John Sayers' Recording Studio Design Forum

Having built a studio in a barn in France a few years back, I thought I was done... but now, I'm going to be spending quite a bit of time in the UK. So, I'm putting together a small studio in the garage of our house in East Devon.

What I need: No control room (I'm my only client, for better or worse) with an iso room for tracking acoustic guitar and vocals away from the computer, and for isolating amp cabinets. I don't monitor at high volume and will never have a full band in the space. I will have a small drum kit, and, as mentioned, will be recording amps, sometimes pretty loud.

What I want: I'm realistic about what can and can't be done, and don't expect acoustic perfection from spaces this small, or complete isolation without rooms within rooms. My goal is to build the most effective space for creating and recording music I can, within the constraints of the space, my budget, and how soon I'd like to be up and running (soon).

Limiting factors:

1. There are height limitations in the space. 2.4 m to the underside of the joists, 2.6 to the tops. So, anything I do creates a trade-off between ceiling height and performance.

2. I'd like to keep the budget under £3000 for the build itself (see below) and time to completion as short as possible. I can do some work myself, but my time will be limited, so I can't do it all. This number was literally pulled out of the air as being sell-able to the other half, so it's not fixed in stone.

3. The house is in a rural area, so external noise isn't a huge problem. The sole caveat is that there's a very small road only about 4 metres from the studio, used mostly by tractors. I'm willing to accept the occasional ruined take if it means I can stand up inside the space...

4. Flanking noise from the slab floor and construction of the building.

The building: The garage is a freestanding concrete block building (on a concrete slab) of recent construction. Above the floor joists is a layer of particle board which is the floor for a storage area with about 2.4m of height to the center of the peaked roof. Basic thermal insulation on the roof, wooden stairs at the back corner lead to the storage space - pretty much perfectly optimized to take up the most space possible . I'll need to keep some access to the storage area, although it'll be infrequent, so I'm going to have that go through the music room rather than have a dedicated (and seldom used) corridor to the stairs.

I had thought of opening up the ceiling of the larger room by pulling up the floor of the storage space above it, and removing some joists while strengthening others, creating a cathedral ceiling in that area, but I don't want to get too involved, both for reasons of money and getting this thing up and running asap. There's no doubt it would be the best option, just don't know if it's realistic.

Budget: My budget is to keep this as far under £3000 as possible, as I'm going to need to do HVAC as well, which I expect will wind up costing about the same amount, at least from my experience. I had extremely good results here in France (dealing with plumbers who'd never seen the inside of a studio before) using a Mitsubishi heat pump, with the general approach of doubling the diameter of normal spec ducting, and using twice the normal length of ducting with a lot of gentle bends. The result is a virtually silent space that still has good air quality. I'm hoping to take a similar approach with this build, but with a smaller heat pump.

Construction: My plan is to create an inner wall along the exterior concrete block wall, 2 x 4 studs on a 4" footer, 2 layers of drywall (with Green Glue in between) on the inside, with the cavity filled with rockwool. Internal walls between the studio/music space and the iso booth will be double walls, cavity filled with rockwool, 2 layers of drywall on each side (different thicknesses), again with GG.

I had thought I might sacrifice some ceiling height to do a slightly raised floor, mostly to keep the floor from being freezing in the winter, and to give some room for cable routing. This isn't necessary, though, and I might not do it. Still thinking - any ideas or suggestions would be really helpful.

My idea for the ceiling was to fill the space between the joists with rockwool which would then be covered with jute/burlap, and then treat the floor above the joists, possibly with a layer of gypsum board, then a layer of plywood.

Questions:

1. Will the ceiling/roof and floor be such weak links in terms of flanking noise that my walls are overbuilt?

2. Will my idea of treating the floor of the storage area have any effect? If it won't, what can I do with the ceiling? Resilient channel on the joists and suspend a drywall ceiling?

3. What can I do with the floor that will provide some thermal insulation without taking up too much height?


Here are a few quick photos and Sketchup exports of what I'm working on:













I'm sure I've forgotten some stuff, and possibly omitted glaringly important information. I'll re-read this in the morning and fill in what gaps I can see. I appreciate any thoughts anyone here might have. Thanks!

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Hi Miles, and Welcome!

I'm trying to understand the purpose of the two rooms. You say that there will be no control room at all in this studio, so I guess that means no tracking, recording, mixing, etc. So this is just a rehearsal space, right? Just a place for you to play music in, maybe with some friends?

Assuming this is true, then the "large room" is the main rehearsal space, and the iso booth is just to put an amp in, right? But then you mentioned that the iso booth is also for "tracking acoustic guitar and vocals", and that you "will be recording amps", and you mention the possibility of "ruined take" from tractor noise, so that leaves me a little confused: If there is no control room, and therefore no tracking or recording, then where are you tracking/record to?

Next confusing thing: You mention that you don't expect good isolation as you won't be building "room-in-room", but then you go on to describe how you'll be doing just that! ... :

That sounds like a room-in-room build to me. The only part that isn't in there is what you ask about next: the ceiling.

But it also sounds like you might be creating three-leaf or coupled walls, so hopefully I just misunderstood that. But just in case, let me describe what your build should look like:

You have a space with solid concrete block walls around three sides, and the other side is a large door with a window. Somehow that forth wall needs to be sealed better. Assuming that you don't want to brick up the door and window, then the next best option is to build a stud wall a short distance away from that forth side of the room, and put a couple of layers of drywall on one side of it. It looks like you also have a workshop and the access stairs to the attic space, so you need to build a similar wall around that area. That completes your outer leaf. You now have your central studio space that is surrounded by one leaf on all sides (yes, strictly speaking the forth wall with the door and window constitutes another leaf, as does the wall behind the workshop/stairs, but the spaces are large enough that it's not going to be an issue).

OK, so you have your single outer leaf in place. Now you build one frame for your "large room" and put drywall on on side of it, and you build another frame for your iso booth, also with drywall on only one side of it. Done! Now you have your two rooms, properly isolated and decoupled. (except for the ceilings: see below).

Why different thickness? That's actually a myth. Well, OK, not a total myth, just not the whole truth. Yes, if you use two different thicknesses of drywall you do get internal refraction going on, and you do get different coincidence dips, and different resonant frequencies, but the combined effect of all that is not enough to make up for the extra isolation you would have gotten from just using two layers of the thickest drywall. So in reality, there is no reason to use layers of different thickness: save yourself some trouble, and just do everything with two layers of 16mm drywall.

Probably not a good idea. Any deck raised above the real floor and having air below it, is a resonant cavity and will act like a membrane trap, to some extent, unless you put very large amounts of rigid mass on top (eg: concrete). It is similar to a badly done floated floor. You could do a sand-filled cavity to prevent that, but it seems like a lot of trouble and expense for very little benefit, if you ask me. If your biggest concern is cold, then you could do laminate flooring on a thick thermal underlay. That can look really good, aesthetically, and is also really good, acoustically.

That leaves the top of your very expensive rooms-in-a-room incomplete, so you would have wasted an awful lot of money on the walls if you only do that for the ceiling!

Think of it like an aquarium (only up-side-down). If you want to build an aquarium, and you put nice glass on all four sides, but then decide to only put cardboard in bottom, how well do you think that will hold water? Well, your room will "hold sound" about as well. If you want the aquarium to hold water, you have to complete the fifth side (the floor in this case). And if you want your room to hold sound, then you have to complete the fifth side too (the ceiling in this case). If not, then then wonderful waterproof glass walls of the aquarium, and the wonderful soundproof walls of your studio, were just a waste of money. Like water, sound takes the easiest path in and out of the room.

Yep. But that isn't flanking, per sé: it's just incomplete isolation.

Yep. each room gets it's own ceiling (one ceiling for the "large room", and a separate one for the "iso booth"). Each ceiling is resilient channel on the joists plus a couple of layers of drywall.

BUT! You first need to beef up that floor above you, if you want good isolation. Right now, it's probably just a layer or two of plywood and/or OSB, which isn't much mass. Adding a layer of drywall to the underside of that would help. Do that by cutting strips of drywall to fit up between the joists, against the subfloor above, and hold it in place with cleats. Caulk around the edges for an air-tight seal.

Apart from the above, it looks like you have a good space to work with, and a good basic plan that should get you where you want to go, if done correctly.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Stuart, it's a recording studio without a control room. This will be the third one I've built. Lots of people use them. It makes more sense for me, as I'm solo, to have the control room be the biggest room, as I spend the most time in it. Computers and drums in big room, small room for acoustic guitar and vocals and then, as I mentioned, used to isolate electric guitar cabs.


No, actually, all I've done is build four walls, which is the easiest part. To me, a "room-in-room" build results in a completely isolated structure sitting on a separate slab which sits on engineered isolation materials spec'ed to the weight of the room. I don't have the ceiling height to float an isolated slab (as I've done here in France), and I'd rather avoid losing much height for a suspended ceiling.


Yes, you did, as above. There are no three-leaf walls in my description. External walls will be concrete/cavity with rockwool/studs/gypsum, internal walls will be gypsum board/studs/cavity with rockwool/studs/gypsum board, with separate footers for each set of studs. However, as these separate footers will be fastened to one concrete slab, I'm wondering if it might be just as effective to use a single 2 x 6 footer with staggered studs? Any thoughts?




Good to know, thanks.




Good, thanks.




If we assume for a moment that the walls I build will be perfect in terms of isolation, and that I add sufficient mass to the floor of the storage area (above the joists) to make that a perfect isolater, the two main sources of sound transmission to and from the outside world will be through the slab floor and through the structure of the building, transmitted through the roof joists, no?

Now, my walls and ceiling will be far from perfect isolators. My question is, given how I'm going to treat them, how much of a problem will sound (particularly LF) transmitted through the slab into the outside world from my monitors and into my studio from the road be?



Why go to the trouble of cutting strips of drywall and gluing them between the joists when I have an open space on the other side of the joists where I can put down as many layers of drywall, plywood or whatever that I want? If the idea is to add mass to the ceiling, then mass added above or below should make no difference, correct? In fact, mass added above should work better, as it prevents energy transmitted through the joists themselves from reaching the storage area, and then to the outside world.



Thanks for your trouble in answering my post. Hopefully I've cleared up some of your misunderstandings about what I'm using the studio for, how I'd like to build it, and what my questions are.

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What is being described is usually referred to as a Project Studio - pretty much everything happens in a single treated room.

What were your results from, or rather how effective were the previous two you built? I assume there were some issues hence why you're seeking some advice for this build. Your experiences with the previous studios should help guide others' assistance.

_________________
Brian
As you slide down the bannister of life, may the splinters never point the wrong way...

A project studio is a fair description, although control-room-less studios have a dedicated following - Daniel Lanois and Mark Howard, for example. I always have an iso room for the reasons I've described - critical recording where any noise is an issue (so, the soundproofing working against noise from the outside as well as computer/hard drive noise from the main room) and recording of loud sources (soundproofing keeping sound inside the iso booth). The iso room in my most recent build sits on a slab floating on Sylomer pads, and is a completely isolated structure, and it's perfect. My main problem in the large room has been noise transmitted through the floor slab, so that's why I'm particularly concerned about this one. Doors are another problem, but that's due to my bad French and trusting my builders... so I'm hoping not to repeat those mistakes. The main point, though, as Stuart pointed out, is that there's no sense in building walls with a high degree of isolation if their function is diminished by other problems.

I'm just trying to arrive at the best balance for what I have to work with - walls and ceilings of generally comparable isolation, guided by the weak links in the existing structure that I can't eliminate - a concrete slab shared between rooms, resting on dirt, and the existing ceiling/joist structure, which is coupled to the exterior walls.

One follow-up note to my reply to Stuart: given that these rooms are small, my hope in treating them as I described (absorbent fill in between joists, adding mass on the top side) is to avoid creating another reflective surface. I'm comfortable working in "dry" rooms, and I'd obviously like to avoid the loss of ceiling height that would come with RC and a couple of layers of gypsum board, especially given that there's a space between the floor on top of the joists and the outside world. Any insight you can give me on what my comparative isolation would be here would be helpful. I'll also go read the section in Rod's book again.

Hope that helps, I appreciate your time and trouble.

_________________
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http://www.myspace.com/mylescochran

So if the big room is a control room where you also record, then why call your thread a studio without a control room?

OK, so at least we are clear that this is a project studio based around a control room that is large enough to track in, with an attached iso booth. What you have is not a studio without a control room, but rather a studio without a separate live room! Semantics, maybe, but terminology is important in acoustics.

A "room-in-a-room" build is any build where the walls and ceiling are fully decoupled, and sitting on a base that has enough mass and isolation to provide the level of isolation required. It might or might not by fully floated, which is what you describe, and it might of might not have a floated floor. A concrete slab on grade provides more than enough isolation for building a room-in-room studio for the vast majority of cases. Floated floors and floated rooms are seldom necessary.

Sorry. but that IS a three-leaf wall! Actually it is even worse! That's a FOUR LEAF wall!! Count them: 1="concrete block outer leaf". 2="rockwool/studs/gypsum". 3="internal walls will be gypsum board/studs/cavity". 4="with rockwool/studs/gypsum board". Your low frequency isolation will be pretty bad with such a system.

Just to clarify the terminology. In acoustics, a "leaf" is any large massive surface that is separated from another surface by an air gap. Period. Your proposed construction is a four-leaf room-in-a room system, but with no ceiling. So it is way overkill. A huge waste of money. If you did put in a similar ceiling, your low frequency isolation would be pretty bad like that. Take out two of those leaves, and you'll save a lot of money while also improving your isolation considerably.

There's a difference of about 6 to 10 db in transmission loss, between a double-stud wall and two separate stud walls on a well damped massive concrete floor. Wood transmits vibrations at some frequencies better than concrete, due to the much lower mass. So even though the sole plates will be firmly bolted to the concrete, they still transmit some vibration.

Assuming you add several tons of mass to the floor above!

That's a single leaf structure above you, and is therefore limited to mass law. Mass law is a principle of physics that describes how isolation increases in relation to mass. It says that if you double the mass you get an increase of 6 dB in isolation. The type of floor you describe is most likely giving you around 25 to 30 dB of isolation right now (assuming one layer of 16mm plywood). The type of wall I described could easily give you 55 dB. So do the math: Double the mass on the floor above, and you'll get an increase of 6 dB. Assuming you had 30 dB to start with ( a generous assumption), adding another layer of plywood will make that 36 db. Double it again (add another TWO layers of plywood, total of 4 layers now) will give you 42 dB. Double it again (add another 4 layers, total of 8 ) gives you 48 dB. And double it one more time (add another 8 layers of plywood, total of 16 layers) takes you to 54 dB, roughly the same as you'd get if you just hung two layers of drywall from RC...

A fully decoupled two-leaf MSM system will beat the pants off mass law every single time, since it is based on a totally different principle of physics.

There's no such thing as a "perfect isolator" (except maybe for the total vacuum of space). Any sufficiently loud sound will get through any conceivable barrier. That's why folks around here don't use the term "soundproofing" very much, since there is no such thing. There are only different degrees of isolation. The very best isolated studio in the world (Galaxy, good for over 100 dB of isolation) will not isolate the sound of a hand grenade exploding, for example, or even of some rifles and shotguns, even though it has amazingly good isolation, and most people would consider it "soundproof".

So the basic question is (and this is the one that we ask all folks who come here, asking about how to design their studios) is this: How much isolation do YOU need, in terms of decibels of transmission loss? You can answer that question very simply, with a sound level meter. Take a reading in your room as it is now, in a typical session (perhaps playing drums and bass at the same time, for example, or playing music loud on a good system). Take another reading outside the room while that is going on, in several locations around the house, inside and out. That set of readings tells you one side of the equation: "How loud are you?". The other side is "How quite do you need to be?". To answer that, get a copy of the noise regulations from your local municipality (which gives you the legal side of things) and also do some more tests with your meter, playing music at various levels to see what you and others around you (family, neighbours, the cops knocking on your front door, etc.) consider to be inaudible, or at least acceptable. The difference between those two numbers is how much isolation you need. Based on that, you can take a look at the tons of research that is available on various types of construction, showing the degree of isolation that you get from each one. Chose one that fits your budget and situation. That's the usual way of deciding how to isolate a room.

The slab is not your problem as far as airborne sound going out. A concrete slab weighs thousands of kilograms, and it takes a LOT of sound energy to make it move. Even if it does vibrate, from extremely, amazingly, loud speakers, it is well damped: It is a slab on grade, so it is damped by the entire planet! That's hard to beat. So airborne noise getting into your slab is pretty much irrelevant. On the other hand, airborne noise getting into the rest of the building structure from your ceiling, is a major issue. That's just a layer of wood on joists: in other words, it is an undamped drum head, and will vibrate rather easily. You can add mass to it, but as I mentioned above, mass law does not make that a good proposition. And you can damp it, but that's not easy to accomplish on a single leaf. Far better is to turn it into a fully decoupled 2-leaf MSM system, by hanging a couple of layers of drywall from resilient channel.

Combined with the walls and floor, that takes care of airborne sound. That leaves structure-borne impact noise and low frequency vibration, where there are two issues: outgoing (from your drum kit) and incoming (from the tractors). The drum kit can easily be isolated with a simple drum riser, so that's not an issue. The real problem here is the tractors. Once again, you need to put real numbers to the problem. Get a spectrum analyzer, and along with your sound level meter, analyze a few of those tractors as they go past, to see what type of problem you have (in terms of frequency and duration) and how big the problem is (in terms of magnitude). With those numbers in hand, once again you can take a look at different possible solutions, and see which one fits your budget and situation. Having said that, low frequency vibration and impact noise are the toughest of all to deal with, and require major mass and major springs to deal with. If isolating that tractor noise is critical to your studio, then a floated floor might well be in the works, but doing that right will blow your entire budget, several times over.

But you should start with the basics: put real-world objective numbers to your problems. Subjective feelings and guesswork is not going to get you to place you want to go.

Well, you sure can add the mass above, but from the look of those stairs and the attic space in the photos you posted, it didn't seem like getting full sheets of plywood and drywall up there would be an easy job...

By the way, I didn't say to glue the drywall to the underside of the sub-floor. That would be a mistake. I said to attach the strips with cleats, and caulk around the edge. That's the correct way of doing it.

Correct. Mass is mass.

There's no difference at all, acoustically. It's a single leaf, and acts as one single body at the frequencies that matter. Adding mass above or below is exactly the same. What mattes is how much mass you add, and how well you seal it. It must be air-tight. So if you can maneuver sheets of 16mm drywall, plywood, or OSB up those stairs and into place, and cut it to fit around the trusses, and get make sure it reaches all the way out to the edges of the floor, and is sealed hermetically, then that will work just as well as doing it from below. As long as the entire surface is beefed up and sealed, it makes no difference which side you do it from.


---

So, in summary, you seem to have a basic misunderstanding about the principles of isolation and the difference between airborne and structure-borne sound, and the difference between how MSM structures work, and mass law. Hopefully I've cleared that up for you. So I'd suggest that you re-think your isolation plan, along the lines of building a true, fully-decoupled, 2-leaf MSM room-in-a-room studio, either on top of the existing damped slab-on-grade floor, or on a new floated floor (if necessary), but based on real numbers obtained from a sound level meter and spectral analysis of both your airborne sound problems and your structure-borne sound problems.

Once you have your numbers figured out, there are several acoustic research publications you can look at that show literally hundreds of different types of wall, floor and ceiling construction, along with the amount of transmission loss you can expect from them, so you can find one that meets your needs, and your budget.

You also mentioned HVAC in your original post, so you are aware of that, and of how to do it right, but there are a couple more issues that you didn't mention, that can also affect your isolation. Those are doors, windows, and the electrical/cabling system. Any isolation plan is only as good as the weakest part, so even if you have wonderful walls, floor and ceiling in place, a poor door or badly done electrical installation can totally negate that, leaving you with lousy isolation again. Once again, there are publications that show different types of door and window construction, and there are guidelines on how to do the electrical and cabling installation properly to maintain isolation.

Hope that helps.



- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

You seem to be confusing isolation with treatment: they are two totally different diametrically opposed issues.

Think of it this way: Isolation stops sound getting out of the room. If it cannot leave the room, then obviously it must stay INSIDE the room, bouncing around until it eventually dies away. So the very act of isolating a room makes it sound bad. There's no two ways about that: If sound cannot escape the room, it stays in. The only way to keep it in is with hard, solid, massive, and therefore acoustically reflective surfaces. You cannot stop it getting out with absorption alone, for the same reason you cannot stop water running out a tap with a sponge alone. Sponges are good at mopping up water that spilled some place you don't want it, and acoustic absorption is good at mopping up sound that spilled some place you don't want it, but just as a sponge cannot stop the flow of water leaving your tap, so too absorption cannot stop the flow of sound leaving your room. To stop the water flow, you can stick a cork in the tap: massive, solid, rigid. To stop sound leaving the room, you put a "cork" in all the holes (wall, floor, ceiling, doors, windows, HVAC, electrical).

So "soundproofing", by definition, means keeping the sound in the room, which of course makes the room sound bad: sound bouncing around between the walls is called "reverberation", so one of the big goals of acoustic treatment is to get the reverberation times under control, correctly for each frequency band. Absorption is a large part of that, especially at low frequencies, but so are diffusion, reflection, and even refraction and diffraction, to a certain extent.

The sound that "bounces around the room" is absorbed either by the air itself or by the absorptive treatment, or it is redirected in different vectors, scattered, until eventually it is absorbed either by the air itself or by the absorptive treatment.

So one thing is isolation, which is accomplished with massive, solid, hard, rigid materials (such as drywall, plywood, MDF, OSB, glass, concrete, steel, etc.), and the other thing is treatment, which is accomplished with soft, light, fluffy, flexible, pliable, fibrous materials, such as fiberglass, mineral wool, and other open-cell materials, plus also tuned resonant devices, most of which also contain the same soft, light, fluffy, etc. materials.

But isolation and treatment are two different things, ans should not be confused. Yes, the isolation plan for a studio can (and should) also consider treatment, and the treatment plan should also take into account isolation (for example, to avoid creating triple-leaf systems with panel traps or slot walls). So the studio needs to be designed all together, as a system, but keeping in mind that there are two basic, separate, independent, and opposite goals at work: One is to keep the sound in, and the other is to get rid of it.

That's just a long way of saying that putting absorption between the joists might or might not help as a small part of your treatment plan, but wont do anything at all to isolate the room.


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Sorry. but that IS a three-leaf wall! Actually it is even worse! That's a FOUR LEAF wall!! Count them: 1="concrete block outer leaf". 2="rockwool/studs/gypsum". 3="internal walls will be gypsum board/studs/cavity". 4="with rockwool/studs/gypsum board". Your low frequency isolation will be pretty bad with such a system.
- Stuart -[/quote]

Stuart, please read what I wrote. "External walls" describes the treatment on the inner face of the external walls. "Internal walls" describes freestanding internal walls, separate from the external walls. You're taking two of my walls and putting them together! Please look at the Sketchup plans I posted.

And I'm sorry, I don't agree with you about slabs. Impact noise on a rigid piece of concrete is easily transmitted through the material, and low frequency content (such as that from a passing tractor) is transmitted through earth quite easily, particularly if it's rocky. Please check with Eric Desart about this.

Thanks for your time.

_________________
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Stuart, excuse me, but... I'm not sure where you got the idea that I'm a complete idiot. Maybe it was something I said, incomplete information... did I spell something wrong?

In this particular instance, my choice of isolation material affects the treatment I'll need in the room, because... the isolation material will be *in* the room. It will form the ceiling of my room, and it will be reflective, above low frequencies. I'm happy to accept that mounting a ceiling on the joists with RC will help me by adding a second leaf to my ceiling. Let's call that a victory and move on.

_________________
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Umm, gee, well, err... that kind of is what the sound field will encounter, now isn't it? Sound waves don't care what you call your leaves: they only care about the mass and the air gap, period. Take a look at the MSM equations: the only controllable variables in there are mass and air gap. The words you choose to describe the "mass" and the "air gap" are irrelevant.

But I did read what you wrote, and I did look at the Sketch (which lacks the details of the construction anyway). Your external walls are grey, and your internal walls are a sort of bluish colour. And that's why I'm correcting your incorrect assumptions.


Why on earth would you need treatment on the face of the outer leaf? You said that the outer leaf is a concrete block wall, did you not? The only treatment that needs, is to be sealed. Concrete block is porous, and the surface needs to be sealed in order for the MSM system to work optimally. So seal, by all means, but you don't need more layers of drywall on your outer leaf (the grey walls, in your Sketchup.) Adding studs and drywall to that is, in fact, adding a leaf, regardless of what you want to call it.

Yup: and your point is.... ? That is another two leaves, separated from the exisitng two leaves by a small air gap.

Walls are walls, leaves are leaves, and sound waves react to them, following the rather well known and rather well understood laws of physics. Sound waves don't care much about opinions on what someone might happen to think constitutes an "internal" wall or an "external" wall: they simply react to what they encounter. And each time they encounter a massive rigid surface, they see a leaf. So if they see a concrete block wall (first leaf) followed by a small air gap and a sheet of drywall on a stud frame (second leaf) followed by another small air gap and a sheet of drywall on another stud frame (third leaf) followed by yet another small air gap and a sheet of drywall on another stud frame (forth leaf), then they have, undeniably, encountered four leaves with three air gaps. And as anyone who understands acoustics will tell you, a 4-leaf system is ALWAYS worse at isolating low frequencies than the same amount of mass in the same amount of space, set up as a 2-leaf system.

You might want to check the Wyle report, to understand this issue. It explains the mechanisms involved, and the principles of physics quite clearly.

Yes, because that is EXACTLY what the sound waves will do! Low frequency waves see all of the walls as a single system, not as individual parts. And the isolation offered by a 4-leaf wall, which is what you describe (even though you prefer to think of it as a pair of two leaf walls) , is ALWAYS worse than the isolation of a single 2-leaf wall, all other factors being equal. You can call it whatever you want: a pair of 2-leaf walls, or a quad of single leaf walls, or a triple leaf plus a single leaf, but the simple fact remains that, as far as sound waves are concerned, it is a 4-leaf wall, and will act like one, and will follow the equations that govern all such walls. Calling it something different will not change the physics behind how it works.

Then maybe you should take a look at IR-802. It deals with that subject rather well, I think.

Ummmm.... and I said something different? I do seem to distinctly recall saying that your biggest problem will be impact noise and low frequency vibration from the tractors... I do seem to distinctly recall suggesting that you might want to quantify that, with a sound level meter and/or spectrum analyzer, in order to determine exactly where and how big that problem is. I guess you must have missed that part of my post, in your haste to reply so angrily....

Eric is a long-standing member of the forum, and posts here occasionally, so feel free to look him up on the member's list and invite him to join this thread. I'm sure he'd be delighted.

One more time: a two-leaf MSM system consists of the outer leaf, which is a single piece of mass, followed by the inner leaf, which is another single piece of mass. Period. That's all you need. adding more walls is adding more leaves. From the point of view of sound waves, each room is surrounded by two leaves (or two "walls" if you prefer), in all directions. The inner wall (or inner leaf) is the first chunk of mass that the sound wave "sees" as it exits the room, and the outer wall (or outer leaf) is the second chunk of mass, on the other side of the air gap.

Dunno. Maybe it was the attitude. Hard to say... Seriously, calm down a little! Lighten up! Or "Chill, dude" as the yanks say! Nobody said you were an idiot. Overly sensitive, maybe, but not an idiot. I'm just trying to help you, and explain why your plan is not what you seem to think it is, and how to do it better. If you don't want advice, then why did you come here asking for it?

Ummm, actually, no it wont. The isolation is the shell around the room. The treatment is what goes inside it. And like I said, the overall design of the room needs to take both into account together, since they can interact. If there is only isolation, then there is no treatment! If there is only treatment then there is no isolation.

Yup. Just like I said: it is isolation, not treatment. If it reflects sound back into the room, (stops it leaving, keeps it inside), then it isolates! That kind of is the definition of isolation. ...

Actually, it does far more than just that. It completes the entire MSM isolation system. Without the ceiling, you don't have a system.

A two-leaf wall is a tuned system: it resonates at a certain frequency, defined by the total mass on the leaves and the depth of the air gap between them. At that frequency it does not isolate at all. At higher frequencies it does isolate, to increasing degrees, starting at 1.4 times the resonant frequency. At 2 x resonant, it isolates reasonably. At 3x it isolates quite well. Isolation increase all the way up the scale, until you hit the coincidence dip a couple of octaves further up, which is caused by the characteristics of the individual leaves acting alone, not the wall system acting as whole, then above coincidence, isolation continues to increase again, right up the rest of the spectrum.

Without the drywall on RC, you don't have an MSM room: you just have leaves that do their own thing, individually, and the total isolation is governed by mass law. Add in that ceiling, and now the entire room has a tuned MSM system around it, which is no longer governed by mass law: now it is governed by the equations for resonant systems, which are a lot more interesting, as they provide for several TIMES what mass law can do, in any given frequency band, except for the zone around the resonant frequency. So the idea is to choose the resonant frequency of your wall to be half of the lowest frequency that you need to isolate.

So that's what you accomplish by adding the ceiling on RC. Without it, you don't have an isolation system, just mass law. With it, you complete the 2-leaf system, and you now have MSM law.

Victory? I didn't realize there was a battle going in!

Seriously, Miles, I'm just trying to help! Don't bite my head off! If you don't want help, then just say so, and we'll all be happy to ignore you. (However, the last guy who did that has a very lonely thread right now, where he seems to be talking to himself all the time, and is making numerous errors that he'll end up regretting.) It's not about victories or defeats, or calling people stupid, or getting angry at responses that maybe you didn't like: It's about your studio, and building it right, that's all. If you don't want people here looking over your shoulder, suggesting ways you can do it better, then fine, just say so, and we'll watch in silence, biting our tongues. But if you do want help, then folks here will be happy to help you: Sometimes the comments might be rather pointed, and could be taken as "insulting" by folks who are very sensitive, but to be honest, personally I'd rather have someone tap me on the shoulder and say "Hey, dummy, that's wrong! Don't do it like that, do it like this!", than to have him waffle on pleasantly and diplomatically, beating around the bush with courteous political correctness, carefully trying to make the point that I screwed up, without hurting my feelings. I'd rather have hurt feelings and a great studio, than wonderful "warm and fuzzy" comments all day long, while meantime I'm building a disaster because I didn't get the point.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.

OK, let's try again.

Please explain to me how this is a quadruple leaf wall (these are not to scale):



Or this:

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OK, so it's a TERMINOLOGY issue! It's the way you are describing it that is the problem. You are not using "exterior" and "interior" the way acousticians use it. The exterior, our external, or outer leaf is the one on the outside of the MSM system, the "other" side of the wall, furthest away from the room interior. The interior wall, or internal, or inner leaf is the one that you see as you stand inside the room, looking around you. With correct use of the terminology, you cannot see the outer leaf, or exterior wall, from within the room, but with the way you are using the terminology, you sure can see the outer wall.

Like I said in my first post: terminology matters.

But in any event, what you show in your second diagram is not correct: the two rooms are coupled through the common inner leaf (what you refer to as the "outer wall"). You have a direct flanking path between them, so there will not be good isolation. You should break that path, and create two separate inner leaves.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Well, it's nice to have that sorted out.

I'm assuming you mean something more like this:

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http://www.mylescochran.com

http://www.myspace.com/mylescochran

For some reason, that last image you posted isn't showing up. There's just some text saying "walls-2a.jpg", but no picture. Maybe you could upload it again?


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Just fixed it - it said it uploaded before, but you know how machines are... and their operators..

_________________
http://www.mylescochran.com

http://www.myspace.com/mylescochran