Sound Insulation

[BillyJoe]

My friend built a deck out the back of his house last year. This year his neighbour built an extension out the back of his house directly in line with my friend's deck. Unfortunately there is a window in the neighbour's extension that looks directly onto his deck. My friend is about to build a wall on the side of his deck to overcome that problem. However he is also concerned about the noise level when the neighbour leaves his window open whilst he entertains his friends.

What material should he use to build his wall so that sound will be cut to a minimum? He is prepared to spend a little extra to achieve this but he is not rich. Should the wall surfaces be made of sound proof material or would the use of sound proof material in the wall cavity be sufficient? Perhaps both? What about fixing something to the outside surface of the wall (facing the neighbour)? Would that be sufficient and what material would be suitable?

Thanks for any suggestions,

BillyJoe

 

[diddidit]

The design of the wall is more important than the materials. You need to decouple the outer wall surface from the inner; the easiest way is to stagger studs so that every other stud contacts the outer surface sheathing. This is easy to do but does require twice as many studs. Using dense fiberglass or cellulose in the cavities will further help, as will using two (or more) layers of drywall on the interior wall surface. Pay extra attention to sealing, too; a small hole will admit quite a bit of sound.

Making the wall out of something like concrete or brick is an option, too.

did

 

[Badger]

How about just using lattice as the wall, then planting leafy vines of some sort, that will cover the lattice and absorb noise from your friends entertaining?

 

[69dodge]

Use a sound-reflecting material to build a wall that is (a piece of) a sphere whose center is located at the neighbor's window.

just kidding, just kidding . . .

I have no experience with this sort of thing, but it seems like you'd want the wall to absorb the sound, not simply be sound-proof. This is just a single wall between his deck and the neighbor's house, right? If he's not entirely enclosing his deck, sound that isn't absorbed when it hits the wall can bounce around and end up coming around the wall. (Two missing walls and a missing roof make for a pretty big hole for sound to leak through. )

 

[ktesibios]

Dididit has the right idea. Eliminate mechanical coupling between the two sides of the wall, fill the cavity with absorbtive material like ordinary fiberglass thermal insulation, and make the wall surfaces as massive as possible.

An example from a former workplace: the studio and control room walls were approximately 12" thick, the framework was essentially that of two walls (each side of the wall had its own plate and studs), the surfaces were three layers of 5/8" gypsum board, installed so that the seams between sheets on one layer were not in line with those of the other layers, the seams were sealed as airtight as we could manage and the cavity was loosely filled with fiberglass insulation.

Using those techniques you can build a wall with an STC (sound transmission coefficient) of 50 dB or so- equivalent to that of a masonry wall.

There are two books by F. Alton Everest that have good info on building isolating walls - Acoustic Techniques for Home and Studio and Master Handbook of Acoustics, both published by TAB Books. Try the Mix Bookshelf (Google it) as a source.

 

[epepke]

What material should he use to build his wall so that sound will be cut to a minimum? He is prepared to spend a little extra to achieve this but he is not rich. Should the wall surfaces be made of sound proof material or would the use of sound proof material in the wall cavity be sufficient? Perhaps both? What about fixing something to the outside surface of the wall (facing the neighbour)? Would that be sufficient and what material would be suitable?

If he's really worried and has budgetary problems, I'd suggest a composite wall. A sheet of plywood on each outside. Cork board glued inside each plywood facing. Fiberglass insulation between the two.

 

[jj]

All I can say in less than book form is that this is not a simple question, and that there is no simple answer.

Sorry.

 

[T'ai Chi]

Construct the wall in such a way that the sound waves get reflected back at the neighbor?

(and yes, I am talking about of my rear)

 

[BillyJoe]

The design of the wall is more important than the materials. You need to decouple the outer wall surface from the inner; the easiest way is to stagger studs so that every other stud contacts the outer surface sheathing. This is easy to do but does require twice as many studs. Using dense fiberglass or cellulose in the cavities will further help, as will using two (or more) layers of drywall on the interior wall surface. Pay extra attention to sealing, too; a small hole will admit quite a bit of sound.

You sound like you know what you are talking about.

The wall will be nearly 9 feet (2.7 meters) high and 15 feet (4.5 meters) long. So, in effect he has to build a 30 foot wall. Okay, maybe he will have to adjust his financial commitmnet a bit, but what do you think of the following objection (see next post).....

 

[BillyJoe]

I have no experience with this sort of thing, but it seems like you'd want the wall to absorb the sound, not simply be sound-proof. This is just a single wall between his deck and the neighbor's house, right? If he's not entirely enclosing his deck, sound that isn't absorbed when it hits the wall can bounce around and end up coming around the wall. (Two missing walls and a missing roof make for a pretty big hole for sound to leak through. )

Yes, I was thinking the same thing. You have to stop the noise from bouncing around and back at you by actually absorbing it.

My friend thought he might use cement sheeting. It's very cheap and he thinks this would reflect the noise right back at his neighbour. Seems to me he will get a reverberating echo back!
I was thinking about lining his cement sheeting with a sheet of polystyrene foam. At the nearby Bargain Centre, they have 1 inch thick sheets for about $25. He will need just four of these.
Anyone have any opinion about this?

 

[BillyJoe]

How about just using lattice as the wall, then planting leafy vines of some sort, that will cover the lattice and absorb noise from your friends entertaining?

I can't see this having much effect for a very long time. And even then. But, hey, what do I know. Anyone else?

 

[BillyJoe]

Dididit has the right idea. Eliminate mechanical coupling between the two sides of the wall, fill the cavity with absorbtive material like ordinary fiberglass thermal insulation, and make the wall surfaces as massive as possible..

As massive as possible.? Are we still talking cheap here?
Yeah, I like the idea of the cavity between, effectively, two walls with a layer of insulation between. (Is fiberglass thermal insulation the best solution for this?)

An example from a former workplace: the studio and control room walls were approximately 12" thick, the framework was essentially that of two walls (each side of the wall had its own plate and studs), the surfaces were three layers of 5/8" gypsum board, installed so that the seams between sheets on one layer were not in line with those of the other layers, the seams were sealed as airtight as we could manage and the cavity was loosely filled with fiberglass insulation.

12" thick? This is NOT going to be cheap!
Also, gypsum? Is that what we refer to as plaster board with which we line the interior walls? How will that fare on an outside wall (sun and rain etc)?

Using those techniques you can build a wall with an STC (sound transmission coefficient) of 50 dB or so- equivalent to that of a masonry wall.

Yes, we thought of, and imediately rejected, a double brick wall. We have to able to do this thing ourselves. Tradesman around here earn more than doctors!

Also I'm still conmcerned about all that noise bouncing around and reverberating back into my friend's deck around the enormously thick and expensive triple lined, double wall.

 

[BillyJoe]

Re: Re: Sound Insulation

If he's really worried and has budgetary problems, I'd suggest a composite wall. A sheet of plywood on each outside. Cork board glued inside each plywood facing. Fiberglass insulation between the two.

Plywood wood (sorry!) be better than cement sheeting for sure. Would the cork board work better if it also covered the outside of the studs to reduce sound travelling form the plywood through the studs to the inside plywood?
And what about that polystyrene sheeting? Any ideas on that?

 

[BillyJoe]

All I can say in less than book form is that this is not a simple question, and that there is no simple answer.

Not even in this very specific situation (as described)

 

[ktesibios]

Something I should have mentioned earlier- if you're not building a room- that is, a completely enclosed space around either yourself or your neighbor, about the best you can hope for is substantial attentuation of mid and high frequencies- those whose wavelengths are small compared to the dimensions of the wall.

Sound at wavelengths comparable to or greater than the smallest dimension of the wall will tend to diffract right around it as if it weren't there. If your neighbor likes to play loud, bass-heavy music you might be SOL.

A look at the anti-noise walls they build alongside freeways should give a clue about the sort of size and construction involved.

As far as the transmission through the wall is concerned, the same basic principles used in building interior isolating walls should still apply- minimize mechanical coupling from one side to the other, go for the highest mass per unit area you can, make the facings of dense and lossy material and fill any cavity with absorptive material. There's a fiber-based "sound deadening board" available which, used beneath a facing that will stand up to the elements, could be helpful in increasing the losses through the wall surface.

 

[WildCat]

I once built a sound-proof wall for a conference room in Fermilab. It was a standard wall built w/ drywall and 2x4's, but w/ acoustical foam between the studs. It was amazingly sound-proof, but the acoustical foam is really expensive, $250 or so for 32 square feet. It was similar to this stuff, but I think it was a different brand. You have to cut it carefully so that it fits snugly, even a small space will let sound through.

If that is too expensive, consider building your wall w/ 2x6 studs and regular thermal insulation. Also, 2 layers of 1/2" drywall over it, be sure to tape the first (underneath) layer also. Use double-layered windows and seal well around them. Even slight cracks will let a lot of sound through.

 

[richardm]

Without completely enclosing the deck, are the soundproofing qualities of any wall going to be worth the cost to BJ's friend?

 

[epepke]

Re: Re: Re: Sound Insulation

Plywood wood (sorry!) be better than cement sheeting for sure. Would the cork board work better if it also covered the outside of the studs to reduce sound travelling form the plywood through the studs to the inside plywood?

Maybe on the studs. But you'd want most of the external wall to be reflective.

And what about that polystyrene sheeting? Any ideas on that?

I don't think it would be particularly effective for low frequencies.

As jj said, it's not an easy question with an easy answer.

 

[BillyJoe]

Okay, I think we have the following suggestions for the wall....

1) The outer lining to be as thick and dense as practicable so as to reflect as much of the sound as possible.

2) Separate studs for the interior lining so as to minimize tranmission of the sound that was not reflected by the outer lining.

3) Filling the empty space between the outer and inner lining and their respective studs with a sound proof material to further reduce the transmission of the sound.


I still have a problem with the outer lining needing to reflect the sound. Wouldn't the sound just bounce around and come in around the wall and through the the open front of the deck. Wouldn't it be better to have a material that absorbs as much sound as possible but also doesn't transmit it? Is there such a material? What do they use in recording studios to help prevent sound reflecting off walls and creating echoes? Can it be used on exterior walls?

Is our quest in vain as richardM suggests

Thanks for any help,
BillyJoe

 

[diddidit]

Look at the pic - that's pretty much what you're describing, and what I'd described. The white layers would be moisure-resistant drywall, the pink stuff is loosely-packed fiberglass insulation, and the studs would be 24" on center on each side.

On either side of the wall, you'd then want a drainage plane material, like Tyvek, Typar, or 15# felt paper. Over that you'd put some sort of siding material like vinyl siding (blech), wood or cementboard clapboards (expensive but pretty), or, my simple-is-better choice, T-111 grooved plywood, painted or stained. You'd have to have a water-shedding cap on top of it all, with some eaves to keep water from hitting the upper parts of the wall. It's not terribly complicated or expensive,and it'll reduce sounds enough that reasonable conversation will be mostly inaudible (or at least muffled). It ain't gonna block the sound of a house party, though; nothing will without being completely enclosed.

Might be cheaper to buy your neighbor some noice-cancelling headphones...

did

Edited to add - stupid picture should show up eventually...