Isolating a room - typical 90's C. European, suburban house

BorysP · Post by **BorysP** » Mon Mar 18, 2019 2:27 am

Hello Everyone,

I'm drawing plans for a remodel of a large house and as part of it I want to construct a mixing+live "one room" type studio with an added iso booth and large iso boxes (depending on final design of the space either within this one bigger room or in a different part of the house).

I am going to eventually have complete drawings, material lists etc. for the two main variations of the yet to be studio space (based on further information gathering and calculations I will choose the most optimal variation last minute after other construction work starts and I can survey the building better) and I am hoping to discuss it with you guys and then report on it as I actually attempt to build it. It's always nice to have someone to bounce ideas off of, even if they have a different opinion on the optimal approach.

Anyway, solving the various problems alone is making it incredibly time consuming to actually arrive at a complete set of drawings so to speed it up I wanted to start this thread where I can ask isolated (pun intended) questions before I present more drawings and information and we can think about it in a more complete fashion. I hope that is ok with everyone!

So to start off - this is wrecking my brain and I can't move onwards to save my life:

The outside walls are (layers from out to in): plaster on a layer of glue and reinforcement grid / 15cm styrofoam insulation / 25cm Porotherm (ceramic or clay type of large brick with cavities inside) / 2-3cm of plaster with paint.

The target room has 3 windows and if I go with the variation that includes a much bigger part of the house there will be even more windows involved!

What I wanted to do in general was either:

A) Change current windows to thick framed aluminimum windows intended for passive homes with an "acoustic glass pack". These windows have normally 2 cavities and 3 panes of glass but the acoustic pack has from what I understand a thicker outer pane + some sort of foil applied or the outer most pane is actually made of two panes with foil sandwiched in-between.
Anyway, reduction is promised to be up to 45-47 dB weighted depending on manufacturer - I have no idea if these count as a three leaf design and thus prone to a possible issue or not.

And thats it for solution A - ofcourse improve air seals, improve leafs that are worse than this outside wall (dividing walls, ceiling etc).

B) Do everything from A (will be done in all of the house eventually anyway) but also build an inner leaf for all the walls of the current room. In this leaf have a thick pane of glass in places where there are windows in the outside wall.

This inner leaf would be made from 12.8kg/m2 gypsum board / damping material of some type / 12.8kg/m2 gypsum board. It would be hanging on something aking to the RSIC clips and hat channels sold in the US (I have yet to find proper solution that I can buy over here) an air pocket away from the outer leaf.

C) Do everything from A but add an additional pane of thick glass on the inner edge of the window openings. Unlike with plan B this would be removable but otherwise properly gasketed and no expensive inner leaf.

So:
Considering this is one floor up and I can't make some sort of heavy floating floor, just a dampened floor and that I would need to add inner windows to any possible inner leaf.
Is there any point in pursuing plan B?
Data for a 2 gypsum board leaf of this type (without inner damping included) shows that it would add about 13 dB weighted reduction tops - I could not find any actual data, just a single weighted value.

The building is free standing, but neighbouring houses are very close, 8m away from mine. I want to limit outside noise hopefully to be able to do some tracking but more importantly at least make it possible for acoustical instruments to be played inside without being tarred and feathered.

Btw. I initially considered sandwiching Tecsound 50 (similar to typical MLV sold in the states but has better fire rating) inbetween the boards for the leaf but I read on this forum that this is a stupid idea (can't say I fully agree or understand the points about it losing it's spring effect when sandwiched between two boards).
I can get the Tecsound stuff for not that much more than green glue over here and it adds another 5kg/m2 so is it really such a bad idea?

In USD terms I can spend say 10k, maybe 15k on that inner leaf not including top floor layer, inner windows, doors for the sound lock etc.
I could live with that sort of expense but will it be worth it in human terms?
What is the real reduction I can get from option B considering there will be windows in that leaf and the ceiling part of it will not be a continuous mass like the wall leaf and definitely reduce a bit less (difficult to explain, will provide drawings later on)?

The rest of the house is not bothered by the noise, it's a matter of isolating against noise from outside the house to allow at least some tracking and allowing say a trio of acoustic instruments including a drum kit to play inside without the community hanging me from a low branch immediately afterwards.

DanDan · Post by **DanDan** » Mon Mar 18, 2019 3:36 am

City, Town, or Rural? The level and type of ambient noise is a big factor.
If you don't have one, get a Sound Level Meter. With a computer the UMIK-1 and REW make a whole acoustics laboratory.
But a Smartphone with a decent Mic is very portable. Use C or Z Weighting to see the full spectrum.
Borrow a small PA and play some music in your space at a level high enough to simulate say a drummer or small band.
Measure and listen out and about.

DD

BorysP · Post by **BorysP** » Mon Mar 18, 2019 7:43 am

DanDan wrote:City, Town, or Rural? The level and type of ambient noise is a big factor.
If you don't have one, get a Sound Level Meter. With a computer the UMIK-1 and REW make a whole acoustics laboratory.
But a Smartphone with a decent Mic is very portable. Use C or Z Weighting to see the full spectrum.
Borrow a small PA and play some music in your space at a level high enough to simulate say a drummer or small band.
Measure and listen out and about.

DD

I will be doing measurements and modelling (ratios, treatment) etc. however I need to narrow down the general concept asap so I can start other construction which is holding up the studio and other work in the house.
Many things will change in the building including an hvac system for the whole building, new windows, sealing of cracks and other openings, redoing roof insulation etc.
I had a whole set of plans, special dispensation from the ministry if you can believe it to do something alternative to code in order to redo parts of the building but got dicked around and effectively screwed over by one dishonest general contractor after the next, lost 3 years of my life, a lot of money and nothing came to pass so I now need to rush and decide on a few key points so that I can finish designing an alternative and in turn start fixing up the building before it suffers more wear and tear.

It's a Suburb of a medium sized city (about 1M people), there is little constant noise but a lot of momentary noise including various birds, trucks hitting speed bumps now and then, various clanging and other such noises from buildings being worked on, church bells and such.
For a lot of the momentary noises I doubt any isolation apart from something above 70 dB would do me any good and there is no chance in hell I'll get that much so it's more about possibly making them less annoying rather than allowing acoustical tracking while they happen. Most of them are limited to morning hours.

I would guess the ambient noise during the calmer hours during which I would mostly use the space is probably ~43 dB.
In terms of noise I would produce it would be mostly from the Dynaudios M1.5 (I think specs are around 115spl at 1.25m) most of the time which would involve mixing and also monitoring what is going on in the ISO boxes/rooms holding the amps. I do all of that at comparatively low levels, I doubt more than 80dB in a typical situation.
For playing or tracking percussion instruments it's impossible to measure really and I would say it makes not a lot of sense, a loud crash cymbal or a djembe slap can be insanely loud but a marimba is a whole nother story.

What I am trying to figure out is how much isolation I can really expect in scenario B.
I would imagine scenario A would give 42 iso and scenario C could maybe bump it up to whatever the wall can do, maybe 45?

As a general aside: It's a whole different situation in Europe overall compared to the US - we don't have any frame construction except passive and zero energy homes which are expensive and there is no expertise or materials on hand to build just typical US style economical frame structures. Almost nobody understands the principles properly and there is no good source for material on the cheap.
Hence all the wealth of the US community is made sour by the fact that we do everything differently here and building a frame building of any sorts would be a luxury, not a common sense thing to do hence why various expensive to the US consumer materials and techniques make sense here.
Import duties and a crushing VAT make stuff like green glue twice as expensive as it is in the US for instance.

Thanks for the UMIK-1 tip off, is that better than the value solutions from years past?
I have some nice clean preamps and some quality omnis too but I guess at 75 USD it sounds like a great deal if it's actually calibrated.

AVare · Post by **AVare** » Mon Mar 18, 2019 9:07 am

borysP wrote:B) Do everything from A (will be done in all of the house eventually anyway) but also build an inner leaf for all the walls of the current room. In this leaf have a thick pane of glass in places where there are windows in the outside wall.

This inner leaf would be made from 12.8kg/m2 gypsum board / damping material of some type / 12.8kg/m2 gypsum board. It would be hanging on something aking to the RSIC clips and hat channels sold in the US (I have yet to find proper solution that I can buy over here) an air pocket away from the outer leaf.

Place damping material in the air pocket. If you build it separated from the outer wall the RSIC etc are not needed.

Andre

DanDan · Post by **DanDan** » Mon Mar 18, 2019 9:37 am

LOL, it's not all about you! If it is a pretty quiet suburb out there, they will hear you. Drumming in particular, without other instruments audible, would be particularly annoying.
Any good omni is fine with REW. The UMIK advantage is that it is USB and comes with a Cal File. The Cal File is pretty good in my experience, making the mic in effect really flat.
I tested a couple of samples and found the absolute SPL to be 1.8dB off, compared to Bruel and Kjaer Meter and Calibrator. This was consistent with different UMIKs so something amiss at the factory. But it was consistent, so I wrote a correction into the Cal File. They seem to have discontinued the PMIK, which is really good with the iPhone.
I have seen Stuart recommend the little W Mic for that job.

What Country are you in? As Andre said a separate stand alone studded wall does not need resilient clips and such. Data I have seen says that Metal studding has benefits over wood in terms of increased isolation. Also note well his recommendation of fibre to damp the void.

ISOVER.png

DD

BorysP · Post by **BorysP** » Tue Mar 19, 2019 1:37 am

AVare wrote:
borysP wrote:B) Do everything from A (will be done in all of the house eventually anyway) but also build an inner leaf for all the walls of the current room. In this leaf have a thick pane of glass in places where there are windows in the outside wall.

This inner leaf would be made from 12.8kg/m2 gypsum board / damping material of some type / 12.8kg/m2 gypsum board. It would be hanging on something aking to the RSIC clips and hat channels sold in the US (I have yet to find proper solution that I can buy over here) an air pocket away from the outer leaf.
Place damping material in the air pocket. If you build it separated from the outer wall the RSIC etc are not needed.

Andre

I was thinking of the RSIC type clips in order to be able to hang the inner leaf on the outer leaf and avoid loading the floor but also to have better decoupling.
I could make a free standing, steel frame partition wall (we do that all the time over here so that is not an issue) but what worries me is that even though you always put foam tape (per code) between the boundary channels and the floor/walls/ceiling, those channels touch the main structure on their whole length and have to be screwed in too.
I would also need to make the framing strong enough to support big windows in that inner frame. My windows are ~1.4m x 1.8m in size so that is a massive, heavy pane of glass for the DIY inner window.

I found a UK supplier of genie clips and their furring channel. The clip solution touches just one wall in a number of points and otherwise the leaf would just hang there, completely decoupled from the other walls, floor and ceiling.
Would you say both solutions are similar in terms of decoupling or is the clip one superior at all?
I am removing about 3-4 tons worth of partition walls from the space but the floor is at it's deflection limit already so my plan was to remove those old partitions, avoid loading it with my outer leaf and then have a nice 4ton allowance for heavy QRD panels and other such gubbins.
Everything will be consulted with a structural engineer at the end of my initial design stage but I would generally like to lessen the deflection in the floor - the engineer already said it will straighten up a bit after I remove all that stupid mass.

All of the typical data on the web including the one for filling inside with glass wool assumes outer leaf is of similar mass, also on a frame construction.
Here is where my problem lies - my outer wall is of a completely different type and order of magnitude of mass and I don't know if on account of all these variables, adding a 30kg/m2 inner leaf will be worthwhile.

Assuming the worst which would be the outer wall being only 39dB - if I did everything correctly and made that inner leaf including the inner windows of same mass per m2 as the wall. How much real world isolation could I expect in total?
Any remote possibility of hitting 60dB? I am worried that I will top out around 54dB after all that money and effort.

I just checked and Tecsound 50 (5kg/m2) would cost me exactly the same per m2 as green glue. Any reason to use green glue instead?
I will be buying Tecsound anyway for building limp mass bass absorbers.

AVare · Post by **AVare** » Tue Mar 19, 2019 3:25 am

It is difficult to help you as you add things and change them. These channels that you could use, are they anything like the channels in fig 4 of IR 586 (http://johnlsayers.com/phpBB2/viewtopic.php?f=3&t=21894)?

Andre

Soundman2020 · Post by **Soundman2020** » Tue Mar 19, 2019 4:51 am

Hi Borys, and Welcome!

Others have already commented on your initial post, so I'll just add my own $ 0.02 here and there...

Any remote possibility of hitting 60dB?

Possible, yes, but not easy to do. And expensive. The dB scale is logarithmic, so the higher you go, the harder it is to get one more dB of isolation. So going from 20 dB to 21 dB is a piece of cake, going from 40 dB to 41 dB is quite a bit harder, and going from 60 dB to 61 dB takes a LOT of effort, time, money, skill, materials.

I will choose the most optimal variation last minute after other construction work starts

Take a look at Andre's signature block... It's preferable to have your design totally complete before you start any construction on the building: it often turns out that there's something you'll need to change later, after you already built it.... even if you didn't think it was related to the studio or isolation.

solving the various problems alone is making it incredibly time consuming to actually arrive at a complete set of drawings

Right. See Andre's signature block...

In addition to drawings, I'd suggest you consider creating a detailed model of your studio first, in "SketchUp Make" (the version for your PC, not the terrible on-line version...) It's a lot easier to identify conflicts and problems with your design when you move around it in 3D, as compared to just looking at 2D plans and elevations.

The target room has 3 windows and if I go with the variation that includes a much bigger part of the house there will be even more windows involved!

Windows can be incorporated into a studio, as long as they are done right. If you need high isolation, you will need thick glass in your windows, preferably laminated, preferably with acoustic PVB interlayer, which is expensive. You should work on your budget at the same time you work on the design. You can't cut laminated glass yourself, so it needs to be ordered to the exact size you need. Important to know in advance....

These windows have normally 2 cavities and 3 panes of glass

A 3 leaf window? Not so good for a studio. Potential to have REDUCED isolation in low frequencies.

And thats it for solution A

I didn't see any mention of HVAC: I highly isolated room is sealed air-tight, and also very well insulated, thermally. So you do need a good HVAC system that provides enough fresh air to keep everyone comfortable and healthy, while removing the stale air, and also providing the cooling and dehumidifying the room(s) will need.

This inner leaf would be made from 12.8kg/m2 gypsum board / damping material of some type / 12.8kg/m2 gypsum board.

What is your "damping material of some kind"?

I can't make some sort of heavy floating floor,

Good, because you probably don't need it. You might find this interesting: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

Considering this is one floor up

Getting high isolation on an upper floor is much harder then getting the same isolation on a ground floor room. Any chance you can move the studio down to the ground floor? (assuming that has a slab-on-grade floor....).

[MLV] inbetween the boards for the leaf but I read on this forum that this is a stupid idea

It's not so much stupid, as expensive and unnecessary. MLV is mass. It works the same as any other mass when sandwiched between two layers of drywall, but it costs several times as much. It doesn't really work very well as constrained layer damping, because it isn't!:

https://www.greengluecompany.com/sites/ ... _vinyl.pdf

can't say I fully agree or understand the points about it losing it's spring effect when sandwiched between two boards

Reading the above link might help with that. It doesn't actually have much "spring effect", and that's not what you need in any case.

I can get the Tecsound stuff for not that much more than green glue over here and it adds another 5kg/m2 so is it really such a bad idea?

It isn't comparable to Green Glue: see above. You'd be paying "not that much more" for a product that does far less.

(difficult to explain, will provide drawings later on)

We sure do need those drawings! Understanding what you have in mind is not so easy, especially considering that it seems to be a moving goal! The details change with every new post...

The rest of the house is not bothered by the noise, it's a matter of isolating against noise from outside the house

So there's no noises inside the house that could trash your tracking sessions? No people walking on floors, doors opening/closing, no water running in pipes, toilets flushing, fans, pumps and other motors, people talking, vacuum cleaners, washing machine, radio, TV, furnace.... All of those are potential issues that could get into your mics while tracking...

I will be doing measurements and modelling ... however I need to narrow down the general concept asap so I can start other construction ...

That's sort of like saying: I'll decide on the size of the engine and the number of passenger seats after I buy the car...

It only takes a few minutes and a few dollars to take measurements of the sound levels that you need to know, in order to determine how much isolation you need. It's really hard to design an isolation system for an unknown amount of isolation. There's no place to plug in "general concept" to the equations for figuring out transmission loss, or lowest isolation frequency...

Many things will change in the building including an hvac system for the whole building, new windows, sealing of cracks and other openings, redoing roof insulation etc.

How will you incorporate all of that into your plans, after it is already done, when you find out it needs to be modified in order to accommodate the studio? I've seen that happen more than once: People build something in a hurry, then have to "un-build" part of it once they get to the studio stage, because what is already built is in conflict with what needs to be done to build the studio.

effectively screwed over by one dishonest general contractor after the next, lost 3 years of my life,

If you lost 3 years, then surely it wouldn't be a big deal if you lost a few more weeks to get the design done right, and avoid problems down the line... such as losing even more time and money because you have to tear down something that's not in the right place, and re-build it....

so I now need to rush

Red flag! Rushing a studio build is always a bad idea. See Andre's signature....

trucks hitting speed bumps now and then,

Vibration in the ground?

...and other such noises from buildings being worked on, church bells and such.

How loud (in dB)? What frequencies?

I would guess the ambient noise during the calmer hours during which I would mostly use the space is probably ~43 dB.

43 seems to be rather accurate for a "guess"! How did you arrive at that? Do you mean dBA or dBC? But in any case, it would be far better to get a meter and find out for sure, rather than guess.

For playing or tracking percussion instruments it's impossible to measure really

Not so impossible, actually. A good sound level meter will measure it quite well. And when you take that into account along with the psych-acoustic perception of sound, you can reach intelligent decisions about how much isolation you need.

I would say it makes not a lot of sense,

Why? Why do you think it doesn't make sense to measure the intensity of the sounds you need to isolate?

a loud crash cymbal or a djembe slap can be insanely loud but a marimba is a whole nother story.

Not sure I understand your point: Measure with a meter, "C" weighting, "Fast" response, and consider that transients might be 10 to 20 dB above that. Better still, use your meter to calibrate REW and measure the actual spectrum over a period of time, then examine it in detail, It's not hard to measure the levels you are producing with enough accuracy to determine the isolation you need. Acousticians and studio designers do that all the time. You don't need laboratory precision here: only enough precision for the job, which is to design the isolation plan for your room. One you know how loud you are for each part of the spectrum it's fairly simple to match that to possible construction methods: compare your curve to the known and published curves (eg, IR-761), and find something that will do what you need.

What I am trying to figure out is how much isolation I can really expect in scenario B.

That's the wrong way to go about things. Rather, first determine how much isolation you NEED, based on actual measurements of the real location, and real instruments, then once you know how much you need, look through the options to find some that produce what you need, and choose one that fits your budget and skill set.

I am removing about 3-4 tons worth of partition walls from the space but the floor is at it's deflection limit already so my plan was to remove those old partitions, avoid loading it with my outer leaf and then have a nice 4ton allowance for heavy QRD panels and other such gubbins

Not following: Your outer-leaf does not sit on your floor, from what you said, so why would you want to "avoid loading it with my outer leaf "? It's the INNER-leaf that would sit on your floor if you did it on a separate frame.... not the outer leaf.

Then again, without a diagram to see what you are doing, it's hard to guess at what you are trying to explain...

All of the typical data on the web including the one for filling inside with glass wool assumes outer leaf is of similar mass, also on a frame construction.

No it doesn't.... you might be looking in the wrong places! You should probably take a look at IR-586 and NRCC-44692 to start with, as well as a report titled "Quantitative comparisons of resilient channel designs and installation methods". The insulation has pretty much the same effect in a wall built wit RC or clips, as it does in a wall built with separate frames. The insulation by itself doesn't do much to isolate, but when used inside the wall correctly, it makes a huge difference: It damps several forms of resonance that would otherwise rob you of isolation, as well as changing the way air deals with heat, and reducing the speed of sound. It does all of that pretty much independent of how the wall was built: it does those same things if the wall is fully coupled, fully decoupled, or only partially decoupled, as with clips or RC.

Here is where my problem lies - my outer wall is of a completely different type and order of magnitude of mass and I don't know if on account of all these variables, adding a 30kg/m2 inner leaf will be worthwhile.

If you don't know, then do the math to find out! The equations are not too complicated...

Assuming the worst which would be the outer wall being only 39dB - if I did everything correctly and made that inner leaf including the inner windows of same mass per m2 as the wall. How much real world isolation could I expect in total?
Any remote possibility of hitting 60dB? I am worried that I will top out around 54dB after all that money and effort.

With either RC or clips+channel, you are placing a limit on how much isolation you can achieve, so you will top out at some point. Where that "some point" happens to be depends on many factors... Until you define all the variables, you won't be able to know. That's why it is better to first define your isolation needs, in dB, ad frequency range, then compare that to the known and tested isolation levels that can be achieved, to find one that meets your goals, and fits your budget.

- Stuart -

BorysP · Post by **BorysP** » Tue Mar 19, 2019 1:56 pm

Hey guys, thanks for the replies, I'll try to clarify as much as I can at this point:

1.
a) The Genie Clips/Furring channel that I can get where the channels are arranged horizontally and outer leaf bears the load:
https://www.customaudiodirect.co.uk/gen ... arch=genie
b) For the the wall standing on the floor option, the type of metal stud system I was trying to describe would be most likely similar to this:
https://old.rigips.pl/system-rigips,110 ... 10-aku.htm
(sorry I can't find an english language version but the plans are self explanatory I think).

So better than figure 4 from the pdf because of those direct hangers, decoupled in a similar fashion like the Genie clips or RSIC clips are.
That is the best system I could find. Wall hangers are mainly for stability there. Wall rests on the floor.

2.
For HVAC there will be mechanical ventilation with heat recuperation and moisture recovery and then an inverter multisplit system for heating/cooling. No water based central heating - all of that will be ripped out because it is too noisy. Electrical mains box will get a hermetically sealed case. Ofcourse duct work will include mufflers.

3.
I din't meant to say the outer leaf would load the floor, that was a mistake - I intended to write inner leaf but fingers did not cooperate.
Unfortunately no way to move the studio space to the basement - basement is 2.45m in height and contains for lack of a better word the machine room type areas for the building so lots of noise. The space I am hoping to use is 3.16m, possibly 3.08m after i relevel the slab and then add my floor layers, it's also about 54m2 in a single room.
I don't want to mess with the ground floor as it's the only floor I can refurbish to a modern home standard and not lose value on the building on account of turning it all into the willy wonka factory that it might turn out to be.
Basement is not proper slab on grade as used in typical US type construction, all walls like most buildings in this part of the world are on their own foundation, a foot of sorts.
So floor is basically a slab floating on some insulation that should sit on yet another slab which in turn does sit on grade but not intended to carry large mass nor weighted down by such. Each basement room has sort of it's own slab for the floor.
I suspect it's exactly the kind of "floating floor" type failure that people end up with when they embark on building a floating studio floor.

4.
With the 3 panes of glass window, if I have a single pane in my inner leaf won't that turn it all into a 4 leaf situation? That would solve the possible issue with the 3rd leaf resonating right?

5.
I do use Sketchup and already have a model of what I am trying to do only incomplete because I was debating if there is any point in isolating at all. I will do one version (the smaller one) based on my initial idea and show it as soon as I have something that is readable enough.

kominak · Post by **kominak** » Tue Mar 19, 2019 7:55 pm

Hi Borys,

I'm in the central Europe, too (Slovakia), and I'm in the process of finishing my small "one room" recording studio. Similar structure as yours (porotherm walls, "floating" concrete slab etc...). Look at my design and build threads, if you like, you may find some answers you need.
From the link you provided I guess you're from Poland? It took me some time to find the right materials(how they are called and how they compare to US names) around here, so if you have any questions, let me know... To start with, I used Voltcraft sound pressure meter and Umik-1 mic (from their German distributor).

Some short comments:

In USD terms I can spend say 10k, maybe 15k on that inner leaf not including top floor layer, inner windows, doors for the sound lock etc.

Just to give you some point of reference: for my much smaller room(16m2), the contractor-built inner leaf did cost me around 4000USD. It consist of 2x gypsum board layers(one of them the heavier "acoustic" blue stuff), 10cm air cavity between leaves is filled with 50kg/m3 mineral wool. With the outer leaf being 30cm thick porotherm the TL is >50dB, enough to record acoustic instruments and even play electric guitar without disturbing anybody around here (neighbors are 7m away). Still, my doors are the limiting factor here and it's possible I'll be able to squeeze a couple dB more, if absolutely needed...

4.
With the 3 panes of glass window, if I have a single pane in my inner leaf won't that turn it all into a 4 leaf situation? That would solve the possible issue with the 3rd leaf resonating right?

No, you need single laminated glass in both leafs (forming two leaf system, same as with the walls). I too, was sold the "acoustic glass pack", but that DIDN'T work at low frequencies - nowhere near the promised 45-47 dB...

Ofcourse duct work will include mufflers

Don't use small prefabricated metal ones. You need big heavy silencer boxes, for your desired sound isolation probably 1 on each leaf (so 2 for air intake, 2 for air exhaust - 4 in total... see Stuart's design for my room, it works).

so I now need to rush

Please don't do it. I had to re-do a couple of the things during my build and it took MUCH more time/effort/money than a little waiting and more proper design would cost me... Consider contacting Stuart if you want design that really works, but even this route would take some time.

Good luck with your build - for me it was absolutely worth it!

Martin

BorysP · Post by **BorysP** » Wed Mar 20, 2019 2:00 am

Hey Martin,

1. Good to know the 45 dB window pack is rubbish for LF! This is very important because I wanted to put it into all of the windows and there is a ton of em because it is a big building. Do you know above what frequency it starts to pick up? Depending on the price difference I could still go for it just to improve overall acoustic comfort in the building but if it's very expensive I'll just skip it.
I already have triple glazed windows just wooden framed ones and they are not as well sealed - wanted to get modern ones with very good thermal insulating properties. Could get ones that are U = ~0.6 if mounted properly which is amazing.

For the windows in the studio space I would have to figure out how get the outer pane looking similar to the rest of the windows or at least presentable, also worried about maintaining thermal insulation.

Would it be feasibly to install my original windows just to get the thermal insulation and then put the thick pane immediately after that? So it would be the two proper panes build like a control room window and then the regular window for thermal insulation outside.

2. I did intend on using the round metal mufflers generally for the house, some of them have very good reduction measurements - mostly to lower noise created by the ventilation unit and another set on the ducts connecting to the outside. Wanted to build some additional DIY ones for the studio itself like you describe but it's good to know the round ones will definitely not be enough!

We also have what seems to be ready made ones very similar to the kind that people DIY:
http://thesslagreen.com/product/tlumik- ... ousticbox/

Also there are box mufflers that have absorptive material hanging much like it would in a giant bass trap but those are for bigger, commercial installations:
http://www.frapol.com.pl/produkt/114/Tl ... okatne-TKF

3. Excellent to hear you are happy with your space! I intend to DIY as much as I can to save cost since I have a lot of area to cover and I am eager to get my hands dirty and get precise results.
Will be putting together a workshop in the basement and thus able to make my own QRD's, some nice studio furniture - it will take a lot of time and effort but should be worth it.
50dB reduction sound correct if we take 39dB for porotherm + the 11-13dB claimed for the inner leaf of that type of construction.
It's not a lot of isolation but if you're saying you are happy you did it, I might go for it too - I don't want to wreck the space then have it be all for naught. Based on my limited understanding I think you could indeed get it up to 52dB if you improve the doors - personally I would go for it if I was you.

I have to muse on that 50dB level, I was hoping to get at least 53-56 but again if you say you are happy with your space at least I know there is a real world example of something similar that works well enough!
I'll continue working on my design and return with drawings - there is one aspect to it that I am sure will come under much criticism, we'll see soon

Soundman2020 · Post by **Soundman2020** » Wed Mar 20, 2019 3:58 am

50dB reduction sound correct if we take 39dB for porotherm + the 11-13dB claimed for the inner leaf of that type of construction.

Actually, it doesn't work like that. You can't just add up the individual isolation numbers for each material. To start with, the decibel scale is logarithmic, not linear, so you can't just do simple arithmetic addition. And even if you could, there's the problem of resonance: An isolation wall is not just several "things" that each stop some sound: Rather, it is a tuned system. All the parts work together as a resonant unit, and it is the resonant unit that defines the isolation. It resonates in several different ways, for different reasons, and each resonance has an effect on the total isolation.

So it is not possible to look at two barriers that each provide 20 dB of isolation, and say that if you put them together you will get 40 dB. It just doesn't work like that at all. It's a lot more complex.

In your example, it might well turn out that the "39dB for porotherm" plus the "11-13dB inner leaf" TOGETHER still only provide 39 dB.... or it might turn out that they provide 60 dB. You would have to do the math, taking into account all of the variables, to find out how much isolation they would provide.

also worried about maintaining thermal insulation.

Thermal insulation should be fine. You will have two very thick panes of laminated glass, plus a deep air gap between them.

Would it be feasibly to install my original windows just to get the thermal insulation and then put the thick pane immediately after that?

That would make a 3-leaf, or 4-leaf, or 5-leaf system: Each time you add a leaf, the isolation potentially gets WORSE in the low frequency region. It gets better for high frequencies, yes, but probably worse for lows.... Unless you use VERY thick glass...

some of them have very good reduction measurements - mostly to lower noise created by the ventilation unit and another set on the ducts connecting to the outside.

Yes, but that's not what you need for a studio. The problem is not just fan noise and air turbulence noise... the problem is sound across the entire spectrum getting out of your room, or into your room. Typical round metal mufflers don't have the insertion loss characteristics that a studio needs.

it's good to know the round ones will definitely not be enough!

Definitely not! No use at all, really, for a studio. A waste of money.

We also have what seems to be ready made ones very similar to the kind that people DIY:

Will be putting together a workshop in the basement and thus able to make my own QRD's,

Why do you think you will need QRD's in your studio? What frequency range do you plan to tune those for? Why did you select that frequency range? Where do you plan to put them? HOw many do you need?

Designing a studio isn't just about making things that look cool, and that you've seen in photos of other studios: Every device has a specific purpose, must be designed correctly for that purpose, and positioned in the correct location where it can actually achieve that purpose.

One thing we don't even know yet, is how big your studio will be: What are the dimensions of the room going to be?

I have to muse on that 50dB level, I was hoping to get at least 53-56

Why do you want 56 dB? How did you arrive at that figure? It sees to be rather precise for a rough estimate. Why not 55 or 57?

- Stuart -

BorysP · Post by **BorysP** » Wed Mar 20, 2019 9:28 am

I have no idea why you are assuming I am aping shapes from famous studios based on pictures.
Right now in that specific room there is a ventilation pipe straight out to the roof so there is almost no isolation on account of that; also there is a metal pipe in an old masonry ventilation duct on the other side of the room, moving about in the wind and making an awful noise; I can hear birds singing outside - What would be the point of me measuring the room before I deal with those issues? What would that tell you about my current wall considering it has the equivalent of a big round hole in it?
I will take "before" measurements at every stage I plan to complete but time is not yet ripe because there is no proper "before" yet to calculate anything in relation to that inner leaf.
The 39dB for the outside wall is from a random lab measurement of a porotherm wall without any plaster or outside insulation that I managed to find and I consider that my lower bracket for what that wall might actually be.

The 11-13 dB for the leaf I mentioned is not data for that specific leaf standalone but the overall promised increase in isolation of a typical masonry wall as built in my region, on which that leaf is then added onto. Some other data I managed to find gave that type of leaf as a standalone partition about 31-33dB of isolation. Obviously it is most likely that anything below 125hz is not taken into account at all in those measurements.
This data is only useful to me in comparing version A of a partition wall with version B of a partition as imagined by the Saint Gobain corporation.
The aim is only to chose the best configuration of a given general type of construction considering they all cost almost the same per m2.
The data was intended for this general part of Europe and we all have masonry walls over here so they are all massive, all above 100kg/m2 for sure.

I din't make any calculations. Martin gave a very useful answer that he achieved 50dB and that seemed correct to me compared to the various two leaf wall assemblies I browsed through.

Any of these values are just good for guestimations and thats good enough for me because the mathematical model of internet audio engineering forums always returns the only true result which is that any sound related device or space must be in Nashville to operate properly.
For now I am doing fine but one day, they will surely catch me operating QRD arrays without a license and then it's jail time for sure.

Soundman2020 · Post by **Soundman2020** » Wed Mar 20, 2019 11:09 am

I have no idea why you are assuming I am aping shapes from famous studios based on pictures.

That's simple: because you have already decided that you need a QRD, without even having designed the studio yet.

One thing we don't even know yet, is how big your studio will be: What are the dimensions of the room going to be?
What would be the point of me measuring the room before I deal with those issues? What would that tell you about my current wall considering it has the equivalent of a big round hole in it?

Because we have no idea what the SIZE of your room is, so we can't actually help you at all until you tell us that.

I will take "before" measurements at every stage I plan to complete but time is not yet ripe because there is no proper "before" yet to calculate anything in relation to that inner leaf.

I never suggested you should measure the acoustic response of your room.... You seem to have misread what I wrote.... (in several places...)

The 39dB for the outside wall is from a random lab measurement of a porotherm wall without any plaster or outside insulation that I managed to find and I consider that my lower bracket for what that wall might actually be.

That would not be correct, no. As I pointed out, the actual isolation provided by your wall could be LESS than that provided by one of the materials from which the wall is made. Or it could be more. There is no way of knowing what the final outcome will be, until you do the math.

Just because a lab measured a specific material to have 39 dB of TL, that does not mean it will always have 39 dB of TL. Very probably, if you measured that same material in the real world it would show LESS than 39 dB of isolation, all by itself, and in combination with other materials it could be more, or it could be less. You'll never know unless you do the math to find out....

Why? Because labs are designed to provide perfect conditions for measuring the acoustic performance of building materials and treatment. The real world isn't. Typical houses and home studios are nothing at all like acoustic labs, and will not necessarily produce the same results.

Since you don't seem to want to believe me, here's the equations you will need, depending on whether you decide to use a 2-leaf wall, or a a 3-leaf wall.

2-leaf-3-leaf-equations.jpg

The math is very simple. Basic high-school stuff. Those equations will give you the predicted resonant frequencies of your wall(s) and ceiling. You can then compare that to the actual frequency spectrum produced by the instruments you plan to record in there, and by the various sound sources that will be located outside and that you need to prevent from coming in. If any of those frequencies are close to the resonant frequencies of your wall, then you have a problem, because the wall does not isolate at all at that frequency, and could actually amplify the sound at that frequency... so it could be LOUDER on the other sound, not quieter.

Do the math for yourself, so you can see that I'm not making this stuff up.

The 11-13 dB for the leaf I mentioned is not data for that specific leaf standalone but the overall promised increase in isolation of a typical masonry wall as built in my region, on which that leaf is then added onto. Some other data I managed to find gave that type of leaf as a standalone partition about 31-33dB of isolation.

Same response: See above. Do the math. Picking and choosing random data from unrelated sources, then putting it together and hoping that it has some bearing on your walls, is not going to give you the right answer. Acoustics is not intuitive in many ways. What SEEMS logical at first glance, actually is not logical once you understand the underlying principles. It would seem to be logical that if a two-leaf wall is good then a 3-leaf wall should be better, and 4 leaves of mass should be fantastic! But that's not correct at all. It would seem to be logical that if one layer of material produces STC-30 then 2 layers should be STC-60, and 3 layers should be STC-90, but that is terribly wrong (you already know that). It would seem to be logical that if pro studios have QRD's on the walls then ALL studios should have QRD's on the walls, but that isn't true either. It would seem to be logical if insulation inside the wall has a huge impact on transmission loss, then the same insulation used outside the wall should also greatly increase transmission loss, but that, too, is wrong. So much of what seems "right" from normal every-day perspective, is not right at all in acoustics. We can't see sound waves, so we just assume that they must behave the same as things we can see.... but they don't.

Obviously it is most likely that anything below 125hz is not taken into account at all in those measurements.

So you were not actually looking at Transmission Los numbers, in decibels? You were looking at STC, which is not related at all to full-spectrum TL?

Interesting point: If you don't look at anything below 125 Hz, then you are ignoring the bottom three octaves of the musical spectrum. Out of a total of ten octaves. So you are missing out on 30% of the entire musical scale, and it's the most important 30%, in fact. That's where all of the toughest problems in acoustic isolation and treatment occur. It's pretty easy to deal with isolation and treatment for the top 7 octaves, but really hard to do both for the bottom 3...

The aim is only to chose the best configuration of a given general type of construction considering they all cost almost the same per m2

But you are going about that the wrong way. Saint Gobain makes building materials, so I'm not sure I see the point of your mentioning them.

The data was intended for this general part of Europe and we all have masonry walls over here so they are all massive, all above 100kg/m2 for sure.

Plug that number into the mass-law equation, and see what your isolation will be for the frequencies that they are NOT telling you about:

Mass Law:
TL(dB)= 20log(M) + 20log(f) -47.2

M is the surface density of the panel (mass per unit area (kg/m²) ), and
F is the center frequency of the third-octave measurement band

So, for example, a bass guitar might put out considerable¿le energy at, say, 40 Hz, so let's try that:

TL(dB)= 20log(100) + 20log(40) -47.2
= 40 + 32 -47.2
= 24.8 dB

Not so very interesting, is it?

Even worse, if you happen to put a leaf of drywall 10cm away from that, with insulation in the air gap, the resonant frequency of that system would be 41 Hz... so it would not only fail to isolate your bass at all, but in fact could AMPLIFY it. Your bass guitar would be heard loud and clear on the other side of that wall. You can use the 2-leaf equation I gave you above to confirm this.

Because acoustics is not intuitive at first glance, and resonance is a powerful beast that changes everything. You can tame it and put it to good use, or you can ignore it and let it run wild on your studio....

Where I live, masonry construction is stock standard too, and often considerably thicker than what you mention, because of the earthquakes: we regularly get medium to large quakes here, and sometimes very large ones. My house has been through many 6.x quakes, a few 7x quakes, one 8.3 quake, and one 8.8 quake. We have to build tough here, so I'm somewhat familiar with reinforced concrete and bricks, as well as partition walls built form studs and drywall, and combinations of both. You aren't teaching me anything I didn't know about construction materials. I'm well aware of how they perform structurally... and also acoustically. From experience, I can tell you that those equations do not lie: they tell it like it is. Where I live, a masonry wall that only had a mass of 100 kg/m2 would be considered low mass, and probably would not pass inspection. We use much thicker, heavier, tougher walls here. The wall behind me where I'm sitting right now is 26 cm thick, which is 20cm of reinforced concrete pillars and beams, with brick infill, and 3cm of plaster on each side. Density is around 600 kg/m2. And sound can get through that... Mass alone is not a good guarantee of isolation.

I din't make any calculations.

You should probably start doing that. The equations are not complicated (see above).

Any of these values are just good for guestimations and thats good enough for me because the mathematical model of internet audio engineering forums always returns the only true result which is that any sound related device or space must be in Nashville to operate properly.

- Stuart -

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