John Sayers' Recording Studio Design Forum Archive

How are the walls around the windows constructed? How heavy are they?

They are as heavy as you could ever imagine them being. I used a 2x6 stud for the base and top plate of the walls, with 2x4 staggered studs 14 inches apart with a stringer between each vertical stud. Then I put 3 layers of 3/4" OSB on each side. Then capped that off with 2 layers of 1/2" drywall on each side mounted on Z channel. That's EACH wall. Then there is something like 7 inches of dead air between them with 2 inch studio foam facing each other to get rid of any sound that might get between the two plates of glass. The two plates of glass will end up being 22 1/2" apart from each other.

wouldn't it pay to calculate the weight of the wall leafs and use glass panes comparable in weight?

Clang, you're confusing me with your wall descriptions - can you state, in order, the material(or frame) a sound would encounter when trying to get from room A to room B?

Also there is a VERY simple way to figure glass - just match the MASS, or go slightly heavier. Gypsum has close to 1/3 the mass per unit thickness of glass, MDF is similar, plywood is slightly lighter - so just generally, if you use 1/3 the glass thickness of your TOTAL panel thickness for EACH SIDE of a wall, then increase the glass thickness to the next available thickness, you'll be fine. 2 feet between glasses is good, it will lower the m-a-m resonance regardless of WHAT thickness glass you use.

The thing I'm concerned about though, is your description; it almost sounds as if you've built TWO walls, EACH with TWO leaves of mass; if so, you've actually WORSENED your isolation at lower frequencies by several dB... Steve

I don't get how going with two separate rooms would worsen my sound isolation at low db.

Ok, right now I'm in the control room so I can describe exactly how the walls are constructed. My memory was a little fuzzy before.

I will now describe what materials/space sound has to travel through to get from the live room to the control room.
1) 2 layers of 1/2" drywall mounted on z channel to help prevent vibrations getting through to the OSB in #2.
2) 3 layers of 3/4" OSB.
3) 2X4 wall.
4) 1/2" drywall.
5) 7" of DEAD AIR with 2" studio foam facing each other.
6) 2 layers of 1/2" drywall.
7) 2x4 wall.
8) 2 layers of 3/4" OSB.
9) 2 layers of 1/2" OSB.
10) 2 layers of drywall mounted on z channel.

All seems staggered and caulked/mudded.

Does that help clarify? I still don't get how that would give me worse low db isolation than if I had a thinner wall. I even differed the thickness of the materials mounted on the 2x4 walls.

Steve means (if I may speak for him) that you have a wall consisting of 4 leafs with 3 airgaps, if I understand right.
It is better to have a wall with two heavy leafs and a large airgap in between.
Such a wall resonates on a very low freq and that is good, your wall has multiple resonances what is less positive for sound isolation.

Bert

No there is only one dead air gap. I don't know how I could better describe my setup than I did in my previous post. Draw out exactly what I typed to see a visual.

Guys,

I'm reading a report about sound isolation with double leaf constructions from the Leuven University(geluidsisolatieverbetering met voorzetwanden, G. Vermeir, P. Mees).

Here is something about windows constructions with very high sound isolation:

They advice a totally seperated construction where you have two brick walls, with in 'm a fixed window with a 12mm glass-12mm gap-6mm glass, then an air gap of 230mm, then a double sealed window that can be opened with a 12 mm glass pane in it.

So in fact a triple leaf construction with a very narrow and a very large airgap.

The R values (Hz-dB):
100 - 45
125 - 49
160 - 45
200 - 46
250 - 51
325 - 54
400 - 57
500 - 61
630 - 64
800 - 67
1000 - 68
1250 - 71
1600 - 73
2000 - 69
2500 - 69
3150 - 67

So: seems that when you have a good thermopane window you don't always have to replace it if you want to avoid a triple leaf construction.

Bert

Looks like the third leaf may be responsible for that dip around 200 hZ... Steve

Yep,

would take knowledge about the source spectrum and a calculation to really predict the effect, but it doesn't look to bad.....

Oh, I have to add..

I said this is a report by the Leuven University, but Eric Desart pointed out to me that the report I name does not contain this information.
I got a photocopy with named report in front and it looked all one report, but it turned out to be a compilation, maybe from a lecture or something. Gonna send Eric a copy, maybe he finds out the real source.... I'm sure it all is certified information, not bullshit.

Bert