Building room in a room / isolation wall construction
Old 28th November 2009
  #1
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Building room in a room / isolation wall construction

Hello guys,

I hope someone can help me with this...

I am planning to build a room in a room for a simple home studio purposes (mixing, recording,...). Existing walls are made from 0.3m thick brick.
I know the best - most economical - way to achieve isolation is to build an inner wall with plasterboard to create a MASS - AIR - MASS system.

I have already obtained low density mineral wool 30kg/m3 (2lb/ft3).

My question is: is it better to use this wool to fill the air gap between new plastered wall and existing brick wall for isolation or is it better to use it for absorption inside the room?

2.) Would there be any benefits for isolation if I would leave addional 2" of air space between new wall construction (i was thinking of 2") and existing brick wall? I know for absorption it is better to have air space behind insulation: whats the relationship between air and absorbtion




Hope somone can help me in a short time

Thanks!
Old 29th November 2009
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With some addional research I have found that...

it is not significant if insulation is touching inner wall or outer wall. The dampening effect is practically not significant... Help with insulation. Most important is that insulation is in there. Is this true?

Since usually more thick insulation - around 50kg/m3 - is advised to use for filling the gap between mass - walls would it be better if existing insulation would be compressed a little bit - a few cm to achieve more density?

Someone?....

...
Old 29th November 2009
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30cm thick brick wall are not bad to start out. I think there's not much sound coming through that, the bigger problem is vibration transmitted by the walls and floor. I'd try to make the walls floating, i.e. with as little contact with the brick walls as possible. You could just build a rectangle of wall inside the existing room and stuff a little rock wool between the the new all and the old wall. Or you can just leave air inbetween and use the rock wool to build lots of bass traps.
Old 29th November 2009
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Quote:
Originally Posted by pankers View Post
Most important is that insulation is in there. Is this true?
Correct.

Andre
Old 29th November 2009
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DanDan's Avatar
Answers

Quote:
My question is: is it better to use this wool to fill the air gap between new plastered wall and existing brick wall for isolation or is it better to use it for absorption inside the room?

2.) Would there be any benefits for isolation if I would leave addional 2" of air space between new wall construction (i was thinking of 2") and existing brick wall? I know for absorption it is better to have air space behind insulation
Wool in the air gap dampens resonances in there. It should be a loose fit, not stuffed.
It can improve the sound isolation by a decent amount, I would expect 6dB or so.

The bigger the air space the better. Again the loose fill.

These two leaf structures with a dampened air gap are a system. The individual elements, e.g. wool, have different meanings else where.

You might take a look over here Noise Control


Inside the room, fabric wrapped 703 makes a fine absorbing panel. DIY versions of these and the StudioTips SuperChunk are covered extensively at studiotips - tips on studio design, acoustics, and wiring

Best, DD
Old 29th November 2009
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MrCrowbar, Andre, DanDan thanks for your replies.

The inner room structure would be decoupled from existing structure, standalone framing built a couple cm from existing walls. See attached picture. The only connection to outer room would be through the floor.
As this room is going to be built inside a garage with a concrete slab I was not planning to float the floor. As I read floating the floor, unless done properly, can be really bad. I was going to use 1 cm rubber foam under the frame and wood flooring to decouple the room from the slab. RUBBER FOAM, SPEC.

Does anybody have any suggestions about the air gap size? To provide decoupling a couple of cm would be necessary I think?

Thanks,
Attached Thumbnails
Building room in a room  / isolation wall construction-wall.gif  
Old 29th November 2009
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Gap etc.

I would go for a 5cm gap. You may be able to find a better 'foam rubber' Neoprene?
Floating the studs is well worth doing but may not be that easy. Rod has quite a bit of practical detail over at john sayers forum. Also he has a book :-)
DD
Old 30th November 2009
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Hello again,

does anybody have any information if inserting a layer of asphalt sheet (Sheet specifications - material used for isolating roof) between gypsium boards is of any benefit for sound isolation or is it just not worth the expense?

Some say it is not worth it "As for the layer of asphalt-sheets - not worth the trouble or expense. If you want great isolation, get the Green Glue."
Need some advice on soundproofing and acoustic treatment of my tiny studio

other use it regulary when building new constructions...
"If you use a double gypsum board structure you reach already 48dB of STC. Add a layer of 4mm of asphalt in rolls in sandwhich between each double layer of Gypsum and you get very close to 56dB (lab measurement, not real life measurement)."
Who is using Green Glue in their studio build?

Thanks,
Old 30th November 2009
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I have decided to go for one room design without any iso booth.

As I read it is better to build isolation shell rectangular shaped to have more predictable modal response and than build splayed inner walls / false ceiling or cloud to create RFZ at the mixing point. This way the room volume would remain at its maximum. What do you think?

Now since the place is high enough - I could build room high up to 3,25m would you recomend building concrete floating slab to isolate even more from flanking sound transmission?

Somebody? Some help please?

Bye,
Old 2nd December 2009
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DanDan, I have read Rod's book.
I have found ethylene propylene diene monomer (EPDM) rubber for decoupling walls from floor.
It it high density rubber used for sound transmission isolation of construction walls at very high loads. It is 5mm thick with 2mm (40%) compression under 9800kg load.
I calculated the weight of my room would be around 4000kg including frame, walls, ceiling construction without the weight of additional inner acoustic elements.

DanDan, Andre?
Old 2nd December 2009
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Quote:
Originally Posted by pankers View Post
It it high density rubber used for sound transmission isolation of construction walls at very high loads. It is 5mm thick with 2mm (40%) compression under 9800kg load.
I calculated the weight of my room would be around 4000kg including frame, walls, ceiling construction.
Yes, that sounds about right.

No one has mentioned it, but be sure not to 'short' out the 2 walls by allowing the figid insulation to be smashed between the two, coupling the walls - or with wiring or any other such thing.

Why so much isolation? Do you have traffic or neighbor problems?

- John
Old 2nd December 2009
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Thanks jhbrandt,

No one has mentioned it, but be sure not to 'short' out the 2 walls by allowing the figid insulation to be smashed between the two, coupling the walls - or with wiring or any other such thing.
The frame would be 5cm away from existing structue, 10cm thick filled with insulation and double gypsium board on the inner side of the frame.
This way there would be 5 cm between wall frame and insulation and 15cm between outer mass - wall and inner gypsium wall. If this still would not be enough I could still use third layer GB with GG.
For the asphalt sheets I still did not get any information is it of any benefit?

Why so much isolation? Do you have traffic or neighbor problems?

Isolation for keeping out the outside noise: There is the main road 15m from the house with medium traffic, most problematic would be trucks I think.
Isolation for keeping sound inside: I'm a drummer and if there would be possibility I'd use this room for practicing drums also.

Nearest neighbours are 10m away. They say they can live with some noise, but will cost me a bottle of wine from time to time.

Bye
Old 2nd December 2009
  #13
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DanDan's Avatar
EPDM

I have seen EPDM more often than Neoprene. I don't know which is better. I don't have the experience to do load calcs but is would imagine that the width changes the amount of compression. I have seen resilient sheets and MLV and Green Glue recommended between layers of plasterboard. Since they are screwed together in any case I doubt that there would be much difference. However, Green Glue at least publish some numbers, so if you do the screwing and glueing as they say I guess you should get the extra they claim. How about using high performance Resilient Channel as well as the proposed floating stud structure. Here's one. WallComp, UK - CMS Acoustics
Lots of other acoustically chosen products on that site also.
DD
Old 2nd December 2009
  #14
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avare's Avatar
 

Quote:
Originally Posted by pankers View Post
I have found ethylene propylene diene monomer (EPDM) rubber for decoupling walls from floor.
It it high density rubber used for sound transmission isolation of construction walls at very high loads. It is 5mm thick with 2mm (40%) compression under 9800kg load.
I calculated the weight of my room would be around 4000kg including frame, walls, ceiling construction without the weight of additional inner acoustic elements.
Impossible to say from what you wrote. 9800 kg over what area? In loading the material, you want spring left in the material so that it does not bottom out and do nothing. Also the width wall plates to calculate the pressure is required.


Andre
Old 2nd December 2009
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Quote:
Impossible to say from what you wrote. 9800 kg over what area? In loading the material, you want spring left in the material so that it does not bottom out and do nothing. Also the width wall plates to calculate the pressure is required.
Rubber STG takes load of 9800kg/m (50mm wide x 5mm thick) with 2mm deformation. (Could not find better quality picture than attached).
The other type rubbers are for lesser loads.
Attached Thumbnails
Building room in a room  / isolation wall construction-rubber.gif   Building room in a room  / isolation wall construction-loadchar.gif  
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File Type: pdf Rubber2.pdf (207.9 KB, 734 views)
Old 3rd December 2009
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I have received test report for EPDM isolation rubber STG50*5.
The testing of the piece gave following result: weighted standard flanking sound level = 39dB.
Anybody has any idea if this is sufficient?
What values should I be looking for anyway?

Pankers,
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Old 3rd December 2009
  #17
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Quote:
Originally Posted by pankers View Post
Rubber STG takes load of 9800kg/m (50mm wide x 5mm thick) with 2mm deformation. (Could not find better quality picture than attached).
The other type rubbers are for lesser loads.
With a 4000 kg total load, you will have to cut the material into patches to achieve the desired loading. Fill the gap with acoustic sealant. You will then have a great floating wall. OF course the wall will have to be attached to the floor with resilient fasteners also.

Great stuff and good luck!


Andre
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