Looking for some help with basic layouts

Hi everyone, I work as a staff recording engineer for the school of music at a large university in the Boston area. The school has engaged an architectural firm to begin drafting up a master plan for renovations of the floor on which our "studio" currently resides, and this means that our current space will most likely no longer exist which is actually quite a good thing as it's virtually useless for audio work. The space we're in predates me by probably a few decades and was never properly constructed as a critical listening environment. It consists of an office area that sits opposing an edit station (in the same room) and a separate "control room" that's used as our main recording and editing room, though it's not isolated from the other room in any significant way. It's regularly home to two full-time employees and occasionally a third part-time/work study student. All of this is in a space of about 300 square feet with about a 6.5 foot ceiling. The location seems to have been chosen because it sits adjacent to our concert hall and is nestled in the middle of three large rehearsal spaces/classrooms to which we have a few mic lines run, though they haven't been used in many years. Our biggest issues are our lack of isolation from not one, not two, but ALL of the aforementioned performance and rehearsal spaces as well as the surrounding hallways. It is not uncommon for the symphony orchestra to be rehearsing in the concert hall while the wind ensemble is in one of the larger rooms, which can bleed into our space to the tune of 60-70 dB at its worst (according to our trusty Radio Shack SPL meter). In addition, there is a railroad track probably 20 yards from the northern outer wall with (wait for it) a highway overpass directly above it. This results in some serious structure-borne noise. We've had acousticians in to measure just how awful this stuff is, and they've said at its worst the structure-borne vibrations are about 85 dB at 12.5 Hz which, while not audible in and of itself, causes the lighting grid in the concert hall to shake noisily and can be felt in the floor. Needless to say, this makes doing any critical audio work impossible. Because of all these issues, I'm really hoping to stake out a claim for a new space for the upcoming renovations. There's one area in particular that may be up for grabs and I'm looking for some advice on the feasibility of this space meeting our needs. I'm not looking to get into the specifics of construction materials and the like (too soon for that now), but rather just some general layout possibilities. I figure if we can point to a very specific footprint and say "that would work for us," it's much easier for everyone to wrap their heads around. Regarding genres we work with, as things stand right now we record only classical music. Our primary function is to provide archival recordings of all the school of music ensemble and faculty concerts and recitals, but we do quite a bit of session work as well (also classical-only -- our sessions primarily take place in the concert hall which causes all kinds of scheduling/logistical/technical problems). I have lots of previous experience with other genres (primarily jazz and pop/rock) so I would love to be able to work with those kinds of artists again and would hope to have a facility that allows for that. Despite our limited current capabilities, sessions account for well over half of our revenue so a dedicated space should allow for a greater variety and volume of work. As far as "must-haves" go, we absolutely need at least two rooms capable of editing, a small office/reception area for processing CD orders and billing and some kind of storage space. Ideally we could also have a small- to medium-sized live room with an iso booth to allow for expanding our ability to record other genres, so one of the editing rooms could also be a control room. The attached room is what we're hoping to work with. As you can see in the picture, it's sort of an odd shape, almost 22 feet at its widest point and about 61 feet long, with a 13.5 foot ceiling (this the measurement to a tiled drop-ceiling) and for all intents and purposes it's on the second floor. The western walls are brick (left and bottom left in the top-down picture), and to the north is the outer wall with tall windows with the train tracks and highway just beyond. I'm honestly not sure about the construction of the eastern walls, but they seem pretty flimsy (not even sure if they're drywall) and I think, for the sake of argument, they can be considered easily demolished and rebuilt with something suitable. The room is currently used as a dance studio, so the floors are hardwood that's raised off the subfloor to provide some "give" for the dancers. The two circular columns along the eastern wall are structural. There has been talk of being able to remove them, but without 100% confirmation from the architects and structural engineer, I'm going to assume they have to stay put. Same deal with the squared support in the middle of the western wall. I've come up with a few layouts myself, but only had time to figure out SketchUp enough for the space as it stands now. Hopefully I can get at least one of them drawn up tomorrow and get it posted here for everyone's consideration, but until then I'd appreciate any and all comments and layout suggestions, even if they're of the "don't even bother!" kind. I built it using the actual architectural plan for the room, so all the dimensions should be near-exact with the exception of maybe the windows. If I've done everything correctly, attached should be the .skp and two .png images. If anyone has any other questions, please let me know! Best, Shane

Ok, so having a bit of a tough time wrapping my head around SketchUp...but here's an initial layout I came up with in a different program. I'm wrestling with the odd angles of the north (top in picture) and south (bottom) walls. Since the north wall is the outer wall and is currently basically covered in windows (they start at about 4 feet from the floor and go all the way to the ceiling) I figure it makes more sense to try to turn that into the office and/or storage area. The problem is that the only doors that could currently work for entrances are the ones on the south and west walls, which means there's really no way to direct traffic to the north part of the room unless they first walk down a long hallway. It's possible, but not ideal. For layout 02, I took a liberty with the east wall and made it straight throughout the room instead of tapered inward at the ends. I think that's totally doable in the grand scheme of things as it's not really usable space in the adjacent room in its current setup. All of the isolating walls are set to 12 inches thick, based upon a basic double wall construction of a 2x4 frame, two layers of 5/8" and 1/2" drywall, and an air gap of 2" (the program I used only allows for whole number values for wall thicknesses). Again, any input on this would be greatly appreciated! -Shane

Hi Shane, and Welcome! :) Looks like you have a nice space there, albeit with strange shape. But I'm confused about where the main entry door actually is: you show it in two different positions in your diagrams: Are those fixed positions, or could the door go anywhere on those two walls?

Since the north wall is the outer wall and is currently basically covered in windows (they start at about 4 feet from the floor and go all the way to the ceiling) I figure it makes more sense to try to turn that into the office and/or storage area.

That's probably a good idea, but not necessarily: depending on the windows and other materials, as well as your isolation needs and your budget, it might be possible to incorporate those windows into the live room, for example.

All of the isolating walls are set to 12 inches thick, based upon a basic double wall construction of a 2x4 frame, two layers of 5/8" and 1/2" drywall, and an air gap of 2"

They might not need to be that thick, depending on how much isolation you need. A one-inch gap between frames is plenty: that's not the air gap: just the gap between frames. That would give you an air gap of 8 inches. Two layers of 5/8" should be enough, unless you have extreme isolation needs, so your total thickness would be 10-1/2". Drop the frame gap to 1/2" and your total wall thickness could be 10". And if you build the inner-leaf wall "inside-out" then you can save even more space, as the stud space then becomes part of the room and can be used for treatment. However, all of the above depends on how much isolation you need, in terms of decibels.

Again, any input on this would be greatly appreciated!

In both of your layouts you have a couple of big issues with the control room: First, you are firing your speakers along the short axis of the room (12'8"), whereas it should be along the longest axis (15'-something). That also results in the second problem: your head is almost exactly in the middle of the room (especially in layout #2), which is the worst possible place for it. And the third (related) problem: your head is too close to the rear wall. To fix all of those, you could either make the control room longer (by sacrificing some space from the other rooms), or you could turn the layout 90° left or right. You don't show the position or orientation of the speakers, but it looks like there might be some issues with that too, based on guessing where they might go. Finally, I think if that were my space, I'd try to put the live room at one of the ends, where the walls are angled already anyway and you could save on the corridor space next to the room. You could have a very nice, large, irregular live room in either of those two locations, I think. My $0.02! - Stuart -

Hi Stuart! Thank you for your reply.

But I'm confused about where the main entry door actually is: you show it in two different positions in your diagrams: Are those fixed positions, or could the door go anywhere on those two walls?

Sorry, this was me taking a few liberties and not really accounting for them the text of my post. There are currently two doors into the room on the south and west walls as shown in the SketchUp diagram, with a third that enters into a small storage area which in turn enters into the adjacent room. Based on the scope of this renovation project, I'm making the assumption that the door could be moved to a number of different spots. Until I know for sure exactly how the surrounding spaces are going to be restructured (if at all), I thought it best to try to work with one of the existing doors as they lead to hallways in the current overall floor plan, and I'd prefer to only have one door in for security reasons. I've attached an image that shows the surrounding area (the room I'm working with is marked by the red arrow) to hopefully make what I'm trying to say a little more clear (yes, it's an emergency egress diagram, hence the large blue "you are here" dot. It's the only thing I had to show the surrounding rooms). As an aside, the room to the right of the one I'm working with in this thread is the one I really want, but I've been told in no uncertain terms that it's off limits, along with the other surrounding large rooms. Gotta work with what you've got I suppose.

depending on the windows and other materials, as well as your isolation needs and your budget, it might be possible to incorporate those windows into the live room, for example.

The thought of natural light in the live room is certainly appealing to say the least. The budget is still very much up in the air, and I'm predicting it will be modest enough to where I'm going to want/need to be as cost-effective as possible. So in anticipation of having to account for proper isolation, HVAC, treatment, cabling, power, etc., I'm just thinking that the added cost of trying to effectively isolate a live room with large windows might not be money well-spent. That said, I can't see the harm in coming up with a design that puts the live room there -- gotta aim high! -- especially since it seems to make the most sense as far as the room layout goes. I'll see what I can come up with.

They might not need to be that thick, depending on how much isolation you need. A one-inch gap between frames is plenty: that's not the air gap: just the gap between frames. That would give you an air gap of 8 inches. Two layers of 5/8" should be enough, unless you have extreme isolation needs, so your total thickness would be 10-1/2". Drop the frame gap to 1/2" and your total wall thickness could be 10". And if you build the inner-leaf wall "inside-out" then you can save even more space, as the stud space then becomes part of the room and can be used for treatment.

Ok, I think I had misinterpreted what qualifies as the "air gap" in an isolating wall. So, if I understand correctly now, the air gap is the entire space between the massive parts of the walls (in this case the drywall), even if some or all of it is filled with some sort of non-rigid or semi-rigid insulation. Is that correct?

However, all of the above depends on how much isolation you need, in terms of decibels.

No matter where we end up in this building, we will almost assuredly be adjacent to a rehearsal space of some kind, and it is fairly likely that such a space will be capable of holding a 70+ piece symphony orchestra or wind ensemble. The room we're looking at here is sandwiched between a rehearsal space (which could be expanded to an orchestra room) and a theater rehearsal/performance room on the left and right respectively in the attached image. A full symphony orchestra can reach levels of 100 dB or more at times, and the theater room on the other side has been known to host classes in what I imagine must be "Obscenity Screaming 101." We've been told that any new spaces will be constructed with acoustic isolation in mind, though I'm not sure the powers-that-be understand what it actually costs to isolate large rooms. I'm not going to assume that they'll end up much over STC 50. So I'm wondering what seems like a reasonable goal for our space. Stuart, based on a post you had made in Shybird's design thread and from research from other sources, I think I should really be looking to get a noise floor of about 30 dB SPL at the most. Knowing that STC ratings account for down to 125 Hz, and that an orchestra with some timpani and a bass drum can get pretty rowdy in the low end, should I be shooting for something like STC 70? I understand the basics of how STC is calculated, but I can't seem to find many plots of STC curves, which I think could be very helpful in understanding what's really going on at all frequencies. I suppose I could ask it a different way: as I understand it, the mass of the isolating walls determines the resonant frequency of the wall. The greater the mass, the lower the resonant frequency and the better the low end isolation. Would a wall constructed as you mentioned above have enough mass to keep the low end of an orchestra in check? In looking through the STC Chart on John's Recording Manual pages, that basic construction without the gap between frames is listed at STC 54. This page tells me that "an airspace of 6" will improve the STC by about 8 dB," so have an 8" airspace I would assume gets, what, 1-2 dB better? I'm just a little confused of how STC numbers compare to one another I found the following diagram on this site for STC 56: How does that plot compare to, say, STC 60? Sorry if this is all a bit of a stream of consciousness kind of rambling...STC ratings seem like useful things if you really know how they compare to each other, but I'm kind of in the dark on exactly how to do so... Granted, the above mentioned large and loud ensembles won't be rehearsing all-day every-day, but the way I see it, that shouldn't matter. I want the space to be usable at all times.

In both of your layouts you have a couple of big issues with the control room

I realized this shortly after posting the pictures as I continued my research. I'm going to try to rework those dimensions and layouts to get to some favorable ratios.

You don't show the position or orientation of the speakers, but it looks like there might be some issues with that too, based on guessing where they might go.

I hadn't quite gotten as far as that with my initial go at a layout, but I guess I shouldn't leave it out. My primary goal was just to see what could realistically fit in this space, and to get a basic footprint for each room that seemed like it would work. But if the room fits and speakers don't work in the room, I suppose there's not much point, is there? Thanks very much for your input, Stuart. I'll take a crack at round 2 and post what I come up with. -Shane

Ok, I think I had misinterpreted what qualifies as the "air gap" in an isolating wall. So, if I understand correctly now, the air gap is the entire space between the massive parts of the walls (in this case the drywall), even if some or all of it is filled with some sort of non-rigid or semi-rigid insulation. Is that correct?

Exactly. When you think about it, the type of insulation used in acoustic isolation is mostly air anyway. So yes, the entire distance between the two leaves is the "air gap", regardless of whether or not there is insulation in it. Curiously enough (and non-intuitively), putting insulation inside the air gap actually INCREASES the size of the air gap, as far as sound waves are concerned. Mathematically, filling hte entire air gap with perfect insulation makes the average path that a sound wave has to travel about 1.414 times longer. So you could say that the sound waves "think" that the air gap is larger than it really is. OK, it's no really that simple, but it's a nice way of thinking about it.

No matter where we end up in this building, we will almost assuredly be adjacent to a rehearsal space of some kind, and it is fairly likely that such a space will be capable of holding a 70+ piece symphony orchestra or wind ensemble. The room we're looking at here is sandwiched between a rehearsal space (which could be expanded to an orchestra room) and a theater rehearsal/performance room on the left and right respectively in the attached image. A full symphony orchestra can reach levels of 100 dB or more at times, and the theater room on the other side has been known to host classes in what I imagine must be "Obscenity Screaming 101."

:shock: Ummm.... "Obscenity Screaming 101" :!: :!: :?: OK, I think I won't ask any more questions about the courses offered by your school! :) But it seems clear that you are going to have loud things around you, without even considering noises made by the building itself. By the way, a full symphony orchestra can easily exceed 100 dB. 110 is more like it, and 120 is not out of the question, some orchestras have been measured well over 130 dB, and if you want to do the full performance of the 1812 overture, complete with carillon and cannon, then all bets are off...! So you are probably quite a bit on the low side with your estimate of 100. It might be an idea to take a sound level meter and a good set of ear plugs into the next full practice session, and measure the actual levels.

We've been told that any new spaces will be constructed with acoustic isolation in mind, though I'm not sure the powers-that-be understand what it actually costs to isolate large rooms.

Perhaps for powers-that-be designing an educational building, "acoustic isolation" might not mean what it does to a studio designer or music room designer! Maybe a drop ceiling with polystyrene tiles is "plenty good enough" for them... :)

I think I should really be looking to get a noise floor of about 30 dB SPL at the most.

Exactly. But you should be looking at NR curves for rating that.

Knowing that STC ratings account for down to 125 Hz, and that an orchestra with some timpani and a bass drum can get pretty rowdy in the low end,

True, but that's not the complete picture. Your timpani and bass drum can account for a very large chunk of the entire sound output of the orchestra, and most of that energy is, as you say, in the low end of the spectrum, which is the hardest to isolate. You might want to see if you can convince your power-that-be to get an acoustician on board to design this.

should I be shooting for something like STC 70?

STC is not what you need for your case. STC was never meant to be used for rating the isolation of studios, concert halls, or music rooms. It is meant for speech and ordinary office type noise, which has very little energy in the low end. STC tells you nothing about how well a wall will isolate a bass drum. Transmission loss is what tells you about that. And Fletcher-Munsen curves are what tell you about how people persevere sound. You should be looking at all of those, finding out what a typical spectrum looks like for one of your worst-case practice sessions, and looking at what type of construction will provide the isolation you need. The IRC documents might be very useful to you there, since most of them give you STC ratings but also more detailed tables and graphs that you can easily use to actually figure out what will work for you.

I understand the basics of how STC is calculated, but I can't seem to find many plots of STC curves,

STC is a bit of a kludge: Take some readings at a few very specific frequencies, then fiddle with some math, nudge things here and there until you force your data to fit one of the pre-defined curves, then you can say that you have "STC-xx" rating. Which basically means very little, for a recording studio next to a live symphony orchestra.

as I understand it, the mass of the isolating walls determines the resonant frequency of the wall.

Well, there is mass-law and then there is MSM "law", which are quite different. Mass law does not deal with resonance. Pure mass just attenuates sound by brute force: just "getting in the way" enough to bring the level down. Double the mass and you increase isolation by 6 dB. MSM "law", on the other hand, is much more promising, since you are using resonance to help you "fight back". With mass law, the wall is not tuned (well, sort of, but not really relevant). However, with MSM it is. Both the mass and the spring are important, and both can be changed to tune the wall.

The greater the mass, the lower the resonant frequency and the better the low end isolation.

Assuming you don't change the spring or the damping, yes. The "spring" in this case is the air between the two leaves, and the "damping" is the insulation in the air gap. Improve any of those and you drive the resonant frequency down, but you still need enough overall mass to get the lowest point (the isolation at the actual resonant frequency) to a suitable point. In other words, you tune the wall such that the worst level of isolation at the lowest frequency that matters to you, is still high enough to bring that instrument down to a suitable level on the Fletcher-Munson curve, as compared to the NR curve that you choose for your room. I hope you understood that, 'cause I'm not even sure that I understood it, and I just wrote it! :) In other words, you look for the worst case: What is the lowest frequency that you need to isolate? Then you figure out: "How much isolation do I need at that frequency, so that the loudest level of that frequency produced by the orchestra doesn't bother me in my room?". The NR curve tells you what the "Doesn't bother me" level is, the Flethcer-Munson curves (which are related) tell you how you perceive that level, and the TL curves show you what kind of wall will give you that amount of isolation. I guess the second try wasn't much better either, was it? I'm confusing myself here!

Would a wall constructed as you mentioned above have enough mass to keep the low end of an orchestra in check?

It's not just the mass, but yes, a proper MSM wall constructed with enough mass and enough air gap will indeed isolate as much as you need, and at the frequencies you need. Arguably the best isolated studio in the world is Galaxy, and they boast over 100 dB of isolation. So your nightmare orchestra plus your "screaming-101" both together would be inaudible inside your room, if you were to isolate like they did. The only problem is that it took then hundreds of tons of concrete on huge isolation springs, and a few million dollars to accomplish that... Probably out of the question for your budget. However, that does not mean that you can't get darn good isolation. Think of it this way: The less you need, the less expensive it gets. The higher you go up the isolation ladder, the harder it is, since this is an exponential curve, so going down a step makes it exponentially easier, too. Galaxy spent millions to get 100 dB isolation, but relaxing that to 90 dB makes it ten times easier, since you only need to stop one tenth of the energy at 90, as compared to 100. Going down to 80 makes it ten times easier again. Same reason. Decibels are on a log scale. So you just need to find the point of compromise where your budget level meets your acceptable isolation level.

In looking through the STC Chart on John's Recording Manual pages, that basic construction without the gap between frames is listed at STC 54. This page tells me that "an airspace of 6" will improve the STC by about 8 dB," so have an 8" airspace I would assume gets, what, 1-2 dB better? I'm just a little confused of how STC numbers compare to one another

That's the problem: STC numbers don't really compare to each other very well, and where low frequencies are involved, they compare even less well. You can have two walls with identical STC ratings, where one is really good at blocking bass guitar while the other is hopeless. Conversely, you can have two walls that block a drum kit to the same level, but their STC ratings can be rather different. And finally, STC numbers are not very well related to actual decibels, or to full-spectrum transmission loss (TL) curves. That's why STC is not a good system for what you need. Look at the full TR curves to get the real story. They tell you the truth.

How does that plot compare to, say, STC 60? Sorry if this is all a bit of a stream of consciousness kind of rambling...STC ratings seem like useful things if you really know how they compare to each other, but I'm kind of in the dark on exactly how to do so...

See above! :) That's why you are confused. Not because you don't get how they work, but because STC does not tell the truth about what you need to know. I'd suggest that you take a look at two things: The famous Wyle report, from way back in 1973 (WR 73-5) that explains many of the concepts behind how isolation actually works, and some of the IR- reports from the National Research Council of Canada, especially IR-761, IR-766, IR-586 and IR-802. Those should really get you on the right track!

My primary goal was just to see what could realistically fit in this space, and to get a basic footprint for each room that seemed like it would work. But if the room fits and speakers don't work in the room, I suppose there's not much point, is there?

:) Very true! It's kind of hard to have a control room work out well if there are no speakers in it... :shock: But seriously, the control room should really be designed around the speakers that you plan to use. The room and the speakers should work together to get the most neutral response possible, in both the frequency and time domains, so starting with the speakers and working outwards from there is a good way to go about it. I hope I'm actually helping here, and not just scaring/confusing the hell out of you, with all my ranting and waffling! - Stuart -