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sound proofing, what has worked?

6433 Views 23 Replies 6 Participants Last post by  MACCA350
I am getting to a stage in my renovations now where I need to consider sound insulation to prevent my neighbours from lodging complaints when this get loud. I have 1.8 metres from my external wall to the fence. What i was wandering was what methods of soundproofing has anyone tried and what has worked. I have done a fair bit of research but before I start spending cash on materials I am hoping someone might have had a bright idea or new approach with good results.


dr f
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Well, you have a huge advantage in that you're not trying to soundproof to another area in the same structure.

A few steps to do it right:

- Make sure any doors/windows are sealed tight. Consider an 'insert' for any windows.
- Make sure all walls, floor, and ceilings are filled with insulation.
- Seal any and all places for air to escape (outlets, switchboxes, lightboxes, etc.)
- Double up on the gypsum board on all the surfaces.

You're needs are similar to many musicians so you might also search out recording studio soundproofing and follow those threads.

One of the best sound insulation techniques is the 'staggered stud' approach. with this technique, you use 2x6's for the top and bottom of the wall, but the uprights are 2x4's you use approx twice as many 2x4's with half aligned to the inside of the all and half to the outside.

The benefit of this technique is that it's reasonably cheap, does not require skilled labor beyond normal construction, and best of all - both halfs of the wall have 2x4's behind them so you can still hang cabinets, install crown molding etc...

you can find a lot of information on this in the insulation companies literature.
Page 3 of this one shows different wall construction techniques:

Avoid the Resilient channel method they show - as you can see the difference in sound control is minor, yet RC is much harder to work with, makes it harder to install floor trim, harder to install crown molding, harder to anchor heavy objects like speakers, etc.. (I did this so I know from experience!)
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If I'm not mistaken... brucek did this for me many years ago:

Here's the results:

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Thanks, unfortunately I have two problems 1) my walls are already built and 2) stagged studs still have to be braced with noggins (in Australia) unless it is not a structural wallor it is clad with bracebaord. I really only need to stop sound from crossing into the neighbours yard/house so anything that can be bolted/built allong the side of the house is what I am more after.

But as I am still curious, how much sound does your stagged stud wall stop?
Well we have the staggered stud walls and R-26 insulation surrounding the room and three sheets of 5/8" sheetrock/drywall on three walls and ceiling and two sheets drywall with outside brick on the other wall. In our great room (about 50' away) all we can hear is what sounds like way off thunder... very faint... on heavy bass scenes. This is mostly traveling through the attic. Outside, we really don't hear anything. Of course we don't have any neighbors close enough to bother either. I don't know what the actual STC rating would be for our walls, but it's got to be pretty good.
Staggered stud walls will provide a lot of control - especially as has been noted in bass transmission. If you can swing it, you can build another set of walls inside the existing ones that would not be considered structural. This will provide exceptional isolation.

My previous recommendations were assuming you weren't going to do any major construction and were designed to work with what you already had.

What's a noggin?

If you have a look at that owens corning link I sent - it has 'STC' values for different construction techniques.

STC is Sound Transmission Coefficient, and If I remember correctly, it's the number of Decebels reduced by the wall.

Standard wall construction runs around STC 30 or so, Staggered Studs run STC 50 or so.

To put it another way, if you are listening to music at 90 dB, throug a standard wall, the volume will be 60 dB on the other side - still very audible. Through a Staggered stud wall, the volume would be roughly 40db. - Probably not audible at all given external environmental noise like trees in the wind.

- Jack
A noggin is your head... at least in ******* hillbilly country it is. :bigsmile:

I think I can actually measure the STC of my wall now that I have this CM-140 SPL meter. It may have enough range for me to work with. I'll see if I can check it for you.

Is it a particular frequency used in the STC rating or is it pink noise?
Thanks Sonnie, I appreciate your time.

A noggin is a horizontal brace that prevents the studs from bowing when weight is placed ontop (i.e a roof).
Ah yes, I remember that about Australia, Not an asphalt shingle roof anywhere to be seen.

All concrete tile if I remember, and probably very heavy!

The basics behind the staggered stud, is that vibration is not carried through the wall.

If it's required that you have wood between the uprights, then you could still make this work, it would just require a bit more work.

for example, you could do a 2x8 footer, with 2x4 uprights. Over here in the US, all these measurements are over by 1/2 inch so a 2x4 is really 1.5x3.5 inches, 2x8 is 1.5x7.5

I'm sure you can find a way to adapt it to local building codes.

Also, as Bryan pointed out - a "wall within a wall' is even more so effective, so if you're limited to that, it's not a bad thing, you just give up a few more inches of floor space.
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I'm not sure which frequenies they use to calculate STC. But you could probably do alot better with 2 overlaid graphs from REW.

STC is only a single number and while it's a good guide, it's not perfect.

If you could do 2 REW graphs, one inside the wall, and another outside, then the difference between them would be what was absorbed by the wall.

I'd love to see such a graph - I think the lowest Frequency that goes into STC is either 125 or 250hz.
I would Like to see graphs down to 15Hz, majority of any sound that disturbs neighbours would be below 125Hz. I might build a second wall on the outside of the house to save on floor space.
I'm questioning how much an external wall would do for you.

But at the same time, I'm having a hard time picturing it.

Would you set a new foundation to support the weight of the new wall?

If you hang it off the existing wall, it's going to need to make contact with the existing wall, and that will pretty much transmit sound right through it.

You'd be better off loosing the extra few inches on the inside wall.

But a few inches is all relative - if this is a 15x15 room, you can loose 4 more inches. if it's a 9'x9' room, every inch counts.
it wouldn't matter whether the wall was built inside or outside it would still have to be fastened to the existing floor/roof structure. Unless of course it was built outside as a total free standing structure.

the room is 13' wide, however floor real estate is at a premium.
As far as REW graphs.... as tight as my two doors are, I don't think there is any possible way to get the mic cord through and shut both doors.

It would seem that playing pink noise would grab the loudest frequency... measuring inside and outside should give us a ballpark idea anyway.

I check and make sure I can't get the mic cord through with the doors shut and if I can, I'll do both measurements.
But as I am still curious, how much sound does your stagged stud wall stop?
It’s surprising – to me at least - how well it works. I didn’t think it would work nearly as well as “room in a room” construction, but when Sonnie says all he gets is “distant thunder” in his living room, that’s saying something, considering the amount of “woofage” he has with those two SVS subs. Of course, much of that can be attributed to the overkill sheetrocking – three 5/8 sheets, wow! :T

Aside from that, making everything as air-tight as possible goes a long way. Windows and doors are the worst culprits, especially the former, as they are so thin and usually have marginal air-tightness (if that’s even a word).

As far as bothering you r neighbors goes, anything that gets outside is dissipated a lot in the open air. And, it has to get all the way through the neighbor’s walls to be a bother to them. Basically, if you both live in free-standing structures, it’s pretty hard for sound to get from your closed-up house into their closed-up house in levels that they will find annoying, if at all.

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I was thinking today about this whole second wall deal, what if I was to cover the entire inside wall with rockwool or equivalent and then suspend 3mm ply over the front of that. I could fix it so the ply was suspended from the ceiling similar to a speaker surround and fasten it to the skirtboard somehow.

this would mean I wouldn't have to frame up a second wall and could compress the rockwool down to 2" or thereabouts to try and keep floorspace. Any thoughts?

Sonnie how did you go measuring the difference between in and out of your room?
Good thought but it won't do much of anything in terms of bass isolation. It's simply not enough mass and it's not going to be sealed air tight. If anything it could cause additional WORSE issues by introducing a 3rd leaf into the equation (though not an efficient one since it's not sealed) that can actually amplify transmission at certain frequencies.

Yeah, I think the plastic is a bad idea...

Can you tell us more about the room?

Is this in a freestanding house?

Are you concerned with sound leaking from one room to the next or just to the neighbors?

Sound control is hard stuff. I dont think there are any shortcuts. Some people have used a heavy limp mass roll (I forget what it's called) in thier wall construction - that might be an option, but it's very expensive.

The stuff thats proven to work in studios & home theaters is all pretty basic, easy to do, easy to understand why it works kind of stuff.

Unfortunately, I think you may need to decide between floor space and sound control. I know this is a tough choice- 13 feet is not very much, removing 5 or 6 more inches is hard to imagine.

The other thing you need to consider are the other walls, the floor and the ceiling. If you just double wall the one exterior wall, that will help some, but low freqency is still going to get out via the other walls.

How important is the sound isolation?
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