# Sound Absorbing wall



## marty1 (Jun 29, 2010)

I believe that it is good to have the whole of the front wall in my home cinema absorbant.

I am considering soundproofing the front wall to give the neighbours a break by building a stud wall.

Since I would be loosing about 6inches of the front part of the room I would rather not add big absorber panels all over the wall loosing even more living space.

What I was wondering is is there a way of changing the layout of the soundproofing stud wall, so rather than having the mineral wool inbetween the plasterboard, I would leave an air gap from existing wall, put up acoustic plasterboard layers, then add the mineral wool last?

If this does work I have 3 things I'm not sure how to achieve:

1. How would I attach the mineral wool onto the wall as I would require the same thickness as a monster trap uses, say around 6inches so it would be quite heavy?

2. How would I cover the entire wall in acoustic fabric and make it look neat like a normal wall?

3. How would I attach my projector screen brackets onto the mineral wool, obviously it is soft material so will not hold any weight?

I'm sure the answers are really obvious and I'm probably being a bit thick but I am not too clever when it comes to diy :dontknow:

I would really love to hear your ideas no matter how out there they maybe, even if there are simpler ways to soundproof a wall besides building a stud wall. 

Thanks in advance.

Martin


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## robbo266317 (Sep 22, 2008)

Have you looked at using what the people in the states call "green glue" and sticking a different thickness of drywall to the existing one? That seems a common method to reduce sound transmission.

The projector brackets would still need to be attached to something that could hold the weight.

Hope this helps.

Cheers,
Bill.


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## marty1 (Jun 29, 2010)

robbo266317 said:


> Have you looked at using what the people in the states call "green glue" and sticking a different thickness of drywall to the existing one? That seems a common method to reduce sound transmission.
> 
> The projector brackets would still need to be attached to something that could hold the weight.
> 
> ...


Thanks Bill,

I think that will definately be a lot simpler but how much of the sound will be cut out I'm not sure?

The trouble is I'm still left with the issue of how to cover the wall with mineral wool and fabric.


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## SAC (Dec 3, 2009)

With all due respect, isolation requires MUCH more than Green Glue.

Isolation is not a trivial issue.

First you must determine and quantify exactly how much isolation is required.

Then, referring the various documents below, identify the type of construction involved, and then refer the to document that matches it and refer to the construction that provides at least as much isolation as you require.

Pay particular attention to the 'flanking' vectors.

Be aware that you can construct the most massive wall ever seen, and it will literally only be as effective as the least capable variable in the system.

Here is a generic listing of downloadable documents available from the NRC on Isolation methods. The NRC is an excellent source of tested construction methods. Pay particular attention to the doc regarding flanking paths.


*Owens Corning Design Guide*
http://www.owenscorning.com/quietzonepro/pdfs/NoiseControlDesignGuide.pdf

NRC (National Research Council) docs (Choose the docs that are appropriate to the construction type):

*Sound Transmission Loss Through Concrete and Concrete Masonry Walls*
by Albert Litvin and Harold W. Belliston
www.cement.org/bookstore/profile.asp?itemid=RD066

*Sound Transmission Loss of Masonry Walls*
by Warnock and Monk
www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/brn/brn217/brn217.pdf

*Sound Transmission Loss Through Drywall and Block Walls*
by Warnock
www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir586/ir586.pdf

*Gypsum Board Walls: Transmission Loss Data*
By Halliwell, R.E.; Nightingale, T.R.T.; Warnock, A.C.C.; Birta, J.A.
www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir761/ir761.pdf

*Controlling Interoffice Sound Transmission Through a Suspended Ceiling*
by R.E. Halliwell and J.D. Quirt
www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc33097/nrcc33097.pdf

Flanking information:

*System Details That Work (Leaks and Flanking)*
by David Quirt
www.nrc-cnrc.gc.ca/obj/irc/doc/leaks-flanking.pdf

*Guide for flanking sound transmission in wood framed construction - airborne sources*
by Nightingale, T.; Quirt, J. D.; King, F. 
http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc49468/nrcc49468.pdf

*Controlling Interoffice Sound Transmission Through a Suspended Ceiling*
by R.E. Halliwell and J.D. Quirt
www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/nrcc33097/nrcc33097.pdf

*Airborne Sound Insulation in Multi-Family Buildings*
by J.D. Quirt and T.R.T. Nightingale
http://www.nrc-cnrc.gc.ca/obj/irc/doc/ctu-n66_eng.pdf


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## marty1 (Jun 29, 2010)

Although I would like soundproofing it isn't my main priority, it's more about making a whole wall 1 giant bass trap, the soundproofing is an added bonus for me.


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## robbo266317 (Sep 22, 2008)

marty1 said:


> Thanks Bill,
> 
> I think that will definately be a lot simpler but how much of the sound will be cut out I'm not sure?
> 
> The trouble is I'm still left with the issue of how to cover the wall with mineral wool and fabric.


I think someone stateside should be able to comment on how well it helped them and what other treatments they found effective. 
Like all things audio it's about minimising the problems within your budget and environment constraints. :spend:


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## bpape (Sep 14, 2006)

While the front wall should be absorbent, likely having the entire thing as a bass absorber isn't the best location. A simple layer of 2" MW or fiberglass would be sufficient. Front corners, side wall reflections, and rear wall are generally better places for more broadband type of bass control.

Bryan


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## marty1 (Jun 29, 2010)

bpape said:


> While the front wall should be absorbent, likely having the entire thing as a bass absorber isn't the best location. A simple layer of 2" MW or fiberglass would be sufficient. Front corners, side wall reflections, and rear wall are generally better places for more broadband type of bass control.
> 
> Bryan


Well the front corners are already treated with tritraps as you know.

Would having the 2 inch fiberglass cover the whole wall be necessary or will the desired effect be achieved with just placing absorbers around the screen be sufficient?

If so then would I only need to add the 2 monster traps I was talking to you about, under the screen and that should be enough. It seems like it will be tricky to cover the wall with fiberglass, then fabric and still be able to cover the wall with the lucia fabric. Also attaching the brackets for the pj screen would be tricky too.

If you are saying that the front corners are the best places for broadband bass control does that mean that I could get away with having thinner absorbers underneath the screen? The Monster trap I tried there raised the dip around 110hz, but the trouble I had was to get a monster behind my sub I would have to move the sub further into the room which put the REW measurement all over the place again.

Martin


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## bpape (Sep 14, 2006)

Sure - you don't need to do behind the screen in your case.

If the monsters helped where they were and you can do that without having to move the sub, that will be fine. You can try just straddling the front corners wiht the Monsters to see if they have the same effect.

There are also other places in the room that will benefit from something more broadband.

Bryan


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## marty1 (Jun 29, 2010)

bpape said:


> Sure - you don't need to do behind the screen in your case.
> 
> If the monsters helped where they were and you can do that without having to move the sub, that will be fine. You can try just straddling the front corners wiht the Monsters to see if they have the same effect.
> 
> ...


I would have to move the sub forward with a monster trap behind it which would mean that apart from the dip at 110hz being lifted, I find dips appear elsewhere. That's why I was wondering if a thinner absorber would sort out that dip without me having to move the sub?

Martin


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## bpape (Sep 14, 2006)

A 244 will help a bit but still takes 5". Anything less is going to do little to nothing to help that.

Bryan


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## marty1 (Jun 29, 2010)

Okay thanks Bryan. It looks like an entire wall absorbed is unnecessary so i will put 2 more monsters below the screen and eventually soundproof the wall but just basic minimal soundproofing so i dont loose too much living space. 

Thanks for your help:T


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