John Sayers' Recording Studio Design Forum Archive

Hello!

First thank you all for this great site and all the info here is!
Been lurking for a while and reading a lot, I think I've learnt a lot and on the other hand gotten very confused on somethings:)

One of the things that is buzzing me is that is what is considered leaf;
in Finland we normally have large temperature changes summer/winter
and we normally have walls that have structure that gets denser toward inner structure
(from inside to outside)
-Gypsum
-thin plastic foil as moisture barrier
-wood frame filled with wool.
-wind protection/sheating board
-"breathing"wood paneling (not airtight but breathing structure)

so is this in example considered two leaf or one leaf structure?
and what is the best way adding sound insulation here;
adding more gypsum(+greenglue) on top of inner gypsum board or disassembling the wall for rebuilding etc?

thanks in advance for replies.
BR;Mikko

I think a leaf is 'caused' by a gap between it and another leaf.
Presuming your outer panelling is attached to your wind protection sheathing board, I would call your wall two leaf.
Yes adding mass to the inside leaf should increase soundproofing. Gypsum board is probably the best value for adding mass, cement board is much heavier.
We don't have a lot of wood frame housing here, but I would be concerned about adding mass to a wooden structure.
Best get a structural engineer's view on that.
DD

DanDan wrote:I think a leaf is 'caused' by a gap between it and another leaf.
Presuming your outer panelling is attached to your wind protection sheathing board, I would call your wall two leaf.
Yes adding mass to the inside leaf should increase soundproofing. Gypsum board is probably the best value for adding mass, cement board is much heavier.
We don't have a lot of wood frame housing here, but I would be concerned about adding mass to a wooden structure.
Best get a structural engineer's view on that.
DD

ok, thank you!
this is stupid question, but in theory if I had stucture of gypsym-frame filled with wool- "cardboard" or something really flimsy as outer layer, that would still count as 2-leaf structure?

I'm referring to cardboard,
because this wind protection/sheating board we use is wood fibre-board
that is much lighter than in example OSB-board:


and the wall structure is normally like this:

so to my understanding this outer "leaf" is really bad for sound insulation:)

Yes it is a leaf. Use the MSM calculator to determine the effect. Not much with a light material making one leaf.

Andre

AVare wrote:Yes it is a leaf. Use the MSM calculator to determine the effect. Not much with a light material making one leaf.

Andre

thank you! just testing msm-calculator

Been testing that calculator and reading more.
this exellent "Gypsum Board Walls: Transmission Loss Data" (that btw has changed and http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4310 still has old dead link.)
had good info, but no examples how bad 3-leaf designs would be and no "outer wall" designs like mine.

One reason for asking all this info, beside learning is that I'm finally getting a house and a garage that I could convert to home studio. I have asked offers on local companies about design but I would like to know what would be right way to get better isolation -so I could filter the bad offers straight away:)


in this case, would the best idea to be (for best sound isolation per used money)
build room within a room like this:
http://johnlsayers.com/Recmanual/Images/Wall%2029.gif

where my outer wall would be that brickwall pictured above.
I understand that this would create 3-leaf wall.

or to open/remove/drill big holes to existing gypsum (now my inner wall or leaf.) and then build new wall as pictured?

and the wall structure is normally like this:

That is a three-leaf wall, yes. So it would not provide high levels of acoustic isolation.

but no examples how bad 3-leaf designs would be

This might help:
That's the exact same wall, but built three different ways. On the left, the wall is built as two stud frames, each one of which has one layer of drywall on EACH side. So four leaves. That wall has an STC value of 44.

The middle image shows the SAME wall, but with one of the internal leaves REMOVED... so there are now only THREE leaves, and LESS total mass in that wall.... yet the isolation as increased by nearly ten points, to STC-53. If you were to listen to the wall now, subjectively you would say that it is twice as good as it was: you can only hear sounds half as loud as they were before.

The final image on the right, shows the situation with the OTHER internal leaf removed and both of the removed layers of drywall now placed on the outside leaves, doubling them up. So that final example is only two leaves, but it is the exact same materials as the one on the left: same mass, same thickness, same everything. And it is ANOTHER ten points better! It gets STC-63. So subjectively, you would say that this last wall is four times better at isolating sound, and any sound that gets through would only be one quarter as loud as the original 4-leaf wall.

That's solid, real, true depictions of how isolation really works, and what penalty you pay for having three leaves or four leaves, as compared to two leaves.

That's why you will always see the recommendation here to try really hard to ONLY have two leaf walls and ceilings in your studio. Avoid 3-leaf as much as you can. And if it turns that you have no choice at some place in your studio: that you really must have three leaves at one place, then you will have to compensate for that problem by adding much more mass to all three leaves (but mostly the middle leaf), and also increasing the size of the gap between the leaves. You can compensate, yes, but it takes up more space and requires more mass, which means more money, and more complexity.

I have asked offers on local companies about design

Only ask companies that have proven experience in designing studios! I have come across quite a few architects, builders, and contractors that say they know all about how to design and build a "soundproof" wall, but in reality don't have a clue. If they use the term "soundproof", that's already a red flag, because studio designers and acousticians tend to avoid using that term: it has no real technical definition, and means different things to different people. If they say they can design your studio for you, ask for a list of customers for whom they already designed and built studios, and call those customers to ask about the design: If possible, go see the studios for yourself.

but I would like to know what would be right way to get better isolation -so I could filter the bad offers straight away

Smart move! I would ask them all what frequency they will tune the wall for, what TL they expect they will get, and what the lowest isolation frequency will be. If they can't answer all of those, then forget about that company. Ask what type of insulation they will use in the wall cavity, and if they answer with some type of closed-cell insulation, forget about them. Ask them if they think it is important to seal the walls air-tight, and if they say no, then forget them. Ask them if it is necessary to put rubber seals around the edges of doors and windows, and if they say no, then forget them. Ask them if you will need some type of HVAC system for the room, with fresh air supply, and if they say it isn't necessary, run like crazy because that's a dangerous company. Ask them if it would be better to have more leaves inside your wall, to get better isolation, and if they say yes, run like crazy... (see diagram above).

There's lots of things like that you could ask them, that would show if they understand isolation and acoustics. Those are just a few.

in this case, would the best idea to be (for best sound isolation per used money) build room within a room like this: ... where my outer wall would be that brickwall pictured above. I understand that this would create 3-leaf wall.

No. That's only a two.leaf wall. The outer leaf is the brick wall, the inner-leaf is the part that is labeled "2 x 16mm plasterboard". The rest is acoustic treatment inside the room: it shows what is called a "slot wall" on the studs inside the room. That's a tuned acoustic treatment device, and is not a leaf.

Regarding the floor, you should probably read this thread to understand about "floated floors": http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173


- Stuart -

Soundman2020 wrote: That is a three-leaf wall, yes. So it would not provide high levels of acoustic isolation.

Thank you for answers!
so my wall is even worse than what I thought
Once we have moved I will measure how bad the isolation really is and now I have set of good questions for the acoustic design companies!

on the original question "what is considered a leaf" I found this in terms/ref-section:

knightfly wrote: Leaf - this is ALL the layers of various wallboard (or other mass) ON THE SAME SIDE of a frame; if you put a layer of plywood, then Durock, then gypsum wallboard, one after the other, with NO AIR SPACE, on the same side of a frame, that is a LEAF.

so LEAF is anything that has higher mass? or density? than insulation or air between leafs?
and so is the sound insulation of 3-leaf(gypsum-homasote-timber) better or worse that 3-"proper leaf"(gypsum-gypsum-gypsum) ? if I got that MSM-calculator right, gypsum would be better?

Soundman2020 wrote:

in this case, would the best idea to be (for best sound isolation per used money) build room within a room like this: ... where my outer wall would be that brickwall pictured above. I understand that this would create 3-leaf wall.

No. That's only a two.leaf wall. The outer leaf is the brick wall, the inner-leaf is the part that is labeled "2 x 16mm plasterboard". The rest is acoustic treatment inside the room: it shows what is called a "slot wall" on the studs inside the room. That's a tuned acoustic treatment device, and is not a leaf.

Regarding the floor, you should probably read this thread to understand about "floated floors": http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

- Stuart -

I'm sorry my question wasnt really clear;
what I meant was that if I would build room(or wall) like in that picture,
inside my current walls (so "brick wall" of that original picture would be replaced with "my wall")
so that structure would be, as I have now learned a 4-leaf design(?)
as in this modified attachment.

So I'm expecting that I will be disassembling my walls guite a lot

That floor part was just left from the original picture,
This garage has its own concrete slab.

Now it looks like I cant start this "garagestudio"-project until next year,
so I guess I'll try to learn more and see what kind of plan I could make by my self.
Quates for design plan cost's varied from 1000-3000€ (+some engineering etc costs)

I still have to figure what I actually want and how much I'm willing to invest.

but on with the theory; I've been going thru a lot of studio builds documented here and I think I have an picture how to deal with walls (disassemble old inner wall, beef up the "outer leaf") if I need a "room within a room"

But what is (generally) best way to deal with ceiling/roof;
If I want to make room with in a room, my new room can only touch floor of my garage. If I just add new walls and attach them to my floor and ceiling my room isnt really "room within a room" and I lose some sound insulation.

in some builds I've seen here 3-layer design is used and I was wondering what would be best for this kind of ceiling;
-remove the gypsum (red dotted line) above my studio room
-or add more layers of gypsum (after getting calculations from structural engineer that my roof would hold the extra weight)

and if I would leave the old ceiling gypsum(and possibly beef it up with new layers)
then how big air gap should be (minimally) left between old ceiling and my room within a room ceiling?
I understand that air gap affects to sound insulation, but I find it hard to calculate because of the angle on the roof (third leaf and air space under it.)etc

But what is (generally) best way to deal with ceiling/roof
-remove the gypsum (red dotted line) above my studio room

The red dotted line sheathing would be your outer leaf. If you have a low ceiling height and want to have the highest ceiling possible, you should remove the sheathing and build inside out modules that slide up between the truss. You will obtain upwards of 4" extra height this way. If you have a nice tall ceiling and don't want to bother with the extra work, then yes, just beef up the existing sheathing (and seal the hell out of it too!)

After that, build your inner room that only touches the rest of the building via the concrete floor. No where else. Your new inner leaf ceiling rests on top of your inner leaf walls. That's how it's held up. Also, acoustically and visually, an inside out inner leaf ceiling is the best so we always recommend that on the forum. Thanks to John for inventing this concept.

then how big air gap should be (minimally) left between old ceiling and my room within a room ceiling?

Calculate how much air gap YOUR studio needs. Bigger gap = more isolation. You can find this out the long way by calculating each scenario, but I thought I'd attach these pictures to shed some light on mass vs gap size: Greg

Gregwor wrote:

But what is (generally) best way to deal with ceiling/roof
-remove the gypsum (red dotted line) above my studio room

The red dotted line sheathing would be your outer leaf. If you have a low ceiling height and want to have the highest ceiling possible, you should remove the sheathing and build inside out modules that slide up between the truss. You will obtain upwards of 4" extra height this way. If you have a nice tall ceiling and don't want to bother with the extra work, then yes, just beef up the existing sheathing (and seal the hell out of it too!)

Ok thank you!
but.. now I have one stupid question;
why this isnt a 3-leaf design? is the roof (plywood/osb&tin etc) so high that it doesnt count?
the gap/airspace on between my ceiling and roof is something over 1m or ~40" on the highest point.

Gregwor wrote: After that, build your inner room that only touches the rest of the building via the concrete floor. No where else. Your new inner leaf ceiling rests on top of your inner leaf walls. That's how it's held up. Also, acoustically and visually, an inside out inner leaf ceiling is the best so we always recommend that on the forum. Thanks to John for inventing this concept.

then how big air gap should be (minimally) left between old ceiling and my room within a room ceiling?

Calculate how much air gap YOUR studio needs. Bigger gap = more isolation. You can find this out the long way by calculating each scenario, but I thought I'd attach these pictures to shed some light on mass vs gap size:

Increasing Panel Spacing.png

Increasing Panel Mass.png

Greg

thanks for those pictures, I think I saw them in acrhitectural acoustics-book I've been trying to go thru but there is just too much to learn

why this isnt a 3-leaf design? is the roof (plywood/osb&tin etc) so high that it doesnt count?
the gap/airspace on between my ceiling and roof is something over 1m or ~40" on the highest point.

It kind of is a 3 leaf design. However, the "attic" is not air tight. Also, it will have way less surface density than your other two leaves which helps as well. PLUS it is far away as you've pointed out. There's no real way around having the third leaf in this scenario.

Greg