Green Building Forum - Sound proofing

Sound proofing

Beau — Sat, 07 Jul 2012 17:36:33 +0100

I am in the process of building a large sound proof enclosure for some industrial machinery.
This is the intended build up from outside to inside.

11mm OSB
140mm CLS with 100mm acoustic wool in between CLS
Resilient bar
Sound block plasterboard

Would MDF work in place of the acoustic plasterboard? The look does not mater but the improved impact protection would be a big bonus.

Sound proofing

TimSmall — Sat, 07 Jul 2012 21:38:40 +0100

Using a mix of materials is generally a good idea, so MDF or OSB over 9mm plasterboard might be a good idea (joins unaligned). You'd also be better off using 2x sets of slimmer studs, staggered (inner skin attached to one, outer skin to the other) , so that there is no direct sound path through the studwork.

Sound proofing

TimSmall — Sat, 07 Jul 2012 21:40:48 +0100

ISTR that "sound on sound" magazine had some good articles on constructing a home studio which are available on the web. Openfaced rockwool is a good sound absorber. Standard rockwool cavity batts are nearly as good as the acoustic batts (just use 30% thicker).

Sound proofing

TimSmall — Sat, 07 Jul 2012 21:41:14 +0100

Search good for Room - in - room studio design.

Sound proofing

Beau — Sat, 07 Jul 2012 22:06:43 +0100

Thanks for the link Tim. I will have a good read through.
I should have mentioned that this enclosure is made in sections that are mounted on wheels to enable access to the machine. This I think will make the double frame idea difficult.

Sound proofing

SteamyTea — Sat, 07 Jul 2012 22:52:26 +0100

Had to make some acoustic enclosures for compressors once. The cover was GRP, seems to remember that it was a 600g/m^2 layup, then 50mm of a foam material, was rigid, brittle and open cell, not so different from that stuff that flower shops use but bigger 'bubbles' in it. On top of that (on the inside) was hardboard with holes in it, about 50mm diameter with 30% coverage (leaving 70% hardboard). I assumed it worked as they asked for several after the first one was made.
Not sure how it would perform in a fire, but did use Class 'O' resin.

Sound proofing

tony — Sat, 07 Jul 2012 23:57:20 +0100

why not build a concrete block wall? heavy = good sound deadening = heavier the better, dont forget to seal all gaps

Sound proofing

Beau — Sun, 08 Jul 2012 07:46:34 +0100

Posted By: tonywhy not build a concrete block wall? heavy = good sound deadening = heavier the better, dont forget to seal all gaps

Could prove difficult to move the frames around Your point about sealing is something I will be doing but sadly I have to have large holes where the materials go in and the product comes out, these will have plastic strip curtains but I know this will be a compromise.

ST
I think the acoustic foam is the same density that you are suggesting. I have read about perforated inner skins but the machine makes a lot of dust so I am worried that this will collect in the frames creating a fire risk. I have already made up most of the timber framing and the external layer of OSB has already been bought so the area that I can still change direction on are the acoustic filling and the inner lining.

Sound proofing

SteamyTea — Sun, 08 Jul 2012 08:35:34 +0100

Glue perpendicular strips of timber, plasterboard, anything that is kicking about, randomly on the inside of the outer face. Then use a thin rubber sheet stretched and tacked for the inner.
No idea if it will work other than a hunch.
Dealing with the dust is another problem, would need a large extractor, so more noise
May I ask what the process is? Actually I have asked

Interesting article:
http://www.newscientist.com/article/mg20928011.200-sonic-doom-making-a-sound-barrier.html

Sound proofing

Beau — Sun, 08 Jul 2012 09:09:32 +0100

Thanks for the ideas so far.

I am afraid off cuts and bits kicking about won't go far as the enclosure is 4m x 4.1m x 12m
I would rather not say too much about the process at this stage.

I have suggested that an expert in sound control should have been used at the design stage but my friend just thinks this would involve a large bill to come up with the same plan so I am a bit out of my depth unless building a few kit Hi Fi speakers 10 years ago counts

Sound proofing

Timber — Sun, 08 Jul 2012 10:21:01 +0100

How much sound do you need to stop? I used to do this sort of thing quite regularly. Getting a BS 4142 assessment might cost some money, but if there is a chance that someone might complain about the new noise source, this is the right thing to do.

The plant will need some sort of cooling air in or out etc. This will be the most likely source of noise breakout, so figure this bit out first. Attenuated louvres or a labarinth type attenuator would be the way to go normally.

Sound proofing

Beau — Sun, 08 Jul 2012 10:36:28 +0100

Posted By: TimberHow much sound do you need to stop? I used to do this sort of thing quite regularly. Getting a BS 4142 assessment might cost some money, but if there is a chance that someone might complain about the new noise source, this is the right thing to do.

The plant will need some sort of cooling air in or out etc. This will be the most likely source of noise breakout, so figure this bit out first. Attenuated louvres or a labarinth type attenuator would be the way to go normally.

Thanks Timber
I think the sound proof enclosure is not legally required so anything it does is a bonus but without it I think it will be a pretty nasty place to work. As for cooling there are two ideas being discussed.
1 Ducted air being drawn in from outside and vented back outside.
2 Maybe a Air-Con unit mounted within the enclosure

" Attenuated louvres or a labarinth type attenuator would be the way to go normally." Sorry what do mean?

As I have said I am out of my depth but they are not prepared to pay for expert advice so I am muddling through as best I can with a bit of help from my friends

Sound proofing

TimSmall — Sun, 08 Jul 2012 12:20:16 +0100

If you have to have "straight-through" holes in the enclosure, then you need to concentrate on absorbing the sound inside it (otherwise the sound will just bounce around inside the enclosure, and then come out the holes) - e.g. 100mm open faced rock wool, covered in fine fibre glass mesh. You can also get sound absorbing tiles on eBay etc. - bit more pricey than the rock wool tho'.

Sound proofing

Beau — Sun, 08 Jul 2012 12:37:59 +0100

Thanks Tim
I have been torn between containment and absorption. Most of the absorption products are expensive but if I use a perforated internal layer with mineral wool behind we have the problem with dust lodging in the enclosure

Sound proofing

TimSmall — Sun, 08 Jul 2012 12:58:14 +0100

Face the rockwool with a thin layer of open-faced acoustic foam? A thin layer of polythene or PP would probably also do the trick (this is what acoustic ducting uses for the same reason). A plastic bag is pretty sound transparent...