies for your wall, which may or may not be big additional problems, depending on the stiffness, thickness and density of your wall.

mika · Post by **mika** » Wed Nov 12, 2008 1:22 am

thakns for this great explanation.

Do you think i will cancel the 3leaf effect when i drill a big hole, 50mm for example (or a few) in every gypsumboeard of the inner leaf of the outer wall?
Or is my consideration of the reason for the 3 leaf phenomenon completely wrong?

cheers
mika

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 2:01 am

The airlock room i planed, has 2 reasons. The first is to reach ech room sepreately without corossing the other, and the second reason is, that i will use the celling area in the airlock for the silence boxes of the ventilation system.

If you want to do that properly, then you'd need to do something like below.

But in that case, the room itself is a third leaf, so you could leave off the door out to the rest of the house entirely, or not seal it at all, put air vents in it, etc., so that it no longer is a leaf.

You can download the model for that here:

http://www.digistar.cl/images/mikasmiet ... me-S01.skp

(I also fixed your door in that model, so that it no longer clashes with the other door, but there are now so many doors in there ... )

mika · Post by **mika** » Wed Nov 12, 2008 2:29 am

I don't want to aggravate you, but i'm talking about a different problem.
in the 2 attached pics you can see my idea of fixing the 3 leaf problem and which walls are the centre of the conversation.

I will/can only have 2 doors to reach each room of the studio. One door from the foyer into the airlock, and another to one of the studiorooms (it's mostly a budget thing).

are we talking about the same?

sorry i have big problems with languages, so i try to understand your adwise as good, as i can

but anyway, i love this forum for live.
best help you can ever have !!!!
cheers
Mika

AVare · Post by **AVare** » Wed Nov 12, 2008 3:02 am

mika wrote:Why is a 3 leaf system not good (in a few words plaese)

I have a sketch of the wallstructure attached, so you can understand my plans.

A three leaf system will give worse isolation at low frequencies than a 2 leaf wall with the same mass. Depending on the wall, it may actually be worse than the original wall with 2 leafs. That is the case with your proposed design.

Andre

mika · Post by **mika** » Wed Nov 12, 2008 3:16 am

A three leaf system will give worse isolation at low frequencies than a 2 leaf wall with the same mass. Depending on the wall, it may actually be worse than the original wall with 2 leafs. That is the case with your proposed design.

Have you see my idea to drill big holes in the middle leaf to counter this effekt?
is it acoustical still a leaf when air can pass?

My problem is, that the room is just rented, and a hole is the only thing i can rebuild easyly when i go out the room one day.
cheers
mika

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 3:17 am

mika wrote: Do you think i will cancel the 3leaf effect when i drill a big hole, 50mm for example (or a few) in every gypsumboeard of the inner leaf of the outer wall?
Or is my consideration of the reason for the 3 leaf phenomenon completely wrong?

cheers
mika

Hey Mika.

If you are allowed to drill big holes all over that wall, then why not just take off the gypsum board completely? Drilling holes might help, but I suspect that the panels would still resonate at some frequency or other, and probably several frequencies all at once due to the drilled holes. That would probably not be good, but I'd leave that up to the acoustic experts to tell you.

But anyway, my point here is: If you can drill big holes, then surely you can also just remove all of the gypsum board? Take off the entire layer from that side, instead of drilling holes in it.

That would be much better. It would also give you access to the inside the wall, where you could use the pieces of gypsum board that you removed to "beef up" the side of that wall, which would help even more. take out the insulation, cut the old gypsum board to the right size to fit between the studs, up tight against the outer layer, seal the edges with caulk, and hold it in place with cleats. Then put the insulation back again. It would help a lot, in my opinion. Much better than just drilling holes.

Regarding your other problem:

I will/can only have 2 doors to reach each room of the studio. One door from the foyer into the airlock, and another to one of the studiorooms (it's mostly a budget thing).

are we talking about the same?

If the budget for doors is a problem, then do it the way xSpace suggested. That's a good design. And easier to build like that, too. Plus it gives you more space in the live room. You could put your air conditioning silencers in the gap between the walls, or maybe even above the ceiling. Or box them in, one corner of the room.

But walking into your "air" space is a problem. You need to have your air gap totally sealed all around, and the way you have it, the airlock is part of the air gap. Keeping that seal totally airtight is going to be tough (to start with, every time you open the door, you beak the seal). Plus, you have a large volume of air in there, and I suspect that, in itself, is not a good idea, although I might be wrong there: the acoustic experts can explain it better, I'm sure.

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 3:32 am

mika wrote: My problem is, that the room is just rented, and a hole is the only thing i can rebuild easyly when i go out the room one day.
cheers
mika

So it's a rented room, and you can afford to spend many thousands of dollars to build your studio inside, but you can't afford to spend a few hundred dollars more if you ever leave to put a new layer of gypsum board and a coat of paint on that wall?

Sorry, but that doesn't make much sense!

If you want good isolation, then you need to listen to what people are telling you here. On your picture, you marked "Office : Silence Needed" on the room next door. The ONLY way you can get close to giving them silence, is to beef up that outer wall drastically, and NOT build three leaves.

Have you done any sound transmission tests on that wall, to see what kind of isolation you are getting at present? that would be your starting point.

Also, how about your floor? What is it made of? That might end up being the weak point.

- Stuart -

mika · Post by **mika** » Wed Nov 12, 2008 4:10 am

So it's a rented room, and you can afford to spend many thousands of dollars to build your studio inside, but you can't afford to spend a few hundred dollars more if you ever leave to put a new layer of gypsum board and a coat of paint on that wall?

The problem is more to explain the owner of the bulding why i have to do this.

If you want good isolation, then you need to listen to what people are telling you here

i belive you 100% an work with your great information.
i only try to find the practicable, best solution for my situation.

On your picture, you marked "Office : Silence Needed" on the room next door. The ONLY way you can get close to giving them silence, is to beef up that outer wall drastically

so when i understad it right, the better (not best) solution is just adding mass to the second leaf.
what i can do easyly, is to glue 2 additional layers of gypsum to the existing wall.

The situation now is, that there is a rehearsalroom inside without any new walls. this works quite good for the owner, because the rooms next door are mostly used at sunday morning.
The room behind the controlroom is the kids worshiproom of the church in that building.

the romm next to the liveroom is a small office of one of the pastors, and used in the morning.

it is not nessesary to soundproof the studio compleatly, but when i mix a record, i want my silence inside there (no kidscrying).
i play musik at a verey low level, only sometimes i boost the volume up for 5 minutes.

Have you done any sound transmission tests on that wall, to see what kind of isolation you are getting at present?

this is planed for friday afternoon.

how about your floor? What is it made of? That might end up being the weak point.

floor is not a problem. it's a very thick industy concrete (the building was a producing plant 18 jears ago.

The celling will become more a problem.

i will make some photos at the weekend to show the given situation.

thanks again for all your help and time
cheers
mika

Ro · Post by Ro » Wed Nov 12, 2008 5:18 am

Soundman2020 wrote:
Ro wrote:Like X said, sounds like a three leaf. Stick with GB/frame/GB (M-A-M=Mass Air Mass)

Skip the Farmacell. For X; it's a Plasterboard with rigid foam attached to it.
"X" ????? And me???? (looks like I need a bigger signature... )

But thanks for the explanation!

- Stuart -

haha, SOOOOORRRRY! you're right, you need a bigger sig

No, I should need BIGGER GLASSED.

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 5:35 am

The problem is more to explain the owner of the bulding why i have to do this.

Maybe just tell him the truth?

"It's so that I don't disturb you with loud noise all the time, and so that you also don't wreck my recordings. If we don't do it this way, then the noise will be really bad in your room." Maybe that would convince him? Especially if you tell him that you will re-finish the wall when you leave.

so when i understad it right, the better (not best) solution is just adding mass to the second leaf.
what i can do easyly, is to glue 2 additional layers of gypsum to the existing wall.

That will help, but only a little tiny bit, because your wall will not be decoupled: "Decoupled" means that the two sides of the wall are not connected at all, especially by studs, for example. Two separate walls, basically.

If you just add mass (without decoupling), then sound (vibration) will still travel through the studs from one side of the wall to the other. Sound makes the gypsum board on one side vibrate, that makes the studs vibrate, and they make the gypsum board on the other side vibrate.

So more mass will work, since it makes it harder to vibrate the wall, but you need a LOT of mass to be effective.

I think you need to look at the numbers:

The wall at present (assuming that there really is insulation inside) has an STC rating of about 42. (If there is no insulation, then it would be only around 38.)

If you add one extra layer of gypsum board, it will go up from 42 to maybe 46, with luck. Two extra layers will make it maybe 49.

But now the physics starts to get scary: if you want to get from 49 to 54, then you now need to add ANOTHER THREE layers (for a total of six layers). To get from 54 to 61, you need to add ANOTHER SIX layers (total of 12 layers). (And to get from 61 to 66, you would need another TWELVE layers, for a total of 24 layers of gypsum board!!)

Those 12 layers will give you roughly the same isolation as if you build a simple decoupled double wall, with Green Glue and insulation, as has been suggested here.

By that I mean that 12 layers of gypsum board will give you roughly the same amount of isolation as if you take off the inside layer of that existing wall, use it to beef up the other layer (so that you have two or even three layers on the "outside" of that wall now) and build another wall about 6 inches away, also with two layers of gypsum board sandwiching a layer of Green Glue, then fill the entire gap in between the two leaves with insulation.

So, sure, if you really want to install 12 layers of gypsum board on your wall (assuming that the studs can handle the huge strain, and that you can find screws long enough and tough enough to attache it all!!), then that would work, and would give you about the same isolation as the kind of wall we are suggesting: two layers of gypsum board on the outsides of a double-stud wall filled with mineral wool or fiberglass insulation.

The numbers don't lie. Those are just rough theoretical numbers, of course, but the truth is in there.

So, you can add a dozen layers of gypsum board. Or you can build a proper isolation wall.

- Stuart -

AVare · Post by **AVare** » Wed Nov 12, 2008 5:59 am

Mika, you are in good hands with Stewart.

the holes will not affect the amount of Transmission Loss (TL) of the triple leaf. It will just change frequency where it occurs. I will still be in the low frequency range.

Andre

Ro · Post by Ro » Wed Nov 12, 2008 6:39 am

Sometimes you've gotta live with what you have.
If it's a rented room and you can't rip of the inner GB, then so be it and you've got 2 options:

Either extend the mass on the existing wall or make a triple leaf after all.

It's not that a multiple-leaf is BAD perse, but it's WORSE against a 2-leaf.

mika · Post by **mika** » Wed Nov 12, 2008 6:51 am

Maybe just tell him the truth?

simple, but brilliant.

the last hours i read all the information from the greenglue site.
seems like your solution is the only way i can go.

So we can go to my next question

Why is it nessesary to have the airlock (for me just a small foyer) have airtight to the walls between the control and the liveroom?

I ask this, because i want to leave it by my root plans with the airlock (small foyer).
the reason is that there is no budget for additional doors to build a seperate frame for the airlok, and that in normal use while there is a recording, all 10 minutes somebody is going out to the toilet, while anotherone is in the liveroom. FOr this reason it is defenetly needed to have a seperate entrance to the liveroom.
The entrancedoor from the big foyer to the airlock is fixend in position, i will only change the door to a soundproof type.
soory when i ask dump questions, but with the time i get cofused about all the information.

Treatment is not a problem, there i have alot of experience, but soundproofing is compleatly new for me

thanks again to all involved angels

cheers
mika

Soundman2020 · Post by **Soundman2020** » Wed Nov 12, 2008 7:42 am

Mika, you are in good hands with Stewart.

Oh WOW! Thanks!

André, you just made my day! Coming from you, that is high praise indeed!

( I guess I must have learned a hell of a lot from you guys already. )

- Stuart -