basement practice space

[natexsteele]

Hello, hoping to get some feedback on a project I am about to start. Still in the planning phase but I’d like to get it done by early summer. I have an unfinished bedroom in our basement that I would like to turn into a “soundproof” drum/band room (lets say 120db max). I wont be doing any recording and my main concern is to not disrupt the other members of the household, incuding our newborn baby. The room dimensions are 11’ 8’x11’5 1/2” and 7’1/2” tall. There is a 36”x60” egress window and a 2’x5’ closet.

Here is my plan

MDF HVAC baffle boxes in the ceiling for the incoming and outgoing air.
Resilient clips w/hat channels on the ceiling
Putty pads around all outlet and light switches
MLV hanging on the walls stapled to the studs
Resilient clips and hat channels on the walls over the MLV
Two layers of drywall w/ green glue in between on ceiling and walls (1/2” then 3/8”) with acoustic caulk on all appropriate seams
Two layers of isoWindow treatment on the egress window (http://isostore.com/shop/product/isowin ... l-windows/)
Communicating doors, I’ll probably use two of these: http://isostore.com/shop/product/isodoo ... tion-door/

Anyone have thoughts on this? Anything I’m missing? My main concern is the HVAC. Will I be able to fit the Baffle Box in the ceiling without using a bulk head, im using standard 12” ceiling joists and I’m hoping to fit the box in between the joists. I know HVAC is super complicated, so I hope im not doing anything to limit the rooms breathability by installing the baffle boxes.
my other concern is flooring, im not planning on doing anything to the floor, as its a concrete basement. just some carpet and rugs. my budget is around $5-7K USD.
let me know if there are any details i'm missing
thanks!

[Gregwor]

There are a few things that went through my head reading your post:
1. Hat channel does not offer a transmission loss as high as a fully decoupled system
2. Hat channel is lousy at isolating low frequencies
3. Putty pads probably won't have enough mass and all of your outlets/switches will probably be weak links in your isolation system
4. MLV is super expensive and you're probably better off spending that money on studs to build a fully decoupled system
5. You didn't mention removing any existing drywall yet in your diagram, it shows a frost wall in front of what appears to be concrete and there are closets framed... so I assume there is drywall up?
6. The ISO window you linked will provide ~<50 dB of transmission loss. With 120 dB inside the room, presuming their system works perfectly as advertised, you're still getting 70+ dB outside. That = mad neighbours and cops called.
7.

The IsoDoor Basic is well suited for any wall with an STC rating of 40 or lower

That means that their door is only capable of providing 40 dB of transmission loss when installed perfectly. That's not very good. And even worse than their window system will provide. That means that outside of your room will be 80 dB. That's LOUD.
8. Jamming bands = hot sweaty people with equipment that puts off lots of heat. And remember, this will be an air tight room. You will need a MINIMUM of 6 air changes per hour, preferably way more.. like 8 or 10. That means a lot of air movement. Luckily you do not need slow moving air. Sadly, you will need your HVAC silencers to provide you with adequate insertion loss (insertion loss = decrease in dB due to a sound attenuating device).
9. Can your existing air handling unit provide this extra CFM that probably wasn't taken into account when designing the HVAC system for the home? I'll repeat myself and say that this is not going to be like a normal band jam room, it will be air tight and NEEDS fresh air.
10. You already have low ceilings.
11. Silencer boxes are large.
12. Where will your supply and return silencers penetrate your leafs (concrete all around the room)
13. To get 6 air changes with your 941.3 cubic foot room, you'll need 94.13 CFM which means you need to supply the room via a 6" round duct that has 28.27 square inch cross sectional area. Your silencer boxes need to have at least 3 baffles in them with 1" duct liner throughout. The boxes need to double it's inlet cross sectional areas and maintain that size throughout all the way to the register (that means that any duct work after the silencers must be that big as well. That = 56.59 square inches. So, inside the duct liner, you could have let's say a 6" X 10" path. To zig zag through the box, you'll have to have that 6" go back and forth, so ultimately, that's 12" X 10" interior dimensions. Add and inch of duct liner all around that, so add 2" do those dimensions. Plus, you will need two layers of 5/8" drywall, not 1/2" and 3/8" in order to achieve baby sleeping on a different floor type levels. That means in order to maintain that mass with your silencers, you'll need the silencers made out of 1" OSB. So add another 2" to your box dimensions. Your exterior dimensions of your box will be 16" X 14". Fitting those inside your room or floor joists above your room will likely be impossible as you'll need one of each leaf for supply and one on each leaf of your return. Granted, you only need to have that impedance mismatch (doubling the cross sectional area) in your inner leaf silencers. So, your outer leaf silencers can be much smaller.

One of the pros could maybe give more solid advice than this but, what I would consider doing if I were you is:
- tear off any drywall within the room that exists. Leave the drywall in the room to the left of the picture and actually add a layer of 5/8" drywall to that rooms wall that is back to back with your band room. You need to have as much mass (drywall is the cheapest mass you can get) for each leaf as you can get.
- Build an inside out room for you band room. This will benefit you in multiple ways. You will want it to sound much better than pure chaos when you jam. Having insulation facing you instead of rigid drywall will clearly sound MUCH better. You will utilize as much of the space as possible with this construction method. It's been proven over and over. You can even make the room look awesome and ultimately even tune the rooms sound with slats of wood on the walls.
- Block off the window. You legally only need windows if it's a bedroom. And well, this isn't a bedroom. If you quit music, you'll probably want to tear this all out anyway, so you can get your window back then.
- Use the existing closet to hold as many of your silencers as possible. I'd have to draw up your plan in SketchUp to see, but maybe you could fit ALL of your silencers in there! You could then run 1 rectangular duct along the ceiling to the far right of the picture as you want your supply and returns to be on opposite ends of your room. This isn't a bad thing as you can just frame up a sort of bulk head and stuff light insulation around the duct work which will act as a bit of a bass trap anyway, so that's rad.
- Build your own awesome doors to actually get good transmission loss or buy two of those ones you linked. Building a room in a room will allow you to have two doors which will make a true MSM system which will = awesome isolation.
- Build a box out of 1" OSB for any electrical penetrations and seal it with backer rod and caulk.

If you do this all yourself, you can probably build it within your budget. You won't need any fancy wood or extreme labour costs. Those doors will be your biggest expense.

I hope this gives you some things to consider. Like many threads on this forum, people will try and go the cheaper/easier route and then have horrible isolation results. They end up tearing it all out and doing it right. You might as well do it right the first time.

I'd love to see you draw this all up in SketchUp and see if we can help you find room for your silencers and stuff!

Greg

[Soundman2020]

Hi there "natexsteele", and welcome to the forum!

Adding to what Greg already said, here's some additional comments:

I have an unfinished bedroom in our basement that I would like to turn into a “soundproof” drum/band room (lets say 120db max).

Right. Drums can indeed hit 120 dBC (Decibels sound pressure level, measured using the "C" weighting curve, which is important). So you know how loud you are: now you need to figure out how quiet you have to be, also in terms of decibels. The difference between those two number is the answer to the question "How much isolation do I need?". With that number in hand, you can then look at construction techniques and construction materials that will get the amount of isolation you need. Right now, you are sort of "guessing" at how to build your place, but that's not a good way of doing it: far better is to first figure out what needs to be done, then design accordingly.

I wont be doing any recording and my main concern is to not disrupt the other members of the household, incuding our newborn baby.

Congrats on the newborn! ! So your goal here is to determine what level of drums sound would wake your baby, and what level of drum sound would annoy the rest of the family, but actually measured in terms of decibels. That's the basis of what you need to do here.

MDF HVAC baffle boxes in the ceiling for the incoming and outgoing air.

Right! But the design of those silencer boxes depends on the overall isolation design. You need to know how many decibels of isolation you need, which in HVAC terms is called "insertion loss", so you can build those boxes correctly. You also need that number to determine how many silencer boxes you need: for low to moderate isolation, you can get away with just one silencer in each duct, but for high levels of isolation you need two: one on each leaf penetration.

Resilient clips w/hat channels on the ceiling

As Greg pointed out, that will get you some isolation, yes, but not as good as if you build a properly decoupled ceiling.

Putty pads around all outlet and light switches

Once again, if you only want low to moderate isolation, that can work, but if you need high or extreme isolation, you would be much better off by NOT having any holes in your walls at all! Instead, do "surface mounted" electrical installation, on top of the drywall, not with huge holes chopped through it.

MLV hanging on the walls stapled to the studs

I'm not sure if you have compared the price-per-square-foot of 1/4" MLV against the price-per-square-foot of 5/8" drywall? If not, now would be a good time to do that. As Greg mentioned, MLV is hugely expensive. It is often hyped as some type of magical solution for isolating rooms, and the truth is that it does indeed work! It works because it is "mass" (that's what the "M" stands for). But the other truth is that there are plenty of other building materials that will give you the same mass for much less money. Drywall, for example. Or plywood, OSB, MDF, fibber-cement boards, and several other options. Here's the thing: sound waves don't care how much you PAY for your mass! The price tag really doesn't impress them at all. It turns out that sound waves can't read price tags, and all they care about is the actual mass. It's the number of pounds-per-square-foot that matters to the sound waves, not the price tag. Here's the equation for figuring out how much isolation you will get from ANY single-leaf wall, no matter what it is made of:

TL = 14.5 log M + 23 dB

Where: M = Surface Mass in lb/ft2

That's it. Complete, entire equation, and it has one single variable in it: mass. There's no place at all to plug in the price tag, or credit card balance: Just mass.

So, here's the rule: Go with the cheapest mass that will do the job! In most places around the world, that turns out to be plain old drywall. High mass, low cost, with the added benefit that it's easy to work with. I don't know if you have ever tried to install MLV, but if not, take it from someone who has: it's a huge pain!

Resilient clips and hat channels on the walls over the MLV

Bad idea. That would leave a very thin resonant cavity in your wall, which will have a high resonant frequency.... implying that it will trash your isolation. If you want to use clips and hat channel, then you need a very large, deep air cavity behind it to get the resonant frequency down low enough that the wall really can isolate.

Two layers of drywall w/ green glue in between on ceiling and walls

Right! It seems that you do want high isolation, of that's your plan.

(1/2” then 3/8”)

Ummmmmm... WHY? It's a myth that you need to have two different thicknesses OK, maybe I should rephrase that to clarify: it's a partial myth. It's actually true that having differing thicknesses can improve isolation due to the impedance mismatch at the interface between them, .... BUT! The difference isn't big enough to be worthwhile when you compare it to hos much isolation you would get from just having BOTH panels the same thickness as the thickest one.

Also, 1/2" drywall and 3/8" drywall are too thin for what you need. Way too thin. What you should have is at least two layers of 5/8" fire-rate drywall. That's a lot more mass, and therefore a lot more isolation. The "fire rated" here is not becuase I think your studio will set on fire one day (hopefully not!) Rather, it's simply because fire-rated drywall is usually a bit heavier than normal drywall, and "heavy" is your friend here.

Two layers of isoWindow treatment on the egress window

You should probably add a layer of unicorn tail hair, and another of pixie dust! Sorry.... Jokes aside, take a look at that equation above one more time: What matters to sound waves is MASS, and plastic (acrylic) has very low mass. That will do basically nothing to isolate drums, and in fact could make things WORSE, since it creates a then resonant air cavity again, which will trash your isolation.

Communicating doors, I’ll probably use two of these:

nearly US$ 3 grand for a pair of doors is pretty steep! You can make them yourself for a LOT less than that. One of my customers in Australia made a pair that I designed for him, for much, much less than half of that, and they are extremely effective. He teaches drums in his studio, so he's in a worse position thatn you are, as he has not one but TWO drum kits going full bore inside his place.

Anything I’m missing? My main concern is the HVAC. Will I be able to fit the Baffle Box in the ceiling without using a bulk head

You are absolutely right to be concerned about HVAC: It's a major part of studio design, and often overlooked. It's great that you took this into account from the start! But there's a little more to it that what you are imagining...

im using standard 12” ceiling joists and I’m hoping to fit the box in between the joists.

What is the spacing between those joists? Are they 16" OC, or 24" OC, or something else? 24" is probably doable. 16.... mmmm..... maybe not.

Here's what we did for that same studio I mentioned above, in Australia. In this case, I did design the HVAC system so that hte silenver boxes could fit between the joists, and it worked, but it wasn't easy. Here's one of the silencer boxes being installed:

Being raised into position on a lifter:

BRAUS-ISO-silencer-box-going-in-SML.jpg

In place:

BRAUS-ISO-silencer-box-in-place-ENH-SML.jpg

Another view, from a different angle:

BRAUS-ISO-silencer-box-in-place-02-ENH-SML.jpg

As you can see, it fits between the joists, but it is still decoupled from them. There's a clear gap all around, and the box rests on carefully calculate resilient pads, on top of the high-strength straps. It does not touch anything.

Here's a view from below, with the camera laying down on the floor, looking up vertically, after most of the inner-leaf ceiling is in place. There's just one module of ceiling that is not yet installed, but you can clearly see how the silencer is mounted here, and how the "sleeve" comes through the inner-leaf ceiling (also without touching it!).

BRAUS-ISO-silencer-view-up-from-floor-SML-ENH.jpg

The register is not yet on in that pic. You can see the flex duct on the other end of the box, which leads to the other silencer box in this path, where the duct passes through the outer-leaf. (As I mentioned, in this case he needs high isolation, so he has to have one silencer on each wall penetration).

So yes, it can be done, but it wasn't easy to calculate the dimensions of that box to get the flow rate and speed correct while still fitting in between the joists.

I know HVAC is super complicated, so I hope im not doing anything to limit the rooms breathability by installing the baffle boxes.

Not at all! You are definitely doing the right thing, for sure! But you do need to do the math, to ensure that you are getting the correct flow rate (air volume) at the correct flow velocity (air speed). If the speed is too high, it will make an audible "hissing" noise, and if the rate is too low, you won't get enough air. so you have to do the math to get those correct.

my other concern is flooring, im not planning on doing anything to the floor, as its a concrete basement.

Excellent! That's the best possible floor for a studio.

just some carpet and rugs.

Right, but skip the carpet: leave the concrete bare across most of the floor, and just put down the rug where the drum kit will actually be, to keep it all in place.

- Stuart -

[natexsteele]

OK, wow looks like there is a lot i havent thougt of. couple of clarifications. the space is completly unfinished, acutally to be 100% accurate it is un-started. it is part of a remodle that we are starting at the end of the month. with that being said, all the engineering permits have been submitted and are pending approval, any changes to the overall structure would set us back in that process.

im surprised to hear that the clips and hat channels are not very effective, everything i have read tells me otherwise, but i trust your opinion. what i'm understanding is that the small gap that it creates would actually turn the wall into a drum head (so to speak)? would insulation behind the channels change this? would using resilent channels work better or is that essentially the same thing?

regarding the window, i dont really have the option of drywalling over it as the city inspector will be giving final approval. getting creative, perhaps the isowindow treatment (removable for the inspector) with some MLV layers glued on the back in coujunction with a removable barrier over the egress hole outside (something sand filled or concret slab?)

so i guess the question of how quite i want to be is difficult, i dont have measuring equipment and even if i did i wouldnt be able to use it as the drum set has yet to be purchased. in unscientific terms, i would like people in the upstairs to be able to watch tv or have conversations while practicing. Full "band practice" will be only once or twice a week and will not go late into the night.

outlets and switches. this is tricky, my wife probably would not sign off on external conduit with surface mounted outlets. would doubling up or tripling up on the puddy pad be worth it? are there other products that could help seal off the holes in the wall?

more questions to follow, (i should probaby get some work done today LOL)
Thanks again for both of your responses

[Gregwor]

im surprised to hear that the clips and hat channels are not very effective, everything i have read tells me otherwise

It's not that it doesn't work. It actually does work as advertised. For the level of isolation you are describing, it just doesn't work THAT good. The only way to provide the sort of isolation you're describing is to fully decouple the walls and ceiling of your jam room from the rest of the house (minus the concrete floor)

regarding the window, i dont really have the option of drywalling over it as the city inspector will be giving final approval.

Unless it's different where you live, my city inspectors told me that legally, the only reason you ever need a window, is for a bedroom. If your room was initially built as a bedroom (which you submitted it as in your permit), cool. But the function of the room has changed now and it's a band rehearsal room where no one will ever sleep (unless your wife kicks you out of bed). You can easily make a quick call and inquire. Just tell them exactly what you're doing with the room.

my wife probably would not sign off on external conduit with surface mounted outlets

I'm too tired to look, but I don't think anyone mentioned external conduit. Surface mounted outlets, yes. However, these would look flush to the wall once your acoustic treatment was up. This method (wire sticking through the drywall, sealed off with backer rod and caulk to achieve the same surface density of the wall that it has penetrated) is only to allow the smallest penetration possible.

would doubling up or tripling up on the puddy pad be worth it?

You could look at the mass of the puddy and figure out how much it would take to equal the mass of the wall that the outlet penetrated. But I figure it would take a lot and would be suspect to not being perfectly sealed. I'm just skeptical.

Greg

[Soundman2020]

im surprised to hear that the clips and hat channels are not very effective, everything i have read tells me otherwise,

As Greg already mentioned, they DO work. They just don't work as well as a fully-decoupled inner-leaf wall does. There's a limit to how much isolation you can get from clips with hat channel (or resilient channel), and for what you need, that limit is not good enough. For someone who needs modest to decent isolation (let's say around 40 to 45 dB, give or take a few), either RC or clips + hat is fine: it can do that. But once you need isolation beyond about 50 dB, you've hit the limit of what can be achieved. That's when you need to move to fully-decoupled framing. It's sort of the same as the issue with staggered studs: You can get more isolation with a staggered-stud wall than you can with a single stud wall, for sure, but there are limits there as well, becuase there are still flanking paths at the top and bottom of the wall, where the studs are on the same plates, and fully connected, mechanically. If you need more isolation that can be achieved with a normal staggered stud wall, then there's no point just adding mass to the wall, as it's a case of diminishing returns: You'd need to add a huge amount of mass to get anywhere, but putting much less mass on a separate from will work better. That's the issue here with clips: You CAN get get isolation with clips, but not extreme isolation. An with clips, you CANNOT add more than three layers of drywall, since there are structural limitations as well: clips simply cannot support the extra mass.

what i'm understanding is that the small gap that it creates would actually turn the wall into a drum head (so to speak)?

Welllll,,,, sort of, but not really! It's a bit complex, but basically you have to stop thinking about the individual parts of the wall, and understand that all the parts working together act as one single resonant system. In other words, the entire wall will resonate at one specific fundamental resonant frequency. If you happen to play that frequency inside the room, then the wall will not only allow it through to the other side, but will actually AMPLIFY it, so it is LOUDER on the other side. And it's not just that one frequency: the effect extends out to a range of frequencies centered at that resonant point, and that range goes all the way up to 1.414 times the resonant frequency. For complex mathematical reasons, the resonant peak amplifies everything up to 1.414 x F0. At that point (1.414 x F0), the gain is unity, so it neither amplifies nor attenuates. However, above that point, for high frequencies, the wall starts isolating better and better. At twice the resonant frequency (2 x F0), it isolates quite well, and at at 3 x F0 it's doing very nicely. The higher you go, the better it gets. In fact, the isolation curve, or more correctly the "transmission loss" curve, always looks something like this:

typical-MSM-transmission-loss-curve-2.jpg

The shape is always the same. The tilt might change for different types of construction, but the shape of the TL curve is always similar to that, due the laws of physics.

You can see the "resonant dip" at around 100 Hz in this particular example. That's the point where the wall provides the least isolation, because it is resonating in sympathy with that frequency. It is "tuned" to that frequency. In this case, it is providing a little tiny bit of isolation (around 10 dB: about the same as a thin sheet of cardboard) because it is damped internally with abundant insulation. If it did not have that insulation, it would have "negative" isolation (less than o dB): in other words, it would amplify. And considering that things like drums and bass guitars put out a lot of energy around 100 Hz, this wall would be pretty lousy for a studio!

So, the curve always has the same shape: Then how do you get more isolation? You move the curve over to the left! If you can slide that entire curve to the left, such that the resonant dip gets down to, say, 60 Hz, then you can see that the isolation for all other frequencies gets better! If you could do that, then the wall would isolate for drums much better... but still not so much for a five.string bass, that goes down to 36 Hz. So then, how about if you slide that curve over to the left even more? Make the resonant dip occur at, say 15 Hz, where it is way below the frequency of ALL musical instruments? Yep, that is, indeed, the solution. Slide the curve over far enough, and the wall will isolate for ALL frequencies.

That leads to the next question: How do you slide the curve over to the left? What do you have to do to the wall, to make that happen?

Well, considering that the curve is really showing you how the wall is tuned, what you have to do to "slide the curve", is to re-tune the wall! And to do that, you need to adjust one of the factors that changes the resonant frequency. It turns out that there are only two factors that you can adjust here (OK, in reality three, but we'll just look at the two big ones for now). Those to factors are the mass of the wall, and the size of the air gap. Make the wall heavier (more massive) and the curve slides over to the left. Make the gap between the two "leaves" of the wall bigger, and the curve slides over to the left. It's that simple. There's a set of very simple equations that you can use to predict what that curve will look like, or rather, how far over to the left you have moved it. By choosing the size of the air gap and the mass (density) of the materials carefully, you can tune the wall any way you want.

There's another benefit to adding mass and increasing the air gap: the curve not only slides to the left, it also slides UP the page a bit. so you get more isolation from that point of view as well. In fact, as you add even more mass, the curve tends to "flatten out" a bit, at a higher level up the graph.

OK, so now that I've explained that, I can also explain why putting clips+channel+drywall directly over MLV is a really bad idea. Think about it: by doing that, you have created a very SMALL air gap, between the MLV and the drywall. Much smaller than the air gap in a normal wall. So, if INCREASING the air gap moves the curve to the left, guess what happens when you DECREASE the air gap? Yup: the curve moves to the right..... And for very small air gaps, it doesn't just slide a bit to the right: it makes a mad dash to the right! The resonant frequency goes way up, and the isolation is lousy all across the bottom of the spectrum.

In fact, for a scenario where you have a sheet of 1/2" drywall on clips over a sheet of MLV; the resonant frequency is about 180 Hz, so the wall does not isolate until about 250 Hz, isolates reasonably above about 360 Hz, and isolates well starting at about 530 Hz. In other words, it isolates terribly across the entire low end of the spectrum, and also the lower part of the mid range!

would insulation behind the channels change this?

That's the "third factor" I mentioned above, in addition to mass and air gap. Adding suitable porous absorption inside the cavity, such as insulation of the correct density, does increase the isolation. It does that in several ways, but basically by acting as a "damper" on the resonances inside the wall. So yes, putting insulation in there would help. However, the situation is so bad that the "help" isn't very useful. Filling that entire thin cavity with excellent insulation would decrease the resonant frequency down to about 125 Hz, so the wall would not isolate until around 175 Hz, isolate somewhat at 250 Hz, and isolate well at around 375 Hz. You improved it a lot, yes, but it is still lousy. Consider that a huge chunk of the energy put out by drums, bass guitars, keyboards and electric guitars (among others) is below 200 Hz, and you'll see that this wall is no use for a studio.

In short, you need a much larger air gap. A thin gap, such as the depth of the clip plus the hat channel, is way too thin.

would using resilent channels work better or is that essentially the same thing?

It's essentially the same thing. Worse, in fact, in your scenario of having it directly over MLV since RC is thinner than the combination of clip+hat channel: the air gap is even smaller!

RC (or clips+hat) is only useful when you put it directly on the studs, with nothing behind it. That increases the air gap to be the full depth of the studs, plus the depth of the clip+hat (or RC). With that much air gap, the isolation improves greatly.... But still not as much as you can get by building a separate frame for that leaf.

regarding the window, i dont really have the option of drywalling over it as the city inspector will be giving final approval. getting creative, perhaps the isowindow treatment (removable for the inspector) with some MLV layers glued on the back in coujunction with a removable barrier over the egress hole outside (something sand filled or concret slab?)

I wound suggest just building a wall across there, with a sliding glass door in it. That does not block your egress path (which is probably a legal requirement), so it should pass inspection. It also adds mass (glass has plenty of mass) and an air gap...

so i guess the question of how quite i want to be is difficult, i dont have measuring equipment and even if i did i wouldnt be able to use it as the drum set has yet to be purchased.

That's fine: You can estimate how loud drums are: it's a known factor. Consider a level of around 115 dBC as typical for drums played normally. That's not too much of a problem. But you DO need the meter to figure out the other side of the equation: "How quite o I need to be?". That's not something I can tell you, since it varies greatly from person to person, situation to situation, and legal code to legal code. What my family considers "quiet", your family might consider "really loud", or vice versa. You have to actually measure the level that YOU feel is acceptable, in YOUR situation. And you need a decent Sound Level Meter to do that. Set it to "C" weighting, "Slow" response, and take several measurements at various points in the house, when you think the ambient level is good. Get someone to turn up the radio or stereo or TV in another room, playing bass-heavy music with lots of drums, until YOU think that the level is no longer acceptable, and see what that measurement is. Turn down the noise until it is just on the very edge of being acceptable. Do that in several locations, average the results, and that answers the question. Subtract that number from the 115 dB number I gave you earlier, and that's roughly the amount of isolation you need. Based on that, you can design your wall for the level of isolation you need, by "sliding the curve" over until it gets where you need it to be.

outlets and switches. this is tricky, my wife probably would not sign off on external conduit with surface mounted outlets.

I didn't mention external conduits! I mentioned a "surface mounted electrical system". Such as those made by Legrand, Kalop and others. They look pretty good, actually:

surface-mount-electrics-01.jpg

surface-mount-electrics-02.jpg

The raceways come in many sizes and shapes, to fit all tastes and all needs:

surface-mount-electrics-03.jpg

And you can even get some types that are disguised to look like crown molding:

surface-mount-electrics-04--crown-molding.png

For high isolation, you can allow yourself exactly ONE single penetration of the wall, to bring in the power feed. From there, it is distributed around the room using this type of surface-mount system, or if you build your walls "inside out", then it can be concealed behind the visible surface of the wall, which is not solid, massive or rigid...

more questions to follow,

- Stuart -

[natexsteele]

OK, lots of more great information. UPDATE: i will be speaking to our contractor to talk about framing in walls and ceiling complety decoupled from the existing structure. 3 out of the 4 walls are concrete: how far of a gap will i need to sufficently "move the curve to the left" as well as up? i was thinking a 1 inch gap between the concrete walls and the new plate.
Would the clips and hat channels then become redundent? I would still want to use the Green Glue with the recommend two layers fo 5/8 drywall, correct?

I didn't mention external conduits! I mentioned a "surface mounted electrical system". Such as those made by Legrand, Kalop and others. They look pretty good, actually:

got it, yeah i see no one mentioned conduit, i must have imagined it. i'll look into the surface mounted options

I wound suggest just building a wall across there, with a sliding glass door in it. That does not block your egress path (which is probably a legal requirement), so it should pass inspection. It also adds mass (glass has plenty of mass) and an air gap.

unfortunately this will not pass code, there needs to be an unobstructed path to the egress, a slidding glass door would count as an obstruction. I only happen to know this because we wanted to put pocket doors in another part of the basement to keep tv room separate from bed room and it was a no-go

You can make them yourself for a LOT less than that. One of my customers in Australia made a pair that I designed for him, for much, much less than half of that, and they are extremely effective. He teaches drums in his studio, so he's in a worse position thatn you are, as he has not one but TWO drum kits going full bore inside his place.

you are right, i was thinking the doors would be my biggest expense. I'd love some resources on door construction. wasnt able to see much in terms of actual construction on this form.

Not at all! You are definitely doing the right thing, for sure! But you do need to do the math, to ensure that you are getting the correct flow rate (air volume) at the correct flow velocity (air speed).

any resources here on calculating the flow rate?

Thanks again, probably more questions will arise the more i dig into this

[natexsteele]

ok, so i have updated my plans (see attachment below). we are trying to achive a 60-80db reduction. in addition to the 2 layers of drywall with green glue
-we are moving the 3 walls 1" away from the concret wall and a 1" gap between practice room and guest bedroom (on the left)
-walling off the closet to make room for silencer boxes
-surface mounted electrical boxes
-ceiling will be decoupled from the ceiling joists above (see additional attachment) 2 layer of drywall with green glue
-communicating doors (i will be following the "Gervais method" for these)
so what i am still not able to find resources on is basic requirements for baffle boxes. keeping in mind that my only goal is keeping sound in the room. not too concerned with noisy air velocity.
How big do they need to be? and why?
is larger better?
how well do they isolate sound? if I had a very thin and long baffle box (10"x13.5"x 10') would that function as well as a larger box (16"x16"x24")?
also it does not seem that i will be able to fit a silencer on the outside of the room, would i get any better isolation from putting two seperate silencers inside the room?
in the drawing i have the intake and outtake almost on top of eachother with the silencers enclosed where the closet should be. i would like to have an additional vent near the window but i dont think i would be able to fit a silencer in that cavity.
am i even asking the right questions?
THanks

[Gregwor]

In your diagram, you're ceiling construction is not utilizing the inside out method. I highly recommend building the ceiling using John's method. It has been proven time and time again to be the ultimate solution for countless reasons.

For the silencer boxes, without getting super intense with it (calculating heat from equipment and such), you can calculate CFM requirements by knowing 2 variables: room volume and the number of air exchanges you want per hour. Your air changes should be a MINIMUM of 6 per hour. More is better... maybe even up to 10 if your air handling unit and space (for duct work and silencer boxes) permits it. If you don't care about air velocity, then don't even think about it. For the boxes, here are the basic requirements:
- make the boxes have the same mass (surface density) as your walls. So if your walls have 5 lbs per square foot, so should your boxes. By the sounds of the materials you are using for you walls, you're probably alright using 1" thick MDF for your boxes.
- use proper duct liner that is 1" thick.
- design your boxes to have at least 3 baffles in them. More = better.
- you want the box to be double the cross sectional area of the supply duct. The return will be exactly this, but backwards.
- don't use soft transition duct adaptors to go from your air handlers trunk to the box. You want a drastic sudden change as soon as the air hits the box. So if you have an 8" round duct, just run it straight into the box with an 8" round hole.
- You want the outlet of the box to maintain the same cross sectional area as it is inside the box... or bigger even (which would slow the air down even more)
- you want any penetrations of the wall to be achieved via a wooden sleeve (the same mass and material as the box itself -- ex: 1" MDF). You want to leave the hole in the wall slightly (a few mm) larger than the wooden penetrating sleeve so that you can backer rod and caulk it, ultimately decoupling it while maintaining the mass and hermetically sealing it.

It's really that simple. Basically, figure out how much space you have to work with. It's probably best if you are able to make little stands that hold the silencers (sitting on the floor) so that you aren't mounting the boxes to any walls. If you do mount them to walls, make sure that the outer leaf ones are mounted to the outer leaf, and inner to the inner. To connect any inner to outer leaf silencers, you can use flex duct or a flexible duct adaptor (google DuroDyne to see what I'm talking about).

You are alright using just 1 silencer for supply and 1 for return. But to achieve the desired insertion loss values you are wanting, you'll probably need one on each leaf, making a total of 4 boxes. Like I said before, the closest is a great spot for these, If you can fit all 4 in there, rad. Otherwise you will have to find more spots for them. Sadly, with 1" MDF and 1" duct liner, plus double the cross sectional area of your required duct size (determined by CFM), these get big. So, until you draw them up in SketchUp, you won't know if and how they'll fit. So far, in my personal design, designing these was the biggest pain in the butt. The general design, plus coordinating with plumbers and HVAC dudes to make sure they didn't interfere with joists I needed to pass things through, has been taxing. Luckily, it sounds like you can plan ahead for this like I was able to. Also, for your ceiling joists, you'll probably have to use LVL studs instead of regular dimensional lumber. Here in Canada, it seems the going rate for it 2x8 LVL stud is ~$4 per foot, so it adds up Worth it for safety and to pass inspection though!

I hope that helps. Again, those HVAC calculations are ignoring a lot of things like friction loss and such, but it is the general idea for sure.

Greg

[natexsteele]

thanks for the response.

In your diagram, you're ceiling construction is not utilizing the inside out method. I highly recommend building the ceiling using John's method. It has been proven time and time again to be the ultimate solution for countless reasons.

i assume you are refering to the method where you put drywall/insulation between the ceiling joists? this would be better than a decoupled ceiling? or in addition to the decoupled ceiling?

you want the box to be double the cross sectional area of the supply duct. The return will be exactly this, but backwards.

ok, so what im figuring with this formula in mind, using 6" round duct (area being 28.27 inches squared) i can make a box 10"x14", with 1" MDF and 1" insulation i get an opening with the area of 60 in squared, this should work. right? if the box is 8' long this should give me 8-9 baffles which should provide plenty of isolation.

So far, in my personal design, designing these was the biggest pain in the butt. The general design, plus coordinating with plumbers and HVAC dudes to make sure they didn't interfere with joists I needed to pass things through, has been taxing.

agreed, everytime i think i have this figured out, i realized i am completly forgtetting about a different aspect of HVAC.

So, until you draw them up in SketchUp, you won't know if and how they'll fit.

it will take me a while to get proficent enough in this program to come up with anyting meaningful. downloaded the 30day trail version last weekend and am still quite useless. i'll keep working on it though


Thanks again for your valuable insight.

[Gregwor]

i assume you are refering to the method where you put drywall/insulation between the ceiling joists? this would be better than a decoupled ceiling? or in addition to the decoupled ceiling?

Here is a link from John's recording manual explaining it in more detail:

http://johnlsayers.com/Recmanual/Titles/Acoustics3.htm

You can also use the search function to find some inside out pictures. Here are a few more:

http://www.johnlsayers.com/phpBB2/viewt ... =2&t=19682
http://www.johnlsayers.com/phpBB2/viewt ... rd#p143149

i can make a box 10"x14", with 1" MDF and 1" insulation i get an opening with the area of 60 in squared, this should work. right?

Yep!

if the box is 8' long this should give me 8-9 baffles which should provide plenty of isolation.

I wouldn't use the term "plenty". It will help. If you have enough room for 8 or 9 baffles, why don't you use that space to have 2 separate boxes, one for each leaf, each with 3 baffles? The benefit to this is that you have fully decoupled boxes that each penetrate their respect leaf with a good beefy sleeve. . . I just said beefy sleeve haha

agreed, everytime i think i have this figured out, i realized i am completly forgtetting about a different aspect of HVAC.

Once you get proficient with SketchUp and start getting into detail, you'll have this feeling with every aspect of the build, not just HVAC. But that's the idea of modelling it. Find the problems digitally before picking up a drill.

it will take me a while to get proficent enough in this program to come up with anyting meaningful.

The program take a bit of time to learn but it is awesome. Here's plenty of pictures of where I'm at with my design and lots of pics of my silencers:

http://www.johnlsayers.com/phpBB2/viewt ... =1&t=21436

[Soundman2020]

we are trying to achive a 60-80db reduction.

60 dB isolation is pretty close to the limits of what can be accomplished in a DIY built home studio. It's close to the flanking limit for the building structure itself. You might be able to get that, if you design and build very carefully, and have a decent budget. But 80 dB is out of the question, unless you have a budget with many zeros on the end.

Think of it this way: A typical house wall will get you about 30 dB of isolation. To get 60 dB of isolation, you need to block one thousand times as much energy as that typical house wall. To get 80 dB of isolation, you need to block one hundred thousand times as much energy.... Yes, those are real numbers, mathematically correct and true.

so what i am still not able to find resources on is basic requirements for baffle boxes. keeping in mind that my only goal is keeping sound in the room. not too concerned with noisy air velocity.

They go together. That's sort of like saying "My goal is to drive at 60MPH on the road in my car, but I'm not too concerned if the car has an engine or not"... If you want good isolation, then you need to properly control the air flow.

Also consider this: Why on earth would you want to have 80 dB of isolation for your room, but then pipe in the sound of a hurricane? In a room that is very, very well isolated, even very quite things sound incredibly loud, because there is nothing else to mask them. An air vent with turbulent flow in a room that is isolated to 80 dB (or even 60 dB) is going to sound VERY loud. There's no point in having good isolation if the room is going to be noisy anyway from poor HVAC.

How big do they need to be? and why?

They need to be as big as necessary to allow the correct amount of air flow (volume) and the correct velocity (speed) while also providing the correct insertion loss (isolation). To figure this out, first calculate the volume of air flow that your room will need. Use the general rule of thumb that you will need about 6 to 8 room changes per hour. So figure out the volume of your room, multiply by 6, and that's the minimum air flow rate per hour that you will need. Divide by 60 to get the flow rate per minute. Then use the rule of thumb that the flow speed at the register should not be higher than 300 fpm, and tat will allow you to calculate the cross-sectional area of the register. Work backwards from there, taking into account that you need at least two places where that area changes suddenly by a factor of two (at least), to figure out what the largest cross sectional area will be. That's how large the interior of your silencer box will be. Now allow for 1" of duct liner in each direction, plus the thickness of the box walls that matches the density of your leaf, and you have the final width and height of the box. Length depends on how many baffles you need to get the isolation you need. but allow for at least 3 baffles, each with the same cross sectional area on each side.

That's how big it needs to be. And "why"? Because of the reasons I cited: in order to provide the correct airflow rate and the correct air flow velocity, while providing the correct insertion loss.

is larger better?

In general, yes.

how well do they isolate sound? if I had a very thin and long baffle box (10"x13.5"x 10') would that function as well as a larger box (16"x16"x24")?

That depends on how you design it, and how you build it, and what materials you use.

also it does not seem that i will be able to fit a silencer on the outside of the room, would i get any better isolation from putting two seperate silencers inside the room?

To get extreme isolation, you WILL need two silencer ON EACH DUCT: Total of four silencers: One where the supply dict goes through the outer leaf, one where it goes through the inner leaf, then another where the return duct goes through the inner leaf, and one more where it goes through the outer leaf. For very high isolation, you have no choice.

In your diagram, you're ceiling construction is not utilizing the inside out method. I highly recommend building the ceiling using John's method.

you're probably alright using 1" thick MDF for your boxes.

Probably more like two layers of 5/8" MDF; or even two layers of 3/4 MDF. Finding 1" MDF is hard, and expensive.

- use proper duct liner that is 1" thick.

- design your boxes to have at least 3 baffles in them. More = better.

You want a drastic sudden change as soon as the air hits the box. So if you have an 8" round duct, just run it straight into the box with an 8" round hole.

- You want the outlet of the box to maintain the same cross sectional area as it is inside the box... or bigger even (which would slow the air down even more)

- you want any penetrations of the wall to be achieved via a wooden sleeve (the same mass and material as the box itself -- ex: 1" MDF). You want to leave the hole in the wall slightly (a few mm) larger than the wooden penetrating sleeve so that you can backer rod and caulk it, ultimately decoupling it while maintaining the mass and hermetically sealing it.

- Stuart -

[richroyc]

Hey Natexsteele!

One thing i noticed in this photo is that the new ceiling joists will likely need cross braces as well. Not sure if there is enough room for them from this photo.

wall%26ceiling.png

I did something similar where I pushed the beams up in-between the existing floor joists, but you have to make sure to leave enough room for the cross bracing. Also, forget about the mid-span cross braces, you will likely need what is sometime called a "block-perimeter" on the ends of the ceiling grid. Both there to prevent twisting of the beams.