Small commercial studio facility design in Oslo, Norway

Hi folks! This is my first post here, but I have read and learned so much from this forum already. Thanks for keeping this amazing resource alive! I'm in the planning phase of building a small commercial studio facility in an office/storage building in Oslo, Norway. Construction is scheduled to start towards the end of this year. I've been running a commercial studio business for a few years already, in a studio that I didn't design or build myself. Now it's time to move on to another location, and I hope that my experience as a producer/engineer along with some advice from professional acousticians, carpenters (and hopefully you gentlemen), will enable me to design the new facility myself. I will not be doing much of the construction myself, though, I'll leave that to the professionals. The budget is somewhat flexible but we'll try to keep it below NOK 500 000 which is roughly $85 000. The studio will house 2-3 engineers and be geared towards recording and mixing of pop, rock, jazz, urban and some classical music. Max SPL generated will be the occational 115 dB peak while tracking drums. Normal activity is more like 85 dB mixing, vocal recording, etc. The facility will be built on the ground floor of a relatively modern office/storage building. The building is huge and the studio will only take up a small fraction of the total space. The neighbouring rooms are mostly storage spaces, which is good because most of the time there won't be any people in there. On the other side, I will possibly have to take into account some occational activity in those rooms, which may or may not include the moving of heavy objects. I will look into this further. There are offices on the first floor directly above the studio. The building structure between the floors is 25 cm concrete, and the height of the ground floor is about 4 m. We have done preliminary sound transmission tests between the two floors and the isolation seems to be pretty decent already. I will have to do more testing though*. The studio floor is concrete on ground, which is why I'm not really considering floating it. I realize of course, that if someone is to run a fork lift in a neighbouring storage space (I don't know yet if that's a likely scenario), I will possibly get some low-frequency leakage through the floor. The outer studio walls are all either concrete, concrete+brick, or LECA (Light Weight Concrete Aggregates; I don't know if this is an internationally available product? They are building blocks made out of compressed clay pellets, with a density of 450-800 kg/m3 depending on pellet size). I believe these walls will serve as good outer-leaves. No drywall to rip off before building the inner-leaves. The facilities will consist of a main live room, two control rooms, two isolation booths, a machine room, a kitchen/lounge and a WC. Total usable area is about 112 m2. As I see it, there are a few primary concerns regarding sound isolation in these rooms: 1. Traffic noise. There is a (not very trafficed) street directly outside the outer long wall. I can hear that the leakage through there substantial, though I suspect it's not the wall (40 cm concrete and brick) so much as the windows. I hope it's enough to seal the windows and double with a second set of glass on the inner leaf. Sound leakage from the studio to the outside world should not be a problem. The building is not in a residential area. 2. Fan noise. The main HVAC fan room for the entire building (I think) is located directly behind a part of the inner long wall. I can hear some summing noise coming through there (the wall is 40 cm LECA). It's not much but it will have to be dealt with. 3. Noise from the storage spaces. As mentioned earlier, there might be some occational activity in these rooms. However, conversely, sound leakage from the studio into the storage spaces should not be a problem. 4. Leakage from the ground floor studio to the first floor offices. As mentioned, the isolation seems to be OK already, but I will have to examine this further. The daytime noise floor in the room now is roughly 54dBSPL (slow) C-weighted. I realize this is quite high and will have to be dealt with. It is most certainly a combination of traffic noise and fan noise from the HVAC room. Unfortunately I forgot to measure the SPL inside the HVAC room and also in the street outside. I will do that for sure. Further, I'm not sure how low a noise floor I actually need - I have no idea what the noise floor in my existing studio is, as my SPL meter won't measure anything below 50 dB. I guess somewhere in the 30-40 dB region would be acceptable. Here is a floor plan of the empty rooms: And here is my studio drawing, including a double-leaf MSM system for the studio rooms (the drawing doesn't include acoustical treatment at this point): (Sorry about the drawings. I'll try to get my head around Google SketchUp as soon as I can.) The inner MSM walls are a sandwich of the following: 1. Double 16 mm drywall (hopefully I can afford to Green Glue them together) 2. 10 cm of insulation between wooden studs (should the studs be double for rigidity?) 3. A 2 cm air gap between the leaves (should I fill this with insulation too?) 4. 10 cm of insulation between wooden studs (should studs be double for rigidity?) 5. Double 16 mm drywall (hopefully I can afford to Green Glue them together) My finished room layout will possibly have a few more angled walls to prevent standing waves, however I'm not sure whether to angle the actual inner-leaves or just the acoustical treatment. I guess the latter is faster and cheaper to build, but I'm not sure what's best for room modes. Are there any differences? Apart from the obvious difficulty of calculating room modes with angled walls? I guess I'd prefer to do a combination of the two: Build the inner-leaf with 90 degree corners wherever the inner-leaf runs parallell with the outer- leaf (which is rectangular), and angle the inner-leaf wherever it runs parallell with another room - to save space. Does this make sense? We are not really planning to soffit-mount any speakers; we use near-fields on stands. Windows, doors, HVAC and electrical system will obviously have to be taken into account pretty soon, and I'll provide thoughts on these things too. Please have a look at this as a starting point and give me your 2 cents if you will. I would love to hear some opinions. Did I forget something really important? Thank you! Sky *) We played music through a Mackie 450SRMv2 and a Genelec 1070B subwoofer (goes down to 19Hz) on the ground floor, and measured the average level to 110dBSPL C-weighted (slow) 1m in front of the speakers. We measured the noise floor of the empty offices above to 54dB with no music playing downstairs and 57dB with music playing. Almost no difference! However, while standing in the offices, holding the SPL meter, I could barely discern which song was playing downstairs. Which makes me believe something funky was going on either with me, my measuring method, my meter, or all of the above. Or, I guess if total isolation is required, one will actually have to take into account that we can hear and discern sounds below the noise floor? Another interesting thing was that the leakage was mostly in the mids and highs; I could not hear any lows. Again, perhaps the test method was flawed, ie, the playback system wasn't able to provide enough low end. I'll definitely have to do more testing, preferably with a real-world scenario like a rock band in there and a pro acoustician to carry out the measurements.

Hi Sky, and welcome! :)

The budget is ... roughly $85 000. Total usable area is about 112 m2.

That works out to roughly US$ 750 / m2, which is very do-able. You should be able to build nice place with a budget like that. That's good, since far too many people come here without a realistic budget, but yours is fine.

The building structure between the floors is 25 cm concrete, and the height of the first floor is about 4 m.

Very nice! Good height, and a good outer-leaf.

We have done preliminary sound transmission tests between the two floors and the isolation seems to be pretty decent already. I will have to do more thorough testing though* ... while standing in the offices, holding the SPL meter, I could barely discern which song was playing downstairs. Which makes me believe something funky was going on with either me, my measuring method, my meter, or all of the above. Or, I guess if total isolation is required, one will actually have to take into account that we can hear and discern sounds below the noise floor.

Right. We actually can discern sounds below the sound floor. As much as 15 dB below, if I recall correctly. That's why you can still hear and understand a conversation on the other side of the room in a crowded cocktail party: our brains have the ability to pick out certain sounds that are quieter than the general level. Just like you can still see the flame of a candle in bright sunlight, so too you can hear quiet sounds in a noisy environment.

Another interesting thing was that the leakage was mostly in the mids and highs, I could not hear any lows.

That makes me suspect that there is an air path between the two rooms, such as through the HVAC system, or through the electrical system, or gaps around the edge of the floor/ceiling, or open doors/windows. I would do a careful inspection for such issues, and seal all of those. Tiny cracks can greatly reduce acoustic isolation. It might just be problems with porous bricks/concrete that need sealing well.

The outer studio walls are all either concrete, concrete+brick, or LECA (Light Weight Concrete Aggregates; I don't know if this is an internationally available product? They are building blocks made out of compressed clay pellets, with a density of 450-800 kg/m3 depending on pellet size). I believe these walls will serve as good outer-leaves.

Yes! It seems like you have a pretty good outer-leaf already, so all you'll need to do to that is to seal it very carefully.

The facilities will consist of a main live room, two control rooms, two isolation booths, a machine room, a kitchen/lounge and a WC. Total usable area is about 112 m2.

Sounds like a tight fit. The two control rooms will take up about half of that, if you plan on meeting ITU/EBU specs. The iso booths need to be at least five or six square meters each, which only leaves you 50 m2 to divide between the kitchen, lounge, bathroom, live room, and the large amount of space used by the isolation walls themselves.

1. Traffic noise. There is a (not very trafficed) road directly outside the outer long wall.

What type of traffic noise can you hear inside? Is it more like the low rumble of heavy engines and wheels running on the road, or is it the higher sound of tyre tread and air noise? Can you "feel" that noise in the floor of the room, if you touch it with your fingertips, or listen with a stethoscope pressed to the floor?

I hope it's enough to seal the windows and double with a second set of glass on the inner leaf.

If done correctly, then yes, that will work. The basic concept is to use glass that matches the surface density of the leaf it is part of. Or at least high enough mass to get the MSM frequency low enough to cover the spectrum you are concerned about.

2. Fan noise. The main HVAC fan room for the entire building (I think) is located directly behind a part of the inner long wall. I can hear some summing noise coming through there

Once again, it would be good to determine if that is structure-borne sound (vibrations in the actual walls/floor of the building) or only air-borne sound, and what frequency the humming is. Also, will that HVAC system by used to cool and ventilate your studio, or will you be using an independent system for that?

The daytime noise floor in the room now is roughly 54dBSPL (slow) C-weighted. I realize this is quite high and will have to be dealt with.

Yep! :) IT would be really hard to track and mix in such a noisy environment.

I'm not sure how low a noise floor I actually need - I have no idea what the noise floor in my existing studio is, as my SPL meter won't measure anything below 50 dB. I guess somewhere in the 30-40 dB region would be acceptable.

You determine that by choosing a "Noise Rating" or "Noise Criteria" for your studio, using the NR (or NC) curves. Probably NR, where you live. They are curves that show the acceptable perceived level for different types of room. You will probably need something like NR 20, or maybe lower, depending on what type of recording you plan to do in the studio. This link might help: http://www.engineeringtoolbox.com/nr-no ... -d_60.html Or Google "NR Curves".

And here is my studio drawing,

A few general comments on that layout: CR #2 seems to be square! :shock: That needs to be fixed, urgently. It also very small, less than half the minimum recommended floor area for a critical listening room. (Assuming 2.5m ceiling, the volume will be only about half of what you need for a critical listening room.) The iso booths seem to be sound-locks, with doors on both ends, are very small, and seem to be the main passages for accessing the live room and machine room. That isn't practical. You will have to constantly move instruments and mics out of the way so people can walk through. The loading dock is at the far end of the machine room, which is at the far end of the iso booth, which is on the other side of the control room... So for load-in and load-out, musicians will have to drag their gear through SEVEN doors, to get it from the loading dock to the live room... Not practical. Even worse, they will have to drag it through the control room... The machine room is far too small. There's no room for racks in there! Standard racks are about 75cm deep, you need at least that much space behind them, for access during installation, operation and maintenance, and at least a meter of free and clear space in front of them, to be able in install, remove and service equipment, and just for easy operation of the equipment. That means at least 2.5 m room depth, plus whatever furniture you need in there (small desk, storage shelves, etc.). That room is nowhere near 2.5m deep. That needs to be much bigger. I'm very familiar with dimensioning machine rooms, as I used to do that for a living: I used to design and build professional video post production suites, so I'm confident that your machine room is not practical the way you show it now. In addition, you should never have a machine room directly connected to the outside world: machine rooms should be clean and sealed off from the world, for many reasons, You'll never find an outside door in a properly designed machine room. CR1 and the LR are practically the same size. The general recommendation is that the LR should be at least twice the volume of the CR, so that you can hear the reverb tails of the LR when listening to the speakers in the CR. If the rooms are similar in size, you will not be able to hear the LR tails since the CR's own decay will be masking them. Ideally, the LR should be about five times the volume of the CR. Doors: You have doors in the rear corner of CR1, exactly where you need bass trapping. You also have a door in the front right wall, which is exactly where you should have your speaker soffits. So those doors need to be moved to better locations.

My finished room layout will possibly have a few more angled walls to prevent standing waves,

You cannot prevent standing waves. Standing waves, more correctly called "room modes" are a simple consequence of the dimensions of the room, not the shape of the room. There are three different types of modes: axial modes occur between two parallel walls, but tangential modes and oblique modes occur between walls that ar not necessarily parallel. A "mode" is just a path that a sound wave can take around the room, then arrive back where it started on-phase with itself. Changing the angles of the walls does not "destroy" or "eliminate" any modes: it just means that you changed the frequency where the mode occurs. It is a common myth that angling walls will eliminate modes: it does not. It just changes their frequency, and makes them much harder to predict. For a rectangular room it is very easy to predict all of the modes: axial, tangential and oblique. For non-rectangular rooms, it is very much more complex, ad requires FEM/FEA software, plus an operator who knows how to set up the boundary conditions correctly, and how to analyze the results.

however I'm not sure whether to angle the actual inner-leaves or just the acoustical treatment. I guess the latter is faster and cheaper to build, but I'm not sure what's best for room modes. Are there any differences? Apart from the obvious difficulty of calculating room modes with angled walls?

Angling acoustic treatment has no effect on room modes, except for large panel traps. Modes are calculated to the hard boundary surface of the room, which is the inner-leaf. Most types of treatment have no effect on the frequency of the room modes, or only a small effect.

I guess I'd prefer to do a combination of the two: Build the inner-leaf with 90 degree corners wherever the inner-leaf runs parallell with the outer-leaf (which is rectangular), and angle the inner-leaf wherever it runs parallell with another room - to save space. Does this make sense?

The inner-leaf does not have to run parallel to the outer leaf. It can if you want, but it doesn't have to. The inner leaf can be angled, if you need to do that. As long as the closest point between the two is still far enough away that the MSM resonant frequency remains below your minimum, then you are OK. So the depth of the gap can vary. That can actually be a good thing, under some circumstances.

We are not really planning to soffit-mount any speakers; we use near-fields on stands.

If you are not planning to soffit-mount, then why is the main control room shaped like that? There's not much point in an RFZ design if you don't also soffit-mount. I mean, it can be done, but most of the benefits are only gained when you soffit-mount. Only soffit mounting eliminates SBIR, power imbalance, early reflections off the front wall, phasing, comb filtering, edge diffraction, and all the other bad things that happen with speakers on stands. If you don't soffit mount but do use an RFZ design, it will be pretty hard to figure out angles and treatment that make sense.

Did I forget something really important?

HVAC. I don't see any provision for HVAC in there, and that takes up a LOT of space in most studios. I also don't see any windows between the rooms. Most musicians and engineers need good sight lines with each other to be able to work at their best.

Please have a look at this as a starting point and give me your 2 cents if you will. I would love to hear some opinions.

I would suggest addressing the issues I have outlined above, and post your updated plans. I would also suggested doing them in 3D in SketchUp: it's just so much easier to design the room in 3D from the beginning: Sound is 3D, so it just makes sense to think of the entire design in 3D. Hope that helps! - Stuart -

Hi Stuart! Thank you so much for your reply, and apologies for the late response - I just returned home from vacation. :)

Another interesting thing was that the leakage was mostly in the mids and highs, I could not hear any lows. That makes me suspect that there is an air path between the two rooms, such as through the HVAC system, or through the electrical system, or gaps around the edge of the floor/ceiling, or open doors/windows. I would do a careful inspection for such issues, and seal all of those. Tiny cracks can greatly reduce acoustic isolation. It might just be problems with porous bricks/concrete that need sealing well.

That makes sense. I'll take the building contractor for an inspection of this.

The outer studio walls are all either concrete, concrete+brick, or LECA (...) I believe these walls will serve as good outer-leaves. Yes! It seems like you have a pretty good outer-leaf already, so all you'll need to do to that is to seal it very carefully.

Right. Are there any preferred ways of sealing a concrete wall? Just ordinary paint?

The facilities will consist of a main live room, two control rooms, two isolation booths, a machine room, a kitchen/lounge and a WC. Total usable area is about 112 m2. Sounds like a tight fit. The two control rooms will take up about half of that, if you plan on meeting ITU/EBU specs. The iso booths need to be at least five or six square meters each, which only leaves you 50 m2 to divide between the kitchen, lounge, bathroom, live room, and the large amount of space used by the isolation walls themselves.

I know, it is a tight fit. That's the one issue with this space - it is great in many ways; ground floor, loading dock, concrete walls, concrete ceiling, concrete floor, good daylight, few neighbors, high ceiling, likable building owner, etc, etc. But I really wish it'd be 30 m2 bigger! Anyway, it's hard to find good spaces in Oslo these days so we've decided to have a go at designing something here. Two things about the building and the rental deal: 1. We haven't signed anything yet. We can still exit and start searching for another building. What we are doing now, is trying to work out a design concept so that the building owner and contractor can estimate a price tag and a time frame for us. Having done that, it is up to us to decide if we wish to proceed. 2. There is a possibility that one of the adjacent storage spaces will become available for rent over the next few years. That is one of the reasons I may want to build something here, even if it can seem a little tight. Perhaps we can build something small but usable now, and then expand into something bigger in the future.

1. Traffic noise. There is a (not very trafficed) road directly outside the outer long wall. What type of traffic noise can you hear inside? Is it more like the low rumble of heavy engines and wheels running on the road, or is it the higher sound of tyre tread and air noise? Can you "feel" that noise in the floor of the room, if you touch it with your fingertips, or listen with a stethoscope pressed to the floor?

Actually, I have never heard a large vehicle pass by the building, so I can't tell if there is any low rumble. Most of the time it is just high-frequency ambient noise from the empty street. I THINK, as long as we seal off the existing windows and the concrete wall, most (or all) of the leakage will go away, but I will have to check for low frequency noise as well for sure.

2. Fan noise. The main HVAC fan room for the entire building (I think) is located directly behind a part of the inner long wall. I can hear some summing noise coming through there. Once again, it would be good to determine if that is structure-borne sound (vibrations in the actual walls/floor of the building) or only air-borne sound, and what frequency the humming is. Also, will that HVAC system by used to cool and ventilate your studio, or will you be using an independent system for that?

It is more like pink noise than humming. I can't hear a specific note in there. I think it is air-borne, but I will take your advice and check if there is any structure-borne leakage. HVAC. Honestly I don't know much about it. I'm trying to read up! What I do know is that there is already a HVAC system installed, and it is connected to the rest of the building. The building contractor says that we can install sound traps in the system to prevent leakage to and from the studio. I have no idea if that will be enough. What is your experience, is a separate system always needed?

I'm not sure how low a noise floor I actually need - I have no idea what the noise floor in my existing studio is, as my SPL meter won't measure anything below 50 dB. I guess somewhere in the 30-40 dB region would be acceptable. You determine that by choosing a "Noise Rating" or "Noise Criteria" for your studio, using the NR (or NC) curves. Probably NR, where you live. They are curves that show the acceptable perceived level for different types of room. You will probably need something like NR 20, or maybe lower, depending on what type of recording you plan to do in the studio. This link might help: http://www.engineeringtoolbox.com/nr-no ... -d_60.html

Thank you! I will discuss this with the building contractor.

CR #2 seems to be square! That needs to be fixed, urgently. It also very small, less than half the minimum recommended floor area for a critical listening room. (Assuming 2.5m ceiling, the volume will be only about half of what you need for a critical listening room.)

Sorry, my bad, I never meant it to be square. It have corrected the mistake in the new drawing below. The size is small but it is OK for this room. It is more like a writing and editing suite than a critical monitoring room.

The iso booths seem to be sound-locks, with doors on both ends, are very small, and seem to be the main passages for accessing the live room and machine room. That isn't practical. You will have to constantly move instruments and mics out of the way so people can walk through.

Yes, you're right. In this tight space, it seems I can really only fit one live room and no ISO booths. However, I thought that if we design the airlocks so that they CAN be used as ISO booths occasionally (like a scratch vocal or a guitar amp) then that would make the facility more flexible. You are absolutely right in that we will have to move stuff out of the way after every session, because the airlocks are main passages, but it's OK, I don't think they will be used as ISO-booths every day, more like once or twice a week.

The loading dock is at the far end of the machine room, which is at the far end of the iso booth, which is on the other side of the control room... So for load-in and load-out, musicians will have to drag their gear through SEVEN doors, to get it from the loading dock to the live room... Not practical. Even worse, they will have to drag it through the control room...

Yeah. It's not ideal. One solution could be to move the live room to the right, but then control room 2 would loose its sight lines. Another solution could be to extend the hallway from the loading dock all the way to the live room, making control room 1 narrower. However, as I'm first and foremost a mixer, I don't think I'm willing to make that sacrifice in control room space. After all, maybe 70% of my work is control room-only, 20% is recording small things like one guitar, one flute or one vocal, and only 10% is recording full bands. In the drawing below I have reduced the amount of doors necessary to pass through, and I think I have solved the machine room issue, but it is still far from perfect. However, we won't be doing big load-ins very often, perhaps once every 2 weeks.

The machine room is far too small. There's no room for racks in there!

Good call. What I can do, is relocate the door to the loading dock to make space for a separate machine room with just about enough space to fit a tall 19" rack and some storage shelves.

Doors: You have doors in the rear corner of CR1, exactly where you need bass trapping. You also have a door in the front right wall, which is exactly where you should have your speaker soffits. So those doors need to be moved to better locations.

I don't need speaker soffits, but the rear corner could be a problem. Unfortunately I can see no way of designing the control room without ending up with a door in one of the rear corners - apart from the solution mentioned above in which I create a hallway from the loading dock all the way to the live room. That way I could have one door centered on the side-wall of the control room instead of two doors in awkward positions. But, as mentioned, I'm afraid that would make the control room too small! Say I decided to stay with the existing location and size for control room 1, is there any way I could provide sufficient acoustical treatment while still having a door in that rear corner? What about taking advantage of the height and mount large bass traps across the entire wall-ceiling corner, and also perhaps build a deep rear-wall trap with the door, like, penetrating it?

My finished room layout will possibly have a few more angled walls to prevent standing waves, You cannot prevent standing waves. Standing waves, more correctly called "room modes" are a simple consequence of the dimensions of the room, not the shape of the room.

Sorry, I meant to say "prevent flutter echo". I realize standing waves will exist in the room no matter what. That's why I'd like to build the inner-leaves rectangular for ease of room mode calculation, and angle the acoustical treatment (which will probably have some reflective surfaces facing the room, like slots) to prevent flutter echo and direct early reflections away from the mix position.

The inner-leaf does not have to run parallel to the outer leaf. It can if you want, but it doesn't have to. The inner leaf can be angled, if you need to do that.

Right. I'll go with whatever is most space-saving then. Another thing, in the name of space-saving: Could I do this inside-out approach: 1. Double 16 mm drywall or concrete outer wall 2. Air gap 3. Double 16 mm drywall 4. 10 cm of insulation between wooden studs 5. Thin fabric cover and wooden planks with randomly spaced slots between them Would that be less effective than the wall I described earlier:

1. Double 16 mm drywall or concrete outer wall 2. 10 cm of insulation between studs 3. Air gap 4. 10 cm of insulation between studs 5. Double 16 mm drywall 6. 10 cm of insulation between wooden studs 7. Thin fabric cover and wooden planks with randomly spaced slots between them

It certainly would save some space! I have studied John's inside-out wall, and I realize it is still a 2-leaf MSM, but I didn't see any calculations on the isolation properties compared to a "standard" MSM wall? Can you get 60 dB isolation with a properly sealed inside-out wall? How wide air gap is needed? Sorry about all the clueless questions, I'm learning! :)

If you are not planning to soffit-mount, then why is the main control room shaped like that? There's not much point in an RFZ design if you don't also soffit-mount. I mean, it can be done, but most of the benefits are only gained when you soffit-mount (...) If you don't soffit mount but do use an RFZ design, it will be pretty hard to figure out angles and treatment that make sense.

Interesting! I wasn't aware of that! How would you suggest shaping a control room for non-soffit-mounted near-field monitoring? Just plain rectangular?

I also don't see any windows between the rooms.

Sorry, I have corrected it now. Here is a new drawing. A few things have changed. Please don't pay too much attention to the orange and yellow fields for now, they are meant to illustrate insulation used for isolation (orange) and acoustical treatment (yellow). However, in this drawing I was playing with the idea of a one-leaf control room, which would clearly open up a whole can of worms, but it produced a nicely sized room with a seemingly acceptable ratio of 1 : 1.5 : 1.6. As I'm now thinking of doing all rooms inside-out instead, this drawing is not 100% accurate, but I'll have to spend some time with this. The general room layout is clear however, as are the doors and windows.

I would suggest addressing the issues I have outlined above, and post your updated plans. I would also suggested doing them in 3D in SketchUp: it's just so much easier to design the room in 3D from the beginning: Sound is 3D, so it just makes sense to think of the entire design in 3D.

I promise you, I would love to master SketchUp! One day in the not-too-distant future I will.

Hope that helps!

It helps so much! You have no idea how much I appreciate your input. I'll continue working on this. Any further advice is more than welcome! Thank you! :) Sky

More specifically, regarding the MSM-walls, these are the alternatives I'm evaluating: Questions: a) I would call #2 and #3 inside-out walls. Am I correct? b) Would #2 and #3 be MUCH worse at isolating than #1? c) How can I calculate transmission loss for these different types of walls? d) #3 has no fiber glass insulation between the leaves, only air. Is that a no-no? I would prefer to go with #2 or #3 because of the space savings. But only if the transmission loss is still decent. Thanks for any advice! Sky

Are there any preferred ways of sealing a concrete wall? Just ordinary paint?

There are some special sealers for masonry: check with your local paint store. But if you can't get that, then any good quality paint will work, if applied properly.

It is more like pink noise than humming. I can't hear a specific note in there. I think it is air-borne, but I will take your advice and check if there is any structure-borne leakage

.That sounds like it is probably due to the air movement itself, in the ducts. As air moves around corners, bumps and dents in the ducts, it generates turbulence, which causes noise. Lining the ducts, making them bigger than then need to be, using duct silencers on all wall penetrations, and using very large ducts and diffusers (registers) inside the studio, will help a lot with that.

I have no idea if that will be enough. What is your experience, is a separate system always needed?

If the existing system can handle the added load of your studio, and is not extremely noisy, then you can probably use it, with suitable dampers, silencer boxes, and good design of your part of the system.

I don't need speaker soffits,

Are you SURE? :) Putting your speakers in properly designed soffits is abot the best single thing you can do for your entire studio. Seriously! Since soffit mounting ( more correctly called "flush mounting") actually takes your speaker out of the room acoustically, it also eliminates ALL of the bad artifacts associated with speakers close to walls. No more SBIR, comb filtering, edge diffraction, early reflections from the front wall, phase changes and cancellation, and best of all, it corrects the basic power imbalance inherent to all small speakers, as well as extending the low frequency response down to much lower frequencies, and smoothing it out. Soffit mounting does amazing things to your speakers, and your entire studio.

1. Double 16 mm drywall or concrete outer wall

You don't need that. Adding drywall directly on top of concrete wont make any real difference to isolation, and it takes up space for no good reason. Just seal the concrete, and add your inner-leaf a few inches (cm) away.

2. Air gap

Right! The "air gap" is the distance across the empty space from the surface of the concrete to the surface of the drywall. The studs are not considered here. The air gap should be at least 4" (10cm), and preferably much more. 8" (20cm) is good, if you can afford the space.

2. Air gap 3. Double 16 mm drywall 4. 10 cm of insulation between wooden studs

You also need insulation inside the wall cavity. That is part of the MSM isolation system.

Would that be less effective than the wall I described earlier:

Yes! Much less effective. The insulation in the cavity is a critical part of the MSM system. It damps resonance inside the cavity, and greatly increases isolation.

I have studied John's inside-out wall, and I realize it is still a 2-leaf MSM, but I didn't see any calculations on the isolation properties compared to a "standard" MSM wall?

It is exactly the same! The only difference with an "inside-out" wall is that the studs are on the other side of the drywall (facing the room, instead of inside the cavity). The studs are irrelevant to the MSM isolation: MSM equations consider only two major variables: the mass of the wall (surface density) and the depth of the air cavity. The location of the studs is not relevant at all. The only other factor that affects MSM is the insulation inside the cavity, which is accounted for with a different constant in the equation.

Can you get 60 dB isolation with a properly sealed inside-out wall? How wide air gap is needed?

Yes, you can, and with the exact same size air gap that would have been needed for a conventional build to get 60 dB. The only purpose of the studs is to hold up the drywall: their location on one side or the other side of the drywall does not affect the isolation at all. :) - Stuart -