Three Leaf System when a concrete wall is in the equation?

[othmanallan]

Hello guys, this is my first post and, before I say anything, I have to thank you all for this amazing knowledge source you have built. I'm a recording engineer from Caracas, Venezuela, starting to build my home studio and this forum has been truly clarifying for many many questions I had. Although there are like a thousand more questions, finally I’m feeling like I’m in the right place to find those answers (real answers). I apologize for my english, I hope it will be clear enough for you to understand what I’m trying to say.

This project has been running for over a couple years (saving some money to develop it, buying equipment, etc.). I have the second floor of my house completely empty for me to build my home studio so I decided to go ahead with it (my wife gave permission finally).

If you're a news guy, then you've probably heard about Venezuela's economic crisis. I say that because there are some things for us right now that seems unaffordable because we don't make it here (like fiberglass wool for example, a 4'x8'x3" panel cost about 15 times the cost of a single drywall board. No kidding here guys). So keep that in mind when I say that I'm considering not putting fiberglass wool inside my walls and ceilings.

The rooms and needs:

I have three consecutive rooms for building a control room (8,68’H x 11,98’W x 15,72L), a tracking room (8,68’H x 10,27’W x 15,19L) (for drums 90% of the time) and an iso booth (8,68’H x 9,94’W x 8,66L). Attached you'll find my SketchUp drawing

Studio Othman.skp

(in it you’ll see the current state of the rooms. There are no door frames and the window opening is already made, the desk is just for reference where the mixing position will be). All the walls you see are made of 4" hollow dual cavity clay blocks, plastered an painted on both sides, the floor has a layer of an old granite and below that there is a thick concrete slab, plastered and painted underneath and the ceiling is made of concrete about 4 inch thick. Below some pictures:

Control Room.jpg

Control Room 1.jpg

Clay Block.jpg

Iso Booth.jpg

Door Window.jpg

Concrete Slab.jpg

Tracking Room.jpg

I want to be able to track drums at any time (2:00 am for example) without disturbing any of my neighbors (hope that’s possible). Also would love a decent Isolation between tracking and control room. My closest neighbor is 26’ away from the closest wall of the room. Both houses are not connected so, flanking paths are not a concern. And about disturbing my wife and kids, not a problem because their rooms are not underneath the studio, in fact, if I play drums right now inside the future tracking room, they can barely hear me playing (without any doors installed) It’s a big house. We live in a very quiet neighborhood, the loudest sound you may hear will be my dog barking (It’s a Rottweiler so he is loud).

Closest Neighbor.jpg

I recently bought Rod Gervais book (honestly, what a great book). When reading about walls, made me realize how critical is the position of the material and that you can really screw things up with this. That makes me wonder about the number of leafs for my project because if I make a room within a room for each room (except Iso Booth), that will make a three leaf system between the control and tracking room (Rod’s advice is to make a two leaf system but never saw any example when it comes to block or concrete walls).

When it comes to deciding on the proportions of the room, I tried a few known ratios and the best match for the control room was Louden’s 1 – 1,4 – 1,9 (the 1,9 dimension is a little tight so I think I’m gonna be lacking 2 inches more or less). For the tracking room the only room ratio that kinda worked was Sepmeyer’s 1 – 1,14 – 1,39 but it takes away about 3,3’ and I really don’t want to lose that space so I would like your thoughts on this. And, finally, for the Iso booth I’m leaving it as it is right now, I will apply some paint, install a wood frame for the door (Door with glass), take care of the seals, and finally, acoustic room treatment.

Also, before reading Rod’s book (and JohnLSayers forum), I thought that I needed a floating floor and I was going to make it using two layers of MDF (12mm and 18mm) on top of ½ inch neoprene blocks. I had already bought all the material and now don’t know what to do with it because I cannot return it now, so, if you have any advice on this I’ll appreciate it.

MDF Panels.jpg

For the walls I already had a lot of ½ inch Drywall. Enough to make a two layer wall and ceiling for the tracking room and a single layer for the control room. Here I cannot find resilient channels or WIC hangers so, what I was planning to do is to fix the wall frames to the floor and existing ceiling but that brings on the concern of creating flanking paths. Need some advice about what would you guys do here. Also, should I angle them or not?

The same thing happen with the ceiling, there’s no Mason hangers here nor anything like that. What I was planning to do is to buy long screws and fix them to the existing ceiling and hang from them the channels for the new ceiling taking care to place neoprene blocks between the screw and the channels to avoid direct contact and flanking paths. if you have a better idea, it will be welcome.

I’m concerned about the window opening being to close to the wall and don’t leaving enough space for a Helmholtz resonator in that corner of the control room. The distance is 1,39’ but with the window frame it will be shorter. What do you say?

For the doors, I was thinking of making them with MDF, solid core, 2” thick, following the advices in Rod’s book (mass). Double door between tracking and control room, single door for the control room entrance, single door with a window for the Iso Booth and single door for the tracking room exit (that door, in case you may asking, it takes you to another room that I’m using as storage). There are no acoustic door suppliers here guys!

The studio window will use 10mm float glass at the tracking room side and 8 mm float glass at the control room side (I cannot find anything thicker than that and laminated glass cost about 8 times float glass). Also should I angle them? Considering that the window will be at my left side when mixing, I was thinking not to angle it for symmetry.

I have a lot of cork sheets about 5 mm thick that I found completely new in our basement, is there anything that this cork can be useful for?

Air conditioner will be two ductless mini split systems, 12.000 btu each. For the tracking room and the control room. My concern on this will be the pipes openings, also, I’m assuming that the indoor units are mounted to the drywall and not to the existing wall right?

Finally my last question is about electrical boxes openings. How do you avoid sound escaping through the outlets and switches holes?

The caulking that I’ll be using is Alex Plus Latex caulk because there’s no butyl based caulks here in Venezuela.

Alex Plus.jpg

Hope you guys are having a marvelous week, best regards from Venezuela and thank you all once again!

[Waka]

I apologize for my english, I hope it will be clear enough for you to understand what I’m trying to say.

Welcome!

Your English is excellent, no need to worry.

If you're a news guy, then you've probably heard about Venezuela's economic crisis. I say that because there are some things for us right now that seems unaffordable because we don't make it here (like fiberglass wool for example, a 4'x8'x3" panel cost about 15 times the cost of a single drywall board. No kidding here guys). So keep that in mind when I say that I'm considering not putting fiberglass wool inside my walls and ceilings.

Yeah, I'm sorry to hear about your troubles. It's not too bad though as sound doesn't care about cost. If plasterboard is cheap use lots of it. If you don't fill the cavity with insulation at all then the constant in the equation for resonant frequency of your wall goes higher.

f0 = C * [(m1 + m2)/(m1 * m2 * d)] ^ 0.5

The constant C is 60 instead of 43 with no insulation for damping.

m1 and m2 are the mass of each leaf in kg/m^2 respectively

d is depth of cavity in m.

Is there an insulation material used regularly in venezuala that is cheap of any variety?

All the walls you see are made of 4" hollow dual cavity clay blocks, plastered an painted on both sides

These are really good walls. Use these as your first leaf. All you should do is make sure there are no cracks and they are sealed. It may not be necessary, but It you aren't sure you could go over them with a masonry sealant.

Now your room within a room is built with one side plaster boarded only. This is your second leaf. You don't want any boards nailed to the other side.

It helps alot for bass damping if your walls contain some kind of insulation though bare in mind.

Also check your floor can handle the additional weight of the new walls and ceiling.

This floor is maybe your biggest issue. Unless you float the floor properly (expensively) with a floating concrete floor. As you only have the one leaf.

Is there a reason you can't use downstairs instead? It's a lot easier with a concrete floor on the ground.

I want to be able to track drums at any time (2:00 am for example) without disturbing any of my neighbors (hope that’s possible).

How loud are your drums?
If you need very big isolation ( like it sounds you do ) you may find it's cheaper where you are to build your second leaf from concrete blocks, so bare that in mind.

I'll let Stuart talk to you about ratios as I'm not as researched on that yet.

Also, before reading Rod’s book (and JohnLSayers forum), I thought that I needed a floating floor and I was going to make it using two layers of MDF (12mm and 18mm) on top of ½ inch neoprene blocks. I had already bought all the material and now don’t know what to do with it because I cannot return it now, so, if you have any advice on this

If you can't return it then use it for your doors and HVAC silencers and the rest on your walls as mass. It's a little less dense then plasterboard, so use it instead of a thinner layer of plasterboard.

The same thing happen with the ceiling, there’s no Mason hangers here nor anything like that. What I was planning to do is to buy long screws and fix them to the existing ceiling and hang from them the channels for the new ceiling taking care to place neoprene blocks between the screw and the channels to avoid direct contact and flanking paths. if you have a better idea, it will be welcome.

Best option is to support your ceiling on their own joists resting on your inner frame walls not touching the original ceiling at all. You may not have the ceiling height though. In which case hangers etc. can be bought online and shipped out maybe?

The studio window will use 10mm float glass at the tracking room side and 8 mm float glass at the control room side (I cannot find anything thicker than that and laminated glass cost about 8 times float glass).

You don't really need laminate glass as you can arrive at the same result with standard glass by increasing the thickness or air cavity.

As you can't get thicker glass (definitely try though) you could increase the cavity in that wall substantially to compensate.

Get the mass of your glass in kg/m2 and put it through the equation above for resonant frequency (constant of 60). Increase the depth of cavity until your frequency is half of the lowest frequency you want to isolate.

Also should I angle them?

Only to reduce reflections (visual) or to redirect reflections (sound)

With your aircon make sure you also have ventilation. Ductless systems don't usually. Remember you're in an airtight room.

Finally my last question is about electrical boxes openings. How do you avoid sound escaping through the outlets and switches holes?

Best way is to not put them in holes
Surface mount them in plastic fittings and use trunking to cover your wiring.

That should get you started

Dan

[Soundman2020]

Hola "othmanallan", y MUY bienvenido al foro!

I'm really glad that Dan replied to your thread, because I had somehow missed it completely!

So I'll just add to what Dan already said (he's giving you good advice!)...

If you're a news guy, then you've probably heard about Venezuela's economic crisis.

Absolutely! There's an awful lot of Venezuelans arriving in Chile over the last few years! Some really great people, too (even if they do have strange accents! ). At the church I attend, we now have a very large group of ex-Venezuelans, and we hear all the horror stories about what has been done to your once-wonderful country: no toilet paper, being told by the government to eat your pets because there's no food, etc. I really feel for you guys. It's sad, and I'm hoping and praying that things improve real soon... although how that would happen is hard to see...

some things for us right now that seems unaffordable because we don't make it here (like fiberglass wool for example, a 4'x8'x3" panel cost about 15 times the cost of a single drywall board. No kidding here guys). So keep that in mind when I say that I'm considering not putting fiberglass wool inside my walls and ceilings.

How about alternatives? Firstly, for example, how about an old building that is being demolished (or falling down!)? You can certain re-use insulation from an older building. Second, what about other fibrous, porous type materials? Mineral wool? Polyester insulation? Cellulose-based insulation? Even recycled denim? Cotton? Wool? Some types of foam? There are probably many alternatives that you could use. They will not be as effective as good fiberglass insulation, of course, but something is better than nothing. The purpose of insulation inside your wall cavities is to damp resonances, and that adds a lot to the overall isolation. As Dan noted in the equation for MSM resonance, the constant changes from 43 to 60 if you have no insulation at all, implying that the resonant frequency of the wall will be 40% higher at least, and the isolation will be reduced.

Attached you'll find my SketchUp drawing

Your basic layout looks fine.

All the walls you see are made of 4" hollow dual cavity clay blocks, plastered an painted on both sides, the floor has a layer of an old granite and below that there is a thick concrete slab, plastered and painted underneath and the ceiling is made of concrete about 4 inch thick.

That's a pretty good basis.

I want to be able to track drums at any time (2:00 am for example) without disturbing any of my neighbors (hope that’s possible).

Perhaps! But that's not so easy to achieve. Drums are loud: easily 110 dBC, 115 dBC likely, and 120 dBC is possible. Most people consider 40 dBC to be "quiet" and under 30 dBC to be "inaudible". So, getting your 110 dB drums down to 40 dB implies isolation of 70 dB. That's huge. A typical house wall (typical for USA, but not for us in Latin America) of studs with drywall on both sides (what we would call "tabique") will get you about 30 dB of isolation, and our walls (brick, concrete, etc.) will get around 40 dB. It's important to understand that the decibel scale is logarithmic, not linear. and that each time you go up ten dB, that implies you need to block ten TIMES more sound than for the previous step. So going from 30 to 40 is ten times more energy that you need to block. Going from 30 to 50 is 10x10 = 100 times more energy. At 50 dB, it is 10x10x10 = 1000 times more energy that you need to block, compared to that 30 dB normal wall. At 60 dB it's ten thousand times more energy. And at 70 dB, it's one hundred thousand times more energy that you need to block, compared to that typical tabique wall.

So you can see that getting your drums silent, is a tall order! Your studio wall system will need to block about 100,000 times more energy than a typical stud wall, or about 10,000 times more energy than your brick-and-plaster wall is doing right now.

Also would love a decent Isolation between tracking and control room.

It's all part of the same system.

My closest neighbor is 26’ away from the closest wall of the room.

8m. That's good, as you have the attenuation of 8m of air, and the advantage of the decreased intensity due to the expansion of the sound hemispherically over 8m: so let's say you manage to get 60 dB of isolation from your walls, so your 110 dB drums are down to 50 dB at 1m from your walls: at 2m they should be down to about 47dB, at 4m around 44 dB, and at 8m around 41 dB.

So if you aim for 60 dB of isolation, you should be able to get your drums reasonably quiet, so as not to have your neighbors banging on your door with flaming torches and pitchforks....

When reading about walls, made me realize how critical is the position of the material and that you can really screw things up with this.

Yep!

That makes me wonder about the number of leafs for my project because if I make a room within a room for each room (except Iso Booth), that will make a three leaf system between the control and tracking room (Rod’s advice is to make a two leaf system but never saw any example when it comes to block or concrete walls).

The way to deal with that is to NOT make the walls between the rooms into 3-leaf! In other words, don't put glass in the window openings in the concrete leaf: only in the other two leaves (the room on each side). So you'll have a situation that is sort of two-leaf and sort-of three leaf, but the huge mass of the brick walls is good.

In your situation, you have no choice. And you can still get good isolation like this. Since your major concern is sound getting out (neighbors), that's what you should be concentrating on: you will only have a two-leaf system in that area (the existing house walls, and the new inner-leaf walls). The 3-leaf issue only occurs between the rooms, but not from the rooms to the outside world: that will still be 2-leaf.

I tried a few known ratios and the best match for the control room was Louden’s 1 – 1,4 – 1,9

You don't need to go too crazy on getting a fantastic ratio: just make sure you are far away from the bad ratios, and close to a good one. It's more important to maximize the room volume and the room dimensions, and also to get good isolation. The ratio takes third priority behind those two.

For the tracking room the only room ratio that kinda worked was Sepmeyer’s

Forget about ratios for your live room (tracking room). Ratios are only really important for control rooms, less so for live rooms. Here too. maximize room volume: use the larges interior dimensions that you can get, while still leaving enough air gap in the wall cavities to ensure good isolation.

And, finally, for the Iso booth I’m leaving it as it is right now,

Hmmm..... that might not be such a good idea... it might be OK, but what are you planning to use the booth for, beside vocals? A guitar amp, maybe? Or a bass cabinet? You might need more isolation than you can get from a single leaf...

I thought that I needed a floating floor and I was going to make it using two layers of MDF (12mm and 18mm) on top of ½ inch neoprene blocks. I had already bought all the material and now don’t know what to do with it because I cannot return it now, so, if you have any advice on this I’ll appreciate it.

My advice is the same as Rod's; You don't need the floating floor! It would make things worse, not better. Here's why: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

You can use the MDF for your walls. You already have it, is is high mass (high density), it has some minimal structural properties (at least good for a nailing surface around the room), and it is easy to work with (relatively). So that would be one option. Another would be to use some of it to make a drum riser inside your tracking room, to stop the impact noise from getting into the floor. A third option would be to use it to make flush-mount "soffit" modules for your speakers in the control room, which is absolutely the single best thing you can do for your control room acoustics. You could also use some of that MDF for your HVAC silencer boxes.... So you won't be wasting the MDF! There's lots of uses for it in your studio.

The neoprene blocks are probably not much use, unless you know what the resilient properties are. If you can find out what the Shore hardness is for those (and which scale), or if you have some other technical data on their resilience, then it might be possible to use some of them for isolating your speakers in side the soffits, or as glazing blocks to help isolate your window glass. But it you don't know the properties, there's not much you can do with it.

For the walls I already had a lot of ½ inch Drywall.

12mm drywall is not optimal: 16mm is better. But you already have the 12mm, so that's what it will have to be!

Here I cannot find resilient channels or WIC hangers so, what I was planning to do is to fix the wall frames to the floor and existing ceiling but that brings on the concern of creating flanking paths. Need some advice about what would you guys do here. Also, should I angle them or not?

Your stud frames can be fixed only to the floor, not the ceiling. Build your walls as proper structural framing, then put joists across the top for the ceiling. Make very sure that the framing does NOT touch the existing building at any point, except where it rests on the floor. Then use a layer of MDF, OSB or plywood on the studs, and put your two layers of drywall directly on top of that. And hopefully some type of insulation in the cavity!

The same thing happen with the ceiling, there’s no Mason hangers here nor anything like that. What I was planning to do is to buy long screws and fix them to the existing ceiling and hang from them the channels for the new ceiling taking care to place neoprene blocks between the screw and the channels to avoid direct contact and flanking paths. if you have a better idea, it will be welcome

See above: your walls rest on the floor ONLY. Your ceiling rests on your new walls ONLY. That keeps everything decoupled, so you don't need isolation hangers, RSIC clips, or resilient channel.

I’m concerned about the window opening being to close to the wall and don’t leaving enough space for a Helmholtz resonator in that corner of the control room.

Why would you need a Helmholtz resonator? Yes, lots of books and websites talk about them, but they don't tell you two important things: 1) It is very, very hard to tune a Helmholtz resonator accurately, much harder than the books make it sound. 2) They are not very effective at low frequencies, unless you make them huge, and in a small room there is not enough space for "huge"! There's also the issue that each Helmholtz resonator is tuned to just one frequency, but your room will have problems at several frequencies, so you'd need to fill up the entire room with a whole bunch of Helmholtz resonators to deal with them all...

So forget Helmholtz resonators. Complicated, not effective, and take up too much space.

For the doors, I was thinking of making them with MDF, solid core, 2” thick,

Double door between tracking and control room, single door for the control room entrance, single door with a window for the Iso Booth and single door for the tracking room exit

Ummm.... nope! you need high isolation, each of your rooms will be a two-leaf system, so you need two doors on each room: one in each leaf.

There are no acoustic door suppliers here guys!

No problem. Build them yourself! Here's a series of photos from one of my customers in Australia, showing how he built the doors that I designed for his studio:

Site-built-door--BRAUS--102+--door-blank-cut.jpg

Site-built-door--BRAUS--106+--all-layers.jpg

Site-built-door--BRAUS--109+--frames-shimmed-and-squared-2.JPG

Site-built-door--BRAUS--112+--inner-door-hung.jpg

Site-built-door--BRAUS--114+--both-open-seals-and-gap.JPG

Site-built-door--BRAUS--115+--Finished-Entry-door-from-outside.jpg

Site-built-door--BRAUS--117+--both-open-from-outside.JPG

The studio window will use 10mm float glass at the tracking room side and 8 mm float glass at the control room side

It would be better to use 10mm on both sides.

I angle them?

No. At least, it's not necessary for any acoustic reason:

angled-glass-myth-doesnt-work--rbdg-com--.jpg

There might be a need to angle the glass to prevent light glare or light reflections.

I have a lot of cork sheets about 5 mm thick that I found completely new in our basement, is there anything that this cork can be useful for?

What type of flooring are you planning for your rooms? That would make good underlay for laminate flooring, for example.

Air conditioner will be two ductless mini split systems, 12.000 btu each. For the tracking room and the control room. My concern on this will be the pipes openings, also, I’m assuming that the indoor units are mounted to the drywall and not to the existing wall right?

Correct, but the mini-split is only part of your HVAC: You also need the "V", which is "Ventilation". You sort of do have to breathe inside your studio, and considering that both of the leaves must be sealed absolutely air-tight, it's important to bring in fresh air an remove the stale air! You need to design and plan your ventilation system accordingly, and since you need very high levels of isolation, that's going to be a challenge...

Finally my last question is about electrical boxes openings. How do you avoid sound escaping through the outlets and switches holes?

Simple. Don't make any holes!

Do all of your electrical work with surface-mounted raceways:

http://www.calcentron.com/Pages/fram-tr ... aceway.htm
http://www.export.legrand.com/EN/dlp-wa ... ng_95.html

surface-mount-electrics-01.jpg

surface-mount-electrics-02.jpg

surface-mount-electrics-03.jpg

The caulking that I’ll be using is Alex Plus Latex caulk because there’s no butyl based caulks here in Venezuela.

Does that dry hard, or soft? You want the type of caulk that remains soft, flexible, rubbery, even after it has fully cured.

- Stuart -