read the rules, read the book, got some plans... Help.

OK... first off, "Hello"... I'm new to this forum. It seems like a place I can learn from. Nice to meet ya. Down to business... I've been working on these plans for several weeks. Other forums recommened Rod G's book. Bought it, read it. I have a good start on the planning but could use some expert critique and advice. The room is an unfinished bonus room on the second floor of my new house. I create music 'in the box' and need a good combo area; mostly mixing, some light tracking. I hope to avoid war with my neighbors (cool people). Isolation is a concern but sonic accuracy is my primary goal. Decent isolation, great sound! Here are some pictures of my starting point. Entrance View, Window Exit View, Door Rear Corner Left Wall Ceiling The general dimensions are 153" x 167" x 97.75" The side walls are 64" before the angle toward the ceiling. The side walls are 24" center studs and outer walls are 16" center studs. HVAC has generic pipes in place but isn't hooked up to the house. Power and data is prewired. Budget: I hope to keep this close to $4k or $5k. I will do as much as possible with a little help from my friends. Current plans: Right now I'm planing on using RSIC-1 clips and double 5/8 sheetrock with Green Glue for the walls and ceilings. I haven't determined how to address the space behind the walls yet. For the floor I had considered a sound absorbing subflooring like this "Acoustik" but now I'm thinking about using a layer of 703 underneath a "plywood/GreenGlue/plywood" sandwich. Either way, I plan to finish with a glue-down engineered hardwood/laminate. Thoughts? The window I had planned to keep. I'm thinking about a "Climate Seal" insert and some super heavy drapes. The door.... I'm thinking about replacing the door with a solid core with a seal kit like this; Seal Kit. I'm not sure how to handle the HVAC. Acoustic treatment - A combination of Auralex (previous purchased kit from several years ago) Lenards, 2" squares, AND some DIY 703 and constructed corner bass traps (fiber filled frames). I plan to cover some obvious early reflections first and then add after a software analysis. SO.... I'm sure something sticks out to the expereince viewer. What advice can you give? (this might sound crazy) Where would you start? (the door, the floor, HVAC) Thanks in advance.... Joe (Edit to add pics per request)

Start with getting and learning Sketchup. You are looking at around 14 sheets of drywall plus ceiling. Doors will be expensive. Run large enough ducts to get 10 air changes per hour with a duct velocity of 500 fpm. That floor design will do nothing for you on the second floor. It was originally designed for a studio on a concrete floor. It will make things worse. Good luck!

soundslikejoe.com...I like that:0 Anyway Joe, how you-uns doing? You read like you are on top of this thing, willing to plan it out and get read up, that is certainly admirable especially considering it is your money right? Some folks just walk in and start popping lines and framing walls. I have a few questions that you can most likely answer with little effort. The area below this bonus room, there are walls below that support the area that you are doing your build in? Like, the added weight which is much, will be supported in such a way as not to create sagging or collapse? Other question is about the short rafter run right above the knee wall and right up to the ganged rafter tie/ceiling joist. At least an inch of air flow(not a technical measurement just a WAG) should remain from the deck plywood down for proper ventilation. Good luck this New Year and with your build, we'll be seeing ya, Brien

I guess I should have added to my O.P.... I will be hiring a structural engineer to review the plans and structure for "dead/live loads." I also plan to consult the city and county for the needed permits.

Start with getting and learning Sketchup.

My "Sketchup Skills" have improved dramatically since late October but I'm still creeping along in that area.

That floor design will do nothing for you on the second floor.

I agree that this is a problem and the weakest area for any isolation plan. So the problem remains. I can't add UBER mass due to assumed weight restrictions. There MUST be some reasonable solution to REDUCE transmission/flanking without creating more problems.

Run large enough ducts to get 10 air changes per hour with a duct velocity of 500 fpm.

Excellent words. Thanks guys. Keep it coming.

JoeNovice wrote:

Start with getting and learning Sketchup.

My "Sketchup Skills" have improved dramatically since late October but I'm still creeping along in that area.

Fantastic!

That floor design will do nothing for you on the second floor.

I agree that this is a problem and the weakest area for any isolation plan. So the problem remains. I can't add UBER mass due to assumed weight restrictions. There MUST be some reasonable solution to REDUCE transmission/flanking without creating more problems.

Get NRC IR 811. Read pdf pages 70 - 72 on improving floors. Study fig. 73, noticing that the lf TL is lousy regardless. If you are set on it, invextigate having structuaral support underneath and adding mass there. Your structural engineer is your friend on this path. Andre

Get NRC IR 811. Read pdf pages 70 - 72 on improving floors....

Cool! Thanks André! Yet more light reading matter, for bedtime!!! :) Hi Joe, and welcome. Looking at your roof, two comments: 1) Are you planning to beef that up for better isolation as your first leaf, then install a new ceiling as your second leaf? 2) Have you thought about ventilation in that roof space, between the two leaves, once you have it sealed up with a ceiling below it? And one comment about your pictures: the general rule here is to up-load all your pictures to the forum itself, rather than linking to them elsewhere, for the sake of posterity. It's frustrating to come across an interesting thread from several years back, with text that says something like "Hey guys, look at this neat thing I built, and it works great!" with a dead link to a picture that no longer exists... - Stuart -

This is a good chance to ask a question. How do you define a leaf?

1) Are you planning to beef that up for better isolation as your first leaf, then install a new ceiling as your second leaf?

My plan was to fill the roof studs with Pink and fill the ceiling framing with something (Pink or 703). Then add clips, hat channel, and sheetrock.

2) Have you thought about ventilation in that roof space, between the two leaves, once you have it sealed up with a ceiling below it?

I haven't thought about ventilation. What do you mean (room or outdoor vents) and why should this be a concern?

This is a good chance to ask a question. How do you define a leaf?

Basically, a leaf is any layer of appreciable mass between the inside of your room and the outside world, with some form of air gap next to it. A leaf can consist of one or more layers of mass that are coupled together. So if you have a normal 2x4 stud wall with sheetrock on both sides, that is two leaves. If you add an extra layer of sheetrock to each side of that wall, it is still only two leaves, since the new sheetrock is coupled to the old sheetorck, as it is in direct contact. You have added mass to the wall, which is good for isolation, but you have not added leaves, which is also good. If you were to take the sheetrock off one side of that wall, then it would be only one leaf. Or on the other hand if you build another 2x4 stud wall next to that original one, a couple of inches away, also with sheetrock on both sides, that is now 4 leaves, which is bad. The best wall consists of two sets of 2x4 studs, separated by an air gap, wth several layers of sheetrock on only one side of each set of studs, and plenty of fiberglass or mineral wool in the air gap. For the roof: if you have a roof deck with shingles on it, that is one leaf. Add a ceiling below that made from one, two, or three layers of sheetrock all together, and your roof is now two leaves. Just count the layers of mass between you and the world, and that's how many leaves you have. If the total number is not exactly two, then you have a problem.

I haven't thought about ventilation. What do you mean (room or outdoor vents) and why should this be a concern?

Heat build up in a sealed attic can be a big problem. search the forum for key words like "attic" and "ventilation", and you'll find a few threads that have discussed the issue. Here are a couple that I found: viewtopic.php?f=2&t=3463&p=25364&hilit=attic+ventilation#p25364 viewtopic.php?f=2&t=1610&p=12068&hilit=attic+ventilation#p12068 viewtopic.php?f=2&t=3542&p=24992&hilit=attic+ventilation#p24992 viewtopic.php?f=2&t=6933&p=51376&hilit=attic+ventilation#p51376 viewtopic.php?f=2&t=11485&p=82976&hilit=attic+ventilation#p82976 Unvented attics are possible, but that's a different ballgame. read the threads, follow the links. Also, you have not yet mentioned how loud you are (in terms of decibels SPL), nor how much isolation you need (what the SPL level needs to be, in decibels, outside your room). Without know that, it's hard to say what kind of isolation you need. You may or may not be able to get away without beefing up the inside of your roof deck, for example, depending on how much isolation you need. That doesn't just mean "my sound going out". It also means "outside sound coming in". For example, do you have heavy traffic in the street outside? An airport nearby? Neighbors with a noisy lawnmower, or who like to party lots / play their stereo loud? Dogs barking? Wind noise? Rain noise? Construction site nearby? Noisy industry nearby? Etc. If you can conceive of having problems with any of that interfering with your work, then you need to take that into account in designing your isolation. You need to put some real figures on your isolation needs, in order to correctly design your room.

My plan was to fill the roof studs with Pink and fill the ceiling framing with something (Pink or 703). Then add clips, hat channel, and sheetrock.

That will work. Depending.... Another note on leaves and isolation: This is a paradox for roofs. In order to get proper isolation, the air space in your roof needs to be sealed: You need to create a "Mass-Air-Mass" system (MSM) for the two-leaf isolation principle to work. That implies air-tight seals. But for an attic space, you also need to ventilate that space, for the reasons mentioned in those threads. Unfortunately, you can't just add another leaf in there, such as a "second ceiling", as that now means that you have three leaves, which is bad. Note: a leaf does not need to be sealed in order for it to act as an acoustic leaf, but it DOES need to be sealed in order to act as a proper MSM system. It's a tough call: Do you go with a vented attic space that does not act fully as MSM, and therefore does not isolate well? Or do you build a third leaf and lose some isolation only at lower frequencies? One solution is to build the third leaf and use lots of mass to make up for the low-end loss (multiple layers of sheetrock with Green Glue), but that means a lot more strain and load on the underlying structure, due the large extra mass. Not to mention cost.... There are no easy answers. - Stuart -

Another comment on your comment:

There MUST be some reasonable solution to REDUCE transmission/flanking without creating more problems.

Unfortunately: Nope. You can't beat the laws of physics. There are only two ways to stop sound transmission: with mass, and with a vacuum. So unless you can figure how to build a vacuum around your room, you are stuck with "plan B": Lots of mass. The trick is to find the balance between how much mass you need to get the level of isolation that you want, and how much you can afford, in terms of the mass itself and the structure that you need to safely support it. If you can figure out those numbers, then the experts here can figure out how much isolation you need, how to get it, and how much mass that is going to take. Then you can call your structural guy to figure out how to support that mass. I wish there was an easier way! I truly do, since I'm in the same boat as you! Gotta add mass, mass costs money, but the laws of physics are inviolable... Damn! If only egg crates and carpet would actually work.... - Stuart -

Unfortunately: Nope. You can't beat the laws of physics. There are only two ways to stop sound transmission: with mass, and with a vacuum. So unless you can figure how to build a vacuum around your room, you are stuck with "plan B": Lots of mass.

Note: I'm not under the dillusion that I can or will STOP transmission. I'm only interested in REDUCING transmission. A question I'm having difficulty gaining clarity on via forum visits; "By adding mass to the floor will transmission be reduced?" My assumption is yes. Adding any amount of mass anywhere would reduce transmission some. A few people agree. Others state that adding mass will CAUSE MORE problems. (ie - enhance transmission) This is confusing. Perhaps it's not black and white. I spent a few hours today talking plans with Lowes people. They were very insightful regarding attic ventilation. The bottom line, I have two soffit vents where the roof trusses meet the walls that feed up through the roof's ridge vent. So long as I don't block that flow of air, I have no problems. I was also told that I can purchase some cathadrel insulation that would fit the roof truss and not block the flow of air. Any thoughts on the usage of cathadrel insulation in this design. Also since I plan to use clips and hat channel I shouldn't be in danger of blocking the ventilation and would retain a "two- leaf system." (i think) :D

A question I'm having difficulty gaining clarity on via forum visits; "By adding mass to the floor will transmission be reduced?" My assumption is yes. Adding any amount of mass anywhere would reduce transmission some. A few people agree. Others state that adding mass will CAUSE MORE problems. (ie - enhance transmission) This is confusing. Perhaps it's not black and white.

Adding mass to a single leaf will NOT enhance transmission: it will always reduce it. There is a basic principle of acoustics, called "mass law". Each time you double the mass, you improve transmission loss by 6 db, all other factors being equal. The only way that you can DECREASE transmission loss by adding mass is if you do not add it to the same single leaf, such as when you create a third of forth leaf. And in that case you are only reducing transmission loss in the low end of the spectrum, in the part of the TL curve before Mass Law takes effect. For all of the rest of the curve, adding mass will ALWAYS increase transmission loss. Adding mass to a single leaf will also reduce the resonant frequency of the leaf (which is good, especially if you can get it below the human hearing range!) but it will also reduce the frequency of the coincidence dip (which is not so good, as it will probably bring it more into the center of the human hearing range, depending on the material, but it's not as big a deal as the low end.) But adding mass to a single leaf will always increase transmission loss, at the rate of 6db per doubling of mass. Edited to add: OK, if you want more detail, this gets a bit hairy. Let me see if I can get this right: If you look at a graph of transmission loss for a given wall panel, there are several different regions were several different acoustic effects govern. At the very low end of the spectrum, it is the stiffness of the wall (not the mass) that governs how well it isolates. That's why 1/4 inch thick glass works better than 1/4 inch thick carpet at stopping bass. At slightly higher frequencies, resonance takes over. It is then the resonant characteristics of the wall that govern how well it stops sound. If you hit the resonant frequency of the glass, it won't block very well at all at that frequency, and in fact will transmit just fine, so the carpet will work much better, at that specific frequency. At higher frequencies, above the resonant frequencies, mass law governs: glass wins again. And at even higher frequencies, you get up to the area where coincidence takes over, and once again you have a dip at the frequency where the critical frequency matches the incident frequency: glass loses again. Finally, above the coincidence dip we are back to mass-law again, and glass wins. OK, that's a very simplistic view, and not strictly true in the comparison of carpet and glass, but it gives you a general idea that this is much more complex than meets the eye. Different things happen at different places on the spectrum, depending on how you build, what materials you use, etc. You need to build your walls such that the stiffness-governed region and the resonant frequency are below the range of human hearing, or at least as low as you can possibly get them (way down in the low double-digit frequencies). If you do that, all the other ducks fall in line reasonably well. The above is for a SINGLE leaf. When you build a DOUBLE leaf wall, you start getting transmission loss that is BETTER than mass-law, from some point just above the resonant frequency, and that is very very good. It means you get more bang for the buck. More dB's of isolation for your kilogram of wall. You no longer need to double the mass to get a 6db increase. With a sealed two-leaf wall, just by stuffing fiberglass or mineral wool insulation in the cavity you increase the loss by about 10dB, and it is NOT due to the mass of the insulation: It is due to the damping. The insulation damps resonance in the cavity, and that improves TL a whole bunch, since the wall no longer resonates very well. If you separate the panels more (move them further apart) you gain yet more dB, just by adding empty space! Air is cheap (so far!) If you increase the mass of the panels, it also increase your transmission loss by MORE than what mass-law tells you, since these effects kind of multiply each other. If you decouple the two sides of the wall, by building independent frames for each, you increase losses even more. And if you sandwich certain types of resilient materials inside your wall (basically, laminating it) then you can increase losses further still, way beyond what mass-law says. That's the good news about adding a second leaf. The bad news is that it also causes a dip in loss at low frequencies, so the TL falls BELOW that of the single leaf at very low frequencies, since you now have resonance of the entire system at some frequency. The wall will be worst at that resonant frequency. So once again, you have to design it so that the resonant frequency is as low as possible, ideally below the range of human hearing. The bad news about adding a THIRD or FOURTH leaf is that doing so will REDUCE transmission loss around the resonant frequency even more, since it makes the curve steeper, so it affects more of the spectrum, even if the resonant frequency is low. Which is why you want to avoid a third leaf if you can. Yeah, it is hard to get your head around this stuff, but it starts making sense eventually. I hope I haven't confused you even more. I've gotten to the point where I'm about to confuse myself! I'm still learning this stuff: A couple of months back, when I first came to this forum, I was where you are now: Pretty ignorant about how walls block sound. I've learned enough to be dangerous now, so I hope I got my explanation right! But if I didn't get it tight, then don't worry: one of the real acoustic experts will shoot me down, real quick. Of that you can be sure. There is little mercy here for folks who screw up with their posts about the basics of acoustics! So if you see me getting roasted in a flame from Andre or Ro or someone, then ignore the above and listen to them. But if I'm not smoking and crispy in a couple of days, then the above is probably accurate, and safe to listen to! :) That's one of the great things about this place: bad theories don't stand long. They get whacked into submission, real fast, with blunt force. Yeah, it hurts your ego, for sure, but what the hell: at least you learn how to build it right, and that's all that matters. And even though the guys here might seem to be harsh and rough at times, they mean well, and they only have one interest at heart: Helping the rest of us to understand acoustics, and build our rooms the right way, so they actually work the way we want them to. - Stuart -

"By adding mass to the floor will transmission be reduced?" My assumption is yes. Adding any amount of mass anywhere would reduce transmission some. A few people agree. Others state that adding mass will CAUSE MORE problems. (ie - enhance transmission) This is confusing. Perhaps it's not black and white.

We are progressing! Adding mass improves isolation. Adding gaps makes it worse! Andre

Also since I plan to use clips and hat channel I shouldn't be in danger of blocking the ventilation and would retain a "two- leaf system." (i think)

Yep, it will be two-leaf... but it wont be true MSM, since the "spring" (the air in your roof space) will be not be contained in a sealed cavity. So your spring will have sprung a leak, so to speak! (Excuse the pun! couldn't resist). Basically, in order to get the full benefit of the MSM system, the cavity needs to be sealed: If you poke holes in it (vents) then it isn't sealed any more. I really can't tell you how much of an effect that will have on your isolation, but I'm sure Andre can. What I do know is that in order for the air to act as a spring, it has to be contained in a sealed space, so that it can be compressed by the sound waves. If there is no seal, then there is no spring. I think. - Stuart - (EDITED to fix spelling errors that made the above hard to read!!!)

Soundman2020 wrote:

What I do now is that in order for the air to act as a spring, at has to be contained in a sealed space, so that it can be compressed by the sound waves. If there is no seal, then there is no spring. I think.

? http://forum.studiotips.com/viewtopic.php?t=1198 Andre

Thanks for the efforts to move me a bit closer to the goal. I think I have a solid understanding of a few terms, principals, and practices. Now... what to do? That's something that will require more consideration. :horse: :lol: Thanks again. Joe

? http://forum.studiotips.com/viewtopic.php?t=1198 Andre

See what I mean? 22 minutes, and Andre is keeping me honest! :) OK, Andre, its time to update my understanding: I do understand that a leaf does not need to be sealed air-tight to be a leaf. But I thought it DOES need to be sealed in order to act properly as MSM? If the air is not sealed, then how can it be compressed and act as a spring? I understand the concept of air stiffness (I think!), and yes I realize that air has stiffness, regardless of whether or not it is sealed in a cavity, but I thought that you need the "A" in "MAM" (the air-gap) to be air-tight, so that can be compressed and act as a spring? Or is it that the stiffness alone or air is good enough for it to be a spring, even if the cavity is not sealed? So if that's not necessary for MSM, then why do we bother sealing our walls so tightly? - Stuart -

Soundman2020 wrote:

Or is it that the stiffness alone or air is good enough for it to be a spring, even if the cavity is not sealed?

If you are driving in your car at 80 kph and put your hand out the window do you feel nothing? The sealing affects the frequency, not the coupling.

So if that's not necessary for MSM, then why do we bother sealing our walls so tightly?

Think of heating insulation in a building. What good is insulation if cracks are not sealed? Where air can go, sound can go, and does. MAM affects lf TL sealing hf. Have a look at fig 20 in [NRC IR 818. The opening is lager than what we are talking bout, but the idea is there. IR 818 is bit longer to fill your evening. Andre

Does insulation count as a mass? (I guess not) When counting leafs, is it necessary for defining the leaf that the material to be parrallel, solid, and seperated by an airgap? (guessing Yes)

When counting leafs, is it necessary for defining the leaf that the material to be parrallel, solid, and seperated by an airgap? (guessing Yes)

No. No. Yes. :) In other words: Parallel doesn't matter. A non-parallel surface separated by an airgap is still a leaf. So, for example, the roof deck itself is still a leaf, even though it is angled at, say, 30 degrees to the ceiling. Hmmmm... I may be wrong on this, but I believe that "solid" doesn't matter, to a certain extent, depending on your definition of "solid". It's the mass that matters. For example, a heavy sheet of thick rubber hung inside your wall, with an air gap on both sides, would still be a leaf. Andre? Is that correct? Air gap does matter. If there is no air gap between two layers of material (for example, sheetrock pressed up tight against plywood), then it is just one leaf. So, basically what makes a layer of "something" into a leaf is just that there is an airgap between it and the next leaf. - Stuart -

Part of my reason for the question is related to the concept of 703 as part of a subfloor. For example in the "Ply-GG-Ply-703" design, would the 703 be part of one leaf or would it constitute a gap between seperate leafs?

JoeNovice wrote:

Part of my reason for the question is related to the concept of 703 as part of a subfloor. For example in the "Ply-GG-Ply-703" design, would the 703 be part of one leaf or would it constitute a gap between seperate leafs?

The insulation is considered part of the air. This would be true only for a short period. As the 703 begin to compress and is no longer able to revert back to the initial state it was in, this begins the process of short circuiting the situation you suggest. Not that it would matter much. Anything you do in this upper area with framing is going to create a drum head effect, even with 703. Not only that, if there is a ceiling below your floor, you also create a three leaf. There goes your lf downstairs:) Mass is what you are looking for. It is the on going problem when you remove the damping effects of the earth and the mass of concrete/brick. It may be one of the areas where reality meets good judgment and a compromise is made?

xSpace wrote:

Anything you do in this upper area with framing is going to create a drum head effect, even with 703. Not only that, if there is a ceiling below your floor, you also create a three leaf. There goes your lf downstairs:) Mass is what you are looking for. It is the on going problem when you remove the damping effects of the earth and the mass of concrete/brick. It may be one of the areas where reality meets good judgment and a compromise is made?

Then the reason for NOT "floating" (in the loosest sense of the term) upstairs is to avoid the 3-leaf scenerio. Would it make sense to add mass DIRECTLY to the current floor, thus retaining a two-leaf? How about adding layers of Green Glue and 1/4 plywood? (original floor, GG, 1/4, GG, 1/2, corkboard, Finishing Floor) Flanking would be an issue but the floor should have a higher TL value and lower resonance frequency. (I'm guessing)

If you are driving in your car at 80 kph and put your hand out the window do you feel nothing? The sealing affects the frequency, not the coupling.

AaaaHAAA! OK, not I got it! That makes perfect sense. So, I guess from the point of view of a sound wave going at 343 m/s, air is an awful lot stiffer that we tend to think about!!! The term "sound barrier" at what it means to airplanes, comes to mind. Man, you should teach this stuff for a living, Andre! :) You always manage to explain it in an easy-to-understand manner.

Think of heating insulation in building. What good is insulation if cracks are sealed? Where air can go, sound can go, and does. MAM affects lf TL sealing hf. Have a look at fig 20 in [url=http://irc.nrc-cnrc.gc.ca/pubs/ir/ir818/ir818.pdf][NRC IR 818/url]. The opening is lager than what we are talking bout, but the idea is there. IR 818 is bit longer to fill your evening.

WOOOOHOOOO!!! Major Gold Mine Alert! That's an EXCELENT document, Andre! It sure will fill my evening! And my day too. Thanks! Fantastic stuff in there. Very much worthwhile! The fan thing explains it perfectly. It's just so clear when you see the data like that. It's all making more and more sense, as the days go by... - Stuart -

JoeNovice wrote:

Then the reason for NOT "floating" (in the loosest sense of the term) upstairs is to avoid the 3-leaf scenerio. Would it make sense to add mass DIRECTLY to the current floor, thus retaining a two-leaf?

The reason for not floating is that the structure cannot support the additional weight. In order to compile enough density you would wind up placing an enormous amount of stress on the building. The thing is, all things should be equal. So if the best you can do is two sheets of 5/8 inch rock on the wall, having two sheets of MDF on the floor is a near match. It's not perfect, but it's not something to loose your shirt over. So, yes, adding mass to the floor directly is a good idea. Andre agreed with this already.