Re using wall. floor ceiling materials.

[princeplanet]

Hi, first post!

I'm considering relocating my current studio (end of lease) to another, as yet unchosen, building. I need to "make good", so I'll be taking down my soundproof walls (3 large "rooms within rooms", all walls drywall/caneite/MLV/drywall). Someone recently said I should consider sawing my walls in panels from ceiling to floor in order to fit them back together in another building. Obviously, the "joins" will compromise the STC rating of the wall, but will it adversely affect 40 to 120 hz being transmitted into adjacent rooms or buildings?

Is this as crazy as it sounds?

[Soundman2020]

Hi "princeplanet". Please read the forum rules for posting (click here). You seem to be missing a couple of things!

drywall/caneite/MLV/drywall

That's quite a "sandwich"! That is VERY old-school. Studio walls are not built like that today. I'm guessing your place must have been built way back in the 1960's, before the science of isolation was understood well? Caneite isn't used much these days. And if all of your walls have a layer of MLV in them, then man did the salesman make a bundle from that! (Not to mention taking the original owner for a ride....). There is absolutely no need at all to line an entire room with MLV. It does have some uses in acoustics, but they are few. About the only three uses I have for it when designing studios, is when I need to get a lot of mass into a thin panel, when I need to build a curved barrier with something flexible, and for limp-membrane traps. The only other use for it, is to make the salesman rich at your expense. MLV is mass. Very, very expensive mass. Sound waves can't red price tags so they really don't care if you used MLV or drywall to get that mass: they react to it in the exact same way. And since MLV costs about ten times as much as drywall, draw your own conclusions.... Yes it works, and I have no doubt that your walls probably do a good job, but boy is that an expensive way of accomplishing isolation!

So basically you have a gold-mine in your walls. The MLV is worth a small fortune. The canite might be useful for a museum, to document the way things used to be done 50 years ago. And the drywall probably won't survive the demolition and transportation process very well, but it might if you work very carefully.

Someone recently said I should consider sawing my walls in panels from ceiling to floor

You'd have to take out your inner-leaf ceiling first! If your studio is built correctly as a proper "room-in-a-room", then the inner-leaf walls are supporting the inner-leaf ceiling, so you'll have to get the ceiling out before you can get the walls out. It might not be easy to cut the ceiling into "modules" if it was not built that way. As soon as you cut a couple of joists to make a "module", the rest of the ceiling will collapse. The ceiling will have to be dismantled is stages: First remove the drywall, MLV, and canite, layer by layer, then remove the insulation, then take out the cross-bracing, then take out the joists, one by one.

in order to fit them back together in another building.

... that assumes that the new building is identical to the existing one! Otherwise, things won't fit. You won't be able to assemble a 6m wall in a 5m space.... and assembling a 5m wall in a 6m space means that you wasted 1m.

Obviously, the "joins" will compromise the STC rating of the wall,

Forget STC. It is no use at all for telling you how well your re-built wall will isolate. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.

“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”

It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.

Here's how it works:

To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.

Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a wall rated at STC-30 that provides much better than 40 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. STC was never designed for that, and cannot be used for that.

So forget STC as a useful indicator, and just use the actual TL graphs to judge if your new wall, door, window, floor, roof, or whatever will meet your needs.

Sorry for the rant about STC, and I know that wasn't really your question at all, but I did want to point out that worrying about STC for studio walls is pointless! I'll get back to your real question below, but it's important to understand this, in order to understand the actual answer.

will it adversely affect 40 to 120 hz being transmitted into adjacent rooms or buildings

If you use STC ratings, there's no way at all to determine that. The question itself is invalid, since STC does not consider any frequencies in that range! Nothing below 125 Hz is used in calculating STC.

OK, this is a real long-winded way of answering what seems to be a simple question, but in reality the issue is a lot more complex than you imagine, so please bare with me...

Isolation is a system, not a set of materials. Isolation is a system, not a wall. Isolation is a system, not a price tag, or a method, or a rating. When you isolate a studio, you are putting in place a tuned system, not just a bunch of building materials that act by themselves. They all act together as one single unit that provides isolation, not as individual parts. You can't take two building products, one rated at STC-20 and the other rated at STC-30, put them together and expect to get STC-50. It doesn't work like that. The same applies if you use the correct term "TL" ("Transmission Loss"). You can't say that if a sheet of drywall gives you 20 dB TL, then two sheets will give you 40 dB (in reality, if one sheet gives you 20 dB TL, then two sheets together will give you about 25 dB TL).

It's a lot more complex than just adding numbers, because of the whole "tuned system" thing. Like it or not, a studio wall is a resonant system that is tuned to a specific resonant frequency. At that specific frequency it does not isolate at all, and in fact it can amplify the sound. It only starts isolating at 1.414 times that frequency, and isolates reasonably well at about twice that frequency and above. The higher you go up the scale, the better the isolation gets. So clearly, you need to design your wall such that the resonant frequency is no more than half the frequency you want to isolate. In your case, you say you want to isolate down to 40 Hz, so therefore the resonant frequency of your wall needs to be 20 Hz or lower.

That begs the question: How do you set that frequency? It's actually not hard: The equation for determining the MSM resonant frequency of a wall takes into account only three major factors: The mass on each of the two leaves of the wall, the distance between the two leaves (often called "cavity depth" or "air gap"), and the damping material between them. It's very logical: If you increase the mass, then the frequency goes down and you get better isolation. If you increase the cavity depth, then the frequency goes down and you get better isolation. If you added damping material, then the frequency goes down and you get better isolation. So you can play with those three parameters until you get the frequency where you want it to be. The equation is simple, if you are interested.

OK, so that's the reason why asking if your new wall would isolate well between 40 Hz and 120 Hz. Simple answer: it is impossible to say! There is not enough information to decide if it would, or not. You would need to know the mass (surface density) of your current walls which will be the new inner leaf of the new building that you move to, AND ALSO the mass (surface density) of the existing outer-leaf walls ion that new building, AND ALSO the damping factor from the insulation you put between them.

It is entirely possible that your old walls plus your new walls would create a system that isolates fantastically all the way down to 20 Hz, and it is equally possible that it would not isolate at all, even at 120 Hz. It all depends on how you build the new studio.

So that's a very long, convoluted, round-about way of getting to the answer to your question:

All things considered: NO it is not worth trying to take the walls down as modules that can be re-assembled: If they were not specifically designed and built with that in mind, it would be very hard to do anyway.

However, it certainly is worth trying to take them apart and keep all the materials! Those materials can be re-used to build your new inner-leaf walls in the new studio. Save the studs, certainly, save the MLV, most definitely, and save the drywall if you can, but realize that you'll probbaly lose a lot of drywall, as it is brittle, easily damaged, and doesn't transport well. But you still might be able to save a decent portion of it, and worst case the smaller pieces it can be used to "beef up" the existing walls in your new studio, if needed.

So take it all apart carefully, layer by layer, and it will be re-usable. The doors and windows especially should be useful for the new studio, assuming they were built properly.

Is this as crazy as it sounds?

The idea of a modular studio is not crazy in itself: I have designed a couple like that. But it only works if the studio was designed to be modular, and built as modular. Trying to take apart a studio that was built conventionally, is likely not going to be possible.


- Stuart -

[princeplanet]

Hi "princeplanet". Please read the forum rules for posting (click here). You seem to be missing a couple of things!

drywall/caneite/MLV/drywall

That's quite a "sandwich"! That is VERY old-school. Studio walls are not built like that today. I'm guessing your place must have been built way back in the 1960's, before the science of isolation was understood well? Caneite isn't used much these days. And if all of your walls have a layer of MLV in them, then man did the salesman make a bundle from that! (Not to mention taking the original owner for a ride....). There is absolutely no need at all to line an entire room with MLV. It does have some uses in acoustics, but they are few. About the only three uses I have for it when designing studios, is when I need to get a lot of mass into a thin panel, when I need to build a curved barrier with something flexible, and for limp-membrane traps. The only other use for it, is to make the salesman rich at your expense. MLV is mass. Very, very expensive mass. Sound waves can't red price tags so they really don't care if you used MLV or drywall to get that mass: they react to it in the exact same way. And since MLV costs about ten times as much as drywall, draw your own conclusions.... Yes it works, and I have no doubt that your walls probably do a good job, but boy is that an expensive way of accomplishing isolation!

So basically you have a gold-mine in your walls. The MLV is worth a small fortune. The canite might be useful for a museum, to document the way things used to be done 50 years ago. And the drywall probably won't survive the demolition and transportation process very well, but it might if you work very carefully.

Someone recently said I should consider sawing my walls in panels from ceiling to floor

You'd have to take out your inner-leaf ceiling first! If your studio is built correctly as a proper "room-in-a-room", then the inner-leaf walls are supporting the inner-leaf ceiling, so you'll have to get the ceiling out before you can get the walls out. It might not be easy to cut the ceiling into "modules" if it was not built that way. As soon as you cut a couple of joists to make a "module", the rest of the ceiling will collapse. The ceiling will have to be dismantled is stages: First remove the drywall, MLV, and canite, layer by layer, then remove the insulation, then take out the cross-bracing, then take out the joists, one by one.

in order to fit them back together in another building.

... that assumes that the new building is identical to the existing one! Otherwise, things won't fit. You won't be able to assemble a 6m wall in a 5m space.... and assembling a 5m wall in a 6m space means that you wasted 1m.

Obviously, the "joins" will compromise the STC rating of the wall,

Forget STC. It is no use at all for telling you how well your re-built wall will isolate. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.

“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”

It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.

Here's how it works:

To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.

Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a wall rated at STC-30 that provides much better than 40 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. STC was never designed for that, and cannot be used for that.

So forget STC as a useful indicator, and just use the actual TL graphs to judge if your new wall, door, window, floor, roof, or whatever will meet your needs.

Sorry for the rant about STC, and I know that wasn't really your question at all, but I did want to point out that worrying about STC for studio walls is pointless! I'll get back to your real question below, but it's important to understand this, in order to understand the actual answer.

will it adversely affect 40 to 120 hz being transmitted into adjacent rooms or buildings

If you use STC ratings, there's no way at all to determine that. The question itself is invalid, since STC does not consider any frequencies in that range! Nothing below 125 Hz is used in calculating STC.

OK, this is a real long-winded way of answering what seems to be a simple question, but in reality the issue is a lot more complex than you imagine, so please bare with me...

Isolation is a system, not a set of materials. Isolation is a system, not a wall. Isolation is a system, not a price tag, or a method, or a rating. When you isolate a studio, you are putting in place a tuned system, not just a bunch of building materials that act by themselves. They all act together as one single unit that provides isolation, not as individual parts. You can't take two building products, one rated at STC-20 and the other rated at STC-30, put them together and expect to get STC-50. It doesn't work like that. The same applies if you use the correct term "TL" ("Transmission Loss"). You can't say that if a sheet of drywall gives you 20 dB TL, then two sheets will give you 40 dB (in reality, if one sheet gives you 20 dB TL, then two sheets together will give you about 25 dB TL).

It's a lot more complex than just adding numbers, because of the whole "tuned system" thing. Like it or not, a studio wall is a resonant system that is tuned to a specific resonant frequency. At that specific frequency it does not isolate at all, and in fact it can amplify the sound. It only starts isolating at 1.414 times that frequency, and isolates reasonably well at about twice that frequency and above. The higher you go up the scale, the better the isolation gets. So clearly, you need to design your wall such that the resonant frequency is no more than half the frequency you want to isolate. In your case, you say you want to isolate down to 40 Hz, so therefore the resonant frequency of your wall needs to be 20 Hz or lower.

That begs the question: How do you set that frequency? It's actually not hard: The equation for determining the MSM resonant frequency of a wall takes into account only three major factors: The mass on each of the two leaves of the wall, the distance between the two leaves (often called "cavity depth" or "air gap"), and the damping material between them. It's very logical: If you increase the mass, then the frequency goes down and you get better isolation. If you increase the cavity depth, then the frequency goes down and you get better isolation. If you added damping material, then the frequency goes down and you get better isolation. So you can play with those three parameters until you get the frequency where you want it to be. The equation is simple, if you are interested.

OK, so that's the reason why asking if your new wall would isolate well between 40 Hz and 120 Hz. Simple answer: it is impossible to say! There is not enough information to decide if it would, or not. You would need to know the mass (surface density) of your current walls which will be the new inner leaf of the new building that you move to, AND ALSO the mass (surface density) of the existing outer-leaf walls ion that new building, AND ALSO the damping factor from the insulation you put between them.

It is entirely possible that your old walls plus your new walls would create a system that isolates fantastically all the way down to 20 Hz, and it is equally possible that it would not isolate at all, even at 120 Hz. It all depends on how you build the new studio.

So that's a very long, convoluted, round-about way of getting to the answer to your question:

All things considered: NO it is not worth trying to take the walls down as modules that can be re-assembled: If they were not specifically designed and built with that in mind, it would be very hard to do anyway.

However, it certainly is worth trying to take them apart and keep all the materials! Those materials can be re-used to build your new inner-leaf walls in the new studio. Save the studs, certainly, save the MLV, most definitely, and save the drywall if you can, but realize that you'll probbaly lose a lot of drywall, as it is brittle, easily damaged, and doesn't transport well. But you still might be able to save a decent portion of it, and worst case the smaller pieces it can be used to "beef up" the existing walls in your new studio, if needed.

So take it all apart carefully, layer by layer, and it will be re-usable. The doors and windows especially should be useful for the new studio, assuming they were built properly.

Is this as crazy as it sounds?

The idea of a modular studio is not crazy in itself: I have designed a couple like that. But it only works if the studio was designed to be modular, and built as modular. Trying to take apart a studio that was built conventionally, is likely not going to be possible.


- Stuart -

Wow! That's quite an answer! I feel humbled and incredibly grateful already! And embarrassed that I seemed to have overlooked the forum rules?... I had another look and I'm not sure I can provide answers to most of the requirements, which are the more important things you need from me? I thought I included my location in my profile... As far as background, the current studio was built in 1998 with design input from Graeme Thirkell, hence the "old school" methods...

It's an indie Rock studio, so lotsa loud drums,bass and guitars obviously. I like to use my large soffit mounted mains (2x 15in + horn and tweeter in each) and am thinking to relocate - don't laugh - to an office space in a high rise! I haven't decided on anything yet, so feel free to talk me out of it! Actually, whatever the new space will be, it will be half the size, so 80sqm instead of 160sqm, just a control room and a recording space (you'll hate this, but I want a larger control room than my recording space this time! (yeah I know, I won't hear the reverb tails etc, I'll live... ).

You got me wondering how much MLV was used, maybe it wasn't in every wall, just the inside ones?... But regardless, It's disappointing to hear that I'd need to unscrew every single layer one at a time in order to re use anything. Sounds like the labour costs won't be worth it?... Is there no way to hope to saw some panels as described above, with the studs attached? Hmm, I just remembered we had resilient channels going on as well, does that make it more difficult still? Oh, pretty sure the smaller control room was made of Straw board which should demountable, right? I remember a T bar type assembly for each 2" thick panel (with drywall added to the insides).

Def saving windows and doors, and maybe the parquetry floors (If I can figure out a way to rescue them!)
And yeah, I hear ya re STC, I'll use TL from now on. Hypothetically, If I somehow did manage to saw out panels of my wall and green glue them back together (maybe reinforce the "joins" somehow?), how much worse than the original TL at low frequencies could it be? I mean assuming every thing was done as carefully and correctly as possible?

Oh, and about the crazy idea to relocate to an office space, should I start a fresh new thread about that, or can we leave it in this thread? - assuming of course that the good people of this forum are willing to participate further ...

Thanks again for your kind interest!
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