What Kind of STC to expect from this Wall

[diogodasilva]

Hi guys,

I have a wall here in my room which I need to improve isolation as it is too prone to flanking noise.
This is an apartment on a 22 story building and I am right in the middle 11th floor.

When playing high SPL's I find the walls vibrates a lot on low frequencies and flanking noise is impacting specially the room below, on apartment 10.

The walls are made of hollow-block ceramic tiles and sand plaster on the walls, very common in Brazil.

My idea was to add a layer of insulation and double dry-wall with green glue to help dampen the vibration and reduce the flanking noise to the floor bellow.

Here is a sketch of the final installation.

Any idea if this will work?

[Soundman2020]

Any idea if this will work?

It won't work, because there is still a direct flanking path: your studs are attached to BOTH leaves, an therefore you have flanking. You would have to decouple that in the normal manner to get any useful increase in isolation... then you would have to deal with the ceiling, the floor, the doors, the windows, the ventilation system and the electrical system as well, if you wanted really good isolation.

- Stuart -

[diogodasilva]

Any idea if this will work?

It won't work, because there is still a direct flanking path: your studs are attached to BOTH leaves, an therefore you have flanking. You would have to decouple that in the normal manner to get any useful increase in isolation... then you would have to deal with the ceiling, the floor, the doors, the windows, the ventilation system and the electrical system as well, if you wanted really good isolation.

- Stuart -

Hey Stuart! How you've been?
Thanks for getting back on this.
The other walls are pure concrete and do not vibrate even with a hammer punch I guess they are structural to the building and so they are reinforced with iron rods and heavy concrete.

The back wall is the real issue.

But I have a concerning question.
How to decouple the studs if this is a lightweight metal construction it won't support itself.
I've seen wood framing wrapping all 4 walls and ceiling do that but is it possible to do that with lightweight metal profiles?

Since I don't have the space to spare and build a complete room within a room wood structure that supports itself, maybe the use of resilient channel or genieclips on the drywall would help flanking?

[diogodasilva]

For the ones interested.
This article was particularly revealing considering the topic
http://www.jhbrandt.net/wp-content/u...4/11/ir586.pdf

From what I gather it will be close to impossible to achieve better isolation for low frequency response considering the limited space I can spare for a massive construction or bigger air gap.

Since isolation within my own apartment is not a concern (I only worry about neighbors below and above) The resonation caused by the new wall will suffer to great extends and will actually vibrate more than a bare wall such as mine.

I migh as well just treat the room for a proper acoustic response and leave the shell as it is?

[diogodasilva]

Any idea if this will work?

It won't work, because there is still a direct flanking path:
- Stuart -

Maybe something like this to isolate the metal studs from the masonry wall:
http://www.kineticsnoise.com/arch/pdf/aa001954.pdf

[diogodasilva]

Stuart
I found another info on one of the resources articles:

"Nonload-bearing metal studs are sufficiently resilient and do not improve with a resilient channel."

http://www.jhbrandt.net/wp-content/u...on_Control.pdf
Page 4-6

Wouldn't this mean that the lightweight metal stud I am using to frame the partition drywall is resilient enough?

[diogodasilva]

Some sketches.

[diogodasilva]

Here is an interesting info I got from the Green Glue Company regarding testing with metal studs, wood and RC channels.

"When compared directly to wood stud constructions steel studs tend to provide higher base levels of STC. Just to give you an idea here are few tests that we have conducted.

Screen Shot 2016-02-25 at 07.47.26.jpg

Resilient channel will add some performance to steel studs, but it is not as large of an improvement as compared to a similar upgrade on wood stud construction."

Seems safe to assume metal studs outperform resilient channels ?

[Soundman2020]

You seem to be complicating this whole thing way beyond what is necessary. Why can't you just move the inner-leaf wall a couple of cm away from the outer-leaf wall, so they are no longer touching? That's all you need to do. That is the normal, common, proven, tested way of building a fully-decoupled 2-leaf MSM acoustic isolation wall.

But I have a concerning question.
How to decouple the studs if this is a lightweight metal construction it won't support itself.

Why not? Is there something wrong with the metal framing that you buy in Brazil that makes it extremely weak, unlike metal framing in other parts of the world? I don't understand why you think Brazilian metal framing will not work the same way as metal framing works elsewhere. What gauge is the metal used to make Brazilian metal framing?

Steel_Framed_House_05.jpg

Steel_Framed_House_02.jpg

If it works for entire houses, why would it not work for one simple non-load-bearing wall?



- Stuart -

[diogodasilva]

You seem to be complicating this whole thing way beyond what is necessary. Why can't you just move the inner-leaf wall a couple of cm away from the outer-leaf wall, so they are no longer touching? That's all you need to do. That is the normal, common, proven, tested way of building a fully-decoupled 2-leaf MSM acoustic isolation wall.

- Stuart -

Sorry!
I am missing the detail on how to construct the wall in such a way it will support itself and not fall over.
If I can't fix the studs on the existing wall how can the wall remain upright?
Can it be screwed into place using the ceiling and floor ?
Or that will also be a problem?

[diogodasilva]

What gauge is the metal used to make Brazilian metal framing?

If it works for entire houses, why would it not work for one simple non-load-bearing wall?
- Stuart -

Our profiles gauge is 0,5mm or equivalent to Gauge #24

[Soundman2020]

If I can't fix the studs on the existing wall how can the wall remain upright?

You attach it to the OTHER inner-leaf walls, and the inner-leaf ceiling. Since those are all at right-angles mutual to each other, they provide the support to keep things together.

Of course, if you don't plan on building the other walls and ceiling, then you have a problem. But on the other hand, if you don't plan on doing the other walls and ceiling, what's the point of doing anything? Isolating one single wall of a room is like trying to build an aquarium with only one pane of glass....

I've seen wood framing wrapping all 4 walls and ceiling do that but is it possible to do that with lightweight metal profiles?

If you can do it with wood framing, then you can also do it with metal framing.

Since I don't have the space to spare and build a complete room within a room wood structure that supports itself, maybe the use of resilient channel or genieclips on the drywall would help flanking?

If you don't have the space to build a proper room-within-a-room, then you don't have the space to get good isolation. You cannot get around the laws of physics by hoping they will go away! Either you sacrifice the space you NEED to get the isolation you WANT, or you don't get the isolation. It is that simple. There are no magic products, materials or techniques that defy the laws of physics. Acoustic isolation REQUIRES space, and mass, and damping, and decoupling. If you don't have that space, or don't want to add the mass or damping or decoupling, then you cannot get good isolation.

From what I gather it will be close to impossible to achieve better isolation for low frequency response considering the limited space I can spare for a massive construction or bigger air gap

Correct.

Maybe something like this to isolate the metal studs from the masonry wall:

That will provide LIMITED decoupling, yes... but how do you plan to attach the ends of that wall to the side walls and to the ceiling? And how do you plan to stop the flanking noise that is already in that wall from getting into the OTHER walls of the room and the the floor, and the ceiling? Your new wall would reduce some of the airborne sound that is being radiated by that wall, but will do nothing at all to reduce the structureborne sound that it is passing on to the walls on each side, and the ceiling, and the floor.... That's why you need a proper room-in-a-room.

"Nonload-bearing metal studs are sufficiently resilient and do not improve with a resilient channel." Wouldn't this mean that the lightweight metal stud I am using to frame the partition drywall is resilient enough?

Your link does not work: it does not go to a PDF. The claim is also strange, since it does not agree with laboratory test results, or theory. In any case, even of that were true, it would not apply in your case since your proposed method does not allow your metal studs to act resiliently...

Your floor plan is fine: That should provide a little extra reduction in sound transmission.

Your ceiling plan will probably also work reasonably well.

... provided that you also solve the wall problem.


- Stuart -

[diogodasilva]

... provided that you also solve the wall problem.


- Stuart -

Hi Stuart.
Yeah, I am convinced I can't have it all. It will be best to live with the limitations of volume and treat the room properly than to invest all the budget on isolation only to realise later that wasn't even on par with expectations.
I am following the construction and treatment on this thread http://johnlsayers.com/phpBB2/viewtopic ... 89#p138589
Thanks again for taking the time to shine some light on this .
Really appreciate it.