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PostPosted: Tue Sep 06, 2016 10:13 pm 
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Location: Margate, England
hello and thanks for having me! im new here, having read the rules i hope i wont break them, I’ve searched the forums for the questions still feel unsure about details about my specific build. also sorry im not putting all questions at the end, i feel that would get really confusing because they relate to specific detail im describing before. so i've made questions bold.



I'm about to start building a studio in Margate, UK. I've spent the last few months reading books , watching tutorials, forums etc.

The studio will be built in a large open warehouse with thick concrete floor (its an old train station, floor seem to be about 1.5m thick, but we dont know how thick the actual concrete is, but it used to be the old platforms of the station which only dealt with heavy loads, not people so we assume its a lot of big stones, soil and concrete int he floor) and brick / breeze block walls. (images attatched - the steel structure is being taken out in next couple of weeks) The size of my studio (inside measurements) will be (all in mm sorry) H - 2730 W - 4100 L - 9000 . This post will not really adress accoustic treatment, more the building of the actual box. There will be no live room / control room. I prefere to work in an open space with artists so Im basically just building 1 medium sized room. Budget is about £20 000

I'm building a double wall / ceiling construction with 3 layers of plaster board inside and outside, trying to achive STC 69. There will be one large window (2 layers of laminted glass, STC 35 each) , and here comes one of my first questions. Can you add 35db + 35db and it equals 70db??? probably the most stupid question ever but want to double check. Same for the doors, am i ok with 2 x STC 35 doors (=70dB) to accomplish the total STC 69 of whole structure?



In Rod Gervias book (second edition) on page 270 (Figure 10.16 - image attatched) he talks about a decoupled floor which doesn't involve floating a concrete slab. Im really curious about this cause it would save money and time.

There is another studio being built inside the warehouse, that guy is building his studio on a floating concrete slab. Im hoping to avoid it. there isn't really any outside low frequency sound in the warehouse apart from what both studios will be making. and the fact that the other guy is putting down a decoupled concrete slab, i get the impression i might get away with not having to do it. (the other studio will start 50cm from my outer wall and being built in a very professional way) BUT there are also some things in Figure 10.16 that confuse me.

- inside the 2 layers of plaster board there seem to be a thin layer of insulation (not specified) which sits ontop of floor, then another layer of somethign that looks like plaster board (but if the drawings are to scale it looks slightly thicker) , has anyone else built this type of floor and can advice???


- Rod suggest a layer of rigid fibreglass insulation (3 pcf) , i've seen other similar decoupled floor where they use 1 layer of 12.5mm soundboard (celotex), then 25mm mineral fibre (33kg/m3) and then another layer of Celotex. The celotex (sound board) confuse me cause its a really light material, but much more expensive than thick floor sheets of styrofoam. The styrofoam is obviously much cheaper than a 3pcf insulation but nowhere near as dense, im just curious if anyone has worked with styrofoam layered under plywood (again refering to figure 10.16), i assume the bass frequencies would just pass through it and into concrete floor, hence why Rod recomends a 3 pcf insulation?



Another thing we’re not 100% sure about is building against the 2 brick walls (window wall, and long breeze block wall) . the long breeze block wall has got cracks in it (next door is a car garage) so we will plaster that wall really carefully to make sure there are no holes. we’re then planning on using the brick wall as our ‘plasterboard layer’ on that side of studio (see attatched drawing but dont mind scale, all walls and ceiling is same thickness and same air gap). Im very curious about what you all think of this idea, and also what you think of the sealing between roof top 3 layers of plasterboard against the plastered wall breeze block wall. we where thinking of stopping roof plasterboard a few cm from the wall (since wall is not perfectly straight) , then filling void between wall and plaster with cement, then a final layer of thick caulk sealant to finish it off  (how important is it using acoustic sealant? or is a good decorators caulk enough?)


Which brings me to another question about sealing, would you seal between layers of plaster boards on walls and ceiling? we'll stagger our seams but im still wondering if there should be accoustic sealant or decorators caulk in the small cracks before you add next layer of plaster board. and if so, how long would you wait to put next layer of plaster board on, since sealant dries by evaporating moisture. i assume we don't want any moisture like that trapped inside the walls??


and a last question for now. I’ve seen different density insulations for walls being recommended, some saying it doesn't matter, and some saying it should be pretty heavy (which make sense). can someone recommend a good insulation density for my build? th structure will be made up of 5x2 so theres plenty of space for thick heavy insulation if needed. Airgap between walls will be about 8cm we're thinking.


Im sure this will only raise more questions for us, but i’d be very grateful for any help.



thanks. Johan


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PostPosted: Wed Sep 07, 2016 2:25 am 
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Hi there Johan, and Welcome! :)

Quote:
The studio will be built in a large open warehouse with thick concrete floor (its an old train station, floor seem to be about 1.5m thick,
Lucky you! That's an excellent base for your studio. many forum members would die to have such an opportunity!

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There will be no live room / control room. I prefere to work in an open space with artists so Im basically just building 1 medium sized room.
Trying to understand: So you will be mixing elsewhere, not here? You'll basically just be rehearsing / jamming / tracking in this studio, then taking the recorded tracks to some other location to mix / edit / master? So this place will be more like just a small-to-medium sized live room? Is that the main goal? I'm just thinking that with all that wonderful space available, you could also add an amazing control room alongside your live room, and do your mixing/mastering there too, on-site. Have you considered that?

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Budget is about £20 000
For a 36 m2 tracking room inside an existing structure that already has a good floor, that's probably about right. Good! Adding a control room within the same footprint for your mixing needs would probably increase that a bit, but not excessively.

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The size of my studio (inside measurements) will be (all in mm sorry) H - 2730 W - 4100 L - 9000
Any reason for that specific size? Is there some limitation that would prevent you from increasing any of those three? There seems to be a lot of headroom available up there, for example, so I'm wondering why you didn't go with a much higher ceiling.

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I'm building a double wall / ceiling construction with 3 layers of plaster board inside and outside,
If you build a double-wall structure inside an existing building that already has walls around it, then you have a triple-leaf situation. That might or might not be a problem, depending on what your goals are. Triple leaf is generally a bad idea, and should be avoided where possible, since it trashes your low frequency isolation. It would be better to go with a conventional two-leaf design for your place.

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trying to achive STC 69.
Forget STC. It is no use at all for measuring isolation in studios. Here's the actual definition from the original standard which explains STC (ASTM E413), and describes the limitations of its use: “These single-number (STC) 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 allies, 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.

The reasons is simple: STC entirely ignores the bottom two and a half octaves of the musical spectrum, and also the top two and a half octaves. It only takes into account a small section of the spectrum, in the mid range, and it only does so at a handful of specific points.

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 curve that is closest to your curve.

I can build you a wall rated at STC-50 that does a terrible job of isolating music, and I can build you another wall rated at STC-40 that does a much better job. STC was never meant to measure studio isolation.

Isolating studios is all about the low frequencies, below about 200 Hz, where STC does not go. A wall system that isolates well at 50 Hz will also isolate very well at 5 kHz, but the reverse is not true. Your walls have to be designed for low frequency isolation.

Quote:
There will be one large window (2 layers of laminted glass, STC 35 each) , and here comes one of my first questions. Can you add 35db + 35db and it equals 70db???
Nope! If it were that simple, then four sheets of plywood would get you 100 dB of isolation... in reality, to get 100 dB of isolation you need a massively thick reinforced concrete bunker floated on huge isolation springs, inside another massively thick reinforced concrete bunker.... there's only one studio on this planet that has 100 dB isolation, and that's how they had to build it.

You cannot simply add decibels , because the decibel scale is logarithmic. Mathematically, adding logs is the same as multiplying the base numbers, and clearly you won't multiply the isolation by just having two walls! In fact, you wont even add.

You can't even work backwards to the base numbers and add those, because sound isn't a simple linear phenomena: it is logarithmic by nature, and even if it were linear, there are still effects such as resonance and phase cancellation/addition to take into account, which can be far larger than simple isolation due to mass.

In reality, doubling the mass of a wall will increase your isolation by about 5 dB. Theoretically it should be 6 dB (which is the logarithmic double of intensity), but in reality there are always losses and other issues that reduce the actual performance below the theoretical performance. So if one sheet of plywood gets you 20 dB of isolation (for example), then adding a second sheet on top of that would get you about 25 dB. And adding another two sheets on top of those two (total of four sheets) would get you about 30 dB. And adding antoher four sheets on top of those four (total of eight), would get you about 35 dB. And adding another eight sheets on top of those eight (total of sixteen sheets) would get you about 40 dB. And adding... OK, I think you get the picture. This principle is called "mass law" for single-leaf partitions, and it is not a very exciting way of getting high levels of isolation, because you need enormous amounts of mass. Fortunately, single-leaf mass-law is not the only game in town.

And finally, you seem to be confusing "35 db of isolation" with "STC-35". They are not the same thing at all, as I explained above. STC-35 is totally unrelated to 35 dB of transmission loss through a wall. STC-35 is just a number. All it does is identify "Curve Number 35" in the library of all possible STC curves. No relationship at all to 35 dB.

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probably the most stupid question ever but want to double check.
Not stupid at all! This stuff is not intuitive, and not common knowledge, and not even taught in most schools! There's no reason why you would be expected to know it.

Many, many years ago I had a teacher in high school whose favorite phrase was: "The only stupid question is the one you didn't ask!". Not asking questions is far more stupid than asking questions!

Quote:
Same for the doors, am i ok with 2 x STC 35 doors (=70dB) to accomplish the total STC 69 of whole structure?
Nope. Not OK. For the same reasons as above. Mathematically, 35 dB + 35 dB does not equal 70 dB: it only equals 38 dB (assuming we are talking about sound levels), or 40 dB (assuming we are talking about just doubling the mass of the original wall). It won't ever be 70 dB. And also STC-70 is not the same as 70 dB of isolation. So two doors each rated at STC-35 would most definitely not get you 70 dB of isolation. Maybe 40 or so, give or take half a dozen, depending on how they doors are built, and the gap between them, and any edge damping, and most of all the seals. Lousy seals could mean that you only get 30 dB of isolation from that pair of doors.... Best case, with excellent doors and fantastic seals, a decent gap, and good edge damping, you might get 50 dB of isolation, with a LOT of luck...

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he talks about a decoupled floor which doesn't involve floating a concrete slab.
Don't' confuse "decoupling" with "floating". It's not really the same.

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There is another studio being built inside the warehouse, that guy is building his studio on a floating concrete slab.
Then he's doing it the right way! :)

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the other studio will start 50cm from my outer wall and being built in a very professional way
:thu:

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things in Figure 10.16 that confuse me. ... inside the 2 layers of plaster board there seem to be a thin layer of insulation (not specified) which sits ontop of floor, then another layer of somethign that looks like plaster board (but if the drawings are to scale it looks slightly thicker)
Read the captions! There is no drywall (plasterboard) in that floor. The labels clearly say that there are two layers of half-inch plywood screwed together in a specific pattern, resting on top of a two-inch layer of a specific type and density of insulation, and with ordinary laminate flooring on top. There's no other "layer of insulation (not specified)" in there. It's just a light-weight decoupled riser floor, suitable for some applications but not all.

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i've seen other similar decoupled floor where they use 1 layer of 12.5mm soundboard (celotex), then 25mm mineral fibre (33kg/m3) and then another layer of Celotex.
That's a different design. Not at all the same as Rod's. In the place where you saw that, did they also provide acoustical test data that shows how that system performs?

Quote:
The celotex (sound board) confuse me cause its a really light material, but much more expensive than thick floor sheets of styrofoam.
Celotex is not sytrofoam is not rigid fiberglass is not plywood is not plasterboard is not mineral wool. They are all very, very different materials acoustically, and you cannot substitute.

Imagine you found a great recipe for making an excellent chicken dinner, but then you remembered that you also once saw another recipe for some type of food that used sugar and peaches. So you skip the chicken and use peaches instead, but when you went to the supermarket you noticed that lettuce is cheaper than sugar, so you change that too: substitute peaches for chicken, and lettuce for sugar. After all, those are all food items, right? Will you still end up with a chicken dinner? :)
:roll: :shock: :shot:

Here's the thing: All studio isolation systems are tuned. There's a recipe for tuning them. They have a natural resonant frequency, which is what governs the maximum isolation that they can provide. If you change anything in the wall design (recipe), then you change the tuning. If you don't know what you are doing, and didn't work through the math to make sure the resonant frequency, rigidity, coincidence dip, and intermediate transition characteristics are all correct for what you need, then you basically have no idea how the wall will perform. It MIGHT be better, but chances are it won't. Your chances of getting better isolation by substituting materials at random are roughly the same as you ending up with a delicious chicken dinner in the above scenario... :)

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The styrofoam is obviously much cheaper than a 3pcf insulation
... and it is totally different! Styrofoam has practically no uses in acoustics, except to make the cup that holds your coffee while you work on the studio... :)

Styrofoam is closed-cell. Fiberglass insulation is open-cell. You can't compare the two at all. Fiberglass insulation is available in versions that have gas flow resistivity over a very broad range, usefully from maybe 3,000 rayls to maybe 30,000 rayls in acoustics. The gas flow resistivity of Styrofoam is essentially infinite, so it is essentially useless.

Quote:
but nowhere near as dense,
Density is not the issue. Gas flow resistivity (GFR) is the issue. The purpose of the insulation layer in a tuned isolation system is not to provide mass: it is to provide damping on the multiple resonances that occur inside the cavity. Styrofoam is useless for that.

Quote:
im just curious if anyone has worked with styrofoam layered under plywood
I'm sure somebody has tried that out of ignorance, and ended up with a terrible floor that does not isolate at all! It might keep their feet nice and warm, since Styrofoam does have good thermal insulation properties (which is why acousticians use it to hold their hot coffee... :), but a floor built on Styrofoam would be very lousy, acoustically.

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hence why Rod recomends a 3 pcf insulation?
Rod does not recommend 3 pcf insulation: he recommends 3 pcf rigid fiberglass insulation: There's a big difference. He did not say that you can use any old insulation that just happens to be around 3 pcf: he said that you can use ONLY rigid fiberglass insulation that has a density of 3 pcf. He also did not say that you can use 1/4" plasterboard instead of 1/2" plywood, or Celotex instead of fiberglass. He provided a recipe that he has cooked many times himself, and he always got a chicken dinner when he cooked it. Any substitutes wont give you a chicken dinner.

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the long breeze block wall has got cracks in it (next door is a car garage) so we will plaster that wall really carefully to make sure there are no holes.
Yes, definitely, but before you do that get a structural engineer in to take a look at that wall and the cracks, to make sure there are no underlying issues that need fixing first. It would be really sad for you to invest 20k in this, then have one wall fall down and kill you a few weeks later... :ahh:

In building your studio, whatever else you do to save money, do not ever skimp on safety.

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we’re then planning on using the brick wall as our ‘plasterboard layer’ on that side of studio
Wellll.... "yes but no": Yes you can use it for your outer leaf, since it does have very substantial mass and will be well sealed, ... but no, it will not be the same as a plasterboard wall. That would make for an Ostrich dinner, not a chicken dinner... :) (Ostrich actually tastes really nice, when prepared well, but that's a different recipe... It's not chicken...)

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all walls and ceiling is same thickness and same air gap).
"All other ingredients are the same, except that there's no chicken in my chicken dinner..."

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Im very curious about what you all think of this idea,
As long you really do want an ostrich dinner, and know how to change the rest of the recipe to that end...

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and also what you think of the sealing between roof top 3 layers of plasterboard against the plastered wall breeze block wall.
Which leaf are we talking about here? For your outer-leaf ceiling you do need to seal it perfectly against your outer-leaf walls, yes, but your inner-leaf ceiling cannot touch any part of the outer leaf. NO part of your inner-leaf can touch the outer leaf.

You are aiming for a very high level of isolation, so you need to be very, very careful here. The inner-leaf and outer-leaf must be entirely separate, mechanically. No flanking paths. Not even a single nail can connect them. If you don't float your floor, then you are already at the flanking limit for concrete by shooting for 70 dB of isolation. That's about the practical limit for what you an expect in your situation. And even to actually get to that point, you need to design with great care, double-check all the math, double-check all the masses, gaps, damping, seals, etc., in each stage of the design, then build it just as carefully. It is borderline-feasible to get 70 dB isolation for your place, but it is going to need very caeful design, and careful construction.

To give you an idea of how important this single point is for your build: If you make a mistake and leave even a tiny crack, just half a mm wide, under the longest of the inner-leaf isolation walls, your overall isolation would drop from 70 dB to about 50 dB: that's a huge loss: it's a factor of about one hundred: you would lose one hundred times more acoustic energy through that crack as you lose through all of the rest of the building. Subjectively, it would be four times louder than it should be...

Don't guess. Do the math, and make sure you account for all the decimal points. For high levels of isolation such as you are aiming at, the design is critical, and the construction is critical too. spend a LOT of time on getting your design right, and double-check all your calculations. Make sure that you have no three-leaf issues, or if you do have to have a three-leaf situation at some point, make sure that you compensated for it with the correct amount of additional mass and the correct increase in gap size, and the correct amount if damping.

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we where thinking of stopping roof plasterboard a few cm from the wall (since wall is not perfectly straight)
Plasterboard is easy to cut: cut it to the same shape as the wall, as well as you can within reason, bolt a ledger board to the wall just above or below the plasterboard to use as a nailing surface, seal that to the wall with caulk, then seal all other joints, cracks and gaps with abundant caulk.

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then filling void between wall and plaster with cement,
:shock: :roll: "Hmmm... cooking the chicken on low heat for two hours is too slow: I'll use a blowtorch instead! Much faster!"....

Don't substitute. Follow the recipe. Unless you are a trained and experienced chef, and understand the implications of switching cinnamon for ground pepper, don't do it.

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(how important is it using acoustic sealant? or is a good decorators caulk enough?)
You can use a good-quality, non-hardening, non-shrinking, non-transparent bathroom or kitchen caulk: It must be the type that never hardens: Even when fully cured it must still be soft and rubbery, permanently. It must not shrink or crack while it cures. Use multiple seals on every joint: At least three: both sides and in the middle. For example, when you put down your sole plates, put three beads of caulk under each one: one bead down the middle, then another two beads about 3cm to the left and right of that, then also caulk the edges after it is in place, and caulk under the bottom edge of each layer of drywall (plasterboard) as it goes on. Multiple seals are critical for high isolation.

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Which brings me to another question about sealing, would you seal between layers of plaster boards on walls and ceiling?
I'm not sure if you are talking about sealing between layers, or in the joints between adjacent sheets on the same layer? You can do both by applying Green Glue between the layers. do not substitute: there are no substitutes. Green Glue is not glue (despite the name): It is a specially formulated visco-elastic polymer that acts as an acoustic constrained layer damping compound between the layers of drywall. It can increase your isolation substantially if used properly. It is not cheap, but it is very much worthwhile if you need high levels of isolation.

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and a last question for now. I’ve seen different density insulations for walls being recommended, some saying it doesn't matter, and some saying it should be pretty heavy (which make sense).
... and both would be wrong! :) It DOES matter, and higher density would NOT be good! Use only the correct density for the specific application.

Don't believe everything you read on the internet, and especially not everything you see in YouTube videos about "How I built my amazing world-class studio on a minuscule shoe-string budget!". (Sub title: "And if you believe this I also have a bridge in NY that I'd like to sell you...!")

Here's how it really works. With porous insulation, the parameter that actually matters is not weight or density: it is gas flow resistivity (GFR): When sound moves through air, it does so in the only way that sound can move through air: by the vibration of air molecules. In other words, the molecules of air move back and forth very slightly, as they transmit the sound wave energy from one to the next. Each particle "bumps" into it's neighbor, which then bumps into the next one, and so on down the line. That's how sound propagates in free air. But inside a porous absorber it is different. Inside, it is mostly air, but there are also fibers. Some of the air molecules bump into the insulation fibers, instead of their neighboring air molecules. That collision causes the fiber to flex slightly, thus absorbing the energy and converting it into low-grade heat. So acoustic energy is lost as heat energy. From the point of view of the air molecules, something "resisted" their movement: they could not move as they normally do. The motion of the air molecules was resisted or impeded. There was a "resistance to the flow of the gas that is called air": In other words, there was "gas flow resistivity". The fibers impeded the movement of the sound by resisting the flow of the gas that we call "air".

That's the characteristic that we acousticians and studio designers are interested in: we want the porous absorber to have just the right amount of "impedance" and "resistivity" to the movement of the sound wave, so that it is attenuated in just the right ways. Each type of fibrous insulation has different properties, and we want to chose the best one for each job. When we design bass traps, we want the right GFR for bass traps. When we design Helmholtz resonators, we want the right GFR inside them for the frequency range that the device is tuned too. When we design speaker enclosures, we want the right GFR for the internal resonant characteristics in there too. When we design ceiling clouds: ditto. When we design first reflection point treatment: ditto. And when we design isolation walls, ditto there too: we want insulation that has the correct GFR for that specific application. Not too high and not too low. Because it matters!

Gas flow resistivity is measured in the rather unlikely units of "MKS rayls". So knowing what we want, all we need to do is to go out to the hardware store and by stuff that has the right MKS rayls number. Simple! ... Except that most manufacturers of insulation don't ever bother measuring that! You wont find it printed on the package... Insulation manufacturers don't measure it, because it isn't important for the primary purpose of their product. They sell their stuff mostly for thermal insulation, not acoustic damping. So they carefully measure and publish the R-ratings, printed in big numbers on the package, and they might also print the density, weight and dimensions, as those are important for shipping, storage, handling, etc. But you will almost never see GFR numbers, simple because that's not what the product is meant for.

However, as luck would have it, for each different type of insulation there is a vague relationship between GFR and the density of the product. You can roughly estimate what the GFR would be, if you know how the insulation was made, and what the density is.

Which is why Rod specifies "3 pcf rigid fiberglass insulation" for his decoupled floor, because that's the insulation that has roughly the correct GFR for that specific application! If you use recycled denim insulation instead, then 3 pcf would be wrong. If you use open-cell polyurethane acoustic foam, then 3 pcf would also be wrong. If you use pink fluffy fiberglass instead of rigid fiberglass, then 3 pcf would be wrong. If you use anything else but rigid fiberglass insulation, then 3 pcf would be wrong.

Which gets us back to your comment: "I’ve seen different density insulations for walls being recommended, some saying it doesn't matter, and some saying it should be pretty heavy". Both are wrong. It DOES matter, and it matters greatly. And heavier is not better. Optimal is better. For damping inside MSM resonant wall isolation systems, the correct insulation will have a density of roughly 50 kg/m3 if it is mineral wool, and roughly 30 kg/m3 if it is fiberglass. Not more and not less. There's a small margin here, so anything from 25 to 35 would be fine for fiberglass, and anything from 40 to 60 would be fine for mineral wool.

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Airgap between walls will be about 8cm we're thinking.
Why are you thinking that? did you do the math? Did you work your way through the equations, and determine that 8cm air gap will produce an MSM resonance that is at a low enough frequency such that your wall will isolate across the full spectrum that you need it to isolate? If not, then you need to do that.

Don't guess.

Your chances of getting it right by blind guessing are about the same as your chances of randomly grabbing products off the supermarket shelf while blindfolded, mixing them all in a pot with a blowtorch for heat, and expecting to get a perfect chicken dinner...

You have an amazing space to build your place. You have a reasonable budget. With careful design, and close attention to detail, you can have an amazing studio in there. Or you can guess, and end up throwing a lot of money into a lousy room that does not isolate and sounds terrible... :)


- Stuart -

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PostPosted: Fri Sep 09, 2016 4:18 am 
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Hey Stuart and thanks soo much for answering. i obviously wasn't detailed enough in my questions (i felt like i wrote an essay and noone would reply, but here comes some more detials and info, and some answers to your questions, and some more questions. And the slow reply is mainly because I realise I obviously need to go back and do a lot more maths (something i'm horrible at, even in its simplest forms) so I'm trying to understand all that at the moment =)

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Trying to understand: So you will be mixing elsewhere, not here? You'll basically just be rehearsing / jamming / tracking in this studio, then taking the recorded tracks to some other location to mix / edit / master? So this place will be more like just a small-to-medium sized live room? Is that the main goal? I'm just thinking that with all that wonderful space available, you could also add an amazing control room alongside your live room, and do your mixing/mastering there too, on-site. Have you considered that?


I don't usually mix, I'm a producer/writer. But i'd love for the room to be good enough for me to mix in (atleast make my mnoitor mixes as good as possible, and where there isn't enough budget i can jump in and mix somethign if i have to).
Basically the room will be as much as an all rounder room as possible. I don't like working in control room/live room studios soo much, i feel i work much better with artists when im in the room with them and dont talk through TB and look through a window. I want the space to be able to house a full band (even though thats not what I do very often, but something i'm moving into more). Most of the time it would be me and a few session players and a singer, or just me working alone. I defenitly don't master anything I do myself , thats an art i leave to the pros =)

Also im limited in space within this warehouse. the area I have to work with is W5m by L10m. but i need to leave enough gap (W) for me to build my studio and enough for other studio in there to be built. I know its not ideal but we'll have about 60cm between the studios i think, just enough to squeeze in there during builds and do the work that needs doing.

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Any reason for that specific size? Is there some limitation that would prevent you from increasing any of those three? There seems to be a lot of headroom available up there, for example, so I'm wondering why you didn't go with a much higher ceiling.


Well, like i said, i have a certain area to play with. I can defenitly build higher if i want to. but im aiming for a pretty dead room (vocal recording is very important to what i do. and i prefere a fairly dead drum sound (unless im in a studio that sounds brilliant obviously), but im not kidding myself, im not gonna get the best drum sound in this room, so i'd rather go for a more dead sound which i can then work with in post prod). Since your answers I've been on the Amroc Andymel calculator and looked and size for studio. the reason i had the messurments i had before was: it staretd with a more normal ratio where studio would be W4100 H2730 and L6800 .. (which the Amroc calculator seem to like a fair bit. but then theres 2.5 meters of unused space in warehouse basically. and i'd really like to maximize space, so I added L to 9000 ... i know its not right to do that, but i thought i'd just have to spend more on accoustics in the end to compensate for my space greed.. any sugestions?? when i use the Amroc calculator i dont even really understand the results im getting, so im spending my time between music trying to understand all this since your last post.. whole new scary world =)

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If you build a double-wall structure inside an existing building that already has walls around it, then you have a triple-leaf situation. That might or might not be a problem, depending on what your goals are. Triple leaf is generally a bad idea, and should be avoided where possible, since it trashes your low frequency isolation. It would be better to go with a conventional two-leaf design for your place.


ok.. obviously im building inside a warehouse that has walls, but for the most parts im far away from these walls. does it STILL count as 3 leaf then??? its only on the wall against the breeze blocks and the wall with windows where im actually building up against the walls. and on those 2 walls i was hoping to use the breeze black/ brick walls as my outer leaf (so no double leaf MSM - THEN the breezeblack) .. i added a bad drawing i did of this in my post. basically it would be Breezblock - stud wall with insulation (touching breezeblock) - air gap - inner leaf stud wall with insulation - 3 layers of plaster board (inside studio). i hope this make more sense. i must have expressed myself badly in last post (sorry im not english) =) ... so basically im not planning any 3 leaf designs anywhere. If the stud wall (with insulation) thats up against the breeze block creates the 3 leaf (even though it doesnt have any plaserboard or such) i'd happily get rid of it. thats a lot of material cost i can save on just letting the raw breeze block wall be the second leaf. is that betetr or am i lost here?

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Forget STC


gotcha. been looking into this a lot more in last few days. i think i understand it better now. the other studio in the warehouse is also basically a very fancy MSM build, and i spoke to the studio designer breifly the other day and hes saying its 45dB per wall. (i know now i cant add that up and say the other studio is 90db haha) SOOoo.. i'd obviously like to achive as close isolation as possible to the other studio so that theres as little risk as possible of us disturbing each other. I've seen the drawings for that studio and its not far off what were tryign to do, but obviously they've done their maths properly. If i can figure out this math, do you think its possible for me to reach similar results???

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You cannot simply add decibels


thanks, such a simple answer helped a lot haha. soo my understanding now is that if im trying to achive 45db walls in a MSM structure, i need to get 45db windows in each leaf to respect the isolation of the walls. or am I still not understanding this?

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And also STC-70 is not the same as 70 dB of isolation. So two doors each rated at STC-35 would most definitely not get you 70 dB of isolation. Maybe 40 or so, give or take half a dozen, depending on how they doors are built, and the gap between them, and any edge damping, and most of all the seals. Lousy seals could mean that you only get 30 dB of isolation from that pair of doors.... Best case, with excellent doors and fantastic seals, a decent gap, and good edge damping, you might get 50 dB of isolation, with a LOT of luck...


Got it. i think that the build itself is the least of my worries, I'm building with an amazing builder whos very anal and knows how important all the detail is. But Im planning on buying accoustic studio doors to save time and we know how hard it can be to build a door. But we'll fit it ourselves obviously knowing how important all the details in the fitting process is.

But again, I should probably get 45dB doors to respect db of the walls I'm building??

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Read the captions! There is no drywall (plasterboard) in that floor. The labels clearly say that there are two layers of half-inch plywood screwed together in a specific pattern, resting on top of a two-inch layer of a specific type and density of insulation, and with ordinary laminate flooring on top. There's no other "layer of insulation (not specified)" in there. It's just a light-weight decoupled riser floor, suitable for some applications but not all.


sorry i obviously didn't formulate my question very well. of course i understand the floor. its the wall im talking about. inside the 2 layers of the wall, there seem to be a layer of insulation, then another plaster board or such (none of these things have any information), and since im trying to stick to the detail im sure its very important layers athat i should pay attention too.

I understand the difference in decoupling and floating a floor. i just dont have the money or time to float a concrete slab. hence why im soo curious about Rod's decoupled floor. you don't think its a good idea in my scenario?

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Celotex is not sytrofoam


got it. i was just curious. i'll stick to the stuff im supposed to use =)

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Here's the thing: All studio isolation systems are tuned. There's a recipe for tuning them. They have a natural resonant frequency, which is what governs the maximum isolation that they can provide. If you change anything in the wall design (recipe), then you change the tuning. If you don't know what you are doing, and didn't work through the math to make sure the resonant frequency, rigidity, coincidence dip, and intermediate transition characteristics are all correct for what you need, then you basically have no idea how the wall will perform.


now this is obviously your most important observation. I havnt done my maths. so this is what im frantically trying to understand and learn now. Im re-reading that chapter of Rod's book. and reading a lot on this forum (a lot of other people have obviously had similar questions and im trying to figure it out through them)

I don't expect anyone to do the math for me or tell me what to do but I'm really confused so far. maybe theres a strategy to it all I'm missing.

- In what order should i do all these things? where do i start? and is there a specific order I should use going through figuring out resonant frequency, rigidity, coincidence dip, and intermediate transition characteristics ???

I've seen your answers to other people about how to calculate resonance frequency. for example. and i can look at that and understand what I'm trying to accomplish. And if i understand correctly i can use the Amroc to get my lowest dominant Hz (right now i have W3800 H2730 L8800) which gives me 19.5Hz.. so i need to get my resonant frequency to be lower than 9.5Hz 'ish if i go with these room dimentions??? I know the x doesnt even end up in the bolt area with these dimensions, am i completley screwing myself if i go with these dimensions?? i've tried soo many but unless i go down to around L6000 it doesnt seem to get into the bolt area. Can this not be compensated for when i do the accoustic treatment of the room??

Fc=c[(m1+m2)/(m1m2d)]^.5

where:

Fc=resonance frequency (Hz)
c=constant (60 for empty gaps and 43 for with insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=interleaf spacing (m)

are there any specific online calculators for rigidity, coincidence dip, and intermediate transition characteristics ?? and any info that tells me in what order to do things? again its all a bit overwhelming and confusing =)

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get a structural engineer in to take a look at that wall and the cracks


sorry my bad. its not structural cracks. the grouting is just not well done and in a couple places its soo bad theres actually small holes into the unit next door. im just talking about making sure i fill any holes and getting a nice even plastered wall basically. make sense??


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Wellll.... "yes but no": Yes you can use it for your outer leaf, since it does have very substantial mass and will be well sealed, ... but no, it will not be the same as a plasterboard wall.


ok. BUT if i do my maths right, and compensate for it in the rest of the build, can i still not use the breeze block wall as the second leaf of that side of studio?? I understand that wall (and window wall) will have different density, rigidity and resonance freq as rest of walls. but surley there must be ways of building so we get around that problem as much as possible?? or do you mean theres no way i can use it at all and i have to build a free standing structure with MSM away from that wall??? that would mean my studio would shrink a lot, and essentially i'd have a 3 leaf system along that wall cause my MSM would sit pretty close to it. It would also make it really hard to put plasterboard on outside of my second leaf. i would basically have to build that whole wall laying in the floor, then raise it up against the breezblock wall. but even then it would still sit close to it. maybe a 10cm airgap only. surley that must be a 3 leaf situation and not a good idea??

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NO part of your inner-leaf can touch the outer leaf


of course, i think we misunderstand each other on this question , totally understand the importance of this.

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Plasterboard is easy to cut: cut it to the same shape as the wall, as well as you can within reason, bolt a ledger board to the wall just above or below the plasterboard to use as a nailing surface, seal that to the wall with caulk, then seal all other joints, cracks and gaps with abundant caulk.


cool!

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For example, when you put down your sole plates, put three beads of caulk under each one: one bead down the middle, then another two beads about 3cm to the left and right of that, then also caulk the edges after it is in place, and caulk under the bottom edge of each layer of drywall (plasterboard) as it goes on. Multiple seals are critical for high isolation.


ok here comes another building question.

the floor in the warehouse is not perfectly even. it varies by about 8cm up and down. so to get the structure straight we where planning on putting down the sole plates with adjustable bolts (into the cement floor), then raise the sole plates untill they are perfectly level (with help of the bolts). which will create an air gap under the sole plates. obviously this air gap will be between 0 - 8cm wide depending on how the floor was where we put the sole plates. and this air gap needs to be filled with something. again, we had thought about filling it with cement so the sole plates basically sit on a layer of cement (obviously there would be a rubber membrane underneath the sole plates for cement moisture not to get into wood). i would assume that we'd need to take the weight of the cement we use and add it to our mass of walls when we calculate our RF, correct? even though its just a small amount of cement down by bottom of the structure?

then inside of the inner leaf wall (which would be leveled with same technique) we would fill with sand until the floor is level. then start building the decoupled floor as Rod's design shows.

if all this is confusing i can draw it from a few angles to show it better.

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I'm not sure if you are talking about sealing between layers, or in the joints between adjacent sheets on the same layer?


i was talking about sealing between the adjecent sheets on the same layer. i wasn't plannign on using green glue at all actually. but i thought we might need to seal between adjecent sheets in each layer, then just screw each layer of plaster board onto eachother (all layers overlapping of course).. what do you think?

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Which is why Rod specifies "3 pcf rigid fiberglass insulation" for his decoupled floor, because that's the insulation that has roughly the correct GFR for that specific application! If you use recycled denim insulation instead, then 3 pcf would be wrong. Optimal is better. For damping inside MSM resonant wall isolation systems, the correct insulation will have a density of roughly 50 kg/m3 if it is mineral wool, and roughly 30 kg/m3 is it is fiberglass. Not more and not less. There's a small margin here, so anything from 25 to 35 would be fine for fiberglass, and anything from 40 to 60 would be fine for mineral wool.


got it thanks! thats perfect, its the correct MSM insulation i wasn't sure about but now i know. On a side note about that. our all our MSM walls where planned to be built with cc60 (not sure if thats that you say in english, but basically with 60cm between each stud, so that a 60cm insulation board fits perfectly in there. it seems to be standard in most builds i've seen. we're also planning 45mm x 95mm studs for all of it (thats 2"x4" roughly). Originally we thought of using 2x5 but we realise that structurally it's not needed. other than creating a different mass for wall which needs to be compensated for in RF calculation, is there any other reason one might go for 2x4 or 2x5???

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Why are you thinking that? did you do the math? Did you work your way through the equations, and determine that 8cm air gap will produce an MSM resonance that is at a low enough frequency such that your wall will isolate across the full spectrum that you need it to isolate? If not, then you need to do that. Don't guess.


No i hadn't done that. But now all my focus is on tryign to understand how to calculate all the things i need to calculate =)


thanks soo much for all the help soo far! hopefully i can get my head around the maths and make this work. defenitly don't want to waist my money.

Johan


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PostPosted: Fri Sep 09, 2016 6:54 am 
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But i'd love for the room to be good enough for me to mix in (atleast make my mnoitor mixes as good as possible, and where there isn't enough budget i can jump in and mix somethign if i have to).
OK. That is possible, but... (BIG "but")... the acoustic requirements of a control room are different from the acoustic requirements of a live room (tracking room). The control room must be neutral: It cannot "color" the sound in any way. It cannot add to it, or subtract from it, and the decay times ("RT-60") must be smooth,even and consistent across the entire spectrum. Take a look at the graphs in this thread : viewtopic.php?f=2&t=20471 to see what the acoustic response in a well designed control room should be.


But for a live room, it is different. The room is supposed tohave some "character" of its own, to make it attractive and pleasant for the musicians to play in. Musicians don't play well if the acoustic "vibe" of the room is not nice. If the room is too "boomy" or too "muddy" or too "tinny" or too "zingy"... or if it is too "dead" or too "flat" or too "cold". They won't perform well, and your recordings wont sound good. So live rooms are normally designed and treated with a specific sound in mind. Or they can also be designed to be variable: You can have acoustic treatment devices that move, slide, rotate, flip, etc. to change the acoustic response of the room. You need one type of acoustics for drums, but a different type for acoustic guitar, yet another type for solo vocals, and something different again for a violin or cello. If you lock into one "sound" for your tracking room, you also pretty much lock into one set of instruments sound great in there, while all the others sound mediocre or even bad. You also lock in to one genre, or one group of genres. A room that sounds great for heavy metal rock won't sound so good for orchestral strings, or a light jazz group.

I'd suggest that you think about doing variable acoustics, and perhaps like that you could have a room that is decent for both mixing (sort of like a control room) and also for tracking many types of instruments, and many genres.

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don't like working in control room/live room studios soo much, i feel i work much better with artists when im in the room with them and dont talk through TB and look through a window.
You could do it as a combined studio: control room set up at one end, with control room acoustics, and live room set up a the other end, with variable characteristics, and no wall between. I'm just finishing up the design for a place in Nashville that is exactly like that...
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I want the space to be able to house a full band
Have you ever tried tracking vocals in the same room as a drum kit, at the same time? :) You might want to consider having a vocal booth in there some place, that you could use to isolate not just vocals but also things like bass cabs and electric guitar cabs, or perhaps for tracking some other acoustic instruments.

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the area I have to work with is W5m by L10m.
50m2 is good! I've done quite a few studios in spaces around that size. It's surprising what you can get in, with careful design.

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but i need to leave enough gap (W) for me to build my studio and enough for other studio in there to be built.
So the amount of space allocated to you also has to include corridors that provide access for OTHER people? Do they have the same restriction? If so, then the guy next to you should be cutting 50cmoff his space, and you cutting 50cm off yours, to provide a decent 1m wide passage.

Also, it would be better to take that of the length, not the width: so cut your length down to 9.5m, but leave your width as 5m.

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I know its not ideal but we'll have about 60cm between the studios i think, just enough to squeeze in there during builds and do the work that needs doing.
I'm not sure if you have ever tried to carry a drum kit or a cello through a space just 60cm wide... :shock: you'll have serious load-in / load-out issues if you only have passages like that.

Something tells me this whole space is not being handled correctly. If the owner of the station wants to rent out sections to various people, then HE should provide the passages, not expect the renters to chop part of their allocation off! That makes no sense.

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I can defenitly build higher if i want to
Great! That's good.

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but im aiming for a pretty dead room (vocal recording is very important to what i do. and i prefere a fairly dead drum sound (unless im in a studio that sounds brilliant obviously),
Drums don't sound good in dead spaces. Drums like large spaces, and lots of "air". Even if you close-mic drums in a dead space and add reverb in the mix, they still don't sound the same as drums recorded naturally in a good acoustic space. I would seriously suggest that you have a separate vocal booth (which should be dead) and a larger main room that is set up as a typical live room, or has variable acoustics.

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but im not kidding myself, im not gonna get the best drum sound in this room,
It is 36m2 of floor area, and you can go up with a high ceiling. I don't see why you can't have great drum sounds in there!

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Since your answers I've been on the Amroc Andymel calculator and looked and size for studio.
Ratios are necessary for control rooms. Not so much for live rooms. If your place is not going to be a control room, then you don't need to worry about ratios. You still should avoid the really nasty ratios (such as having one dimension that is exactly twice or three times another, etc.), but there is no need to go crazy about ratios for a tracking room.

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and i'd really like to maximize space,
:thu:
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but i thought i'd just have to spend more on accoustics in the end to compensate for my space greed.. any sugestions??
The rooms will need treating in any case. That goes without saying. It is a small room (acoustically speaking) so it will need considerable treatment. Selected on ratio or another won't change that. So gowith whatever size gives you the largest footprint, then choose the highest ceiling you can get within reason, that also fits the rule I outlined above.

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ok.. obviously im building inside a warehouse that has walls, but for the most parts im far away from these walls. does it STILL count as 3 leaf then???
Yes-and-no! :) Any time you have two large massive surfaces with an air gap between them, you automatically have a resonant system. It is tuned to a specific frequency. If you add another large massive surface in between those two, or on the other side of one of them, then you have a resonant system that has three fundamental resonant frequencies. So yes, strictly speaking, it is still "three leaf". HOWEVER! ... If the resonant frequency(ies) is( are) low enough, then you don't need to worry about it. The bigger the air gap, the lower the frequency. With a gap of 60cm, you are pretty much guaranteed that the frequency is plenty low enough, way low, not a problem.

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on those 2 walls i was hoping to use the breeze black/ brick walls as my outer leaf
Right. No problem. That's correct. You then need to build single-leaf walls around the other two sides of your allocated space, and put a ceiling on top of them, to complete the outer leaf, then within that shell you build your actual studio, which consists of a free-standing single-leaf structure made of four walls and its own ceiling.

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stud wall with insulation (touching breezeblock)
Why? What purpose does that "stud wall with insulation" serve, if there is no drywall on it? Why do you want to put up framing that does not support anything? That's a waste of money, time and space. If the breeze block wall is rendered and sealed, then that's an excellent outer leaf. No need to add framing to it.

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If i can figure out this math, do you think its possible for me to reach similar results???
It should be very possible, yes. Once you get the concepts clear in your head, and work through the math, then you should indeed be able to come up with a good isolation system.

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soo my understanding now is that if im trying to achive 45db walls in a MSM structure, i need to get 45db windows in each leaf to respect the isolation of the walls. or am I still not understanding this?
Don't' think of each leaf individually with MSM isolation. They act together, as a single system, to give you isolation. The whole is greater than the sum of its parts. So your entire studio, which consists of a fully decoupled "room inside a room" will have a total isolation of 45 dB. The individual parts of the walls would have very different isolation characteristics if you measured them separately: it's only when you put them next to each other and create the two-leaf system, that they actually give you the isolation you want.

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But Im planning on buying accoustic studio doors to save time and we know how hard it can be to build a door.
Not really:
Attachment:
door-buildup--Photo 16-02-2016 3 29 08 pm-B-SML.jpg


Attachment:
door-threshold-Photo 16-02-2016 12 31 58 pm_ENH-SML.jpg


Attachment:
door-seals-in-Photo 28-02-2016 3 51 31 pm-SML.jpg


Attachment:
Entry-door-from-outside-20160417 164004-SML-ENH.jpg


Attachment:
finished-door--Photo 13-02-2016 3 52 55 pm-B-SML.jpg


Designed by me. Built by a carpenter and one assistant, in a few man-hours. Gets better than 50 dB of isolation.
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finished-door--Photo 13-02-2016 3 52 55 pm-B-SML.jpg
The surface density of each door should be as close as reasonably possible to the surface density of the leaf it is in, and higher if possible. The air gap between them should be at least the same as the air gap between the two leaves, and greater if possible.

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- In what order should i do all these things? where do i start? and is there a specific order I should use going through figuring out
Now there's the 64k US$ question, isn't it! :) The answer is: "All of the above". You need to go through each part of the design several times over, and tweak things along the way, over and over. Rinse. Repeat. But start with the MSM resonance, since it's always the low frequency isolation that will get you. If your low frequency isolation is good, then the isolation for the rest of the spectrum pretty much falls into place, and you likely won't even need to worry about coincidence dip. Coincidence occurs up in the top end of the mid range, where isolation is already good, assuming that the low end is good.

Quote:
nd if i understand correctly i can use the Amroc to get my lowest dominant Hz (right now i have W3800 H2730 L8800) which gives me 19.5Hz.. so i need to get my resonant frequency to be lower than 9.5Hz 'ish if i go with these room dimentions???
No. You are confusing two unrelated issues. Both are important, but they are not related to each other. Room mode calculators (such as Amroc) predict what the problematic frequencies will be inside the room due to the music you play inside the room. Room modes are resonant problems that occur inside the room itself, not inside the walls. Rom modes are standing wave resonances that will only be triggered if the music happens to hit that frequency. When that happens, the mode will "ring", very loud, and will carry on ringing after the note has stopped. Room mode calculators just tell you what those notes will be, based on the interior dimensions of the room. Not related to isolation.

The equation you mentioned in your post has nothing to do with room ratios or modes. It predicts what the resonant frequency of the wall itself will be. It tells you what the MSM resonance will be. If you happen to be playing a note inside the room that coincides with the MSM resonance frequency of the walls, then that note will be clearly heard outside the room. In fact, under some conditions the wall can actually amplify that note, so it will be heard louder outside than inside! Now here's the bad part: All frequencies that are close by will cause the same problem, up to 1.4 times the resonant frequency. So for example, if the MSM resonant frequency of your wall was 100 Hz, then all notes up to 140 Hz would go right through the wall and be heard on the other side. from 1.4 times and up to 2.0 times the resonant frequency, you get a bit of isolation, and above 2 times the resonant frequency, you get good isolation. That's why we recommend that you should tune your wall so that the MSM resonant frequency is no more than half the frequency of the lowest note that you need to isolate. So if the lowest note is, for example, a male singing voice: that doesn't go much below about 100 Hz, at the very lowest, so you could tune your wall to 50 Hz and be fine. but if you have a kick drum in there, the lowest note is probably more like 60 Hz, so you'd need to tune to 30 Hz. And if you have a six-string bass guitar in there, that gets down to about 32 Hz, so you'd need to tune your wall to below 16 Hz. And if you want to record church organs, grand pianos, earthquakes and cannon fire, all of which go right down to 20 Hz at least, then you'd need to tune beloe 10 Hz.

It all depends on what the lowest note will be: go down one octave 8halve the frequency), tune to that, and you will be fine.

There's no relationship between modal response and wall tuning. It might happen, by sheer bad luck, that you have a room mode at the same frequency as your MSM resonance, but that would be unusual, and it would just be a sad coincidence.

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the grouting is just not well done and in a couple places its soo bad theres actually small holes into the unit next door. im just talking about making sure i fill any holes and getting a nice even plastered wall basically. make sense??
Yup! Render that as thick as you can afford, then paint it with a good masonry sealer. Cement is porous, so the surface need to be sealer.

Quote:
BUT if i do my maths right, and compensate for it in the rest of the build, can i still not use the breeze block wall as the second leaf of that side of studio??
You sure can! That's a great wall to use as your outer leaf. Actually a great pair of walls, since two sides of your studio will be up against that. you just need to provide the other two sides and the ceiling to complete the outer leaf, then build the actually studio inside that, as a single-leaf room (for walls and a ceiling). The inner-leaf room does not touch the outer-leaf room.

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the floor in the warehouse is not perfectly even. it varies by about 8cm up and down.
Then level it! 8cm is too big a gap to deal with using rubber or caulk, and you need to have your floor as flat and level as possible. And elf-leveling cement isn't that expensive.... Buy a few sacks, mix it up, spread it around, wait for it to do it's thing and cure properly, and you'll have a perfectly flat, smooth, level surface on which to build your studio. Level the entire area, of course: not just the parts where the walls will be.
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but i thought we might need to seal between adjecent sheets in each layer, then just screw each layer of plaster board onto eachother (all layers overlapping of course).. what do you think?
Just "mud and tape" the joints, as for any other drywall. The joints will be directly over the studs, so there's no problem with lack of mass.

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cc60 (not sure if thats that you say in english, but basically with 60cm between each stud,
that would be "60 cm OC", which is the same as 24" OC. The "OC" part means "On Centers". 60cm OC is fine.

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we're also planning 45mm x 95mm studs for all of it (thats 2"x4" roughly)
That's also fine for your studs. No problem.

However, for your ceiling joists (both the outer-leaf ceiling ans also the inner-leaf ceiling) you will need much larger dimensions, probably 2x6, 2x8, or maybe even 2x10. You will need a structural engineer to do the calculations for you. He will take into account the live load, the dead load, the deflection, the type of wood, and other factors to determine what type of wood you need up there for your joists.

Quote:
No i hadn't done that. But now all my focus is on tryign to understand how to calculate all the things i need to calculate =)
Welcome to the wonderful world of studio building, where nothing is as simple as you first thought, and you'll spend way more time doing things you never realized where necessary! :) :thu:


- Stuart -


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PostPosted: Fri Sep 09, 2016 11:09 am 
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you're a legend Stu.. thanks again. few more things that instantly come to mind

Quote:
OK. That is possible, but... (BIG "but")... the acoustic requirements of a control room are different from the acoustic requirements of a live room (tracking room). The control room must be neutral: It cannot "color" the sound in any way. It cannot add to it, or subtract from it, and the decay times ("RT-60") must be smooth,even and consistent across the entire spectrum. Take a look at the graphs in this thread : viewtopic.php?f=2&t=20471 to see what the acoustic response in a well designed control room should be.


i know... and this is where i thought i had to make real sacrifices. the control area being correct is actually more important than live area. but i hoped theres a wonderful compromise between the 2. =) im intrigued by the idea of making a higher ceiling and and variable acoustics , i assume they go hand in hand depending on where in the room you have high ceilings and where you have lower, and angels etc??

Quote:
You could do it as a combined studio: control room set up at one end, with control room acoustics, and live room set up a the other end, with variable characteristics, and no wall between. I'm just finishing up the design for a place in Nashville that is exactly like that...


obviously this would be ideal! i work with everything from african choirs, accoustic msuic, film/tv, pop, dance music, rappers, rock bands, classical... so i need a really diverse space. i know this is hard to accomplish with what i have, and with the budget i have... but the closer to that i can get the better.

Quote:
Have you ever tried tracking vocals in the same room as a drum kit, at the same time? :) You might want to consider having a vocal booth in there some place, that you could use to isolate not just vocals but also things like bass cabs and electric guitar cabs, or perhaps for tracking some other acoustic instruments.


yes i know this wont work of course. i'd like to be able to have a whole band set up, recording, but obviously having to overdub vocals an some other parts depending on band. to do a straight up live recording in my room wont really be possible the way i see it. depending on music style and mic choices... but yea sorry i dont expect to be able to get amazing isolated sounds from drums, guitar, bass, piano and vocal all at the same time. I'll always be able to use the big studio being built next to mine for the projects when i might need this too.

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So the amount of space allocated to you also has to include corridors that provide access for OTHER people? Do they have the same restriction? If so, then the guy next to you should be cutting 50cmoff his space, and you cutting 50cm off yours, to provide a decent 1m wide passage.

Also, it would be better to take that of the length, not the width: so cut your length down to 9.5m, but leave your width as 5m.


hahaha no thank god. no access for anyone down this corridore apart from acces for us while building. it will basically be a little alley with a dead end. but we need enough space to move in that alley during build to put up plaster board, seal joints etc. the studio being built next to me is just that big. we both have ownership of this warehouse together but we have different needs for our studios, and different budgets. so this is where we ended up basically. im left with 5 x 10 m ... but yes that needs to include the 'labour alley' between us for us to be able to build. so my INSIDE messurment is at 9m right now. i could go up to 9.5m and still stay within my 10m L ... im just strugglin to find anything on the Amcron that likes any of these long spaces... how high do you think i should make my inner ceiling to help?

Quote:
Drums don't sound good in dead spaces. Drums like large spaces, and lots of "air". Even if you close-mic drums in a dead space and add reverb in the mix, they still don't sound the same as drums recorded naturally in a good acoustic space. I would seriously suggest that you have a separate vocal booth (which should be dead) and a larger main room that is set up as a typical live room, or has variable acoustics.


yes and no... of course sometimes i prefere drums in a great large amazing sounding spaces. but i really doubted i could get that in this studio so i opted for a more dead sound. which i often like anyways, sorry =) ... i love a very neutral drum sound i can really mess with after recording. i don't like talking about records i've worked on here sounding like a prick, but ill send you some stuff on DM and maybe you can understand what i like and do (might not be what you like but hopefully it will show you what i mean). i usually find recording drums (specially overdubbing drums) with a dead'er sound gives me soo much more flexibility to fit them into mix after recording rather than getting a natural reverb im stuck with... saying that im very curious about what could be done with the space, without trying to make a "drum sound" unique to my place, but great sounding drums i can still tweak into many different genres..

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Ratios are necessary for control rooms. Not so much for live rooms. If your place is not going to be a control room, then you don't need to worry about ratios. You still should avoid the really nasty ratios (such as having one dimension that is exactly twice or three times another, etc.), but there is no need to go crazy about ratios for a tracking room.


im probably being very confusing here but i still need it to be a control room. more so than a live room. im sure what youre saying earlier about variable accoustics is probably the key to this. cause i really need both. but i need a great control room sound. the one thing i got going for myslef is i can go to studio next to me and tweak final mixes or make sure i do the right thing, whenever i need to. so if mine is 90% i can go there and be sure what im doing sounds great.

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The rooms will need treating in any case. That goes without saying. It is a small room (acoustically speaking) so it will need considerable treatment. Selected on ratio or another won't change that. So gowith whatever size gives you the largest footprint, then choose the highest ceiling you can get within reason, that also fits the rule I outlined above.


agreed. this is what i was thinking from the start.. apart from the ceiling. i obviously need to add to that.

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Yes-and-no! :) Any time you have two large massive surfaces with an air gap between them, you automatically have a resonant system. It is tuned to a specific frequency. If you add another large massive surface in between those two, or on the other side of one of them, then you have a resonant system that has three fundamental resonant frequencies. So yes, strictly speaking, it is still "three leaf". HOWEVER! ... If the resonant frequency(ies) is( are) low enough, then you don't need to worry about it. The bigger the air gap, the lower the frequency. With a gap of 60cm, you are pretty much guaranteed that the frequency is plenty low enough, way low, not a problem.


ah cool thats what i thought. so no need to worry about this, thanks

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ight. No problem. That's correct. You then need to build single-leaf walls around the other two sides of your allocated space, and put a ceiling on top of them, to complete the outer leaf, then within that shell you build your actual studio, which consists of a free-standing single-leaf structure made of four walls and its own ceiling.


this is exactly the plan, thanks

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Why? What purpose does that "stud wall with insulation" serve, if there is no drywall on it? Why do you want to put up framing that does not support anything? That's a waste of money, time and space. If the breeze block wall is rendered and sealed, then that's an excellent outer leaf. No need to add framing to it.


amazing, we wherent sure about this. if we should still insulate it as if the breeze block wall was the plasterboard layer, or if it was enough to just let it be the outer leaf with nothing else. that saves a bunch of cash! might still need a simpler frame to support the joists of outer leaf layer though. even if we bolt a bit beam into the wall to support it i think we'd need some support from underneath. agree? (ill talk to builder, hes a structural engineer)

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It should be very possible, yes. Once you get the concepts clear in your head, and work through the math, then you should indeed be able to come up with a good isolation system.


thank you this has already calmed me down and re-focused me on getting this right, instead of just thinking it cant be done =)

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Don't' think of each leaf individually with MSM isolation. They act together, as a single system, to give you isolation. The whole is greater than the sum of its parts. So your entire studio, which consists of a fully decoupled "room inside a room" will have a total isolation of 45 dB. The individual parts of the walls would have very different isolation characteristics if you measured them separately: it's only when you put them next to each other and create the two-leaf system, that they actually give you the isolation you want.


this sounds like such a low level of isolation though, no??? 45db. surley i shoudl be aiming higher than that?? and surley the guy building next to me (high end pro studio, designed by some of UK's top studio designers) should be aiming for more than 45db total too????
if we ignore the maths for a second - a MSM wall with 3 layers of plasterwall on each side, with amazing build, seals and all the details really paid attention to - what would a structure like that roughly give in -db??? only about 45?

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The surface density of each door should be as close as reasonably possible to the surface density of the leaf it is in, and higher if possible. The air gap between them should be at least the same as the air gap between the two leaves, and greater if possible.


ok i think you need to bang this info into my head more. you say that
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The surface density of each door should be as close as reasonably possible to the surface density of the leaf it is in, and higher if possible.
, that density got nothing to do with db then? so if i was to buy 2 x 45db doors it still would only give me 45db isolation (if they where mounted on tick cement decoupled walls. basically what im saying is if you say my whole structure will only be 45db, then how much db should i get each door to be?? 45db doors (2 of them) seem very exesive if my combined MSM wall structure is only 45 db.. right???

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Now there's the 64k US$ question, isn't it! :) The answer is: "All of the above". You need to go through each part of the design several times over, and tweak things along the way, over and over. Rinse. Repeat. But start with the MSM resonance, since it's always the low frequency isolation that will get you. If your low frequency isolation is good, then the isolation for the rest of the spectrum pretty much falls into place, and you likely won't even need to worry about coincidence dip. Coincidence occurs up in the top end of the mid range, where isolation is already good, assuming that the low end is good.


ok i thought it was just me being stupid but this is the holy grail then =)

now this obviously poses some questions in my case. on the walls where breezeblock and brick is the outer layer, these walls will obviously have a lot more mass than my normal MSM walls and my ceilings. how do i make sense of the calculation in a case like that?? cause i can only messure RF of my MSM walls and ceiling, then i have to do a seperate calculation of mt breeze black wall, then a seperate calculation of my brick wall with window. how do i somehow combine that into a correct RF for whole space? or do i do them seperatly and the difference is actually what will show me the extra mass, air gap etc on the walls and ceiling that doesnt have breeze block or brick???? but even then... how do i go about it?
also can you recommend some online calculators for rigidity, coincidence dip, and intermediate transition characteristics, they seem a lot harder to find than RF.. i understand i should put my focus on RF but i obviously want to do this as best as i can so i want to try to figure out these things properly too..

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And if you want to record church organs, grand pianos, earthquakes and cannon fire, all of which go right down to 20 Hz at least, then you'd need to tune beloe 10 Hz.


ok i will need a really low RF in my studio , even though im yet to record an earthquake i do record a lot fo werid stuff. and im specially fond of sub freq instruments... now that i undertand RF calculation more atleast i know how to calculate for my mass and air gaps etc. thank you, this has been a big worry sicne your last reply =)

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Then level it! 8cm is too big a gap to deal with using rubber or caulk, and you need to have your floor as flat and level as possible. And elf-leveling cement isn't that expensive.... Buy a few sacks, mix it up, spread it around, wait for it to do it's thing and cure properly, and you'll have a perfectly flat, smooth, level surface on which to build your studio. Level the entire area, of course: not just the parts where the walls will be.


well yes i see you point. that was out first idea too. but slef leveling cement is crazy expensive here. i totally striped and redid our kitchan last year and its really small 7m2 and only 4cm needing to me leveled on about 50% of surface and it cost me £500 also you can only really self level cement at about 2-4cm in each go, then you need to let it dry. so for my studio foundation i might need 3 layer ... to level this whole floor would probably cost me about 3 - £4000 .. thats close to my HVAC system (which i have questions about later too =)

i'll go back and calculate exactly how much self leveling cement i would need, and the cost. but do you think our other solution is really shit???? we spent weeks thinking about ways around the self leveling cement and this is the cheap and easy solution we came up with.i dont see why it wouldnt work unless u told me cement under the sole plates has waaaaay worse db loss than the walls themselves right???

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Just "mud and tape" the joints


sorry i dont know what "mud" means... tape i assume is plaster tape that you use to seal joints between sheets, same way you would do on a normal wall or ceiling to make a smooth finish?

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However, for your ceiling joists (both the outer-leaf ceiling ans also the inner-leaf ceiling) you will need much larger dimensions, probably 2x6, 2x8, or maybe even 2x10. You will need a structural engineer to do the calculations for you. He will take into account the live load, the dead load, the deflection, the type of wood, and other factors to determine what type of wood you need up there for your joists.


yes of course, the inner leaf will have 2x5 and the outer leaf will have 2x6 , we've checked that thats fine structurally... we only thought of 2x5 for studs cause i want to use top of the studio as storage, and now that we might raise the ceiling height we might stick to that but i need to talk to the builder to make sure.


thanks again, and again Stuart!


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PostPosted: Fri Sep 09, 2016 5:24 pm 
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Quote:
but we need enough space to move in that alley during build to put up plaster board, seal joints etc.
Nope! Actually, you do not need access to the other side of the wall at all, believe it or not! You build it the same way that upper story walls are built, or inside-out walls are built. You build the wall laying down flat on the floor, complete with drywall and everything, then you lift it into place with a device called a "wall jack", or by winching it, or with a team of half a dozen beefy workmen. You do NOT need any gap on the other side. You can build right up to the edge of your space, and only leave enough gap to ensure that there won't be acoustic problems. Don't sacrifice your precious floor area! Maximize it.

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but yes that needs to include the 'labour alley' between us for us to be able to build.
Forget the alley!! You don't need it, and he doesn't need it, if you both build correctly.

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how high do you think i should make my inner ceiling to help?
With 2x4 studs, you can probably go up to 12 feet (check your local code). Beyond that, you'd need to go to 2x6 studs. So to keep costs down, shoot for about 12 feet.

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im probably being very confusing here but i still need it to be a control room. more so than a live room.
Then design it as a control room! But make some of the treatment variable, so you can change the sound to be more live or more dead, as needed for tracking, but flip back to the "normal" position for mixing.

And in this case, yes, the room ratios takes on more importance. But you still don't need to go crazy about getting a "perfect" ratio. First, because there is no such thing, and secondly because the ratio is just one of many parameters that you need to take into account, and probably not even the most important. The basic advice still stands: Stay away from bad ratios, get reasonably close to a good one, and that's as far as you need to take it.
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if we should still insulate it as if the breeze block wall was the plasterboard layer, or if it was enough to just let it be the outer leaf with nothing else.
You do still need insulation on that wall, yes, but you don't need to build a frame to hold it in place. There's a clever little device called an "impaling clip" that is an awful lot cheaper than lots of lumber and nails. This is how it works:

Attachment:
impaling-clips-2.jpg


Attachment:
impaling-clip-4.jpg


It works with semi-rigid and rigid insulation panels. You just screw them to the wall in several places, then "impale" the panels on them, and that's it! They stay there. then you erect your inner-leaf wall right next to the insulation, and the insulation will never come down.

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that saves a bunch of cash! might still need a simpler frame to support the joists of outer leaf layer though. even if we bolt a bit beam into the wall to support it i think we'd need some support from underneath. agree?
A ledger board bolted to the wall would work fine for that, but the dimensions, bolt spacing and additional support should indeed be OK'd by a structural engineer. To me, your wall looks plenty capable of handling that, but I'm not there to look at it closely, and I'm not a structural engineer anyway, so you do need to hire a real one to get that approved.

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this sounds like such a low level of isolation though, no??? 45db. surley i shoudl be aiming higher than that??
I was merely taking your example number and using the same one! Yes, your wall should give you quite a bit more than that, depending on how you build it. I have not run the numbers, but I would guesstimate that your TL will probably be around 55 dB, maybe more.

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and surley the guy building next to me (high end pro studio, designed by some of UK's top studio designers) should be aiming for more than 45db total too????
I would expect so, but you did say that their guy told you it was designed for 45 dB...

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if we ignore the maths for a second - a MSM wall with 3 layers of plasterwall on each side, with amazing build, seals and all the details really paid attention to - what would a structure like that roughly give in -db???
As above: rough guesstimate, 55 dB or a bit more. I'd have to do a lot of math to figure that out more accurately, but somewhere in that region.

And once again, don't confuse STC-45 with a TL of 45 dB! Not the same. TL 45 dB is much better than STC-45.

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, that density got nothing to do with db then?
Yes it does, but indirectly.

More waffling from me:

If you have a single-leaf wall, the isolation it can provide is governed mostly by mass law. Mass law goes like this:

TL(dB)= 20log(W) + 20log(f) -47.2

Where:
W is the mas (surface density) of the panel, and
f is the frequency.

So you'd calculate that for each 1/3 octave frequency band, then draw a graph, and you'd have the predicted isolation curve for your wall.

But there's a simpler version, called "empirical mass law" which considers the entire spectrum, not specific frequencies. It goes like this:

L = 14.5 log (Ms * 0.205) + 23 dB

Where:
Ms = Surface Density (in kg/m2)

So for a wall made from just one single layer of 15mm drywall, you would get:

L = 14.5 log (11 * 0.205) + 23 dB
= 14.5 log (2.25) + 23 dB
= 5.1 + 23
= 28 dB (aprox)

Add a second layer of drywall, and you get about 32.5 dB
Add a third layer of drywall, and you get about 35 dB
Add a forth layer of drywall, and you get about 37 dB
Add a fifth layer of drywall, and you get about 38 dB
Add a sixth layer of drywall, and you get about 39 dB
Add a seventh layer, and you get about 40 dB...
Add layer number 8, and you get a whoppingly non-impressive 41dB

As you can see,this ain't goin' no place fast!

If you look at those numbers more closely, you'll see that each time you DOUBLE the mass, you get an increase if barely 5 dB. Not very spectacular.

That's mass law. Mass law is not your friend. You need a LOT of mass to get decent isolation.

But things get very different when you have two leaves separated by an air gap, and with a damping material in the air gap (insulation). Mass law no longer applies. Now you have resonance as part of the issue. The wall "wants" to resonate at one specific frequency, and it does not "want" to resonate at all others. It lets sound through really well at that frequency, and blocks sound really well at all others.

But there is no longer one simple equation to describe how it isolates, because it behaves in different ways at different regions of the spectrum, and different equations apply to each region. Here are the regions:

Attachment:
four-regions-of-isoaltion--transmission_loss-V2.gif


At the very low end of the spectrum below the resonant frequency, what matters most is the stiffness of the wall: how rigid it is. Not mass, mot resonance, not damping, just stiffness.

Then comes the resonance region, where isolation dips to the lowest value: at the resonant frequency of the wall, it does not isolate at all, or isolates only poorly.

Then something interesting happens: above the resonant-controlled region, you have he "mass controlled region", but this is not mass law any more. Isolation does not increase by 6 dB each time you double the mass, as stated by Mass Law. In this region, it increases by 18 dB each time you double the mass! That's a lot more impressive! And a lot more useful.

Yeah I know I said "5dB per mass doubling" for mass law before, and here I'm talking about "6 dB per mass doubling", but there's a reason for that. 6 dB is theoretical for perfect panels in a perfect world. In the real world, the actual increase is more like 5 dB each time you double the mass.

The same applies to the two-leaf situation: It is 18 dB in theory, but more like 12 to 15 dB in real life. But that's still a hell of a lot better! It's an order of magnitude better! So you can get much higher levels of isolation with a lot less mass.

So, for two-leaf walls, in the region above resonance, each time you double the mass you get an increase of about 12 to 15 dB... until you hit the coincidence region. Coincidence is rather complex to explain, since it has to do with bending waves inside the wall surface coinciding with certain frequencies of wave in the air hitting the wall at certain angles, but in summary, it reduces the isolation again in that region. But who cares? Up that high, there's already so much isolation that it really does not matter. And above the coincidence dip, we get back to mass-controlled once again.

Here's a typical TL graph for a typical two-leaf wall:

Attachment:
RC-double-stud-2x16-2x16.jpg


You can see all the regions on there. Clearly, for this wall resonance is at around 63 Hz. Below that stiffness takes over, so there's a slight increase, and above that comes the mass-controlled region, then the coincidence dip at around 2 kHz, then mass controlled again beyond that.
the purple line on there shows where the contour for the STC-56 curve is with respect to the actual TL curve. This wall would be rated at STC-56, but the actual TL is more like 60 dB. You can see that STC only considers a small part of the spectrum, and not even the most important part for studios.

That's a pretty good wall, in fact. Something like what you'll get for your walls that face inside the building.

Here's a graph that shows something similar to what you'll get for the other two walls, where you have concrete block as one leaf:
Attachment:
TL-isolation-graph-concrete-block-plus-2.16-dmp.gif

TL is more like 80 dB in that one.

WOW! 80 dB? You must be jumping up and down, but hold your horses: you wont be getting 80 dB isolation from your room, since there are other factors involved. Firstly, isolation is only as good as the weakest link. If you have two walls rated at 80, and two rated at 60, then you get 60. If your ceiling for that same place is only rated at 55, then your total is 55. If your doors and HVAC are only rated at 50 dB, then you get a total of 50. Whatever the weakest part is, that's what your total isolation will be. Which is why you have to design and build everything to the highest level that you can!

OK, it's not quite as bad as I'm painting it there, but it's close. The weakest link rules.

Then there's flanking: Flanking is when sound takes another path around your isolation system. In your case, the flanking limit will be the slab, since it is common to both leaves and also to the other studio. The flanking limit for that type of situation is about 70 dB, so no matter how good your walls, windows, doors, and HVAC system are, you could never get better than about 70 dB of isolation. If you wanted more, you'd have to float your floor, or better still, float your entire studio.

So what about the "decoupled" floor instead? (back to your original question!) Well, yes and no. Again. Cryptic....

Decoupling is not quite the same as floating. The issue here is resilience. How "springy" things are. Air is one type of "springy"!, rubber is another, and insulation is yet another. The problem here is the "weakest link" issue again. If you have two types of resilience in a system, the worst one wins. In fact, you add them together, so it's the combination of the worst one plus the best one, and a higher result is worse than a lower result. But that obviously means that the worst one is the limiting factor. Air is the best, steel springs second best, rubber third best, and insulation forth best. A properly floated floor is springs + air ("best plus second best), which is still pretty good. And it has lots of mass. A decoupled floor is insulation + air, but that is "forth-best plus best", which ain't so very good. It's still better than nothing at all, but not as good as a properly decoupled floor. So there's a flanking limit here to, and I'm really not sure what it will be, but it very likely won't be higher than 70 dB, so there's not a lot of point in bothering....

HOWEVER! We are talking about airborne sound here. Vibrations in the air that cause the floor to vibrate. Not an issue in your case, I suspect. But what about impact noise and structure-borne sound? Impact noise is things that hit the floor and cause it top vibrate directly, such as when you drop something on it...or walk on it... or have a drum kit set up on it... or a bass cab... In all those cases, the noise source is in direct contact with the floor, and transmits energy into it very efficiently. There is no air in between, so no resilience at all! For these sounds, yes, it makes sense to put in a decoupled floor, since it does stop impact sound and structure-borne sound getting in and out. It adds a layer of resilience. Even though that layer isn't all that great ("forth-best plus best"), it is still better than nothing.

So what you could do here is to just build a "drum riser", instead of trying to decouple the entire floor. A decoupled platform, done the way Rod shows, that is large enough for a full drum kit, or a bass cab, or anything else that might transfer vibration directly into the slab. Doing a full decoupled floor won't increase your total TL at all, since what it adds doesn't make much difference to airborne noise, which is what we are mostly interested in. But it does help for impact noise and direct structure-borne noise.

Not sure if I explained that well, but this gets' to the heart of your original question, so it is important: Summary: a decoupled floor won't improve your overall TL, which is a measure of the isolation of airborne sounds. But it will help considerably for impact sounds. So it makes sense to build a drum riser platform for that purpose, but not for the whole room.

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so if i was to buy 2 x 45db doors it still would only give me 45db isolation
No, it would give you more than 45 dB, but nobody can say how much more unless you know all the parameters. If you were to set those two doors just 1 cm apart, then it could give you LESS than 45 dB, since resonance would happen at a rather high frequency. But if you set them 1 m apart, you'd probably get upwards of 65 dB. You'd have to use the equations for two-leaf partitions to predict that. Here's what they look like:

Fc=c[(m1+m2)/(m1m2d)]^.5

where:

Fc=resonance frequency (Hz)
c=constant (60 for empty gaps and 43 for with insulation)
m1=mass of first leaf (kg/m^2)
m2 mass of second leaf (kg/m^2)
d=interleaf spacing (m)

I think you'll recognize that! :) But that's only part of it. That just tells you what the resonant frequency will be. You then need this:
Attachment:
Full-spectrum-TL-isoaltion-equations.jpg


The top equation is for calculating TL up to the MSM resonant frequency of the wall, the middle one is for the region between resonance and an arbitrary point given by 55/d (roughly where the coincidence dip is), and the third one is for the region above that (which you really don't need to worry about too much). In fact, for practical purposes you can simplify the third equation to R = R1 + R2 + 6. R1 and R2 are the TL figures calculate for each leaf using mass law.

Quote:
on the walls where breezeblock and brick is the outer layer, these walls will obviously have a lot more mass than my normal MSM walls and my ceilings. how do i make sense of the calculation in a case like that??
Simple: The equations use surface density. So you'll need to found out the surface density of your concrete blocks, and of your drywall, and of your doors, and of your glass.... That's easy to do: take the absolute density, and factor in the thickness. So for example, the density of glass is about 2500 kg/m3, so if you have a pane of glass 10mm (1cm) thick,the surface density would be about 25kg/m2. If it was 20mm thick, it would be 50 kg/m2, and if it was only 5mm thick, the surface density would be 12.5 kg/m2.

So using the above equations, if you have two panes of 20mm glass 20cm apart, then you get a resonant frequency of:

Fc=60 [ (50+50)/(50 x 50 x .2) ]^.5
Fc=60 [ (50+50)/(50 x 50 x .2) ]^.5
Fc=60 [ (100)/(500) ]^.5
Fc=60 [ (100)/(500) ]^.5
= 26.83 Hz

At that frequency, you would get this:

R=20 log (f(m1+m2)) -47
R=20 log (26.83(50+50)) -47
R=20 log (2683) -47
R=21 dB

So at resonance, you would get 21 dB of isolation, and from there it would rise to about 75 dB

etc.
Quote:
how do i somehow combine that into a correct RF for whole space?
calculate for each pair of walls, doors, windows, ceilings, etc. And the lowest value wins. The weakest link wins.

So let's say that you figured 75 dB for your block walls, 60 dB for your drywall walls and ceiling, 58 dB for your windows, and 53 dB for your doors. Your total isolation is 53 dB, since that is the weakest point. (It's actually a bit better than that, but not enough to be happy about).
Quote:
also can you recommend some online calculators for rigidity, coincidence dip, and intermediate transition characteristics, they seem a lot harder to find than RF..
I have never found any online calculators for those, since the calculations are rather complex and you have to factor in so much: But there is a paper that explains all the equations, titled "Accuracy of Prediction Methods for Sound Transmission Loss" by K. O. Ballagh. See if you can find that on-line.

Quote:
im specially fond of sub freq instruments...
:shock: Be prepared for some rather large mass and air gap requirements! You probably won't like what you come up with... sub-sonic frequencies are a MAJOR issue to deal with. Don't forget that all of this is exponential: it gets exponentially harder to isolate, the lower you go. If you compare isolating for 990 Hz, and 980 Hz, its pretty much the same, even though they are ten Hz apart. But the difference between isolating for 90 Hz and 80 Hz is a lot harder, even though they are also only ten Hz apart. And the difference between isolating for 20 Hz and 10 Hz is hugely, massively harder, even though they are also just 10 Hz apart.

Quote:
but slef leveling cement is crazy expensive here.
Then get a load of concrete! Four cubic meter of concrete will cover your entire 50m2 floor to a depth of 8cm. The going rate in the UK seems to be about £100 per cubic meter, including delivery to the site. Add some extra for getting it from the truck to your studio floor location (it has to be moved fast), and some more for labor to level and smooth it, plus setting up and removing the formwork, and even some for bonding compound, clean-up, coffee breaks, whatever else.... even then, it shouldn't cost you more than about £1000, max. Call a local contractor and ask for a quote.

Don't complicate your studio build with patchwork solutions. Bite the bullet and get the job done right. It will save you time and money in the long run, and you'll have a much better studio. Let the pros do jobs like that, then you can concentrate on doing what you can do yourself. A contractor will have your floor poured smooth and level inside a couple of days. Allow a few more for good curing, and you'll have the best floor ever for a studio.
Quote:
and this is the cheap and easy solution we came up with.
Not trying to be a SOB, but with studio building, you'll find that "cheap and easy" never is. It might look that way at first, but when you actually try it, and it doesn0t work out the way you planned, and you have to do it again, and re-do it... well then , it wasn0t so cheap or so easy after all. Been there, done that. I would highly recommend that you get your floor fixed before you start building. A smooth, flat, level slab is very, very useful to have for a job site! Especially for when you build your walls laying down, before you raise them: you don't want to build them warped and twisted because of the uneven floor! You want them built flat, plumb and true. And many other reasons too...

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i dont see why it wouldnt work unless u told me cement under the sole plates has waaaaay worse db loss than the walls themselves right???
And if it cracks or separates from the underlying slab? What then? How would you even know, until you noticed that your isolation is shot: How much would it cost you to tear down the finished wall to get at the crack and fix it?... If i were in your shoes, I would NOT run that risk. I would just get a whole new floor poured and be done with it. Then I'd have a wonderful job-site floor to make my whole build easier, simpler, faster, cleaner, cheaper, safer... and a wonderful floor for the actual studio itself, with no further cost needed. Concrete is about the best possible studio floor you can ask for...

You are looking at the trees, and not seeing the forest. Trying to save a few quid on the floor is going to have far-reaching consequences in many, many other ways during the build and afterwards, and I guarantee that you'll regret it rather fast.

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sorry i dont know what "mud" means... tape i assume is plaster tape that you use to seal joints between sheets,
"Mud and tape" is a yank term for how you deal with joints in drywall. You apply drywall compound ("mud") to the joint, press into it a strip of a special type of gauze-like or paper-like tape that covers the joint comepltely, then apply more drywall compound over that, pressing it into the tape, then wiping off the excess with a trowel.

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yes of course, the inner leaf will have 2x5 and the outer leaf will have 2x6
I'm talking about the ceilings, not the walls. I very much doubt that you'll be able to span 5m with that much live load and dead load on 2x5 joists....

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i want to use top of the studio as storage,
So where will you put your HVAC then? :)

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PostPosted: Fri Sep 09, 2016 10:24 pm 
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amazing thanks yet again. this is well enough for me to go away and work on this for a while and make sure everything is right. but i understand it now!

by the way the HVAC unit will go ontp of studio too the way we have thought of it. storage wouldnt take up much space there =)


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PostPosted: Mon Sep 12, 2016 7:36 pm 
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Hey Stuart, a couple of things have come up that i'd like to ask before i post final calculations and my new build plans.

for insulation in stud walls you gave me the density for mineral insulation and glassfibre insulation, but what thickness should it be? it must make a difference right???

also when we calculate the resonance frequency, trying to bring it down as low as possible we can get it to 18.24 which suggest a TL of 15.62 dB. Does this sound reasonable to aim for after everything we've talked about?? I understand its unlikley i get those actual numbers ones its built, but surley i want to try get RF as low as i possibly can if i work with Sub in some music. the air gap in walls at RF 18.24 vary slightly but range between 0.18m - 0.30m so if i add any mroe to that the inner dimesions start to get really affected. (and this is assuming we raise the wall and dont have much air gap between the 2 studios.

Say we raised walls and had 10cm air gap between the studios. then we obviously have a 4 leaf system between the studios. how would that work???

I've also read the article you suggested for the rest of maths. Its hard to totally understand but I think we're doing pretty good if we aim for everything i just explained above. Obvioulsy the rigidity of the structure will be really important which we will focaus really hard on when we build. But i've also seen you suggest 16mm plaster board rather than 12.5mm ... im going to check today if i can get 16mm in UK. we have calculated to use 3 layers of 12.5mm right now..

thanks!


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PostPosted: Mon Sep 12, 2016 11:21 pm 
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for insulation in stud walls you gave me the density for mineral insulation and glassfibre insulation, but what thickness should it be? it must make a difference right???
Right! It must be as thick as the entire cavity, or as close to that as you can get, reasonably. It works by damping the resonances in that air cavity, and also changing the way the air behaves. In effect, it makes the path that sound waves take across that gap "seem" longer. For each inch of insulation, the path "appears" to be 1.4 inches long. So it pays to fill the entire cavity as much as possible, as long as you don't overfill it, cramming it in so tightly that it is compressed and causes flanking! So if you have a a 10cm gap, then put 10cm of insulation in there. If you have a 15cm gap, put in 15 cm.

However, also check your fire code! There might be specific requirements on how that has to be done, and having fire-blocking inside the wall cavity. There are methods for achieving that too.

Quote:
when we calculate the resonance frequency, trying to bring it down as low as possible we can get it to 18.24 which suggest a TL of 15.62 dB.
I guess you mean 15 dB at 18 Hz, right? If so, that's reasonable. But if you came up with a total of 15 dB for the entire spectrum, then you didn't calculate right!

Quote:
but surley i want to try get RF as low as i possibly can if i work with Sub in some music.
Yep! very true. To get it lower, you have to add more mass to the leaves, or increase the air gap. Those are the only parameters that you have.

Quote:
so if i add any mroe to that the inner dimesions start to get really affected.
Then increase the mass! You can put more layers of building material on there (such as an extra layer of drywall on each side), or you can replace one layer of drywall with something that is more massive (higher density). For example, fiber-cement board has a surface density about twice as high as drywall, so one sheet of that is the same mass as two sheets of drywall. If you really want to get exotic, you can put in a layer of steel plate, or better still, lead sheeting. Lead is about seventeen time more dense than drywall, so a layer of lead sheeting just 3mm thick has the same mass as 51 mm of drywall. Lead is also considered "limp mass", because it has remarkably low self-resonance. Of course, it is quite a bit more expensive! :shock:

There's also something else you can do that does not figure into the basic equations, since it works on a different principle. You can add something called "constrained layer damping" in between your sheets of drywall. I mentioned this before. The product is called "Green Glue", and it works by damping the sheer waves and bending waves inside the "sandwich" of materials that make up each leaf. It isn't cheap, but it works very well, and is especially good at increasing isolation performance at low frequencies.

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Say we raised walls and had 10cm air gap between the studios. then we obviously have a 4 leaf system between the studios.
Yep. That's why I mentioned that you need to "eave enough gap to ensure that there won't be acoustic problems." A four-leaf wall is even worse than a 3-leaf wall at low frequencies, but is even better than the others at high frequencies: isolation increase at 24 dB per mass doubling and 24dB per octave above the resonant frequency. So yes, you need to drive down that resonant frequency even more, by adding more mass to all the leaves... or by leaving a larger air gap. If you leave a gap of 20cm between you and the studio next door, and have some serious mass on both sides of that gap, you can have really good isolation. For your outer leaf on that wall, I would probably do something like first putting a layer of 18mm MDF on the studs, then a layer of 12mm fiber-cement board with Green Glue, then a layer of 16mm fire-rated.drywall, also with Green Glue. That will give you a surface density of close to 45 kg/m2 on that leaf, but you also have the extra CLD effect from the Green Glue, so the frequency is a few Hz lower and the isolation is a few dB higher than predicted by the basic equations. If you have a 20cm gap between that and the next studio, and you put insulation in that gap, then you can have some serious isolation there without needing to worry too much about 4-leaf problems.

Quote:
I think we're doing pretty good if we aim for everything i just explained above.
:thu:

Quote:
But i've also seen you suggest 16mm plaster board rather than 12.5mm ... im going to check today if i can get 16mm in UK. we have calculated to use 3 layers of 12.5mm right now..
Also look at cost, and at those other higher-density options, such as fiber-cement. Replacing one layer of drywall with one layer of fiber-cement board makes that layer twice as heavy in the same thickness. So if fiber-cement board is less than twice the price of drywall, then it is well worthwhile substituting.

Also, take a close look at Green Glue. That would be very recommendable in your case, since you need high levels of isolation at low frequencies. That's exactly what GG does for you.

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PostPosted: Tue Sep 13, 2016 5:03 am 
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Right! It must be as thick as the entire cavity, or as close to that as you can get, reasonably. It works by damping the resonances in that air cavity, and also changing the way the air behaves. In effect, it makes the path that sound waves take across that gap "seem" longer. For each inch of insulation, the path "appears" to be 1.4 inches long. So it pays to fill the entire cavity as much as possible, as long as you don't overfill it, cramming it in so tightly that it is compressed and causes flanking! So if you have a a 10cm gap, then put 10cm of insulation in there. If you have a 15cm gap, put in 15 cm.


ok... just need to make sure i havnt totally misunderstood this until now. so were planning on using 2x4 studs. you mean i should fill the air gaps between the studs (in my case using something something as close to 4" insulation? you don't mean to fill the whole air gap between 1st and second leaf in wall right?? there has to be a air gap right???

this also makes me question how i used the FC formula. d = interleaf spacing (m) , i assumed that to be the air gap between insulation, not air gap between plasterboards. so my wall right now looks like this = 3 layers plaster board - 2x4 stud wall with insulation - 30cm air gap - 2x4 studs with insulation - 3 layers of plaster board. so my d = 0.3m .. this gives us the RF 18. and thats us using 43 as the constant in calculation. is this correct or have i misunderstood this?

Or is it that when i use the formula with 43 as constant for insulation it means thats a cavity totally filled with insulation???

If that is the case, the formula gets confusing cause what is my 'd' in that case???


Quote:
I guess you mean 15 dB at 18 Hz, right?


correct


I will look into prices of all the mass adding alternatives you mentioned. but just out of curiosity, if i can't afford to go up in mass and have to go down in size, how big air gap should we have between studios if i get my RF to be 18Hz, and the TL at 18Hz is 15db??

we created an excel sheet that we put all the calculations, dimensions etc into, which automatically adjust price of material, RF and dB etc. so everything moves together... and the price is already going up more than i was hoping =)

J


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PostPosted: Tue Sep 13, 2016 5:28 am 
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you don't mean to fill the whole air gap between 1st and second leaf in wall right??
Actually, yes! That is what I mean. Fill as much of that as possible.

Quote:
there has to be a air gap right???
Right! The place where the insulation is, IS the air gap! Insulation is mostly air.... It's just a bunch of fibers with lots of air in between them. Putting insulation in the "air gap" does not mean that there's no air: it just means that there is air and also fibers, which act together. The air is the spring, the fibers are the damper. Just like the suspension on your car: you have a spring, and inside that you have a damper, except that in a car it is called a "shock absorber", but technically the correct name is "damper". It does not absorb shocks (the spring does that): it damps resonant motion, oscillation.... Just like your wall: Taking the shock absorber out of your car and leaving just the spring, is the same as taking the insulation out of your air gap, leaving only air. Insulation is mostly filled with air.

Quote:
d = interleaf spacing (m) , i assumed that to be the air gap between insulation, not air gap between plasterboards.
Nope! It's the distance across the entire cavity, from the face of the drywall on one side of the gap to the face of the drywall on the other side of the gap. Forget about the insulation for this measurement: consider it to be air, because that's what it acts like.

Quote:
so my wall right now looks like this = 3 layers plaster board - 2x4 stud wall with insulation - 30cm air gap - 2x4 studs with insulation - 3 layers of plaster board. so my d = 0.3m
Nope. 2x4's measure about 9cm deep, so your total air gap in this case is 9 + 30 + 9 = 48cm. That's a pretty big air gap! I know you want good low frequency isolation, but you can probably still get it with less space than that. Bring the spacing between frames down to about 15 cm, and you'll still have plenty: 9 + 15 + 9 = 33. You could get three thicknesses of 4" insulation in there.

Quote:
Or is it that when i use the formula with 43 as constant for insulation it means thats a cavity totally filled with insulation???
Right! If you have less than fully filled, you'd have to increase that constant a bit.

Quote:
If that is the case, the formula gets confusing cause what is my 'd' in that case???
Distance across the gap, drywall to drywall (or whatever the first layer is on each side...).

Quote:
I will look into prices of all the mass adding alternatives you mentioned. but just out of curiosity, if i can't afford to go up in mass and have to go down in size, how big air gap should we have between studios if i get my RF to be 18Hz, and the TL at 18Hz is 15db??
Do the math! :) Try several options, keeping the mass the same but changing the depth of the air gap, until you the numbers you want.

Quote:
and the price is already going up more than i was hoping
Welcome to the world of studio design! That's the way it always goes.... At some point, you'll have to compromise. If you cannot go over a certain budget limit, then you'll have to make do with less isolation, or a smaller room inside (larger air gaps), etc. That's what studio design is all about: compromise. Juggling a dozen parameters all at once, and trying to get the best values for each one such that the final outcome is as good as as you can get it. Normally, the parameter that suffers must, and goes up quicker than all the others, is the one with the dollar sign in front....


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PostPosted: Tue Sep 13, 2016 9:56 am 
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oh wow.. everywhere i've seen images of these MSM walls theres an actual air gap between. this makes it interesting in a lot of ways. obviously we've been calculating very big air gaps as 'd'. so one quick question - if we couldnt afford to fill it with insulation (3 layers in your example) but felt we could still have a 33cm air gap, but with 2 layers of insulation. could we calculate a new constant for the formula like this?

43 = 0% and 60 = 100%.
so using 2 layers of insulation would mean we have used 66.6%.

60 - 43 = 17

17 / 3 = 5.6

so 5.6 + 43 = 48.6 which would be our new constant if we used 2/3 of insulation????


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PostPosted: Tue Sep 13, 2016 2:05 pm 
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if we couldnt afford to fill it with insulation (3 layers in your example) but felt we could still have a 33cm air gap, but with 2 layers of insulation. could we calculate a new constant for the formula like this?
I'm not sure if the constant can be adjusted linearly between 0% and 100% fill... I have a feeling it isn't linear, but I don't recall which way it is skewed. I do have a paper on that somewhere, but I can't find it right now. But it will be somewhere in between 60 and 43 ... ! :shock: :roll: 8)

Not very helpful, I know. But if you calculate for both extremes, that will give you a good idea of the best-case and worst-case scenarios. As long as the worst-case is sort of reasonable, and the best-case is great, then you'll be OK.

I'm going to dig through an old backup that I have from a previous computer, and see if I can find that paper.


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PostPosted: Tue Sep 13, 2016 6:06 pm 
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thanks stuart! didin't think it would be that easy =)


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PostPosted: Wed Sep 14, 2016 8:20 am 
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couple small questions for now..

since the whole air gap gets filled with fibre, we cant really talk about a mass per wall anymore, or not the same way i imagined. any insulations thats between the studs actually filling where the 'air gap' should have been. can we divide that insulations amss and add half to each wall mass??

and say we accomplish a RF 18Hz on studio. but i can't get any closer than 40cm from other studio, could i add more mass and air gap only to the wall facing the other studio wall, and that would help situation? or it wouldnt make sense to have 15Hz on that wall and 18Hz on rest??

J


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