John Sayers' Recording Studio Design Forum Archive

So I’ve worked out I need about 50db isolation for my studio I’m building in my garden.

Just deciding to go with a double stud wall type or single wall and RISC-1 clips.

What I’d like to know is, what’s the best choice for insulation like rock wool for example, what density should it be?

I’ve seen quite a few products at specialist acoustic websites for sale where they sell stuff they say performs better than most insulation. Is this to be avoided? Or can you get good results without their special insulation.

Uk based here.

Thanks for any help

Once again, sound waves don't care about exotically named materials, or exorbitant price tags. When it comes to porous absorption, they care about basically one single thing: acoustic impedance. That's a number that measures how much the porous material interferes with the passage of the sound wave. One way of measuring that is with something called "Gas Flow Resistivity" (GFR). It's basically the relationship between how much air flows through the materials for a certain applied air pressure. Some manufacturers do measure that, and publish it. Others don't. If you can find that number for the insulation you are looking at, then you can see if it is useful for the purpose. If you can't find that number, then there is a very rough relationship between GFR and the density of each type of insulation: If you are using fiberglass insulation, then you would need something with a density of around 30 kg/m3. If you are using mineral wool insulation, then you need something with a density of around 50 kg/m3.

Related: it would be much better to keep all your questions about your build together in your own thread about your build. Spreading them all around the forum makes it much harder for you (and others) to keep track of what you asked, and what answers you got. It also makes it much harder to see the context of your question, in relation to the rest of your questions, and to the design itself.

specialist acoustic websites for sale where they sell stuff they say performs better than most insulation. Is this to be avoided?

Yes! Definitely avoid those places! There are no magical materials: all materials must follow the laws of physics. If someone makes a claim that sounds too good to be true, then take it for granted that it is too good to be true. Reputable manufacturers have their products tested in independent acoustic test laboratories, then they publish the results openly, and the results speak for themselves. If you find a product that has no published independent tests, then RUN! Drop that product like it was a ticking bomb, and run. Instead, look for antoher one that actually does work...

- Stuart -

Ah my apologies for starting a new thread. I thought it was a new question but makes sense what you say.

Thanks for the info about the density.
Will keep things into my own thread now.

Does it matter what type of sheetrock you'd be using in this situation? Does that help to dull the sound waves as well as the insulation? I know that there are types of drywall boards that reduce the amount of sound (like the ones at this site [SPAM LINK REMOVED]) getting through for example.

Thanks in advance for your help.

P.S. I think it's called quiet rock?

Giroguy2000 wrote:Does it matter what type of sheetrock you'd be using in this situation?

No. The TYPE does not matter. The MASS is what matters. The surface density is the key issue. Materials with higher surface density attenuate sound transmission better than materials with lower surface density. Materials with teh same surface density will always attenuate sound transmission in the exact same way, regardless of brand name or price tag.

Does that help to dull the sound waves as well as the insulation?

The insulation by itself does not attenuate the sound transmission much at all, actually. It acts to damp the resonances inside the wall cavity, mainly, as well as reducing the speed of sound in there, and also changing the way air deal with heat from adiabatic to isothermal. Those are the things that have the greatest impact on the MSM system.

I know that there are types of drywall boards that reduce the amount of sound ... getting through for example.

All types of drywall reduce sound transmission in exactly the same way, purely according to the mass. There are not magical materials that somehow beat the laws of physics. It is the mass of the drywall that governs isolation, not the brand name, rice tag, or the volume of spam spewed by the manufacturer or seller of a dubious product. All materials work in exactly the same way, and all materials of the same mass will produce the same reduction in transmission. Spam does not make them more effective: it just annoys people.

(like the ones at this site [SPAM LINK REMOVED])

Well, that spam link didn't last very long, now did it?

P.S. I think it's called quiet rock?

You mean the extremely expensive stuff that offers no real advantages over normal cheap drywall, when you compare samples with identical surface density? Is that the product you are referring to?

And strangely enough, the place that you linked to does not even mention the product you suggest we should look for over there! Very curious.


- Stuart -