Residential/commercial area personal studio

[saemola]

DISCLAIMER: this topic contains many informations which are probably going to throw you off track. It was due to a misunderstanding on what the actual purpose and initial conditions of the room were (bad communication on my side). Unless you are willing to go through the whole topic in order to find out what was correct and what wasn't, I would suggest you avoid taking these info into consideration when you build your studio.

Hello folks,

I'm a long time reader of this great forum and now that I'm ready to build my studio I thought I'd ask for some advice.
I have some very basic knowledge of studio design, but I'm essentially a newbie.

The room will a be a personal studio and will only be used be myself and I'm going to be alone in it 95% of the time, with the exception of the occasional visit from directors. The purpose of the room is film work, specifically:
- sound design (that is, ultra clean recording of tiny sounds to be manipulated; by tiny I mean pencil drawing on paper tiny)
- film mix (dub for indie movies/documentaries/animations, pre-mix for bigger productions)
- film scoring (the only acoustic elements to be recorded, other than the occasional guitar and small percussions, are really just sound design elements again, so I assume this point could be taken out of the equation)
This means that I'll be working most of the time targeting -23/-24 LUFS with speakers calibrated between 76 and 78 dB-C. Same goes for music, I always mix at low levels.
There is only going to be one room: the control room acts as a small tracking room for synthesizers and a few acoustic instruments.
This also means no windows: only one door to get in and out of the room.

The room will NOT be used for:
- band rehearsals
- drum recording
- guitar amp recording

Room:
- trapezoid shaped room with two entrances; the southern section will be used as an office (not by me) and will have a separate, independent entrance from the northern section (my studio); the studio will also have its own bathroom
- whole area is ~44 m2 / ~475 ft2; ceiling is 3,65 m / 12 ft high
- ground floor in residential/commercial area (no industries around, only bars, barber shops, clothing stores...) the room is standing on 3cm/1.2" thick tiles of a mix of marble and concrete on top of a 12 cm / 4.7" slab of concrete [edit: I previously said it was a 5-7 cm slab only] and then it's only earth
- north wall adjoins with a hairdresser shop; west wall adjoins with a garage; south and east walls have nothing but open air; there is a terrace ( should be concrete on hollow bricks which look a whole lot like these http://bit.ly/1mfV6fC ) on top of the room and nothing else on top of that, just clear blue sky

The only noise from the street is cars going by and occasionally kids blasting music. Next door you've got the usual noises of shops. I measure between 40 and 50 dB on noise coming in. I know I'll be louder than that but I still need to isolate the room to the point where I can record very small sounds.

Ratio:
- By taking advantage of the high ceiling, and assuming 15cm / 6" of space for the walls (air gap + mineral wool + two layers of drywall [edit: with GreenGlue in between]) I came up with these figures: h 3,5m : w 3,07m : l 4,27m (imperial 11.48' : 10.07' : 14') which, by switching width with height (I'm assuming that's possible, right or wrong?) gives me a Sepmeyer ratio of 1 : 1,14 : 1,39.
- I read that 1500 ft3 / 41,5 m3 is the absolute minimum volume suggested by ITU/EBU. Mine would be 1618 ft3 / 45,8 m3, however the surface is kinda small, 13,1 m2 / 141 ft2
- I'd like to have a decent sounding room, but I know this isn't going to be Skywalker Sound and the biggest compromise here is that I need to leave room for the office

Questions:
- what do you think of the room ratio and how important is it? I could make the room 4,85m/15.91' long, but I can't seem to find a good ideal ratio to fit into. Calculators ( http://amroc.andymel.eu and others) tell me making the room longer makes it worse. However, narrowing the width (which in these calculators I have to input as height) to 2,85m pushes me closer to the Bolt area/EBU/ITU recommendations. [picture attached]
- I'm assuming I don't need a floating floor; am I wrong?
- can I cut the concrete slab to the shape of the room in order to decouple it from the rest of the building/street or are there risks of it cracking? Will it achieve what I assume it will, or am I oversimplifying the issue? How thick does the slab need to be in order to achieve my target isolationisolation? Meaning, do I need to pour more concrete and is it doable?
- what do you suggest to fill the walls to achieve the right sound blocking for the job? I was considering 5 cm / 2" 40 kg/m3 mineral wool + 2 or 3 layers of 1,6cm / 5/8" drywall. Right now I don't know what the one separating me from my next door neighbor (the hairdresser) is made of, but it should be either a mix of cement and lapilli (not it is used anywhere outside of volcanic areas as it is literally material created in volcanic eruptions https://en.wikipedia.org/wiki/Lapilli ) or tuff (again a rock made of volcanic ash https://en.wikipedia.org/wiki/Tuff ). I don't know the size either, but I will in the next few weeks. What I do know is that I conducted a little test on a wall that is supposed to be the same as that, and by playing a pink noise from one room to the other I had about 45 dB(A) or reduction [edit: I previously said it was 24 dB. That was a mistake]. I'll conduct further, more accurate tests.
- since the west and east walls confine with nothing "noise sensitive", the north wall has the hairdresser shop on the other side, which basically has hairdryers and other noisy stuff going on all the time, and since the noise coming in is only about 50 dB, would it make sense to design the room to block the 50dB coming in and only design the south wall built between the room and the office to block more noise so as to not disturb the office with the noise I will produce?
- does it make sense to angle the side walls and the front corners (where the speakers are placed) of the room to create a RFZ in such a small space?
- how much space should I consider for the HVAC duct + silencer? I would like to place it on the east wall to avoid lowering the ceiling. I could even build a small cavity inside the entrance room in order to accomodate it.

Floor plan:
- yellow walls is what I was thinking of building and they don't exist yet. Everything else is already there.
- I can dig into the ground as much as I want in roder to increase the height of the room, but that would add up to the cost.
- areas in green and blue are the garage and the hairdresser shop.

Budget:
- building the wall between my studio and the surrounding rooms, building the bathroom, and cutting the concrete slab will cost me about €2000
- I'll be able to do the electrical system for pretty cheap (a little complicated, maybe I'll explain later).
- I will build the inside walls myself (wood/metal studs w/ insulation and drywall or whatever is required) with some help from some people.
- I have some leftover timber for the wood floor.

I'd like to avoid going over €3000 for the remaining expenses, which I reckon should be:
- door
- HVAC
- insulation/acoustic treatment material


Can I include studio design questions here or should I create a whole other post in the dedicated section of the forum?

Thank you for this incredible resource.
Hope my post was clear and I am eager to read your suggestions!

Andreas

studio 2.jpg

Bolt Area.jpg

[Soundman2020]

Hi Andreas, and Welcome!

- sound design (that is, ultra clean recording of tiny sounds to be manipulated; by tiny I mean pencil drawing on paper tiny)

In other words, it will be a Foley studio? In addition to the actual control room, you'll also have a separate extremely well isolated Foley stage, with several pits for various types of materials that are commonly used in Foley work?

- film mix (dub for indie movies/documentaries/animations, pre-mix for bigger productions)

So it will also be an ADR studio? So you will also need decent sized vocal booth with good acoustics

- film scoring (the only acoustic elements to be recorded, other than the occasional guitar and small percussions, are really just sound design elements again, so I assume this point could be taken out of the equation)

There's two possibilities here: make the vocal big big enough and variable enough that you can track those instruments in there, or track them in the control room.

This means that I'll be working most of the time targeting -23/-24 LUFS with speakers calibrated between 76 and 78 dB-C. Same goes for music, I always mix at low levels.

Actually, your speakers should be calibrated at 86 dB. That's the standard for cine. You might well only mix at 78 dB, but the system should still be calibrated at 86 dB.

But I'm a bit confused about the "-23/-24 LUFS" and the "film work". The LUFS scale is meant mostly for broadcast TV, not cine. Are you doing work for both, of only for broadcast TV?

There is only going to be one room: the control room acts as a small tracking room for synthesizers and a few acoustic instruments.

That would be a bad, bad, bad idea. You do NOT want all the materials form a Foley stage inside your control room! Water, sand, gravel, ball bearings, bits of paper, broken glass, and the all the other messy stuff has no place at all in a control room. You do not want that stuff anywhere near your equipment! Also, you'd never be able to record the really quiet stuff in the control room: there's too much noise from the gear itself, and the HVAC, plus it would be very expensive to isolate an large control room well enough to do Foley work. It's much better to have one small room for the Foley work, with extreme silencing on the HVAC and extreme isolation.

- trapezoid shaped room

Why? There's nothing wrong with that, provided there's a valid reason for choosing that shape. Why do you want it to be trapezoidal?

- whole area is ~44 m2 / ~475 ft2; ceiling is 3,65 m / 12 ft high

Excellent size. Plenty big enough for a good control room and also a good Foley stage.

I'm told the room is standing on a 5-7 cm / 2-2.5" slab of concrete (covered in tiles) and then it's only earth. I'm still investigating the size of the slab. I'm also told that legally I can dig down as much as I want

Do you need to dig down? Is there a need for more ceiling height? Or are you talking about digging the Foley pits down below the level of the slab?

The only noise from the street is cars going by and occasionally kids blasting music. Next door you've got the usual noises of shops. I measure between 40 and 50 dB on noise coming in. I know I'll be louder than that but I still need to isolate the room to the point where I can record very small sounds.

You would need upwards of 60 dB isolation for a good Foley stage. That in turn implies NR (or NC) of 15 or below. That's really hard to do. I hope your budget is fairly substantial!

- what do you think of the room ratio and how important is it?

It's fine, and it isn't all that important. It is just one of many factors that studio designers consider when designing control rooms.

- I'm assuming I don't need a floating floor; am I wrong?

Correct. For the control room, at least. You might need one for the the Foley stage. Probably not, but perhaps.

- can I cut the concrete slab to the shape of the room in order to decouple it from the rest of the building

No, because the edge of the slab needs to be supported on foundations, and the slab might also be part of the structural design of the building. You can solve the first problem by digging back under the edge of the slab and pouring proper foundations, but you might not be able to solve the second problem. For both of those issue, you'll need to hire a structural engineer to tell you if it is safe to do that, and also tell you how big the foundation needs to be, and how to pour it (where to place the rebar, type of concrete, depth, width, bonding agent, etc.).

- what do you suggest to fill the walls to achieve the right sound blocking for the job? I was considering 5 cm / 2" 40 kg/m3 mineral wool + 2 or 3 layers of 1,6cm / 5/8" drywall.

What are the existing outer-leaf walls made of? And are you talking about the CR or the Foley stage here? The Foley stage will need a lot more isolation that the CR.

by playing a pink noise from one room to the other I had about 24 dB of reduction

That's not very much at all! that's less than a typical stud-framed house wall gives you. Also, how did you measure that? dBA or dbC? Fast or slow?

would it make sense to design the room to block the 50dB coming in and only design the south wall built between the room and the office to block more noise so as to not disturb the office with the noise I will produce?

No, because the entire studio is a single isolated system, and the total isolation is only as good as the weakest part. If you have three walls that give you 55 dB of isolation, one wall that gives you 45, and the ceiling only gives you 40, then the entire isolation is 40 and you wasted a lot of time and money getting 55 on the three good walls...

- does it make sense to angle the side walls and the front corners (where the speakers are placed) of the room to create a RFZ in such a small space?

You said you have 475 ft2, so you that's not small. You can get a good sized RFZ control room in there, no problems. That can be done in about 200 ft2, roughly. Allow anther 175 ft2 for your Foley stage, and 100 ft2 for your office. Plenty of space. Not small, so RFZ makes sense.

how much space should I consider for the HVAC duct + silencer?

Silencers. Plural, not singular. You need four silencer for each room. On the inlet duct you need a silencer where that pass through the outer leaf, and another silencer where it passes through the inner leaf. On the exhaust duct you need a silencer where that pass through the inner leaf, and another silencer where it passes through the outer leaf. So it's four for each room, total of eight. In fact, you can get by with just six, if you combine them intelligently.

How big should they be? You can only know that after you have settled on the size of each room. Once you know the size (volume) you can calculate how much air you need to move through there (CFM), and based on the maximum allowable air velocity (FPM) you can calculate the size of the ducts you need. For the Foley stage, the velocity will have to be really low. Much lower than for the CR. Air makes a noise as it moves, so it cannot be permitted to move fast in the Foley room.

I could even build a small cavity inside the entrance room in order to accomodate it.

"Them". Not "it" Eight of them, or maybe six. And they need to be large. The more isolation you need, the larger the silencer boxes have to be. The slower the airflow you need, the larger the silencer boxes have to be.

Floor plan:

I don't see your Foley stage in there! There's only a CR, but you cannot use that to as a Foley stage.

- I have some leftover timber for the wood floor.

Stucio floors are not made from timer: they are either left as plain concrete (maybe polished / stained to look good), or finished with laminate flooring.

I'd like to avoid going over €3000 for the remaining expenses,

I think you missed a zero off there. A typical high end control room costs about €400 to €800 per square meter to build. You have 45 m2. It will cost around 18,000 to 36,000 to do that place. Ok, so part of it will be office, but even part of it will be Foley, which is expensive to do. I would estimate somewhere around 20,000 to do this correctly.

Can I include studio design questions here or should I create a whole other post in the dedicated section of the forum?

No problem! Include them here. It is best to keep all the questions about your studio in one single thread, so you can find them all easily in the future, when you need to check the answers.

Hope my post was clear

- Stuart -

[saemola]

Hey Stuart,
first of all, thanks for replying.

I think we started off on the wrong foot as all your answers seem to imply that I'm trying to achieve something I'm not. My post was probably NOT clear AT ALL.
I'll try to clear a few things up in this post (and maybe edit the original post for future reference) and using the next post to ask some follow up questions:

- this is a personal studio: nobody other than me will record, mix or compose in there.

- the room won't be used for foley. The only sound design oriented recording happening in there will be, how to call it, field recording material? All stuff that will be heavily manipulated by myself, turned into music or into abstract film sounds (think Richard Devine or Star Wars, rather than Tom Waits or No Country For Old Men). Nothing realistic, nothing that will require another person in the room. No foley pits. Things I'll record by myself in front of the computer, import in my DAW or sampler and manipulate.

- no ADR and there will be no vocal booth (I'm really not sure how I could have hinted at this one [edit- I think I just realized how: dub is probably more of a European way of describing the final mix, whereas in American countries that usually means overdubbing? what I meant is re-recording for indie films... in a nutshell, the final mix!])

- the only acoustic instrument I'll record will be guitar, but forget about that. Again, it's just me in front of a computer doing everything, so all recording will happen in the control room. There won't be any gear noise as there is basically no gear: other than a modular synthesizer and my audio interface, I'm 100% in the box and the Mac Pro only outputs about 12dbA of noise when idle (a tiny more when stressed but still less than any HVAC I could afford. I will consider putting it in the entrance room if too noisy)

- the trapezoid 475 ft2/44 m2 space is the whole room which already exists now, but as mentioned I'm going to have to split it in two and only be able to use the north half; in that north half I'll build my rectangular control room, a bathroom and an entrance. you can see on the floor plan the yellow walls: those are the walls I'm planning on building. The south half of the trapezoid space will be dedicated to an office (the part labeled "Space to be dedicated to office space"), whereas the north half will be my space, in which I'm going to build my studio (you can see from the drawing that there is an entrance and then the actual control room). The only room dedicated to audio will be the one that is marked as 3,07x4,27 on the floor plan! I'll be able to stretch it up to 3x4,85 m, so the control room (and, again, the only room dedicated to audio) is actually going to be ~14,5m2 and ~50m3.

- I don't need to dig down for the foley pit as there won't be any: I was just pointing out that, should you suggest a higher ceiling, I do have the option of digging if necessary, but for economical reasons I think this is falling out of the equation

- as far as noise reduction is concerned, forget the foley, I mislead you by hinting at the tiny sounds: noise reduction should be appropriate to a mixing room and to avoid nuisance to the office next door when mixing (again, at very reasonable levels). I'll make compromises as far as acoustic recording goes by doing it during quieter hours. That's going to be only 5% of what I do in there. It's not ideal, but again, that's my budget and I'm not aiming at becoming a big post studio. Also, the noise from the street that I quoted was: taken at peak hour (it is otherwise a very quiet place); calculated through the current entrance door which is basically a thin sheet of glass which is going to be replaced with a heftier, double-layer, thermic one. That measurement really was worse case scenario.

- when considering cutting the slab, I meant only under the control room (again, marked as 3,97x 4,27, but I'll be able to make it 3x4,85). I already consulted an engineer and the floor is not part of the structural design of the building [edit: and he also mentioned pouring foundation, I just lost it in the mix of the conversation]. Other than decoupling, is there anything else I can/should do to achieve proper low end isolation for the office next door? Is there a way to even know how much decoupling from the rest of the building will help me with low frequency transmission loss and whether it is actually necessary? Right now I'm thinking of having a 5cm/2" air gap.

- I'll have to recalculate the existing wall isolation and report back to you. I did the calculation based on a different wall which I assumed was built the same way, but turns out it's not (this is going to be thicker, but I assume it still won't isolate much). The wall is made of a mix of cement and lapilli (there are links in the previous post, if you don't know what these materials are) [edit: calculated: it blocks ~45 dB(A)]

- I am aware that a room's isolation is only as strong as its weakest link, but when I mentioned designing the CR to block the 50dB coming in and making a stronger south wall what I meant was to have the 5 walls of the control room (4 walls plus roof) block 50dB, and making the wall between the CR and the office (the one that's 5,9m long in the floor plan) very strong. The thinking behind this is that the office (remember, it's going to be a stranger in there) needs more isolation than the hairdresser or any of the other walls. They basically need none as I'm not bothering anyone there. It was more about saving money on the fact that I need to cut noise from outside coming, but there is little noise outside, I'll be making more for my office neighbor. Either way, I've gone on to make all the walls equal.

- studio floors don't have timber laid on concrete?! This blows my mind. I have seen it so often that I just assumed it was actual wood. Is it for acoustical reasons? What about all those barn studios? Or am I mixing terms up and timber and hardwood are two different things?

Hopefully this clarifies things!
Thanks for your time, Stuart, and I'm sorry I wasted it by not making things clear.

Cheers!

[saemola]

I've updated the floor plan to clarify even further.
The colored walls (yellow, red, purple) are what I'm gonna need to build. Everything else is already there.
The yellow walls are for the audio room (mixing room, control room, recording room, however we want to call it) and serve the purpose of a room within a room design.
Red walls are the entrance/lounge and bathroom leaves.
The Purple wall is what separates my studio from the office (the grayed area... as you can see I'm a photoshop wizard ) and it is the one I was suggesting building with a higher NR because the office space is really the only noise sensitive area, but I abandoned the idea.

Hope this makes it all clearer.

studio 3.jpg

[saemola]

Construction work has started.

What I have:
- 5cm gap has been dug in the concrete floor around the whole perimeter
- walls built and plastered (2cm or ~3/4") on both side
- final room dimensions after the 5cm gap are as described in the attached floor plan
- floor is 3cm/1.2" thick tiles of a mix of marble and concrete on top of a ~12cm/4.7" concrete slab on earth
- Daikin Ururu Sarara which acts as an air inlet as well ( http://www.daikinaircon.com.au/daikin-s ... lit-system )
- 2 glass doors made with double-glazed (gass in between) Saint Gobain Glass Stadip Silence mounted on equivalent Rw value (Rw 45) aluminum frame (sorry, can't find an English brochure for that one)

Next step is building the internal room: I'm planning on using 5cm air gap/85 fiberglass in 75mm metal joist/drywall/Green Glue/drywall.
Specs: 85mm ~30kg fiberglass; 5/8" (~15mm) drywall; 10 gallons of Green Glue for a total 69m2 surface (the equivalent of 2 tubes per 4'x8' panel). Joist sitting on joist insulating tape. Mud for each layer of drywall and acoustic caulk + backer rod for each layer at the seams with the ceiling, floor and walls. The backer rod I'm going to use is the Mapefoam and caulk is the Mapeflex PU45 which has a density of 1,42g/cm3 and has a "high modulus of elasticity" with 0,8N/mm².

My questions...
Insulation material and HVAC:
- How does using 10mm backer rod and place the drywall 8mm off the floor/ceiling sound? That would give me a vertical gap of 8mm and a horizontal gap of a little less than 5mm for the caulk to fill. The 300ml tubes of caulk I'm buying supposedly fill 3m of 10x10mm gaps. Since my gaps are smaller (9x5 with backer rod) and to exaggerate I have 110m to fill, I'm getting 18 tubes. Should end up with 1 or 2 leftover tubes.
- Is it ok to have the exhaust duct on the same wall or even right next to the inlet or should it go on the opposite wall? towards the ceiling or the floor? By the way, Stuart, your post in another topic about not putting the fan in the exhaust to create positive pressure was enlightening.
- Do I need to leave space between the yellow and the red leaves for the inlet and outlet silencers or can I just put them on the outside (red leaf) and use spray polyurethane and insulated flex duct with Rockwool for the 13cm between the two leaves? Rockwool actually sells several "HVAC pipe" products, ranging from 20 to 100 kg/m3 density. Are those any good? Would they nullify my decoupling?
- How to seal electric conduits coming from the outer room? The cables go into a 4cm ø flexible plastic pipe. Should I fill that with foam in the spot where it goes through the leaf or should I just strip the pipe and pass the cables only?
- What's my CFM, my FPM and what equation should I plug them into in order to calculate the size of my baffles? The volume of my room will be ~51 cubic meters.
- Any experience in tube-baffling the Ururu Sarara? Other than air inlet, the unit has 3 more tubes (gas, water draining). Should all 4 tubes go to silencers or is it only required for air inlet? How do I block sound going into the gas and water tubes?
- Does my studio qualify for a one-baffle-system? HVAC is only going to serve the audio room (yellow leaf). The drawing mistakenly mentions 3 silencers. I read in another topic that, given enough space between two leaves, only one baffle is required. In my case, I can make that space as wide as I want (look at the protrusion I've drawn in the room plan).
- Any suggestion on how to deal with the pipe pictured? It is the rain water drainage for the terrace above my head (the pipe is actually going to be dismissed in about 9 months, but I'll have to live with it in the wall...) Right now it is deep into the wall, but there's a corner sticking out, and not a small one. Of course it'd be easy to avoid having to go around it with the drywall.

Walls:
- Is it necessary for the wool to touch the drywall in the ceiling? My installer doesn't know how to do that without leaving a gap the size of the joist (like this)
- If I know how much noise one leaf blocks, what is the formula to calculate how much the whole system with my second leaf is supposed to block in order to achieve my desired target? I know that two walls blocking 45dB with an added air gap should give me a little more than 50 rather than 90dB of reduction, but how do I calculate precisely the added isolation provided by the air gap? I'm especially curious for my doors since the entry to the mix room (red leaf going to the yellow leaf) will have two parallel, decoupled glass doors blocking 46dB each.

Bonus question: in order to get the 5cm gap between floors, I dug down to the base of the concrete slab (15cm). A question has been haunting me: should I go lower than that?

Cheers!

hvac duct.png

IMG_20161031_113407.jpg

[saemola]

Here's a few pics.
Unfortunately I've been pretty busy with work, but here's a few pics.
Still some work to do before the internal room can be built, but I should be able to do it either by the end of the week, or early next week.

IMG_20161011_125448.jpg

IMG_20161007_152922.jpg

IMG_20161012_083843.jpg

IMG_20161025_170004.jpg

IMG_20161025_164904.jpg

IMG_20161025_165921.jpg

IMG_20161025_165941.jpg

IMG_20161026_122035.jpg

[Soundman2020]

- the room won't be used for foley.

This is confusing! In your first post, you said: " ultra clean recording of tiny sounds to be manipulated; by tiny I mean pencil drawing on paper tiny". That, by definition, is Foley work. Ok, so you might not be doing sand, water and broken glass, but you still need the isolation and the silence. You still need NR-15 or better.

- no ADR and there will be no vocal booth (I'm really not sure how I could have hinted at this one

Because you said: "dub for indie movies/documentaries/animations," Dubbing implies dialog replacement. That's what it is.

what I meant is re-recording for indie films... in a nutshell, the final mix!])

However, you mentioned "documentaries" and "animation". Those imply dialog. I don't know of two many documentaries that are sung to music!

Narration for documentaries and animated movies (shorts, features, commercials, whatever) implies recording voices. Recording voices usually implies a vocal booth, and is basically very similar to ADR. ("Usually", but not always. Some people do record vox in the CR, but once again, in order to do that successfully, you need high isolation and low NR numbers.

- as far as noise reduction is concerned, forget the foley, I mislead you by hinting at the tiny sounds:

Then why did you talk about needing to record the sound of pencils writing on paper??? It doesn't get much quieter than that.... Maybe butterfly wings flapping, or feathers falling on carpet...

noise reduction should be appropriate to a mixing room

Not if you will be recording narration and pencils-on-paper! Most control rooms are done to NR-25 or NR-20. For the kind of work you are talking about, you should really be shooting for NR-15 or even better.

calculated through the current entrance door which is basically a thin sheet of glass which is going to be replaced with a heftier, double-layer, thermic one. That measurement really was worse case scenario.

I'm not sure I understand the point you are trying to make here: The level that you measured is what it is! That's the actually level you measured, full-stop. End of story. That's how loud it is. So it reflects the amount of TOTAL isolation that you will need for the studio, regardless of what other things you do to various parts of the building.

Other than decoupling, is there anything else I can/should do to achieve proper low end isolation for the office next door?

If you are going to the extreme of cutting and re-pouring part of the slab, but also say that you don't need much isolation, then I'm really not understanding the plan very much! If you don't need much isolation, then why cut the slab? And if you DO need that much isolation that cutting the slab is so important, then why do you keep insisting that you don't need much isolation?

But anyway. If you really are doing that,, then you need to make sure it is done properly: You have to cut EVERYTHING. If there are electric conduit connections, or water pipe connections, or gas lines, or sewer lines, or alarm wiring, or telephone wiring, you need to cut and seal all of those, or re-route them around the slab. Isolated slab means 100% totally isolated: the slab can only touch the earth below, nothing else. (Well, OK, so it also touches the vapor barrier that it must be sitting on, and that vapor barrier in turn must also touch the gravel bed that is between the earth and the slab, but you get my point...)

Is there a way to even know how much decoupling from the rest of the building

If you do it right, it would allow you to increase your total isolation to beyond 70 dB. In most project studio builds, the limiting factor is flanking through the slab. Since you will be eliminating that, you'd be able to go higher. Of course, getting to 70 dB isolation in the first place is a major expensive thing to do, and way beyond the capabilities (and budget!) of most DIY builders. Most home studios get around 50 dB of isolation, with or without cutting the slab. The builders run out of money a long way before they run out of headroom to the flanking limit.

The other reason you might want to isolate your slab is if you have a vibration problem in the building itself, such as from a noisy elevator, pumps, electric gates, HVAC, doors slamming, that kind of thing. OR also if you have vibration from the road outside... and we are also assuming that the vibration is only in the building structure, not also in the ground under the slab.

and whether it is actually necessary?

That depends on how much isolation you need, which is a very confusing issue right now! You keep on saying that you don't need much, but then talk about plans for having a large amount!

Right now I'm thinking of having a 5cm/2" air gap.

Between what and what?

[edit: calculated: it blocks ~45 dB(A)]

Nope. It blocks about 45 dB, not 45 dBA. Transmission loss is a simple calculated difference between two measured "things", and is not weighted. It cannot be weighted! That would be invalid, mathematically, and also illogical. "A" weighting refers to a scale for adjusting SPL levels, which has nothing to do with the actual isolation provided by the wall. A ratio of 45 dB is 45 dB, regardless of what the measurement system was. It would be very valid and very logical to say that the difference in temperature between the surface of the sun and the surface of the earth is 45 dB. It would be very valid and logical to say that a tree is about 45 dB taller than an ant. It would be logical and correct to say that a mountain is about 45 dB heavier than a car. But it would not be correct to say that level inside your room is 45 dBA louder than outside. It is just 45 dB louder. dB is just a measure of a simple ratio between two numbers. dBA is a measure of sound pressure level, as a ratio with respect to the quietest possible sound that the human ear can detect, modified according to the "A" weighting curve. . There's no relationship between the two, other than that they both measure ratios. but you cant measure the ratio of two ratios like that!

I am aware that a room's isolation is only as strong as its weakest link, but when I mentioned designing the CR to block the 50dB coming in and making a stronger south wall what I meant was to have the 5 walls of the control room (4 walls plus roof) block 50dB, and making the wall between the CR and the office (the one that's 5,9m long in the floor plan) very strong. The thinking behind this is that the office (remember, it's going to be a stranger in there) needs more isolation than the hairdresser or any of the other walls.

You are contradicting yourself there! On the one hand you are saying you know that having one strongly isolated wall is useless since sound will flank around it, but on the other hand you are saying that you want to have one strongly isolated wall anyway because you are hoping that sound won't flank around it! How does that work???

Either way, I've gone on to make all the walls equal.

- studio floors don't have timber laid on concrete?!

They can if you want, and that's not what I was implying! There ight be a semantics problem, but "timber" normally implies "joists" that are supporting the actual floor surface. Joists implies air cavities under the floor surface. That implies resonance, which can potentially trash both your isolation and your room acoustics. Studios do not normally have subfloors raised on timber joists, since doing that correctly is not easy. It can be done, but needs careful design. If you are just talking about wood that is laid flat directly on the concrete, then that would be a solid-wood floor, or a parquet floor, or something like that. Not a "timber" floor.

Can I include studio design questions here or should I create a whole other post in the dedicated section of the forum?

That's fine! It's best to keep all your questions about your studio in one single thread. If not, then you will quickly lose track of where you asked what, and in which thread you got the information you need...

- Stuart -

[saemola]

Oh boy. Ok, looks like my clarifying post didn't clarify a thing. Probably too much scattered information.
I'll reset and start from scratch.

I'm building a mixing room.
I will not record actors in there. None. No singer. Nada. And I don't sing. If I did I wouldn't even need wall insulation because my neighbors would run as far away as possible.
When I mentioned "dub" I meant "dub mix". In several regions of the world a "dub mix" is a "movie mix". What some people call a "re-recording mix".
No actors, no voiceover. Nothing.
Occasionally, I will record acoustic material in there, but that's an exception and I can work around that since making the place as quite as a Foley room would be overly expensive for the amount of foley recording I do. i.e. the place is whisper quiet most of the day except for about 1h (the one hour when I took that noise measurement). We can virtually take recording away from the equation.

Let's consider this a mixing room.
What I'm trying to achieve is to not disturb my neighbors with the noise I make with my film mixes.
I mix at very reasonable levels.

The level that you measured is what it is! That's the actually level you measured, full-stop. End of story. That's how loud it is. So it reflects the amount of TOTAL isolation that you will need for the studio, regardless of what other things you do to various parts of the building.

Again, I probably wasn't clear. When I said that it was measured through a weak door, the door I was referring to was not the mix room entry door: it was the door on the grey wall on the right of the floor plan, which is the door that from the outside leads you to the entrance/lounge of the studio.
That door is an old, no-more-code-compliant piece of glass which I think doesn't stop more than 3dB. It was virtually like measuring with no door at all. That door will be replaced with a new glass door which alone blocks 33dB so the measured 45dB are much less significant.

You have to cut EVERYTHING

That's what I did: I dug down to the base of the concrete slab which is now only laying on the earth underneath. I cut the slab in order to try and isolate the room by the low end generated by the occasional car going by on the road outside and by the electric gate which is on the outer leaf, right outside the left outer wall.
I was actually wondering if there was something to be gained by digging lower than the base of the slab.

There ight be a semantics problem, but "timber" normally implies "joists" that are supporting the actual floor surface. [...] If you are just talking about wood that is laid flat directly on the concrete, then that would be a solid-wood floor, or a parquet floor, or something like that. Not a "timber" floor.

Gotcha. As I thought it was a terminology issue. I meant solid-wood floor/parquet. Either way, I am missing 2 sqmt, so I'm gonna go with snap-together vinyl flooring. It doesn't even need underlayment as it has rubber on the bottom.

You are contradicting yourself there! On the one hand you are saying you know that having one strongly isolated wall is useless since sound will flank around it, but on the other hand you are saying that you want to have one strongly isolated wall anyway because you are hoping that sound won't flank around it! How does that work???

I'm sorry but I'm really not sure how to better explain myself here. If you try to read what I wrote while looking at the colored floor plan that should help you understand what I meant.
The stronger wall was the purple one, which is the wall between me and my neighbor. It is not one of the walls of my internal leaf. But it doesn't really matter as I've decided to reinforce my whole room. Median noise floor in peak hour might be 45dB, but I don't want to be bothered by surface contact noise (not sure of the English name here: basically people walking above me).

Nope. It blocks about 45 dB, not 45 dBA.

I need to clarify this. I did all my measurements playing back 3rd octave bands of pink noise, full pink noise, a piece of music, ... The attenuation was different at different frequencies (higher at high frequencies, lower at low ones) but around 45db overall. In order to give you a simpler, single figure I used an A weighted metering plugin to measure the full-range pink noise recorded both with the mic right in front of the speaker and with the mic on the others side of the wall I wanted to measure. The difference was 45 dB-A. Is that a useless measurement or was it my lack of explanation that made it useless?

[5cm/2" air gap] Between what and what?

That's the decoupling between floors. That is 5cm between the floor of the yellow leaf and the floor supporting the red/purple/grey walls. Add to that 8cm of glass wool and I have 13cm of air space.
I think I made things much clearer in the last post, the one with the attached picture of a pipe.
In that post I tried to clarify things and bring better aimed questions. Hopefully you have answers!

I really do hope I made this mess clearer now!

As always, thank you Stuart!

[saemola]

Internal leaf joists going up.
Before proceeding with fiberglass and drywall I need to be taking care of the pipe in the upper corner and the electric conduits, but I'm still not sure if the methods I described are the way to go.
Hopeful to get a response, meanwhile digging deeper in researching the subject.

IMG_20161117_133733.jpg

[Soundman2020]

The level that you measured is what it is! That's the actually level you measured, full-stop. End of story. That's how loud it is. So it reflects the amount of TOTAL isolation that you will need for the studio, regardless of what other things you do to various parts of the building.

Again, I probably wasn't clear. When I said that it was measured through a weak door, the door I was referring to was not the mix room entry door: it was the door on the grey wall on the right of the floor plan, which is the door that from the outside leads you to the entrance/lounge of the studio.

Actually, you were clear, but you are missing the point! It does not matter if you measured that through a door, or plastic bag, or a goldfish bowl! What those numbers show is the T O T A L isolation that you will need. I don't know how to put it any more clearly than that. Read over that post again, and see if maybe I missed out on something that would make it clearer.

That door is an old, no-more-code-compliant piece of glass which I think doesn't stop more than 3dB. It was virtually like measuring with no door at all. That door will be replaced with a new glass door which alone blocks 33dB so the measured 45dB are much less significant.

Again, you are missing the point. Before you can decide on how to build your studio (a bit late now!), you FIRST need to define how much TOTAL isolation you need. Not how much you need through the door, and how much through the window, and how much through the ceiling, and how much through the floor, and how much through one wall, and how much through another. That's not the issue. What matters is first defining your goal: Your TOTAL isolation. You do that by measuring how loud you are inside and how quite you need to be outside (that's one issue), and you also do that by measuring how loud things are outside and how quiet you need them to be inside. (that's the other issue). In each case, you subtract the smaller number form the larger one to get your answer. If one of those measurements already took into account some wall, door, window or whatever, you need to remove that form the calculation, to get the TOTAL ISOLATION THAT YOU NEED, regardless of what you are getting at present through any specific barrier.

Together, those two "issues" will lead to a definition of: "How much TOTAL isolation do you need?". That's the number that EVERY PART OF YOUR STUDIO must meet. Not just some parts.

Here too, I don't know how to describe it any simpler than that.

I dug down to the base of the concrete slab which is now only laying on the earth underneath.

Did you then also dig down under the edge of the slab, and pour new footings? If not, then you have a major problem.... A slab by itself won't support the large amount of mass you'll be applying to it, from the walls and ceiling. It needs footings around the edges. It used to have them, but you cut them off...

I was actually wondering if there was something to be gained by digging lower than the base of the slab.

Well, you SHOULD do that, for sure! You HAVE to do that in order to pour the new footings! I'd suggest that you need to dig down at least 18", make the footers at least 12" wide, and slope the inner edge at an angle of 45° to 60° to where it meets the bottom of the slab itself. Those are typical dimensions for a monolithic slab, which is what you need. You destroyed the structural integrity of the one you had. What is left is no longer capable of structurally supporting what you plan to build on it. You MUST fix that.

To do it properly, you'll also need to put crushed stone or gravel on top of the dirt, and a plastic barrier, then pour the concrete. You should also probably put some rebar in there, towards the bottom of the footing. Probably two pieces of #4 rebar all around the perimeter would be fine.

This is what a monolithic slab typically looks like:

foundation-monolithic-sm.jpg

But don't rely on what I'm saying here! Hire a qualified structural engineer to take a look at your situation, and tell you what to do.

Playing with load-bearing structures is tricky business. And dangerous. It would be really sad if you went to all the trouble and expense of building this place, only to have it collapse on your head one day and kill you.

so I'm gonna go with snap-together vinyl flooring. It doesn't even need underlayment as it has rubber on the bottom.

That's fine.

But it doesn't really matter as I've decided to reinforce my whole room.

Ummmm.... that's the way you ALWAYS design an acoustic isolation structure! It's the ONLY way to do it! It MUST be done such that you have the same level of isolation on ALL sides! That's what I've been trying to tell you all along. You CANNOT have different isolation in different directions.

but I don't want to be bothered by surface contact noise (not sure of the English name here: basically people walking above me).

"impact noise". That's the term in English.

Impact noise is different from airborne noise. Impact noise is structure-borne: it runs in the actual building materials. It is in the walls / floor / ceiling / etc. That's a different problem, and needs to be addressed differently.

Nope. It blocks about 45 dB, not 45 dBA.

I need to clarify this. I did all my measurements playing back 3rd octave bands of pink noise, full pink noise, a piece of music, ... The attenuation was different at different frequencies (higher at high frequencies, lower at low ones) but around 45db overall. In order to give you a simpler, single figure I used an A weighted metering plugin to measure the full-range pink noise recorded both with the mic right in front of the speaker and with the mic on the others side of the wall I wanted to measure. The difference was 45 dB-A. Is that a useless measurement or was it my lack of explanation that made it useless?

You did the measurement wrong, to start with: It should have been done with "C" weighting, not "A" weighting, since we are talking about loud full-spectrum sound here, and the way human ears perceive that is very similar to the "C" curve. There can be a difference of easily 10 dB or more between "A" and "C" for full spectrum sounds.

But even if you had measured with "C" weighting, you are still misunderstanding the decibel scale. It does not matter which weighting curve you used, the DIFFERENCE between the measurements can only, ever be measured in decibels. You cannot describe differences as being "dBA", or "dBC", or "dBu" or "dB VU" or "dBm" or "dB-anything else"! There's a fundamental problem or misunderstanding of what the term "decibel" means. Most people think that "#decibels" means "how loud is the music". It does not. Not at all. "Decibel" is simply a mathematical method for comparing two magnitudes or powers. It does not matter what those "magnitudes" are. It does not have to be sound at all! It would be perfectly valid for me to say that the distance between Campobasso and Turin is 6dB greater than the distance between Campobasso and Perugia. Or I could say that the temperature of the surface of the sun is about 46 decibels hotter than the temperature of Rome in summer. Both are correct, mathematically, since both compare the "intensity" of two related measurements. That's what decibels do: they compare two levels of "somthing". And notice that I did NOT use kilometers or degrees Celsius in those comparisons, because decibels compare only numbers, not units of measurements.

There are two ways of doing that: you can compare the signal magnitude of the two things, or you can compare the power. (In the above examples, I'm treating the distance and temperature numbers as though they were a signal magnitude, which is unusual but is a valid way of looking at them). If you are measuring magnitude, then the equation use 20 log the difference, for power it is 10 log the difference.

When some instrument is used to measure signal level or the power, then when that number is written down, it should always be written along with a "subscript" which describes what was measured, and what it was measured "with respect to". So if I measure the voltage of a signal at some point inside a mixing console, and I want to display that on a meter on the front panel (as many consoles do), then I'd mark the reference point on my meter as "0 dB", and I'd have a scale going up and down either side of that point, showing how much bigger or smaller the signals is, WITH RESPECT TO the reference level. In a digital console, that reference level is called "FS" for "Full Scale" (digital all ones), and the scale only goes one way: downwards (less than 0 dB). On an analog console, with VU meters, that reference level is "0 dB VU", and the scale goes both ways. Or on an analogue console bar graph "peak meter", the reference point might well be 0 dBu or 0 dBv, with the scale going both ways.

A sound level meter is the same: it measures the SPL ("Sound Pressure Level"), and shows you a number that is referenced to a level of 0 dBSPL, which is 0.00002 pascals, which is the quietest sound the human ear is capable of hearing. From there, the scale goes both ways: it is possible to measure sounds that are quieter than what we can hear, in which case they would have a "minus" sing in front, such as "-8 dBSPL". But only very sensitive laboratory instruments can measure such quiet sounds. The type of meter you and I use is only capable of measuring sounds louder than 0 dBSPL, and often only from about 30 dBSPL upwards.

dBSPL is what the meter actually MEASURES, but it might DISPLAY that measurement in several different ways, such as by applying "C" weighting or "A" weighting, or "X" weighting, or no weighting at all, in which case it is called "flat". So if you measured a sound level, then viewed that with "C" weighting, the normal convention is to write that as "dBC", such as for example "115 dBC" might be what you measure for a drum kit, or "35 dBC" might be the ambient level late at night inside your studio.

That's the actual measurement that I'm talking about, but when you compare measurements, that is something very different: That is the same as comparing the distance between cities, or the temperatures of different objects: it is looking at the DIFFERENCE between two NUMBERS. That's all. You CANNOT consider what the measurement method actually was, or any weighting that was applied: The difference is ONLY concerned with the magnitudes of the numbers, not the methods used to measure them.

So, if you measured those drums at 115 dBC and then measured a quite place at 45 dBC, the difference between those two numbers is 70 dB. It is NOT 70 dBC. Just the same as the difference in distance between those three cities is 6 dB, and NOT 6 dB-kilometers. And the same as the surface temperatures: the difference is 46 dB, NOT 46 dB-degrees-Celsius. You are simply comparing two numbers: it is not mathematically valid to then add on the way those numbers were originally measured: it is meaningless, and pointless. There is no such things as "isolation of 45 dBC". There is only "isolation of 45 dB". Adding the "C" in there means nothing at all, since what you are comparing is numbers: you are not comparing sound pressure level with respect to 0.00002 pascals.

I'm not sure if that helps you to understand the issue. Decibels are complex. Much more complex than most people realize, since they are logarithmic, there are two different ways of measuring (intensity and power), and they are relative measurements, not absolute. They are unlike any other measurement that most people would make during their typical daily life: distance, time, area, volume, weight, speed, and all other things like that are linear and absolute, and people are familiar with that. They expect decibels to be the same, but they aren't, since they are neither linear nor absolute: They are logarithmic and relative. People easily understand that a distance of 80 km is four times as far as a distance of 20 km, so they expect a sound level of 80 dB to be four times louder than a sound level of 20 dB. But it isn't. Depending on what the terms "sound level" and "louder" means in that sentence, a level of 80 dB could be either one-hundred-thousand times greater than level of 20 dB, or it could be one thousand times greater, or it could be four hundred percent greater. You MUST define what you are talking about with decibels, because if you don't, then at best what you said is meaningless, or at worst it can be totally misunderstood.

If you told a sound engineer that you needed "an increase of 10 dB" in the sound system at a venue, he could quite validly do any one of four things: He could push up the master fader on the console from the "-30" mark to the "-20" mark, or he could pull out his sound level meter and push up the faders until he sees that the SPL increased from 80 dBC to 90 dBC, or he could pull out his sound level meter and push up the faders until he sees that the SPL increased from 80 dBA to 90 dBA, or he could notice that your speakers are rated at a total of 1000 watts, then go out and buy another 9000 watts worth of speakers and amps, for a total of ten thousand watts. All of those would get you an "increase of 10 dB". But that's four very different things, with four different results! And if he did something that you did not expect, it would be your fault for not specifying what you meant by a "10 dB increase".

It is very, very important to not confuse things by using the word "decibels" incorrectly.

[5cm/2" air gap] Between what and what?

That's the decoupling between floors. That is 5cm between the floor of the yellow leaf and the floor supporting the red/purple/grey walls. Add to that 8cm of glass wool and I have 13cm of air space.

Then your air gap is NOT 5cm! It is 5+8+13 = 26 cm! The "air gap" is the TOTAL distance across the cavity, from one surface to the other. That usually does include the structural gap between the two framing systems, and also the space inside the "bays" between the framing members on each leaf. And ALL of that should be filled with insulation. If you only have 8cm of insulation in a cavity that is 26 cm deep, then you won't get optimal isolation. The insulation is there to damp internal resonances inside the cavity. If you only fill part of the cavity with insulation, then you are not damping all of the resonances effectively.

All of the above is the reason why you should always plan a studio completely, in full detail, before starting to build anything. It seems there are several things that you need to do before you can proceed, and some of them will mean that you have to undo things you already did...


- Stuart -

[saemola]

Stuart,
I don't understand how I gave you the impression that I wanted to use different isolation for the internal leaf ceiling and walls.
I thought I made it clear in another post (looks like I haven't) that I have already consulted an engineer. My question was on sound isolation alone.
The 3rd octave bands walls isolation measurement was not conducted with A or C weighting, it was not weighted at all: after all the measurements, I thought it could be useful to give you difference (expressed in dBA) between the full band pink noise recorded with the mic in front of the speaker and the pink noise recorded through the wall. It's clear to me now that it is useless. On the other hand, interesting as it was to refresh my memory, your dB scale explanation is perfectly understandable to me as I have a pretty good understanding of how the dB scale works and a pretty good knowledge of how weighting works: my mistake was in thinking that a dBA-weighted noise reduction value could be useful to calculate transmission loss. Again, that's wrong and it's all clear now so I'm sorry you wrote all of that. That being said, thanks for taking the time, that was really cool.
Lastly, I have no clue how the 23cm of air gap calculation came up (it's 5cm of space + 8 of wool between joists which equals 13... how does that even approach 23...?).

Either way, it is clear to me that there is a serious communication problem here. It probably has to do with my bad communication skills and my lack of knowledge of the topic and its technical terms. Right now I am only concerned that whoever reads this topic in the future will be misled by the misinformation (again, caused by me). I'm not sure whether I should edit the topic (wouldn't know where to start), put a disclaimer on top of the first post or just delete the topic altogether.

If I wasn't clear enough (yet again ), I am really grateful for the time and effort you put into this and I am really sorry that it didn't lead anywhere. On my hand, you have provided me loads of useful information in the studio design forum (topic "To flush or not to flush").
The studio will be 100% built within 48h and I will move on to acoustic treatment.
Thank you SO SO much for your time, Stuart!