Littlewater Studio - Norway (Europe)

[Soundman2020]

I've found similar STC ratings for similar setups

Yes, but STC is not what you need to measure isolation of STUDIO walls. STC is a single-number rating system that tries to depict roughly how a wall will isolate typical sounds found in homes, offices, schools, hotels, shops, and suchlike. It does not consider the entire audio spectrum: In fact, it completely ignores the bottom two and a half octaves of the musical scale! Notes played down low are not be taken into account with STC. So you could have a wall, door or window with a great STC rating that is really lousy at stopping studio sounds, and you could have another wall whose STC rating is not so good at all, but actually stops studio sounds really well...

So don't rely on STC rating to tell you how well a wall or window will isolate. You need to look at the complete transmission loss curve, to see how it performs in the regions that are of most interest.

So I'm guessing I need a glass with about the same density as the double layer of drywall I plan to have on the walls, right?

Right, but that's SURFACE density, not VOLUMETRIC density. In other words, your window needs to weigh the same as your wall per square meter of wall area, not per cubic meter of construction materials. Which basically means that it is a combination of volumetric density and thickness. Glass is very roughly three times the volumetric density of drywall, so it can be roughly one third the thickness for the same SURFACE density. So with 2 x 5/8" drywall, a piece of laminated glass about 3/8" thick, or 7/16", or even 1/2" thick, would be about right. Or in metric: 2 x 16mm drywall would be matched by laminated glass about 10mm to 12mm thick. So probably you should order 5+5 laminate for that (two panes of 5mm glass, laminated together with an acoustic interlayer), or 5+6, or 6+6.

- Stuart -

[ask]

So don't rely on STC rating to tell you how well a wall or window will isolate. You need to look at the complete transmission loss curve, to see how it performs in the regions that are of most interest.

Okey. I've gotten a few offers from window vendors and one of them sent me the attached report (edit: reuploaded):

sp report.pdf

Would you consider this a good sound studio window? As you can see it consists of 6+6mm laminated glass / 24mm argon gas / 4+4mm glass. Would this cause a quadruple leaf effect with the existing window which consists of 4mm float / 15 argon / 4mm "planiterm one", although it would be more than 14cm apart from the new window glass?

On a different note, going back to something you said earlier:

There won't be much transmission through that slab, except for impact noise. And you can take care of impact with a small drum riser, if necessary. Double stud will give you better isolation than just clips or hat channel.

Does this mean you wouldn't consider it worth while to float my walls since I'm doing a double stud solution? (I'm hoping for a big DON'T here ). In case I did float the walls, how much reduction could I expect to gain?

Thanks!

-Andreas

[ask]

Hi again and sorry for bumping the thread, but I was really hoping to decide if I could order this window or if I need to to do some more searching to find a one leaf window.

I really appreciate all your help Stuart! Hope you haven't forgotten me already...

Cheers,
Andreas

[Soundman2020]

it consists of 6+6mm laminated glass / 24mm argon gas / 4+4mm glass. Would this cause a quadruple leaf effect with the existing window which consists of 4mm float / 15 argon / 4mm "planiterm one", although it would be more than 14cm apart from the new window glass?

Yes, there would still be a 4-leaf effect. 14 cm isn't that much for low frequencies. What frequencies do you need to isolate? What is the lowest frequency that you need to isolate?

Does this mean you wouldn't consider it worth while to float my walls since I'm doing a double stud solution? (I'm hoping for a big DON'T here ). In case I did float the walls, how much reduction could I expect to gain?

Floating your walls is very much like floating a floor: Very hard to do right, and very seldom needed. This thread explains why:

http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173


- Stuart -

[ask]

Floating your walls is very much like floating a floor: Very hard to do right, and very seldom needed.

Thanks! It would probably not be worth the effort in my case then. I guess I could consider doing what Rod suggests in this thread (http://www.gearslutz.com/board/studio-b ... table.html). But that doesn't seem to involve the walls at all if I'm not mistaken:

If the walls are isolated - and their only contact to the existing building is the slab - and you want to take it 1 step further - just build an inexpensive floating floor.

You can do this through the use of a couple of layers of 1/2" plywood resting on top of a couple of inches of 3pcf rigid insulation.

What frequencies do you need to isolate? What is the lowest frequency that you need to isolate?

The band that would be practicing in the basement consist of drums, electrical guitars, a bass guitar and synth. As I'll be practicing on my drums more often than we'll have band practice, isolating as low as a kick drum would be the primary goal, ie down to 58Hz. All the way down to 40Hz supporting a four string bass guitar would be preferable though.

Yes, there would still be a 4-leaf effect.

Ok. I guess it's clear I need one layer for my inner window if I am to keep my existing window. Then at least I'll only get a triple leaf effect. I've read somewhere that in a triple leaf system the middle leaf should preferably be the thickest. Would this apply in my situation? And does this mean I really should change my exterior window so that a get something like 4+4mm glass / 24mm argon gas / 6+6mm laminated glass for the exterior window then 140mm air gap then 5+6mm laminated glass? (I'm suggesting a double layer of glass for the exterior window as I'm assuming this gives better isolation from the cold winters here in Norway which could easily be minus 20 degrees Celsius.)
Thanks again!

Cheers,
Andreas

[Soundman2020]

I guess I could consider doing what Rod suggests in this thread ... But that doesn't seem to involve the walls at all if I'm not mistaken:

Correct! As he says there, before you do his floor system, you have to: "Build the walls first - including the finished drywall".

And in the same thread, this is what he says about floating the entire room, including the walls: "A completely floated room is always the best of the best - however it is extraordinarily expensive to do it right - and makes no sense whatsoever to do it wrong." Very true!

The band that would be practicing in the basement consist of drums, electrical guitars, a bass guitar and synth. As I'll be practicing on my drums more often than we'll have band practice, isolating as low as a kick drum would be the primary goal, ie down to 58Hz. All the way down to 40Hz supporting a four string bass guitar would be preferable though.

OK, isolating down to 40 Hz means that you need to tune your MSM isolation system to below 20 Hz. The general rule is that the tuned frequency should be half of the lowest isolation frequency. An MSM system actually amplifies frequencies around its own resonance and up to 1.4 times its resonance, which is why you need to have the lowest isolation frequency at least 2 times the MSM resonance.

So now you have a starting point: your wall and ceiling design must consider a resonant frequency of not more than 20 Hz.

Now we just need to know how much isolation you need, in terms of decibels. You mentioned drums, so we are talking about levels of 115 dB at least, but the question is, how quiet does that have to be on the other side? If you only need to get it down to 75 dB, that's simple. Piece of cake! But if you need to get it down to 35 dB, that's an entirely different matter.

Each time you increase the amount of isolation that you need by 10 dB, you are talking about blocking ten times more sound energy. A typical house wall will give you about 30 dB of isolation. If you need 40 dB of isolation, then you need to block ten time more than a typical wall. If you need 50 dB, then that's one hundred times more energy you need to block. 60 dB is one thousand times more energy than a typical house wall. 70 dB is ten thousand times more energy that you have to block. Etc. The decibel scale is logarithmic, not linear. Each time you go up 10 dB, you go up by one order of magnitude.

In other words, getting very high levels of isolation is very hard to do, and very expensive. So it is important to work out exactly how much isolation you need (how many decibels), in order to design the isolation plan. I can show you how to isolate a room to 40 dB, and I can show you how to isolate it to 70 dB, but the building materials and the cost will be very, very different for those two cases.

Then at least I'll only get a triple leaf effect. I've read somewhere that in a triple leaf system the middle leaf should preferably be the thickest.

Right. The optimum configuration for a triple-leaf wall is where both cavities are the same size and the mass of the middle leaf is the same as the mass of the other two leaves COMBINED. So the glass on the middle leaf should be TWICE the thickness of the glass for the other two leaves.

Would this apply in my situation?

Yep! Basic laws of physics... They apply everywhere in the universe.

And does this mean I really should change my exterior window so that a get something like 4+4mm glass / 24mm argon gas / 6+6mm laminated glass for the exterior window then 140mm air gap then 5+6mm laminated glass?

You can only calculate the glass thickness if you know how much isolation you need. But as an example, assuming you had 4x4 on the outer leaf and 5+6 on the inner leaf, that's a total of 19mm, so you'd need 10+9 for your middle leaf. That's the scary thing about 3-leaf systems: the amount of mass you need to compensate is pretty high. However, in the example you give, you do have a larger air gap on one side (140mm vs 24mm), so you don't have the optimum arrangement. You'd probably need more mass on the inner leaf too.

However, the above numbers are just extrapolations of the example you gave, which might of might not be the right numbers for your case. You really need to determine how nay decibels of isolation you need first.

- Stuart -

[ask]

Thanks for the quick response. I really do appreciate your help!

Now we just need to know how much isolation you need, in terms of decibels. You mentioned drums, so we are talking about levels of 115 dB at least, but the question is, how quiet does that have to be on the other side?

That's a very good question indeed and one that very much depends on my abilities, time, effort and economical limitations. Still hopefully something we can figure it out together...

The goal is to be able to have my band practice while my kid is sleeping one floor above and my wife is watching TV two floors above (without any more walls between the stairway and the living-room where the TV is). My kid is not a light sleeper, so I don't worry too much about him, but my wife is slightly more allergic to sound/noise So I guess she should be able to follow the dialog of Greys Anatomy if we get it down from 115dB to around 55dB, right? Ie a reduction of 60dB...

I was hoping me beefing up the existing ceiling with two layers of drywall and building a separate shell within the existing room would get me there. From what I can tell from the GG website (http://www.greengluecompany.com/sites/d ... 0Sheet.pdf) I'll get 73dB reduction for my ceiling and 53dB reduction on the one wall facing into the stairway and washing room. The other three walls I'm not sure about since they are almost completely underground covered with earth. But at least I should get about 40-45dB from the inner leaf of isolation and double layer of DW with GG, right? Btw I plan to have 2x4 framing for the walls and 2x6 for the ceiling with isolation in between in the new framing. The new framing will be 25mm from the existing framing and the new DW plates will be 25mm from the existing ceiling joists.

I realize now that it might be a good idea to beef up the inside if the existing wall facing into the stairway as well, but I'm not sure if it's worth the effort considering I have two entire floors (of air) before the sound reaches its target. Shouldn't this distance work to my advantage?

The general rule is that the tuned frequency should be half of the lowest isolation frequency. An MSM system actually amplifies frequencies around its own resonance and up to 1.4 times its resonance, which is why you need to have the lowest isolation frequency at least 2 times the MSM resonance.

Ok. I did not know this. I guess my immediate question is; Do I have enough mass then with 3 or 4 layers of 12mm DW? Does 16mm drywall help or I'm I barking up the wrong tree?

Best regards
Andreas

[Soundman2020]

My kid is not a light sleeper, so I don't worry too much about him, but my wife is slightly more allergic to sound/noise So I guess she should be able to follow the dialog of Greys Anatomy if we get it down from 115dB to around 55dB, right? Ie a reduction of 60dB...

The only way to be sure is to measure it with a sound level meter: They aren't expensive, and you'll need one anyway for the calibration of your room once it is built. So set it up where your wife will be when you are recording / mixing / rehearsing, and set up some god speakers at the location where you'll be making all that noise. Know belt out your loudest music on that system while you slowly turn down the volume until your wife says that the level is fine for her. Whatever reading you are getting on the meter is the answer to the question.... (Set the meter to "C" weighting and "Slow" response for these tests).

I'll get 73dB reduction for my ceiling

I'd take that with a large grain of salt! Getting 70-something dB of isolation in a typical home is really hard to do. Realistically, I'd say more like 50-something, maybe 60-and-a-bit if you are lucky.

But at least I should get about 40-45dB from the inner leaf of isolation and double layer of DW with GG, right?

Right. That is realistic. And if that's what you get for your "worst" wall, then that is what you get overall for the entire room, regardless of how fantastic your ceiling is. Keep that in mind: an isolation system is only as good as its weakest link, so if one part of your system gives 45 dB, then that¿s what the entire system gives, even if all the rest gives 90....

I realize now that it might be a good idea to beef up the inside if the existing wall facing into the stairway as well, but I'm not sure if it's worth the effort considering I have two entire floors (of air) before the sound reaches its target. Shouldn't this distance work to my advantage?

Provided that there is no flanking going on, yes. "Flanking" refers to sound that gets into the building structure itself, and therefore bypasses your efforts at isolation. Once sound is in the building studs, then it can be all over the building, and pretty loud. This is why decoupling is so important.

Ok. I did not know this. I guess my immediate question is; Do I have enough mass then with 3 or 4 layers of 12mm DW? Does 16mm drywall help or I'm I barking up the wrong tree?

definitely you want 16mm drywall! Always! Never thinner: 12mm is too thin, too flexible, the mass is too low, and the resonant characteristics are not so good. 2 layers of 16mm is actually better than 3 layers of 12mm, under most circumstances.

You can estimate the resonant frequency for a 2-leaf wall with the equation:

F0=c[(m1 + m2)]^.5 / [(m1 x m2 x d)]^.5

C is a constant, and is 43 for imperial units or 1897 for metric units
m1, m2 = the surface density of leaf #1, leaf #2 (pounds per square foot, or kg/m2)
d = depth of air gap between the leaves (inches or mm)

so you need to figure out your wall properties such that the solution to the above equation is no more than half of your lowest isolation frequency.


- Stuart -

[ask]

The only way to be sure is to measure it with a sound level meter: They aren't expensive, and you'll need one anyway for the calibration of your room once it is built.

Great! Should the Radio Shack Digital Sound Level Meter 33-2055 be up for the task?

Thanks!
Andreas

[Soundman2020]

Should the Radio Shack Digital Sound Level Meter 33-2055 be up for the task?

It is probably OK for basic measurements, but not too accurate in the high end when used as a measurement mic.

Here's an interesting article that compares several mics, in that respect:

http://realtraps.com/art_microphones.htm

- Stuart -

[ask]

Here's an interesting article that compares several mics, in that respect:
http://realtraps.com/art_microphones.htm

Thanks! It seems like the Nady is a better choice then. I'll get that

I'm sorry, but I can't really put my mind to rest about floating my walls/floor... One "tiny" detail I might have forgotten to mention regarding the slab is that it's sharing the slab with the stairway next door to the studio going all the way up to through the house. Wouldn't the floor in the stairway then act as a large loudspeaker membrane transferring all the sounds that get into the concrete from the studio? If that's the case, what frequencies do I need to worry about with regards to a 5cm concrete slab (reinforced with 6mm steel in a 15x15cm pattern) resting on 20cm polystyrene then grade? If it's only impact noise (ex from the bass drum) I could easily fix that with a drum riser. But if we're talking most frequencies, then that would be an argument for floating the floor/walls, right?

Here's some drawings of the house if that helps... The basement is as mentioned 90% under ground.

basement.png

1st floor.png

2nd floor.png

Thanks,
Andreas

[Soundman2020]

One "tiny" detail I might have forgotten to mention regarding the slab is that it's sharing the slab with the stairway next door to the studio going all the way up to through the house.

The slab is "on grade", right? Meaning that it is poured on top of the ground, with no other rooms or gaps below it? If so, then yo have the entire planet down there, acting as a damper on your slab.... It's as if you had thousands of people down there, all pressing their hands up against your slab to stop it from vibrating...

Wouldn't the floor in the stairway then act as a large loudspeaker membrane transferring all the sounds that get into the concrete from the studio?

If this is a bog concern for you, then just build a drum riser or amp riser for anything that might create impact noise in the slab. Airborne noise is not an issue, since concrete is extremely massive (a single square meter just 10cm deep weighs well over 200 kilograms), so airborne sound is not going to make it vibrate, especially considering the Planet Earth camping effect....

Now, if you REALLY want to float your floor, then go ahead! Nobody will stop you! Just make sure that you do it right, as in this thread:

http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

And make sure that you have the budget to do it: It will cost you several thousand dollars. These are the floor jacks you will need:

mason-floating-floor-isolation-jacks.jpg

Or these:

properly-floated-floor-spring02-SMALL.jpg

This is how you do it:

properly-floated-floor-01-SMALL.jpg

As long as you know how to do all the calculations, and have the budget, then there's no problem in doing it.

If that's the case, what frequencies do I need to worry about with regards to a 5cm concrete slab (reinforced with 6mm steel in a 15x15cm pattern) resting on 20cm polystyrene then grade?

You would need to build your floor such that the resonant frequency is below 10 Hz. That means that your floor will start isolating at about 14.1 Hz, and will isolate reasonably well at 20 Hz. From there, it gets better and better as you go up the spectrum. That's why you need the mass of concrete: to get the resonant frequency low enough. You cannot accomplish that with wood. Not even with a dozen layers of 3/4" plywood. Concrete is the only material at reasonable cost that can accomplish this.

But if we're talking most frequencies, then that would be an argument for floating the floor/walls, right?

For airborne sound, it would have to be EXTREMELY loud! How much energy do you think it takes to make the entire planet vibrate?


- Stuart -

[ask]

The only way to be sure is to measure it with a sound level meter

Alright. I've done some measurements. I put on some pink noise playing at 105dbC (measured 1m from the speakers pointing the mic directly towards the speakers). Measuring at the top/2nd floor where my wife will be watching TV i got a 30dbC reduction. I left all the doors open, so the sound basically had free passage up the stairway. I also measured in my kids bedroom on the 1st floor which is right above the studio with the door to the bedroom closed and got a 35dbC reduction.

I then lowered the volume so that my SPL meter was showing 55dbC 1m from the speakers. It seems almost too good to be true, but I could hardly hear anything on the 2nd floor. Measuring didn't give any results other than what I get from the background noise which is about 44dbC. Am I doing something wrong? In case this would be the expected noise I would hear when finished, 50dbC reduction should be more than enough for all my purposes.

definitely you want 16mm drywall! Always! Never thinner

It seems impossible to get hold of 16mm in Norway. I can get 15mm fire rated plasterboard which weigh 12kg/m2 or 12,7mm Fermacell fibre gypsum board which weigh about 15kg/m2! The downsides to using the latter is that it would have to be plastered all over and it costs about twice as much. I'm thinking I could go for one layer of 12,4mm fibre gypsum and then a layer of 15mm fire rated plasterboard for the inner shell. Would that do the job? Does it matter in what order I place the two materials considering their density and weight?

On the subject of drywall. I've beefed up the part of the wall facing the stairway with an additional layer of DW inbetween the studs and sealed it tight with caulk. Then remains the part of the wall facing into the technical/laundry room (called "Bod" in the basement floor plan). The problem is that it's kinda hard to fit any drywall inbetween the studs since there are lots of water pipes coming from the water supply cabinet mounted in this wall:

wall bod.JPG

Say I don't care that much about sound coming into this room, could I leave this wall as it is, only calking all edges so it becomes airtight and still get -50dbC in the stairway with the door to the laundry room closed (ps there is a 2cm airgap under this door for ventilation)? If I do need to add mass to this wall as well, are there other solutions I could use that would be easier to fit than drywall? I guess one solution would be to finish the room, then do some measurements and if needed add an additional layer on the laundry room side of the wall?

[ask]

Hi again Stuart, and sorry for bombarding you with questions, but I'm finally getting some momentum in the building process and the questions just keep coming...

I hired a carpenter to set up my inner framing which only point of contact is the concrete slab and a minimum of 3 cm from every part of the outer framing. As you can see from the picture below I've started putting in some insulation (fiber glass). So my first question is; Should I fill everything with insulation or should there be some gap of air between the inner and outer shell here as well? Ie, what is considered better; picture A or picture B (or non )?

insulation A.png

insulation B.png

If alternative B is the better option; Should I try to fasten the insulation somehow using some kind of string to make it slightly pressed to the drywall above and so it doesn't accidentally fall down on the inner joist?

IMG_2266.JPG

How about in the corners where there are no inner joists in between. Should I fill this hole with insulation or leave a bit of air there as well?

IMG_2267.JPG

The new ventilation ducts (which are attached to the outer framing) are in some places only 1 cm from the inner framing joists. Is this enough or should this distance also preferably be 3 cm or more? Should I put insulation between the inner joists and the ducts (making sure it's not compressed of course) or is the gap of air preferred?

IMG_2268.JPG

I guess all these questions really boil down to; How well does non compressed fiber glass transfer vs absorb sound and is fiber glass always preferred over a gap of air?

Thanks again for all your help Stuart. It's highly appreciated!

Cheers,
Andreas

[Soundman2020]

what is considered better; picture A or picture B

"A" is better, for sure. But Rod has pointed out that you might not be allowed to do that, due to the quirks of some building code regulations. So check your local code to see if you can, and if so then fill the cavity completely, but without forcing the insulation in: you don't want it shoved in so tight that it creates a flanking path...

How about in the corners where there are no inner joists in between. Should I fill this hole with insulation or leave a bit of air there as well?

Fill it completely.

The new ventilation ducts (which are attached to the outer framing) are in some places only 1 cm from the inner framing joists. Is this enough or should this distance also preferably be 3 cm or more? Should I put insulation between the inner joists and the ducts (making sure it's not compressed of course) or is the gap of air preferred?

1cm is OK, but do fill that gap with acoustic caulk to make sure that the duct cannot touch the wood, or vibrate against it...

How well does non compressed fiber glass transfer vs absorb sound and is fiber glass always preferred over a gap of air?

Fiberglass is a porous absorber, just like mineral wool. It absorbs sound at the microscopic level when the vibrating air molecules transfer some of their energy to the fibers, which then convert it into low grade heat. Fiberglass insulation will only transmit sound (transfer it across the air gap due to flanking) if it is compressed. If it is just laid in place, even touching both sides, it won't actually transfer much sound like that. But if you force it in tightly, compressing it, then it will.

- Stuart -