Sound Insulation

[BillyJoe]

Didididitit ,

I think you have to use it as an "attach file" (look at the very bottom of the "Post Reply" page) but I think I get the picture

I'm not sure what "drywall" is though. We have "plasterboard" here (generally used to line all interior walls) which I thought was equivalent to what you call "drywall" but it isn't waterproof. The only options I know of for exterior use are brick, weatherboard and fibro-cement sheeting.

BillyJoe

 

[diddidit]

The pic's too big to attach, so I'm trying to host it on my own web space, and it's not bloody working. Feh. Anyway, you get it.

Drywall = gypsum board. For exterior use, you'd want the stuff that's moisture resistant (I think it's referred to as "greenboard" here), or better yet use cement board (tile backer board).

did

 

[diddidit]

Here we go:

Musta had the addy wrong.

did

 

[Iconoclast]

I'm not sure what "drywall" is though. We have "plasterboard"...

Drywall = gypsum board.

Do you also call it Gyprock?

When it comes to the US/European translations it's usually possible to understand what the other person is talking about, but never when it comes to discussions of building materials.

From your second to last post, I don't have a clue what Tyvek, Typar, 15# felt paper, clapboards, or T-111 grooved plywood are, for all I know they're just a bunch of words you made up on the fly. At least you didn't mention Spackle or WeedWackers.

 

[jj]

Not even in this very specific situation (as described)

Well, the situation actually isn't very specific.

Sound travels roughly 1150 ft/second.

In order to block sound very effectively you need something several wavelengths long.

If you want to absorb much sound, you need something a good fraction of a wavelength.

Consider, 20Hz (low bass) has a wavelength of 1150/20 feet.

Highest frequencies an unimpaired young adult can hear have a wavelength of 1150/20000 feet.

So, you need to know, first, what frequencies you want to block.

If you put up a hard barrier it will reflect both ways, yours back at you, theirs back at them. IF you put up a soft barrier, it will absorb some sound and disperse the rest in all directions, of course depending on what the 'soft' barrier really looks like, which matters.

So, what do you want to block? Bass? Treble? Conversations? Everything?

That's where you need to start.

 

[jj]

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.

This is part of the recipe for how to keep the wall from transmitting sound through the wall. As such, that's fine, but if it's open on the ends you'll have to deal with diffraction around the wall, which will be a substantial at low voice to bass frequencies even for a very long wall. The wall will have to touch grade at the bottom, and be quite high, too, or sound will diffract OVER it as well as around it.

I'm not worried about how to make a wall to reflect the sound back at them, that part's easy. Iam worried about how one keeps a great deal of that sound from just going "around", and, yes, sound does just go "around".

 

[BillyJoe]

Drywall = gypsum board. For exterior use, you'd want the stuff that's moisture resistant (I think it's referred to as "greenboard" here), or better yet use cement board (tile backer board).

I'm betting that: drywall = gypsum board = gyprock = plasterboard.

And I think I saw what you refer to as "greenboard" when I was sniffing around about a week ago. But you mention "cement board (tile backer board0" which I'm betting is what I referred to as "fibro-cement sheeting" because that is used as a tile backing board around here. Perhaps we'll go with that. But do we need three thicknesses of that as well.

[It costs $Aus25 for a 900 x 2700 (3ft x 9ft) sheet. For only a single layer, we will need five sheets for each side of our 2700 x 4500 (9ft x 15ft) wall for a total of $250. Three layers on the outside surface makes that $500.]

BillyJoe

 

[BillyJoe]

jj,

In order to block sound very effectively you need something several wavelengths long......Consider, 20Hz (low bass) has a wavelength of 1150/20 feet.

We're stuffed.

1150/20 = 58 feet. So our wall needs to about 180 feet long! Unfortunately, our wall is only 15 feet long so we are not going to be able to block low bass sounds.

If you want to absorb much sound, you need something a good fraction of a wavelength.

Is 1/4 a "good fraction? If so we may have to go for something that absorbs sound rather than blocks/reflects it

So, you need to know, first, what frequencies you want to block.

I think it is bass sounds unfortunately

If you put up a hard barrier it will reflect both ways, yours back at you, theirs back at them. IF you put up a soft barrier, it will absorb some sound and disperse the rest in all directions, of course depending on what the 'soft' barrier really looks like, which matters.

What do you mean by "depending on what the 'soft' barrier really looks like"

So, what do you want to block? Bass? Treble? Conversations? Everything?

"Everything" would be good but I think the bass sounds (rock music and loud male voices) are the most annoying.

BJ

 

[BillyJoe]

jj,

....if it's open on the ends you'll have to deal with diffraction around the wall, which will be a substantial at low voice to bass frequencies even for a very long wall. The wall will have to touch grade at the bottom, and be quite high, too, or sound will diffract OVER it as well as around it..

Okay, our wall is not LONG. In which case it doesn't matter how high it is (9 feet). There is a roof though (I'll tell you it is "laser-light" but it probably has another name over there)

[BI'm not worried about how to make a wall to reflect the sound back at them, that part's easy. Iam worried about how one keeps a great deal of that sound from just going "around", and, yes, sound does just go "around". [/B]

This is what I was afraid of all along - the sound going around the wall - which makes me think it would be better to try to absorb the sound. Can this be done?

bj

 

[richardm]

Perhaps it would be simpler to make sure the neighbour was invited to all the parties?

 

[ktesibios]

This is what I was afraid of all along - the sound going around the wall - which makes me think it would be better to try to absorb the sound. Can this be done?

bj

Even if your wall is a perfect absorber, if its largest dimension isn't large compared to the wavelength of the sound, sound will just diffract right around it.

BTW, making a surface highly absorbtive at long wavelengths isn't easy. Porous absorbers like fiberglass, Sonex etc. maintain high absorbtivity figures only at wavelengths which aren't large compared to the thickness of the porous material.

It's possible to build low-frequency absorbers which aren't of impractical dimensions- perforated panel, slotted panel and diaphragmatic absorbers come to mind- but these are not broadband- they produce maximum absorbtion only in a relatively small frequency range centered on the absorber's resonance. They're commonly used in studios to tame troublesome room modes.

Check out the Everest books I recommended above for more info, including details about LF absorbers.

 

[Ove]

This is what I was afraid of all along - the sound going around the wall - which makes me think it would be better to try to absorb the sound. Can this be done?

I would try to keep both feet on the ground, that option sounds rather expensive/impossible as someone mentioned, the sound will just travel around the wall. All the solutions suggested here are fine when the object is to shield two rooms from each other but i doubt it would work when one of the walls are missing. What you would want was is to make the wall as solid as possible so that yo at least will have very little noise transmitting through the wall.

One rather cheap solution (and easy to work with) are those porous-gas-concrete building blocks, they will make a rather solid wall with a minimum of transmitted noise.

 

[Skeptoid]

BillyJoe wrote:
I'm betting that: drywall = gypsum board = gyprock = plasterboard.

= sheetrock

"Greenboard" is moisture resistant and is used in damp/high humidity areas like bathrooms (but not the shower stall or tub surround if tiled). It is not waterproof and will be ruined by direct contact with water. Cementboard or fibro-cement sheeting is also known as Wonderboard.

 

[BillyJoe]

Even if your wall is a perfect absorber, if its largest dimension isn't large compared to the wavelength of the sound, sound will just diffract right around it.

So what applies to blocking/reflecting sound applies to absorbing sound as well.
Goddamn!

It's possible to build low-frequency absorbers which aren't of impractical dimensions- perforated panel, slotted panel and diaphragmatic absorbers come to mind- but these are not broadband- they produce maximum absorbtion only in a relatively small frequency range centered on the absorber's resonance.

Goddamn, we ARE stuffed.

Check out the Everest books I recommended above for more info, including details about LF absorbers.

Thanks and I may do that in the long term but, in the mean time, my friend is planning to do this during the school holidays (he's a school teacher) and they start tommorrow.

 

[BillyJoe]

I would try to keep both feet on the ground, that option sounds rather expensive/impossible as someone mentioned, the sound will just travel around the wall. All the solutions suggested here are fine when the object is to shield two rooms from each other but i doubt it would work when one of the walls are missing. What you would want was is to make the wall as solid as possible so that yo at least will have very little noise transmitting through the wall.

Yep, seems we have to give up hope about blocking the sound out. Maybe we have to be happy with just blocking out the neighbours view onto the deck and perhaps reducing the sound just a bit.

One rather cheap solution (and easy to work with) are those porous-gas-concrete building blocks, they will make a rather solid wall with a minimum of transmitted noise.

I don't want to suggest this to my friend otherwise I may be invited to help him dig a fifteen foot trench.

 

[diddidit]

From your second to last post, I don't have a clue what Tyvek, Typar, 15# felt paper, clapboards, or T-111 grooved plywood are, for all I know they're just a bunch of words you made up on the fly. At least you didn't mention Spackle or WeedWackers.

Tyvek and Typar are synthetic fabrics that are used here to wrap wood-frame houses before putting on the outer layer of siding. Their primary purpose is to shed water that makes it through the outer layer of siding.

15# felt paper is asphalt-impregnated felt. It used to weigh 15 pounds per square yard, way back in the good ol' days, but now weighs about 8 lbs. per yard. Couldn't tell ya why the name hasn't changed. It's used the same way as Tyvek and Typar, and also on roofs under the top layer of roofing material (which is typically asphalt shingles here).

Clapboards are wood boards, typically cedar or redwood, used for siding a house.

T-111 is exterior-grade plywood that has grooves cut in it every 8 inches or so, and a rough outer surface. It can act as both the sheathing for a wood-frame house and as the exterior siding, assuming it's painted or stained properly.

Spackle is a light plaster-like compound used for filling small holes in a drywalled or plastered interior wall.

Weedwhackers (spell it right, you damn forriner!) are lawn tools used for cutting grass or weeds in placed inaccessible to a regular mower. They can be gas or electric powered. They will also do a bang-up job of destroying vinyl siding, which, of course, looks like crap anyway, so no great loss.

See? I didn't make nuthin' up!

Also, in the interest of fairness, the wall design comes from Modern Carpentry, more or less.

did

 

[Ove]

I don't want to suggest this to my friend otherwise I may be invited to help him dig a fifteen foot trench.

Well if he provides the Beer and perhaps a "post-dig-barbeque" it could be quite fun .

 

[richardm]

Weedwhackers (spell it right, you damn forriner!) are lawn tools used for cutting grass or weeds in placed inaccessible to a regular mower.

We calls 'em "Strimmers" in these parts, which is at least easier to say. I believe it's a trademark of the company that introduced them here. (They might have invented them for all I know).

 

[Iconoclast]

Weedwhackers (spell it right, you damn forriner!) are lawn tools used for cutting grass or weeds in placed inaccessible to a regular mower.

The most common trade name for that in Australia is "Weed Eater", which is a pretty stupid name as well.

 

[Iamme]

(Diddidit)

15# felt paper is asphalt-impregnated felt. It used to weigh 15 pounds per square yard, way back in the good ol' days, but now weighs about 8 lbs. per yard. Couldn't tell ya why the name hasn't changed. It's used the same way as Tyvek and Typar, and also on roofs under the top layer of roofing material (which is typically asphalt shingles here).
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I think you mean per "square", don't you? A "square" is 100 square feet. (or a 10 x 10 area). 15 or 30 pounds would be an awful lot for tar paper felt to weigh for only one square yard I think.

Also, regarding Tyvek-like products: They are magical in the sence that not only do they sheet water (tar paper can do this), but, unlike tar paper, these products can "breathe".