John Sayers' Recording Studio Design Forum

Just to put that in perspective, the very best, top, multi-million dollar studios in the world aim for that type of isolation. That's really hard to do for a small facility on a limited budget. 85 dB is a LOT if isolation. Most folks here are happy to get 50-something, really happy to get low 60's, and wildly, ecstatically, dizzily happy if they even get close to 70.

An average house wall of 2x4 studs with drywall on both sides will get you around 30. To increase that to 50, you need to absorb 100 times as much energy. To get 60, you need to absorb one thousand times the amount of energy. 70 means ten thousand times the energy, and 80 means that your walls floor and ceiling will need to stop one hundred thousand times more energy than a normal house wall. That's a LOT of energy that you need to stop! It can't be done with simple, low-cost methods, and requires some construction materials and techniques that are beyond the ability of the average DIY studio builder.

So I'd shoot for something more reasonable, such as maybe 60-something. That is doable on a reasonable budget with common techniques and materials. It is an attainable goal.

Yes, 30 dB is the equivalent of a soft whisper a few feet away, but you'd need to be in an extremely quiet environment to even hear something so quiet! Such as maybe the middle of a windless desert, or inside an anechoic chamber... Ambient noise is way higher than that in most towns and cities, even late at night. With a TL of 65, for example, your PEAK level will be down to 50 dB, and your AVERAGE level down to around 40, which should be plenty good enough, even for stringent noise restrictions.

To get a better idea of what you are dealing with, I'd really suggest that you get a sound level meter and do some real-world tests. A decent meter is not expensive, and goes for about US$ 50 to US$ 100 on e-bay, Amazon, etc. It's also a useful tool to have around anyway, for any sound guy or musician.


- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

Thank you Stuart - for the clarification on cleats...GG....and the links on ventilation.
Thank you too for the db info...I will certainly get a monitor...that's clearly the way to go.

Alas, I have also realised a significant problem in the meantime.
Running between the joists that are above the music room is an aircon (heating) duct that starts under the middle of the house (where the heating system is) and runs to a vent at the front in the floor of the living area by the windows at the front.

If I remove this duct, my ability to keep the living room warm will be significantly reduced...I can do it...but I'm not going to be liked for it!

But if I leave it in place....at worst,

Scenario 1: I won't be able to get any beefing up between those two joists - which going by the principal that one 'gap' in the isolation system negates all the rest...is a tragedy and effectively means there's no point beefing up any of the space between the ceiling/floor joists....

Plus that aircon duct is going to faciliate noise transfer into the living space above...just what I'm trying to avoid!

Scenario 2...there may just be enough space to beef up the gap between the joists and let the duct run in the air-gap/insulated gap between the inner room and the outer room...but I assume that if I do that, then I am still going to get significant noise transfer, along the duct, into the living room...again negating the benefit of the 'beefing'.

Both these scenarios basically make the Inner room isolation pretty much the only isolation against noise travelling into the living room.

What are your thoughts?

Do I just HAVE to remove the air duct and live with the heating problem?

Or can I do something with it (it's a 10" flexible duct) to minimise the noise transfer along it - NB it is a heating duct not an aircon duct - this means it has to be wider as the airflow is slower than in an A/C system.

If I leave it in place, is it still worth doing the beefing up between the other joists...

OR do I just go mad with the inner room and do three or even four layers etc?

What a shame!

Thank you as ever.

P

The normal method for dealing with problematic ducts like that is to build a "soffit" around it, that remains part of the outer leaf. That basically means boxing it in with drywall that is attached only to the floor above. Fill the gap between the duct and the drywall with insulation.

Yes, it will compromise your isolation a bit, but it doesn't have to be a big deal, if you box it in well. You won't lose that much.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

So not so much of a disaster! I get it - with this box construction around the duct I will effectivley have a mini 3 leaf system - inner room (leaf) - airgap - box (leaf) - duct - floorboard (leaf) - but because it is just a small part of the overall structure - not too much of a problem.

Thanks Stuart.

As a matter of interest - when I do the beefing up - do I try and get the extra drywall BEHIND the duct and onto the floorboards above - so that the joist/drywall mass is even all the way across the ceilling..... (and then put a bit extra in to box the duct) - image 1 on attached jpg... or

Do I beef to the floorboards between all the other (non duct carrying) joists...and box in the duct with the equivalent 2-3 sheets attached to the joist image 2 on attached?.

Thank you (I presume it's 1. recognising that this will lower my headroom probably - but that's ok!)

P

I'd go with 2.

Perhaps you could also add a bit of light loose insulation around the duct.

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Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

Yup, I'd go with #2 as well. And also with plenty of insulation in the gap.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

You still attempting to make this build in an elevated wood structure Peter?

Because if you are, I have a few documents you want to look into. As stated before, there are far too many issues in this type of build that a ground level build does not have.

And the issues are not going to be what you "google" or what even some of the most well intentioned might say on the Internet. In my on-going attempt at writing a book on construction for audio purposes, your room, a room in an elevated wooden structure that is part of the residence...on a scale of 1 to 10, 10 being the least desirable choice, this one is at number 8, right after a wooden framed floor structure at ground level in a typical residence/home and right before a thin metal sheathed shed with a concrete floor but minimum floor space.

I'm just saying, this is not something that will transfer if you look at the numbers that might be given for a supported wall assembly on concrete damped by Earth transposed to an upper level wooden structure.

You have to, simply have to get educated or your about to blow a wad of cash on something that may or may not give you anything.

We have seen it before recently.

Good luck.

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Brien Holcombe
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Sound: You can't stop it, you can only try to contain it.

No, he's building it in his basement, on a slab, but with a wood framed floor above him. The problem is that he has about three or four threads going at once, in different areas of the forum, with different questions in each one. So it's a bit hard to follow and keep track of all the parts of the basic plan! That's probably why you thought it was an upstairs build, Brien. But fortunately, it's a basement build, and the issue he's talking about here is a problematic HVAC duct up between two joists in the floor above where the room is going to be.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

Thanks for the clarification - and appologies once again for my having started separate threads with separate questions earlier.
Is it possible for you to simply delete the threads other than this one - for clarity?
I am so grateful for the help - I don't want to be making things difficult for those people who are trying so hard to help me!
P
PS Thank you for the comments re boxing in the duct (and for putting up with my hand/mouse drawn pics!).
When you talk about putting insulation in with the duct - are you talking glasswool/batt style insulation or a more solid foam kind of product?

Naah, not a good idea to delete the threads: they are good questions, and might be useful for others, years from now. But maybe you could choose one of your threads to be your main one from now on, then edit your very first post there to add links to these other threads (and on each of the others add a link back to your main thread): That will help to keep things neatly tied together.

Don't sweat it!

Ordinary pink fluffy fiberglass is fine. So is mineral wool. The purpose is just to provide a bit of damping on possible resonance in the cavity, and also to reduce the levels a bit.

Solid foam doesn't have much use in acoustics: most types are closed cell (you need open cell for acoustics), and the more solid it is, the more it conducts sound. So pretty much all references to "insulation" on the forum are about plain old fiberglass or mineral wool.


- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

Ok - thanks to this lovely forum I have now had the chance to look at lots of different people's solutions and designs for ventilation that I can do my best to emulate...they clearly vary in terms of size...the number of baffles....and then more sophisticated things to do with air entry/exit opening sizes etc...

But I still have a couple of fairly basic questions...

1. Looking at the pic below (which is a relatively small build) - I am still finding it hard to see how, having created lets say 5 layers of plasterboard in two leaves...with not a single air gap - to mimimise sound transfer from inside the inner room - to outside the outer room....if I then build two air ducts (albeit with a couple of twists and turns for the air) that are 6" or so across - then surely I am going to massively undermine my sound isolation?? Or am I missing an obvious bit of physics here??

2. I haven't managed to work out what people are doing to make sure that the ventilation system doesn't effecitvely become a 'contact' between the inner and outer rooms. Stuart was kind enough to reply to a PM of mine re electricals that said On the electrical cable: Yes, it does have to touch both, but it isn't really a problem. Use PVC conduit for that cable, and angle it vertically or horizontally over a couple of feet between the two leaves (on other words, where it comes through one leaf, put a 90° curve so it runs parallel to the drywall, run it a couple of fee then put another 90° curve so it can go through the other leaf. Then cut out a section in the middle, an inch or so long, and wrap that gap with a trip of soft flexible rubber, to de-couple the conduit from both leaves. The wiring itself won't flank much. When you have it wired, stuff a small piece of insulation into each end of the conduit, then put a db of caulk over that, to seal it. The key to good isolation is to seal EVERYTHING! Both leaves must be totally air tight. Is there something equivalent I should be doing with the ventilation ducts?

I am assuming that these silencer boxes will be located between my inner and outer rooms...and physically attached to the inside of the outer wall? The fan could be inside too - but I imagine it will be easier...and smarter from a maintenance persepctive, to locate the fan on the outside of the outer wall...in an adjacent room - where I can get at it if it fails! But at the point where the duct (solid or flexible) meets the inner room wall, it will have to be fixed in place?

3. Just an aside - just in case there are any Aussies reading this fab forum - do you know a good place to get the lining duct for ventilation boxes that is mentioned widely on this site - is it a plumbing supplier? And what about those backing rods used when beefing up walls - any suggestions on suppliers down under?

Thank you once again

P

Ok, you say basement, but peter has mentioned once, a rehearsal room on an elevated wooden floor and second a brick house...I have not seen the word basement.

So peter...could you clarify for me at least since each type of structure has its own known issues and methods to overcome and some known "live with its", what type of structure(where is the room located) is it you are actually trying to do this build inside of?

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Brien Holcombe
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Sound: You can't stop it, you can only try to contain it.

Hi and thanks for keeping an eye on the thread.
Yes it is definitely NOT an elevated structure....it is the lowest level of a 2.5 level house built on a hill (there's a picture in an earlier post).
The music room sits on the concrete slab.
The main living area is directly above (it's a timber framed, brick veneer construction)
The sleeping area is above and back...you can crawl over the retaining wall at the back of the music room, up the hill (the house is on piers at the back) - to the area under the bedrooms.
P

If you have settled on this thread to be the main one, then maybe you could let us have some pictures of all these things you discuss, you know what they say...a picture speaks a thousand words.

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Brien Holcombe
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Sound: You can't stop it, you can only try to contain it.

Sure - all the pictures are on this thread - here's the main one again....it says it all - well most of it!
Thanks again.
P