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PostPosted: Mon Nov 27, 2017 1:41 pm 
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Hi Everyone,

I have tried for months to find a conclusive answer to my question, forgive me if it's been answered here but I cannot find a definitive answer.

1. Is it possible to achieve the same level of isolation by using a timber frame external wall with say 2 layers of ply and cladded in timber with a sealed air gap of say 1' between said wall and the internal wall INSTEAD of using block work for the external wall?

2. Is it best to have both walls made from block work with a sealed air gap between them each on their own independent concrete slab?

3. Or the external wall built from block and the internal wall built from timber frame with a sealed air gap?

Which one (assuming all 3 options were done correctly) is most likely to reduce the sound of a kick drum escaping to the outside world?

I'm guessing that option 2 is the best due to it having the most mass, but is that over kill where timber would do?


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PostPosted: Mon Nov 27, 2017 2:16 pm 
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Location: Santiago, Chile
Quote:
1. Is it possible to achieve the same level of isolation by using a timber frame external wall with say 2 layers of ply and cladded in timber with a sealed air gap of say 1' between said wall and the internal wall INSTEAD of using block work for the external wall?
It is possible, yes, but maybe not with those parameters.

Quote:
2. Is it best to have both walls made from block work with a sealed air gap between them each on their own independent concrete slab?
If you want very high isolation, and have lots of money, then that would be a good way of doing it.

Quote:
3. Or the external wall built from block and the internal wall built from timber frame with a sealed air gap?
That will also work.

Al three are options, but without knowing more about what you are trying to achieve, it isn't possible to tell you which is "better". All three options are valid, but each has it's own pros and cons, and depending on what you want to do, one might be more suitable than the others. Your question is sort of like asking: "Which is better: a limousine, a Mack truck, or an minivan?". They are all valid vehicles, they all work fine, they are all good at what they do, but they each have pros and cons for different situations.

Quote:
Which one (assuming all 3 options were done correctly) is most likely to reduce the sound of a kick drum escaping to the outside world?
All of them can accomplish that, if designed correctly. It's not the type of material that matters by itself, but rather how that material is used, and how the wall is built over all.

Quote:
I'm guessing that option 2 is the best due to it having the most mass, but is that over kill where timber would do?
Let me answer that with a comment on my own hypothetical analogy: "I'm guessing that the Mack truck is best due to having the most horsepower, but is it overkill where the limousine will do?". It's a meaningless paragraph, unless you first know what the full situation is.

If you explain what it is that you are trying to accomplish, for what purpose, and on what budget, then we might be able to give you a more useful answer.


- Stuart -

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


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PostPosted: Mon Nov 27, 2017 9:56 pm 
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Joined: Sun Mar 02, 2014 8:42 am
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Location: Wales, UK
Soundman2020 wrote:
Quote:
1. Is it possible to achieve the same level of isolation by using a timber frame external wall with say 2 layers of ply and cladded in timber with a sealed air gap of say 1' between said wall and the internal wall INSTEAD of using block work for the external wall?
It is possible, yes, but maybe not with those parameters.

Quote:
2. Is it best to have both walls made from block work with a sealed air gap between them each on their own independent concrete slab?
If you want very high isolation, and have lots of money, then that would be a good way of doing it.

Quote:
3. Or the external wall built from block and the internal wall built from timber frame with a sealed air gap?
That will also work.

Al three are options, but without knowing more about what you are trying to achieve, it isn't possible to tell you which is "better". All three options are valid, but each has it's own pros and cons, and depending on what you want to do, one might be more suitable than the others. Your question is sort of like asking: "Which is better: a limousine, a Mack truck, or an minivan?". They are all valid vehicles, they all work fine, they are all good at what they do, but they each have pros and cons for different situations.

Quote:
Which one (assuming all 3 options were done correctly) is most likely to reduce the sound of a kick drum escaping to the outside world?
All of them can accomplish that, if designed correctly. It's not the type of material that matters by itself, but rather how that material is used, and how the wall is built over all.

Quote:
I'm guessing that option 2 is the best due to it having the most mass, but is that over kill where timber would do?
Let me answer that with a comment on my own hypothetical analogy: "I'm guessing that the Mack truck is best due to having the most horsepower, but is it overkill where the limousine will do?". It's a meaningless paragraph, unless you first know what the full situation is.

If you explain what it is that you are trying to accomplish, for what purpose, and on what budget, then we might be able to give you a more useful answer.


- Stuart -


Hi Stuart, thanks for your reply.

Okay so I'll do my best to explain the situation.

I want to build a live room in which I can record bands but mainly only need to worry about containing the sound of the drum kit as that's the instrument that will be tracked there the majority of the time. The nearest neighbours will be about 50 meters away, so not super close but not super far either. I think an average drummer can be as loud as 110 - 140db but if I could at least knock off 70db when standing outside the room that would be great.

The room will be around 25'x18'x10' (12' if I can) and on a concrete slab. So now it's a matter of knowing how to achieve this in the most cost efficient manner.

My plan was to build a block work external wall, seal it with paint, clad it with timber all on it's own slab.
12" air gap with rock wall insulation.
Then for the internal walls, timber stud work with 2 layers of 1/2" and 5/8" plaster board all on it's own slab.
The internal ceiling would be the same as the internal walls, the roof would be timber frame with ply, roofing felt and clad with box profile corrugated zinc.

BUT if I can build the external walls with timber frame work instead of block work and still achieve what I need, then of course I will due to it being faster and easier (blocks get heavy after lifting them all day).

If this is possible then I would build them very much like the internal walls, but use ply (Osb3) instead of plasterboard.

I'm not sure if you have all the information you need in order to assess this, but I'm not sure what other info you need.

thanks for your help


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PostPosted: Wed Nov 29, 2017 12:24 am 
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Joined: Thu Aug 21, 2008 10:17 am
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Location: Santiago, Chile
Quote:
I'm not sure if you have all the information you need in order to assess this, but I'm not sure what other info you need.
:thu: That's excellent! Just what I needed to get you started on the best path.


Quote:
I want to build a live room in which I can record bands but mainly only need to worry about containing the sound of the drum kit as that's the instrument that will be tracked there the majority of the time.
That's also the loudest instrument in a typical contemporary band, so that's what defines the entire isolation. The drum kit produces the most acoustic energy of any acoustic instruent, and also puts out a lot of that energy in the low frequency range, below about 200 Hz, which is the hardest to isolate. Low frequencies have very long wavelengths, which are difficult to contain. Drum noises are also percussive (sudden short, sharp, high intensity sounds), which are far more noticeable and annoying than a continuous sound. In short, drums are the hardest of all to isolate: High energy, percussive, low frequency. If your room isolates well for drums, it will isolate spectacularly well for everything else.

Quote:
I think an average drummer can be as loud as 110 - 140db
110 dBC, certainly, and even 120 is feasible, but not 140. 140 is about the level you'd find at the tailpipe of a 747 jet engine, or about the level of many firearms fired a short distance away. However, even 115 dBC or 120 dBC is still very loud. What most musicians don't realize is that if they were to play their drums in a typical workplace, such as an office or shop, on a normal working day, everyone in the room would be required by law to wear hearing protection! If the level goes above 85 dBC during an 8-hour work shift, employers are required to provide hearing protection for their employees, to prevent hearing damage. 115 dBC is one thousand times louder than 85 dBC. Yes, very literally one thousand times: Each time you go up the dB scale by ten points, that means there is ten times more intensity. So 85 to 95 is ten times, 95 to 105 is another then times (10x10=100) and 105 to 115 is another ten (10x10x10=1000).

I mention that, to clarify that you need to block a huge amount of energy to quite down your drums to acceptable levels.

Quote:
but if I could at least knock off 70db when standing outside the room that would be great.
70 dB isolation is achievable, certainly, but that's pretty much the limit for a project studio, home studio, or small pro studio. Getting to that level needs a substantial budget, careful design, and very careful construction. Once again, this is due to the exponential logarithmic nature of the decibel scale. A typical house wall (wood studs with drywall on both sides) will give you about 30 dB of isolation. To get 70 dB of isolation, you need to block ten thousand times ore energy than the typical house wall. Once again, because each time you go up ten dB, that represents ten times more energy. From 30 dB to 70 dB is four steps of ten points each, so 10x10x10x10, thus, your studio will need to isolate ten thousand times better than a typical house wall.

Quote:
The nearest neighbours will be about 50 meters away, so not super close but not super far either.
That works in your favor, since distance and air both provide natural attenuation of sound. Distance, because each time you double the distance from the source to the receiver, the sound eneryg is now spread over a much wider area since the wavefront expands spherically, and therefore you get a drop of about 3 to 6 dB each time you double toe distance. And air also attenuates sound-waves that are traveling though it. Not much, but enough to be useful over 50m. I would expect that, at that distance, you'd see a drop of maybe 15 to 18 dB. So if you manage to achieve 60 dB of isolation, in order to get 60 dB outside your wall (120dB inside, less 60 dB isolation = 60 dB outside), then at fifty meters away, the result would be around 40 to 45 dB. If you are lucky, that should be legal. But do check your local noise regulations, to make sure.

Quote:
The room will be around 25'x18'x10' (12' if I can) and on a concrete slab.
That's a good size, and the concrete slab is excellent! If you possibly can, make sure that the slab is isolated from any other buildings around you. In other words, your slab should not touch the slab of the house, garage, shed, or anything else. It should be complete alone.

Quote:
So now it's a matter of knowing how to achieve this in the most cost efficient manner.
Right! :thu:

OK, you already know that the only way you can get high levels of isolation: using what I commonly call "fully-decoupled two-leaf MSM isolation system), often also referred to as "room in a room". You need to have a massive, sealed outer "shell" building, and within that you need to build the actual room, also as a massive sealed shell, with the inner shell not touching the outer shell at any point. Not even a single nail, cable, or pipe. No physical contact between the two.

You cannot do this with just one leaf, as it would have to be a 2m thick solid reinforced concrete bunker all around, to get such a high level of isolation. Two-leaf MSM is what you are looking for: "the most cost efficient manner.".

Next, high isolation implies high mass, and the most cost-effective manner of getting lots of mass in a small thickness, is concrete or brick. Yes, as I mentioned in my previous post, it is possible to use things like drywall, MDF, OSB, ply and suchlike, but when you need a very large amount of mass, as you do, then it's easier and cheaper to go with high density materials. The math should convince you: A typical brick wall is about 10cm thick, and each square meter of that wall weighs about 230 kg (ie, the surface density is 230 kg/m2). To get the same mass with drywall, you'd need 34 layers of 16mm drywall, and it would be 54 cm thick. It would work, for sure, but if you think carrying bricks all day is heavy work, try carrying 34 sheets of drywall! :) :shock: :!:

So, for your case (high isolation), at least one of the walls should be masonry with the highest mass you can get. In other words, you do need the Mack truck, since an SUV or limo can't carry the load you need it to carry in one trip.

So I'd suggest concrete block for the outer leaf, and use dry sand or mortar to fill the hollow cores of the blocks after they are in place, for more mass.

Your inner-leaf can be either another brick wall, or just a stud frame with a few layers of sheathing on it (drywall, OSB, etc.)

You can do the math yourself to figure out how many layers, and what type of sheathing. I have posted the equations for doing that in a couple of places: hopefully you already found those. If not, I can post them again. You are shooting for overall isolation of 70 dB, and a resonant frequency of 20 Hz or less, depending on how you normally tune your kick drum, and if you'll be using a 6-string bass along with it.

Quote:
My plan was to build a block work external wall, seal it with paint, clad it with timber all on it's own slab.
12" air gap with rock wall insulation.
Then for the internal walls, timber stud work with 2 layers of 1/2" and 5/8" plaster board all on it's own slab.
That will probably work, but you do need to do the math! Also, you don't need any timber on the inside of the block wall, nor on the outside: I would suggest going with a stucco finish on the outside, as that adds yet more mass and thickness, and can look really good. Of course, if you REALLY are dying to have a timer look, then you could do timber siding, but do be careful that you don't accidentally create a third leaf...

Also, you might need more than just two layers of drywall on the inner-leaf studs: I would suggest a base layer of OSB, as thick as you can (hopefully 19mm or more), plus two layers of 16mm drywall, at least.

Quote:
the roof would be timber frame with ply, roofing felt and clad with box profile corrugated zinc.
Nope! That's where your plan goes wrong. In order for a two-leaf MSM system to work, ALL of the sides of the leaf must have the same surface density. So if you build your walls with very high mass concrete blocks, but just put a thin flimsy light-weight plywood roof deck on, that means that you wasted a hell of a lot of money on those walls! The sound will totally ignore the walls, and exit through the roof instead. In other words, the sound will "flank" around the walls, through the non-isolated roof. Therefore, your roof must be the same mass as your walls. I'd suggest a concrete "block and beam" solution would work well in your case.

So your outer shell would be: concrete block walls filled with sand or mortar, a large air gap filled with insulation, and an inner-leaf consisting of a stud frame with thick OSB as the first layer (on the studs), then at least two layers of "somthing" on top of that. It could be drywall, or MDF; or ply, or OSB. I would not use OSB as the fianl layer, as it looks pretty ugly and does not take paint very well. I mean, you can paint it, but it still looks ugly...

I hope that sets you on the right path! The most important thing for you to get this right, is to do the math, using the equiations for 2-leaf MSM walls.


- Stuart -

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


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PostPosted: Wed Nov 29, 2017 1:00 am 
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Joined: Sun Mar 02, 2014 8:42 am
Posts: 153
Location: Wales, UK
Soundman2020 wrote:
Quote:
I'm not sure if you have all the information you need in order to assess this, but I'm not sure what other info you need.
:thu: That's excellent! Just what I needed to get you started on the best path.


Quote:
I want to build a live room in which I can record bands but mainly only need to worry about containing the sound of the drum kit as that's the instrument that will be tracked there the majority of the time.
That's also the loudest instrument in a typical contemporary band, so that's what defines the entire isolation. The drum kit produces the most acoustic energy of any acoustic instruent, and also puts out a lot of that energy in the low frequency range, below about 200 Hz, which is the hardest to isolate. Low frequencies have very long wavelengths, which are difficult to contain. Drum noises are also percussive (sudden short, sharp, high intensity sounds), which are far more noticeable and annoying than a continuous sound. In short, drums are the hardest of all to isolate: High energy, percussive, low frequency. If your room isolates well for drums, it will isolate spectacularly well for everything else.

Quote:
I think an average drummer can be as loud as 110 - 140db
110 dBC, certainly, and even 120 is feasible, but not 140. 140 is about the level you'd find at the tailpipe of a 747 jet engine, or about the level of many firearms fired a short distance away. However, even 115 dBC or 120 dBC is still very loud. What most musicians don't realize is that if they were to play their drums in a typical workplace, such as an office or shop, on a normal working day, everyone in the room would be required by law to wear hearing protection! If the level goes above 85 dBC during an 8-hour work shift, employers are required to provide hearing protection for their employees, to prevent hearing damage. 115 dBC is one thousand times louder than 85 dBC. Yes, very literally one thousand times: Each time you go up the dB scale by ten points, that means there is ten times more intensity. So 85 to 95 is ten times, 95 to 105 is another then times (10x10=100) and 105 to 115 is another ten (10x10x10=1000).

I mention that, to clarify that you need to block a huge amount of energy to quite down your drums to acceptable levels.

Quote:
but if I could at least knock off 70db when standing outside the room that would be great.
70 dB isolation is achievable, certainly, but that's pretty much the limit for a project studio, home studio, or small pro studio. Getting to that level needs a substantial budget, careful design, and very careful construction. Once again, this is due to the exponential logarithmic nature of the decibel scale. A typical house wall (wood studs with drywall on both sides) will give you about 30 dB of isolation. To get 70 dB of isolation, you need to block ten thousand times ore energy than the typical house wall. Once again, because each time you go up ten dB, that represents ten times more energy. From 30 dB to 70 dB is four steps of ten points each, so 10x10x10x10, thus, your studio will need to isolate ten thousand times better than a typical house wall.

Quote:
The nearest neighbours will be about 50 meters away, so not super close but not super far either.
That works in your favor, since distance and air both provide natural attenuation of sound. Distance, because each time you double the distance from the source to the receiver, the sound eneryg is now spread over a much wider area since the wavefront expands spherically, and therefore you get a drop of about 3 to 6 dB each time you double toe distance. And air also attenuates sound-waves that are traveling though it. Not much, but enough to be useful over 50m. I would expect that, at that distance, you'd see a drop of maybe 15 to 18 dB. So if you manage to achieve 60 dB of isolation, in order to get 60 dB outside your wall (120dB inside, less 60 dB isolation = 60 dB outside), then at fifty meters away, the result would be around 40 to 45 dB. If you are lucky, that should be legal. But do check your local noise regulations, to make sure.

Quote:
The room will be around 25'x18'x10' (12' if I can) and on a concrete slab.
That's a good size, and the concrete slab is excellent! If you possibly can, make sure that the slab is isolated from any other buildings around you. In other words, your slab should not touch the slab of the house, garage, shed, or anything else. It should be complete alone.

Quote:
So now it's a matter of knowing how to achieve this in the most cost efficient manner.
Right! :thu:

OK, you already know that the only way you can get high levels of isolation: using what I commonly call "fully-decoupled two-leaf MSM isolation system), often also referred to as "room in a room". You need to have a massive, sealed outer "shell" building, and within that you need to build the actual room, also as a massive sealed shell, with the inner shell not touching the outer shell at any point. Not even a single nail, cable, or pipe. No physical contact between the two.

You cannot do this with just one leaf, as it would have to be a 2m thick solid reinforced concrete bunker all around, to get such a high level of isolation. Two-leaf MSM is what you are looking for: "the most cost efficient manner.".

Next, high isolation implies high mass, and the most cost-effective manner of getting lots of mass in a small thickness, is concrete or brick. Yes, as I mentioned in my previous post, it is possible to use things like drywall, MDF, OSB, ply and suchlike, but when you need a very large amount of mass, as you do, then it's easier and cheaper to go with high density materials. The math should convince you: A typical brick wall is about 10cm thick, and each square meter of that wall weighs about 230 kg (ie, the surface density is 230 kg/m2). To get the same mass with drywall, you'd need 34 layers of 16mm drywall, and it would be 54 cm thick. It would work, for sure, but if you think carrying bricks all day is heavy work, try carrying 34 sheets of drywall! :) :shock: :!:

So, for your case (high isolation), at least one of the walls should be masonry with the highest mass you can get. In other words, you do need the Mack truck, since an SUV or limo can't carry the load you need it to carry in one trip.

So I'd suggest concrete block for the outer leaf, and use dry sand or mortar to fill the hollow cores of the blocks after they are in place, for more mass.

Your inner-leaf can be either another brick wall, or just a stud frame with a few layers of sheathing on it (drywall, OSB, etc.)

You can do the math yourself to figure out how many layers, and what type of sheathing. I have posted the equations for doing that in a couple of places: hopefully you already found those. If not, I can post them again. You are shooting for overall isolation of 70 dB, and a resonant frequency of 20 Hz or less, depending on how you normally tune your kick drum, and if you'll be using a 6-string bass along with it.

Quote:
My plan was to build a block work external wall, seal it with paint, clad it with timber all on it's own slab.
12" air gap with rock wall insulation.
Then for the internal walls, timber stud work with 2 layers of 1/2" and 5/8" plaster board all on it's own slab.
That will probably work, but you do need to do the math! Also, you don't need any timber on the inside of the block wall, nor on the outside: I would suggest going with a stucco finish on the outside, as that adds yet more mass and thickness, and can look really good. Of course, if you REALLY are dying to have a timer look, then you could do timber siding, but do be careful that you don't accidentally create a third leaf...

Also, you might need more than just two layers of drywall on the inner-leaf studs: I would suggest a base layer of OSB, as thick as you can (hopefully 19mm or more), plus two layers of 16mm drywall, at least.

Quote:
the roof would be timber frame with ply, roofing felt and clad with box profile corrugated zinc.
Nope! That's where your plan goes wrong. In order for a two-leaf MSM system to work, ALL of the sides of the leaf must have the same surface density. So if you build your walls with very high mass concrete blocks, but just put a thin flimsy light-weight plywood roof deck on, that means that you wasted a hell of a lot of money on those walls! The sound will totally ignore the walls, and exit through the roof instead. In other words, the sound will "flank" around the walls, through the non-isolated roof. Therefore, your roof must be the same mass as your walls. I'd suggest a concrete "block and beam" solution would work well in your case.

So your outer shell would be: concrete block walls filled with sand or mortar, a large air gap filled with insulation, and an inner-leaf consisting of a stud frame with thick OSB as the first layer (on the studs), then at least two layers of "somthing" on top of that. It could be drywall, or MDF; or ply, or OSB. I would not use OSB as the fianl layer, as it looks pretty ugly and does not take paint very well. I mean, you can paint it, but it still looks ugly...

I hope that sets you on the right path! The most important thing for you to get this right, is to do the math, using the equiations for 2-leaf MSM walls.


- Stuart -


Great, that's a big help and answered a few questions I had.

Thank-you for correcting me on the roof - I knew that it should be the same mass as the walls ideally but had no idea how to create such heavy mass on something that needs to float above our heads! I will look into this concrete block and beam solution - Do you know if they can be constructed with a slight pitch? (maybe around 10 degrees) - it rains A LOT here.

Now, how would I avoid creating a third leaf with either the zinc roofing sheets or the timber cladding? I perhaps wrongly assumed that if a layer was physically attached to a leaf then it would become part of the same leaf?

Also, what if I use solid core 100mm blocks instead of the thicker but hollow blocks?

Cheers for now


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