Rooster studio - new space in existing basement

[missmoo]

Hello kind folks -
We finally have a home of our own and finally making this studio dream a reality. We would love to get some feedback on our plans - and, in particular, the construction details. We've been doing research for more than a year now and believe we have come a long way, but we are really hoping to get an outside opinion on our approach for where the walls meet the ceiling and, beyond that, just get a sanity check on whether our approach will provide the desired reduction in sound transmission (details below).

Location: Massachusetts, suburbs, residential neighborhood, (owned, family with small kids), single family home, victorian built 1900.

Neighbors: Direct neighbors - 25 feet away. But they have limited windows facing us (stairs on that side of their house) and they are always running their central air so their windows are never open. They are not picky. Our other neighbors are not picky either. In fact, they include several professional musicians who are always practicing. Our own children upstairs are the picky ones.

Intended purpose: Music room: 110 db . playing music/recording own band (jazz drummer at moderate volume, unamplified trumpet, electric guitar). We want the music to sound quiet upstairs and outside so our kids and neighbors can sleep. The purpose of the adjacent space (see the plan image) is solely for hanging out and maybe quiet mixing.

Budget: We need to keep the project under 10k. It’s a 10 by 10 room - but has to achieve a certain level of soundproofing (the kids have to sleep). We are also planning to build a cheap 'hangout' space next to the soundproofed room, but it's not a high priority we'll compromise on it (or skip it) if we can't keep both rooms under 10k combined.

Existing basement: Music room will be here. Stone and mortar foundation with interior parge. Existing concrete floor. Ceiling above is pine plank underlayment and nailed strip oak wood floors above. There is a sump pump. This saw that most action when our hot water tank exploded. All the existing equipment will remain in place.

Joists: 2x9 at 16” oc
Span 13’ from the exterior foundation wall to the 7.5x10.5 center beam.
Height is 7’2” to the bottom of the joists.
A structural engineer will check loads for us.

See plan showing existing layout and proposed finish space.

Proposed layout:
It is our intention to only “finish” the 2 spaces. The rest will remain as is - unfinished utility space.

The music room location was selected because that is where we can get the ceiling height the highest and have the best chance at the sound proof ceiling. The hang out area ceiling has a ton of existing cast iron heating pipes that come well below the joists. While we could remove all these pipes and go back with flex tubing, that is not in our budget right now.

We have left a hallway at the back door to the yard. Our sanitary drains and our main sanitary line from our bathrooms comes down and then over through this space and we just need to keep access to it.

Heat: Out heating system is an old cast iron, gravity fed coal burning one that was retrofited with a gas burning furnace. The plumber says it is crazy. We had looked into pulling a zone off the existing furnace because it is literally right there. But it was going to cost 2k. We would have to add another pump, etc. So, we are sort of resigned to electric baseboard.

Electrical: 2 electricians have come by to talk with us. There already is a second panel so we have plenty of room.

Attached information:
1. Floor Plan showing existing stuff of note and what are plan is for the new spaces.
2. Detail 1 : a draft construction detail for the exterior wall at the existing ceiling.
3. Detail 2 : a draft construction detail for an interior wall that needs to deal with some existing pipes...
4. Picture of the area from Detail 2

The attached images provide full detail. But here are a few key aspects of our approach:

1. Ceiling: We are planning to use Whisper Clips attached to the existing floor joists, then the hat channel attached to two layers of 5/8 drywall with Green Glue in between.

2. For the walls, we are thinking staggered stud with two layers of drywall on each side (Green Glue in between).

3. Existing windows: We would like to leave the existing windows in place and construct removable window plugs.

4. For doors, we’re planning to use solid core “super doors” (as recommended in Rod Gervais’ books) but haven’t figured out the details yet (that’s coming in round 2 after your first round of feedback).

that's high level, but again, all the details are in the images. I would love to get feedback on the details.

Questions:
1. What is the best way to deal with these existing pipes and acheive desired soundproofing (even though we aren’t finishing the other utility space)? Does our approach work? How should the walls meet the ceiling?
2. Would isolation clips work better than nailers?
3. At the interior walls, would it be better to have 2 layers of Gb on each side of the staggered stud (as opposed to on just one side)?
4. Should we add mass loaded vinyl at the ceiling (we don’t have much room to spare with regards the ceiling height)? If we need it, how do we integrate it what we are thinking now?
5. Should we treat the underside of the floors between the existing joists with sealant and GB in addition?

Thinking ahead -
Soundproofing at the existing concrete floor. Do we use a strip of neoprene under the sill plate?
Door and door frames
Baseboard heat

Thanks so much!

[missmoo]

I apologize in advance if there is a typical delay of a few weeks for a response... but I'm just getting paranoid that I am not following the proper etiquette and maybe that's why I'm not getting a response. Is there something wrong or missing from my post? I would greatly appreciate if anyone could tell me where I need to provide more detail because I'm dying to get some feedback.

[Soundman2020]

Sorry about that, "missmoo"! Welcome to the forum!

It seems I'm the only active moderator right now, and there's whole bunch of threads line up for me to answer all the time, so somehow I missed yours completely!

Thanks for bumping it. It can indeed take a few days to get a response here, but if it gets beyond that then please do feel free to bump your thread!

OK, on to responding! (Better late than never! )

Neighbors: Direct neighbors - 25 feet away. But they have limited windows facing us (stairs on that side of their house) and they are always running their central air so their windows are never open. They are not picky. Our other neighbors are not picky either. In fact, they include several professional musicians who are always practicing. Our own children upstairs are the picky ones.

Neighbors are important, and so is family, but there are also legal limits on how much noise you can make, so that should be your final goal in isolation. Your current neighbors might be fine, but they also might move and be replaced by more "sensitive" folks, with an itchy trigger finger poised over the 911 button...

So it would be advisable to pick up a copy of the noise regulations from your local municipality (you can probably download it from their web site), and see what your legal requirements are. IT varies from place to place, and normally there is one level for daytime, and another, much lower one, for night.

Intended purpose: Music room: 110 db . playing music/recording own band (jazz drummer at moderate volume, unamplified trumpet, electric guitar). We want the music to sound quiet upstairs and outside so our kids and neighbors can sleep.

OK, so good isolation is high on your list of priorities.

Also, it seems that this is just a rehearsal room, not a true tracking room, or a control room? In other words, just a place to set up a bunch of instruments and jam, without disturbing family / neighbors, but not really with any intention of recording?

Budget: We need to keep the project under 10k. It’s a 10 by 10 room

Sounds realistic. That's about US$ 100 per square foot, which is probably fine. Way too many people drop in to the forum with unrealistic budget expectations: there was a guy on here recently who wants to build a full-blown studio about four times the size of yours, with several rooms in it, and thinks he can do it for one third of your budget!

So your budget is reasonable, but the "10 by 10" dimension is not so reasonable. A square room is not good, acoustically, since all the modes in one direction will occur at exactly the same frequencies as all the modes in the other direction. Even worse would be if you also had a 10 foot ceiling, which would make your room a cube (the worst possible shape). Fortunately, this issue is fairly easy to fix, with suitable design of the isolation wall.

Existing basement: Music room will be here. Stone and mortar foundation with interior parge. Existing concrete floor.

Good start! You already have a fine floor there, and the walls should be good for your outer-leaf isolation.

Ceiling above is pine plank underlayment and nailed strip oak wood floors above.

Not so good: that's a potential big issue, that will need careful attention in your isolation.

There is a sump pump.

Not good! That implies a Bad Thing: Water! You don't want to spend 10 grand on a beautiful room that could then be ruined by water! Is there a problem with damp in your basement? High humidity? Condensation on the walls or floor? One good test is to tape a square of plastic to the floor for a couple of days, and see if you get condensation under it. If so, you have a problem that needs fixed BEFORE you build the studio.

Height is 7’2” to the bottom of the joists.

Ouch! That doesn't leave much room for isolation or treatment. The final finish ceiling is going to be very low.

Joists: 2x9 at 16” oc

Anything up there between the joists? HVAC ducts? Plumbing? Wiring? If it is all clear up there, then there is a technique you can use to save space (height).

But it was going to cost 2k. We would have to add another pump, etc. So, we are sort of resigned to electric baseboard.

Maybe not. HVAC is a big part of studio building, and often is not even on the radar. But it is VERY important: In order to be soundproof (isolated) the room must be sealed airtight. Twice. There will be two air-tight walls around it. So no air will be going in or out anywhere. This is a basic requirement for studio isolation: no air-tight seal means no isolation. So, if you have half a dozen musicians jamming away merrily in a 10x10 space, two things happen: 1) it gets hot, humid, smelly, and ugly real fast. 2) They run out of oxygen, real fast! In other words, HVAC is not a luxury in a studio: it is a basic life-sustaining necessity.

There are two parts to HVAC. There's the "V" part, meaning "ventilation", and the "H-AC" part, meaning "Heating - Air Conditioning". The second part is easy to deal with: A simple mini-split system that both heats and cools will work just fine, and should be well within your budget. One part (the quite part) goes on the wall of the room, where it de-humidifies, cools (or heats). It is connected to the other part (the noisy part) with a couple of copper pipes for the coolant, an electrical cable, and a drain pipe, for the condensate. That's your best bet for the H-AC part.

The "V" part is a bit more complex, but less expensive: you need to bring in a supply of fresh air from outside, and you need to exhaust the same amount of stale air to the outside. You do that using inexpensive flexible ducts, in-line fans, and most important of all, silencer boxes. Since the entire point of sealing the rooms air-tight is to keep sound in, obviously poking huge holes in the walls to get the ventilation ducts through totally screws that up. That's what the silencer boxes are for. They stop the sound while allowing the air through. Basically, they just contain a series of baffles that force the air to take a "long and winding road", while preventing the sound from getting through. You can build those yourself. Not complicated.

So the HVAC part is very, very important, and not too expensive. (But not cheap either).

1. Ceiling: We are planning to use Whisper Clips attached to the existing floor joists, then the hat channel attached to two layers of 5/8 drywall with Green Glue in between.

That's fine for your inner-leaf, but you do still need to totally seal and beef up the existing floor above you, which is your outer leaf, before you hang the inner leaf. Sealing is critical: You cannot leave even a single tiny crack up there. In fact, sealing is the most important thing you can do to guarantee success in isolation. And NOT sealing is the bet way I know of to guarantee failure.

2. For the walls, we are thinking staggered stud with two layers of drywall on each side (Green Glue in between).

That will probably work too, but it would cost you very little extra money or space to do separate stud frames for each side. that would allow you to angle two if the interior walls, which you absolute need to do here, to deal with your "10 x 10" issue.

3. Existing windows: We would like to leave the existing windows in place and construct removable window plugs.

How are you gong to get to the plugs? They will be on the other side of the inner-leaf wall! If you want the light, then just seal those windows air-tight, and put glass in your inner-leaf wall, to complete the isolation plan.

4. For doors, we’re planning to use solid core “super doors” (as recommended in Rod Gervais’ books) but haven’t figured out the details yet (that’s coming in round 2 after your first round of feedback).

Superdoors are one option, but rather expensive (sheet lead is not cheap), and do require very, very close attention to the seals around the edges of the door. A pair of back-to-back doors is another good option.

1. What is the best way to deal with these existing pipes and acheive desired soundproofing (even though we aren’t finishing the other utility space)? Does our approach work? How should the walls meet the ceiling?

Photos! We can't see the pipes from here, so without photos there isn't much to go on!

2. Would isolation clips work better than nailers?

For what? You already said you were planning to use clips and hat channel, so where were you thinking of putting the nailers?

3. At the interior walls, would it be better to have 2 layers of Gb on each side of the staggered stud (as opposed to on just one side)?

For staggered stud and high isolation, yes, you need two layers on each side. The amount of isolation you get is directly related to the amount of mass you put around your room, and also to the size of the air gap between your leaves. Increase mass or gap and you increase isolation.

4. Should we add mass loaded vinyl at the ceiling (we don’t have much room to spare with regards the ceiling height)? If we need it, how do we integrate it what we are thinking now?

Not necessary. MLV is over-hyped and over-sold: it only has some very limited uses in isolation, but you don't need it. Mass is mass, and sound waves don't care how much you pay for the mass. (They can't read the price tag!) So use the cheapest mass that does the job, which is normally plain old 5/8" fire rated drywall.

5. Should we treat the underside of the floors between the existing joists with sealant and GB in addition?

Absolutely! See above.

Soundproofing at the existing concrete floor. Do we use a strip of neoprene under the sill plate?

Not necessary, unless the floor is very uneven. Rubber under the wall does not help much to decouple, since the wall still has to be bolted to the floor, thus creating major flanking paths through the rubber. But it can be useful to help get a better seal if the existing floor is uneven and you are concerned about not getting a good seal from the three beads of acoustic caulk that you will be laying under it.

Anyway, overall you seem to be on the right track, with just a couple of "caveats".

but I'm just getting paranoid that I am not following the proper etiquette and maybe that's why I'm not getting a response. Is there something wrong or missing from my post? I would greatly appreciate if anyone could tell me where I need to provide more detail because I'm dying to get some feedback.

Naah,. nothing wrong with you or your post! What's wrong is me: there's only one of me here right now! Not sure where the other mods area....


- Stuart -

[missmoo]

Hi Stuart -

Thank you so much for your response. I so greatly appreciate it!!!!!!

So it would be advisable to pick up a copy of the noise regulations from your local municipality (you can probably download it from their web site), and see what your legal requirements are. IT varies from place to place, and normally there is one level for daytime, and another, much lower one, for night.

I have located the Noise Ordinance for our town. It seems that the range is between 50-60 dbl depending on the time of day and the length of the "noise."

Also, it seems that this is just a rehearsal room, not a true tracking room, or a control room? In other words, just a place to set up a bunch of instruments and jam, without disturbing family / neighbors, but not really with any intention of recording?

This is going to be a multi-purpose room. It will be used for rehearsal, tracking, and... wait.... mixing! Yes, I know it's tiny for that many purposes and it's absolutely not ideal acoustically. But I can't make the room any bigger due to various obstacles in the basement and there really is only a 10x10 space for all of these purposes. I'll be crafty in how I lay it out and I'll set up bass traps, etc. I'll do my best to make it usable, knowing it's bad for mixing and tracking. Given the small size, I'd prefer to keep the room maxed out in size at 10x10 rather than cut out usable space for acoustic purposes.

Budget: We need to keep the project under 10k. It’s a 10 by 10 room...Sounds realistic.

I'd rather not pay 10k, but that's my max. I just need it to be usable and relatively quiet upstairs for my sleeping kids.

So your budget is reasonable, but the "10 by 10" dimension is not so reasonable. A square room is not good, acoustically, since all the modes in one direction will occur at exactly the same frequencies as all the modes in the other direction. Even worse would be if you also had a 10 foot ceiling, which would make your room a cube (the worst possible shape). Fortunately, this issue is fairly easy to fix, with suitable design of the isolation wall.

I agree the 10x10 room is bad acoustically. But since I'm going to use the room for mixing, I actually figured the symmetry would help and I'd have to treat the corners with bass traps and put up some diffusion/dampening on some of the wall surfaces. I know it won't be a good sounding room, but it just needs to be good enough for me to be creative, jam with friends, and for me to get used to the terrible mixing environment so I can eventually "figure out the room" and create non-terrible mixes. All that said, I'd be happy to hear any suggestions you have to make the room asymmetrical or change the plan otherwise to improve the outcome.

Ceiling above is pine plank underlayment and nailed strip oak wood floors above.

Not so good: that's a potential big issue, that will need careful attention in your isolation.

If I don't put gypsum board between the joists, can I still get a decent amount of soundproofing from the clips, two layers of drywall, and green glue? Or is it absolutely essential that I treat the underside of the floor above?

There is a sump pump.

Not good! That implies a Bad Thing: Water! You don't want to spend 10 grand on a beautiful room that could then be ruined by water! Is there a problem with damp in your basement? High humidity? Condensation on the walls or floor? One good test is to tape a square of plastic to the floor for a couple of days, and see if you get condensation under it. If so, you have a problem that needs fixed BEFORE you build the studio.

There's no condensation down there. We have a dehumidifier in the basement,too. The sump pump is for 100 year storms... but I will reinforce it before building to make sure it's really dry.

Height is 7’2” to the bottom of the joists.

Ouch! That doesn't leave much room for isolation or treatment. The final finish ceiling is going to be very low.

That's why I was looking at Whisper clips and two layers of 5/8 drywall... I thought the height would end up 6'11'' after finishing.

Anything up there between the joists? HVAC ducts? Plumbing? Wiring? If it is all clear up there, then there is a technique you can use to save space (height).

There is some wiring and a few pipes in the joists. Most of the joists are clear, though...I have included a picture of the most problematic joist cavity.

So the HVAC part is very, very important, and not too expensive. (But not cheap either).

I was thinking I could get away without any HVAC... and when I start suffocating or getting hot I'll open the door to the room and stop playing. Or I could open the window for a while and stop playing. Dumb? How expensive it "not cheap"?

1. Ceiling: We are planning to use Whisper Clips attached to the existing floor joists, then the hat channel attached to two layers of 5/8 drywall with Green Glue in between.

That's fine for your inner-leaf, but you do still need to totally seal and beef up the existing floor above you, which is your outer leaf, before you hang the inner leaf. Sealing is critical: You cannot leave even a single tiny crack up there. In fact, sealing is the most important thing you can do to guarantee success in isolation. And NOT sealing is the bet way I know of to guarantee failure.

How should I seal up there? Caulk? Do we need drywall between the joists? Or can I just caulk and put fiberglass insulation up there? Any detail you can provide would be great.

2. For the walls, we are thinking staggered stud with two layers of drywall on each side (Green Glue in between).

That will probably work too, but it would cost you very little extra money or space to do separate stud frames for each side. that would allow you to angle two if the interior walls, which you absolute need to do here, to deal with your "10 x 10" issue.

How much extra space would be required for separate stud frames for each side?

3. Existing windows: We would like to leave the existing windows in place and construct removable window plugs.

How are you gong to get to the plugs? They will be on the other side of the inner-leaf wall! If you want the light, then just seal those windows air-tight, and put glass in your inner-leaf wall, to complete the isolation plan.

We really would love to be able to still open the windows at some point. No?

4. For doors, we’re planning to use solid core “super doors” (as recommended in Rod Gervais’ books) but haven’t figured out the details yet (that’s coming in round 2 after your first round of feedback).

Superdoors are one option, but rather expensive (sheet lead is not cheap), and do require very, very close attention to the seals around the edges of the door. A pair of back-to-back doors is another good option.

I'd love back to back doors, but we would have to sacrifice too much space in the room. The basement obstacles won't permit double doors, I'm afraid. The main support beam is too low to allow a door to open below it - this is why the doors need to swing in to the room. See picture 2.

1. What is the best way to deal with these existing pipes and acheive desired soundproofing (even though we aren’t finishing the other utility space)? Does our approach work? How should the walls meet the ceiling?

Photos! We can't see the pipes from here, so without photos there isn't much to go on!

Gotcha. See picture 1.

2. Would isolation clips work better than nailers?

For what? You already said you were planning to use clips and hat channel, so where were you thinking of putting the nailers?

See Picture 1 - and detail 2. This is the detail to frame around the most problematic joist space. I figured we would need nailers to frame low enough below and around these pipes...this is the detail I am really struggling with.

3. At the interior walls, would it be better to have 2 layers of Gb on each side of the staggered stud (as opposed to on just one side)?

For staggered stud and high isolation, yes, you need two layers on each side. The amount of isolation you get is directly related to the amount of mass you put around your room, and also to the size of the air gap between your leaves. Increase mass or gap and you increase isolation.

4. Should we add mass loaded vinyl at the ceiling (we don’t have much room to spare with regards the ceiling height)? If we need it, how do we integrate it what we are thinking now?

Not necessary. MLV is over-hyped and over-sold: it only has some very limited uses in isolation, but you don't need it. Mass is mass, and sound waves don't care how much you pay for the mass. (They can't read the price tag!) So use the cheapest mass that does the job, which is normally plain old 5/8" fire rated drywall.

I was only thinking MLV because it's so extremely thin I thought maybe it would make up for NOT putting drywall in between the floor joists... and maybe it would also not make any impact on usable headroom. Sounds like No?

Soundproofing at the existing concrete floor. Do we use a strip of neoprene under the sill plate?

Not necessary, unless the floor is very uneven. Rubber under the wall does not help much to decouple, since the wall still has to be bolted to the floor, thus creating major flanking paths through the rubber. But it can be useful to help get a better seal if the existing floor is uneven and you are concerned about not getting a good seal from the three beads of acoustic caulk that you will be laying under it.

The existing floor kicks up dust. But, I am reading your response as saying we can smooth in down and seal it and then, as long as the surface will take a bead of caulk, we will be ok. Yes?

Thank you very much!!! Thank you!!!!

[Soundman2020]

It seems that the range is between 50-60 dbl depending on the time of day and the length of the "noise."

That's actually good news, for you. Bad for your neighbors, but good for you. It's unusual to see 50 dB limit at night: 50 dB is fairly loud at 3 AM, for example.

One other thing you should check, is how they measure the level: Is it "A" weighted, or "C" weighted: There's a big difference for low frequencies at low levels.

This is going to be a multi-purpose room. It will be used for rehearsal, tracking, and... wait.... mixing!

OK, so it does need to be set up as a control room (mixing room), that can also be used for rehearsal, rather than the other way around. It's not easy to explain all the reasons why, but let me give you this analogy: If you need a vehicle that usually will transport just two or three people, but sometimes needs to transport 8, then you need a van or SUV, not a small sedan. Same here: if you need a room that is normally used for rehearsal, but must sometimes be used for mixing, then it needs to be an SUV (= "control room"). Maybe not a good analogy... Oh well...

I'll be crafty in how I lay it out and I'll set up bass traps, etc. I'll do my best to make it usable, knowing it's bad for mixing and tracking. Given the small size, I'd prefer to keep the room maxed out in size at 10x10 rather than cut out usable space for acoustic purposes.

If you keep it at 10 x 10, it won't be any good for either! Maybe that sounds like a rather categorical, brick-wall kind of statement, so let me explain why first, then what you can do about it after.

All rooms have "modes". A "mode" is a specific frequency at which the room itself vibrates, in sympathy with whatever caused that note. So if, for example, your room happens to have a mode at 65 Hz., then every time the bass guitar hits a C, the entire room will vibrate along with that note, and it will sound much louder than it should: but only at some places in the room. At other places, it will sound much softer than it should. You've probably heard this many times yourself in rooms that seem to "eat" some notes and amplify others.

So what you hear depends on where you are in the room!

The reason for this is simple: in reality, a "mode" is just a path that a sound wave can take around the room, bouncing off the walls, until it gets back to exactly where it started, in phase with itself. So each time it goes around that path, it gets a boost from itself, reinforcing itself. So the energy "builds up" for that note. In technical terms, there is a "standing wave" in the room, and even though the wave itself is moving, the pressure peaks and nulls are stationary in the room: they always occur in the exact same spot (which is why it is called a "standing" wave). So the standing wave stores energy. But then when the note STOPS, the sound doesn't! Since there is energy stored at that frequency, even though the speaker stopped making that sound and the cone is motionless, the wave still carries on bouncing around the room for several more cycles, until it eventually runs out of energy (it loses a bit just from moving through the air, and another bit on each bounce). So the room "rings" or "resonates" at that specific frequency, and carries on doing so for quite a while after the sound stops.

Obviously, this is not a good situation! It means that each time you play a C in that hypothetical room, it will sound much louder or quieter than it should, depending on where you stand, and then it will carry on going after you stop playing! But if you play a B or a D, then it sounds normal and cuts off instantly, like it should! Bad. You can't play well like that, and you certainly cant mix well like that, no matter how hard you try, because the room itself is badly distorting the levels of some notes, and the long, draw-out tail of the ringing is masking other things that you NEED to hear, but cannot.

It turns out that modes are directly related to the dimensions of the room. For each distance between walls, there is a specific frequency (mode) associated with it.

Now here comes your problem: If TWO of the dimensions of your room are the same (such as "ten feet", for example... ) then the problem is MULTIPLIED. Not only do you have a mode that runs around the width dimension, but you also have the EXACT SAME MODE running around the length: So now there are TWO paths that the energy will take, setting up TWO standing waves, so the problem is TWICE as strong. But it gets worse: Since there are two paths for the same tone, there are now also interference patterns in the room, where the nulls and peaks are cancelling and reinforcing each other in ADDITIONAL patterns. So at some points you can get extra high peaks, and at others extra deep nulls.

The only thing you can do worse for a room, is to make it a cube: same in all three dimensions. But a square section is already plenty bad, and must be avoided at all costs.

And no, you cannot get rid of modes with acoustic treatment: They will always be there, simply because the room is that size. All that you can accomplish with treatment is to attenuate the modes to a certain extent, so that they aren't too much of an issue.

And no, you cannot get rid of modes by angling your walls. All that you do there is to move the mode to a different frequency, and make it much harder to predict how the room will behave.

Those are two common myths: "I'll kill the modes with bass traps." and "I'll kill the modes by making the walls non-parallel". Nope. It doesn't work like that. Bass traps help to damp the modes (attenuate, reduce the Q and broaden it), and angles help to redirect modes, but neither will actually "kill" the mode.

But there is one other thing you can do: you can choose dimensions for your room such that NO mode falls at the exact same frequency as any other mode. In fact, you can choose dimensions that spread the modes around as evenly as possible. If you choose your dimensions wisely, you get a nice even smooth spread of modes, so that none of them is overpowering, and no mode can trigger an adjacent mode.

OK, I'll get back to this point later in other comments, but its important to understand that keeping a square shape for your room is a really bad idea.

But since I'm going to use the room for mixing, I actually figured the symmetry would help

Symmetry, yes, but not in all directions! "Symmetry" in a control room refers only to the left-right axis, not the front-back axis. In other words, the left side of the room should be a mirror image of the right side. But NEVER in the front to back, or top to bottom directions.

The reason for this is quite simple: your ears are on the left and right side of your head, not the front and back! So left-right symmetry is critical for a control room, and we'll get to that later, but you NEVER want the room to also be symmetrical front to back. Your ears must hear the left and right signals, from the left and right speakers, in exactly the same way, un-touched and un-colored by the room. But the front an back of the room have totally different purposes, in acoustics. The front of the room should be designed to keep all early reflections away from your ears, and send them off to the back, which should be as far away as possible and treated suitably so that the sound is attenuated as much as possible, and stays away as long as possible, before it gets back to your ears. Technically, the back part of the room should keep the sound away for at least 20 ms, and when it does send it back to your head, it must do so at a level of at least 20 dB lower than the direct sound from the speakers. In reality, that's really hard to do, and the smaller the room, the harder it is, but that's the goal.

In any case, the front and back cannot be symmetrical, since each serves a different purpose.

and I'd have to treat the corners with bass traps and put up some diffusion/dampening on some of the wall surfaces.

Your room is way to small to benefit from diffusers. Most diffusers (especially number-sequence based ones, such as RPGs, skylines, binaries) work very well to diffuse sound, both spatially and temporally, but in doing so they create "lobes" close up, where the timing (phase) and pressures produce marked patterns. It takes some distance for those anomalies to smooth out. At least three full wavelengths, according to some acousticians: others say 6 or 7, minimum. Others say 10 feet, minimum. Others say more. But everyone agrees that you need distance for the lobes to even out and smooth over, and if there is one thing that small rooms do not have, it is distance. So most types of diffuser are a bad idea in small rooms. Of course, that doesn't stop some manufacturers from trying to sell their diffuser for use even for broom closets! But in reality, small rooms and diffusers do not go together well.

So your only options for treatment are absorption, panel traps (membrane traps), and Helmholtz resonators. The last two are rather complex and generally used only as last resorts, so your treatment will be almost exclusively absorption. And that's a good thing, since absorption is cheap!

I know it won't be a good sounding room, but it just needs to be good enough for me to be creative, jam with friends,

Actually it CAN sound good, if you build it right! It does not have to be terrible.

and for me to get used to the terrible mixing environment so I can eventually "figure out the room" and create non-terrible mixes.

Easier said than done! The critical frequency for a room measuring 10 x 10 by 7.2 is 161 Hz (Schroeder frequency). There are a total of 28 modes, just in the spectrum below that point! You have 6 axial modes, 12 tangential modes, and 8 oblique modes just in that range. But diffusion doesn't take over in that room until 644 Hz, and there are a grand total of 30 axials, 297 tangentials, and 968 Obliques up to that point. I sure hope you have a really, really good auditive memory, for keep track of all those one thousand two hundred and ninety five modes! (And also of the millions of possible ways that they can interact with each other....)

OK, so I'm exaggerating a little: In reality you only need to worry about the first 200 or so, (the ones below 300 Hz), and the major issues will be at about 57 Hz, 79 Hz, 97 Hz, 112 Hz, 126 Hz, 148 Hz. and 167 Hz. And those just happen to be A, E and G in the second octave, plus A, B, D and E in the third octave. In the words, bass guitar will sound really bad in there, with some notes screaming at you, others whimpering, and still others behaving normally. Plus the fundamental frequency of the kick drum is often around 80 Hz (matches 79). And one of the toms is also most likely a dead ringer for one of those too. But not all of them.

So I think you can see the issue.

All that said, I'd be happy to hear any suggestions you have to make the room asymmetrical or change the plan otherwise to improve the outcome.

Keep it symmetrical, but only from side to side.

Besides, symmetry isn't the issue: identical dimensions are the issue. The only way to deal with that is to change one of the dimensions just enough so that the modes no longer line up, and the spread is smoother and more even. Since you say that it is impossible to go even one inch bigger, then you are stuck with going smaller. If you make that room 9'6" wide, instead of 10" wide, then all of a sudden your modal spread is looking an awful lot more promising!

If I don't put gypsum board between the joists, can I still get a decent amount of soundproofing from the clips, two layers of drywall, and green glue?

That depends on how much mass is up there, and how well it is sealed, but most likely the answer would be "no".

Once again, a little theory: The way to isolate ("soundproof") a room at the lowest cost is with the "fully decoupled 2-leaf MSM" construction technique. That is a tuned system, as I mentioned in my last post. The wall (or ceiling, in this case, which is basically just a horizontal wall, acoustically) is tuned to a specific frequency, and at that frequency is does not isolate at all. But at all higher frequencies it isolates increasing better, starting at 1.4 times the resonant frequency. So if you tune it to a frequency lower than the lowest one you need to isolate, then you can isolate the entire spectrum. You "tune" it with the right amount of mass, and the right size of air gap. If you don't have enough mass, or the gap is too small, then the resonant frequency will be too high, and isolation will suffer. So if you don't have enough mass on your sub-floor, then your isolation will be compromised.

Or is it absolutely essential that I treat the underside of the floor above?

At the very least, it must be sealed air-tight. Every tiny crack must be fully sealed.

That's why I was looking at Whisper clips and two layers of 5/8 drywall... I thought the height would end up 6'11'' after finishing.

You actually might be able to get it a bit higher. There are some techniques that can be used to squeeze out every last fraction of an inch. You might be able to make it to 7', or even a tiny bit more. Maybe. Maybe not.

There is some wiring and a few pipes in the joists. Most of the joists are clear, though...I have included a picture of the most problematic joist cavity.

That makes it harder to maximize height. It even looks like some of those pipes run UNDER the joists, not through them, so you might not even be able to make 6'11". It might be worthwhile calling a plumber to re-route those pipes outside of the studio area, or through the joists.

I was thinking I could get away without any HVAC... and when I start suffocating or getting hot I'll open the door to the room and stop playing. Or I could open the window for a while and stop playing. Dumb?

Air wont move unless you give it a reason to. Opening the door isn't a reason! Even with the door open, the air will just sit there, doing nothing, unless you force it to move. So you'd need to set up some fans to push fresh air in through the lower party of the doorway, and more fans to push stale air out through the upper section. Then you'd have to take them out, close the door, record for another few minutes, set them up again, open the door. Rinse. Repeat. ...

But that doesn't take care of the humidity issue. Most musical instruments, some mics, and some equipment are sensitive to changes in humidity. The tuning and tone change, quite noticeably. So if you are opening and closing the doors every few minutes, setting up the fans then taking them out again, well, the humidity inside the room is going to take wild swings for each cycle, so you'll be constantly re-tuning every instrument, and repositioning the mics, each time you do that. I think that would get tired, really fast! Not funny.

How expensive it "not cheap"?

Where I live, I can pick up a nice little mini-split system for a couple of hundred dollars. Installation costs a couple hundred more. The total would be under or around US$ 500. But I hear that mini-split haven't really caught on yet in the USA, so the prices are still high. Not sure, but maybe double the above figures. But call around, and ask for prices of 12,000 BTU mini-split air conditioning systems.

How should I seal up there? Caulk? Do we need drywall between the joists? Or can I just caulk and put fiberglass insulation up there? Any detail you can provide would be great.

Yes, you absolutely do need to seal, and yes caulk is a good possibility. Best is proper acoustic caulk, but any good bathroom caulk that does not harden an remains flexible forever, will work OK.

On the drywall question: the answer is "probably", but it all depends on how much isolation you need (decibels) and for what frequencies.

How much extra space would be required for separate stud frames for each side?

Maybe two inches. You'd use 2x6 sole plates for staggered studs, and those measure 5-1/2" inches wide. A pair of 2x4s with a 1/4" gap will take up 7-3/4".

However! If you go to dual frames, then you have the option of building the inner-leaf "inside out", meaning that you gain 3-1/2 inches!. So overall, you could gain an inch and a half on each side of the room, for a total of 3 inches. That's worthwhile, for sure.

We really would love to be able to still open the windows at some point. No?

If the windows are operable, then they are not sealed! No seal = no isolation. You can still use them for light, but not for air. They need to be sealed, if you want isolation.

The main support beam is too low to allow a door to open below it - this is why the doors need to swing in to the room. See picture 2.

Simple solution: Use a sliding glass door on that side.

I was only thinking MLV because it's so extremely thin I thought maybe it would make up for NOT putting drywall in between the floor joists... and maybe it would also not make any impact on usable headroom. Sounds like No?

Mass for mass, it isn't that thin. I used some MLV last week to isolate a noisy toilet soil pipe. The MLV was 3.5mm thick and weighed 3 kg/m2. a sheet of 5/8" drywall is about 12 kg/m2, so I'd need four sheets of MLV to get the same mass as a single sheet of drywall. Four layers would add up to 14mm. 5/8" is about 15mm. So all I'd save is about 1mm of space (about 1/32"), but for about five times the price.

If you REALLY want to save space, use fiber-cement board. That stuff is twice as dense as drywall, so it can be half as thick for the same total mass. Or if you really don't mind spending big money, use lead sheet, which is about 14 times as dense as drywall. So with 2mm of lead sheet (about 1/16"), you'd get roughly the same mass as a sheet of 5/8" drywall. But the cost...

But there are other techniques you can use to save space, such as inside-out construction, and beefing up between the joists, instead of outside them. Etc.

The existing floor kicks up dust. But, I am reading your response as saying we can smooth in down and seal it and then, as long as the surface will take a bead of caulk, we will be ok. Yes?

Yup!

Looking at your photos, it seems that the sub-floor above is not very even, and is not in great condition. It won't be easy to seal that like it is. Beefing it up with a layer of drywall would make it very easy to seal.

- Stuart -

[missmoo]

One other thing you should check, is how they measure the level: Is it "A" weighted, or "C" weighted: There's a big difference for low frequencies at low levels.

It is A-weighted.

If you keep it at 10 x 10, it won't be any good for either!

The room is approximately 10'7" by 9'. These dimensions are approximate only because it seem we may be changing the thickness of the walls based on your suggestions. Sorry to make you explain so much about the importance of dimensions when I was misstating them. But, I certainly appreciate the lesson and it helped me realize a lot!

You've now made me realize that the room can sound decent (or even good) if we use the proper dimensions. I'd be perfectly happy to give up an inch here or there if it would make a substantial difference in the sound/modes. How do I know if 10'6 x 9 is better than 10'7 x 9?

In any case, the front and back cannot be symmetrical, since each serves a different purpose.

Point taken. I need to figure out where the front and the back are - for mixing is it preferable to have the monitors on the long or short wall? How do we go about making the front and back asymmetrical?

It even looks like some of those pipes run UNDER the joists, not through them, so you might not even be able to make 6'11". It might be worthwhile calling a plumber to re-route those pipes outside of the studio area, or through the joists.

We had a plumber move all the pipes he could within reason/budget. The ones that are left are 1 inch high copper lines and only in a few places. We are planning to use the isolation clips on the joists anyway, and those clips with the hat channel are taller than that 1 inch pipe. So the gypsum board would sit just below those few copper pipes... which adds up to 6'11 ceiling height (or slightly less) based on my calculations (I could be wrong).

My big worry is soundproofing around that PVC pipe in the picture. Based on our current layout, the wall should be coming up right in the joist space here - so that the PVC pipe is "outside" the sound room. This is detail 2 and this is where I thought about nailers to bridge between the joists? But I am not sure how to soundproof the wall given that we are not finishing the other space.

If you go to dual frames, then you have the option of building the inner-leaf "inside out", meaning that you gain 3-1/2 inches

Wow - I need to read about this technique! I'll do a search on the forum. I will so do some research on the HVAC. Thanks!! I really appreciate your help. So amazing...

[Soundman2020]

It is A-weighted.

Even better! Less sensitive to very low frequencies.

The room is approximately 10'7" by 9'. These dimensions are approximate only because it seem we may be changing the thickness of the walls based on your suggestions.

Good! One thing to keep in mind here is that it is the FINAL dimensions of the INNER leaf that matter. That's what the sound waves see. So when you figure dimensions, imagine yourself standing inside the finished room (but before any treatment goes in): the surfaces of the walls that you see are the ones that matter. That's the inside surface of the inner leaf. So that's what you should be measuring and talking about.

Sorry to make you explain so much about the importance of dimensions when I was misstating them. But, I certainly appreciate the lesson and it helped me realize a lot!

No problem! That's what the forum is all about: helping each other out with information.

I'd be perfectly happy to give up an inch here or there if it would make a substantial difference in the sound/modes. How do I know if 10'6 x 9 is better than 10'7 x 9?

You can calculate it by hand if you want! But fortunately there are several free calculators, spread sheets and web sites that will do all that for you. I'm pretty sure there is a "sticky" thread here on the forum somewhere with a list of links to a few of those. But do make sure that you use one that calculates all three types of modes (axial, tangential, oblique). Some only calculate the easy axial modes, and forget about the other two types, but all three are important.

What you are looking for is a "room ratio" that gives you an even spread of modes, with none of them too close or to far away from it's neighbor. Some rather clever scientists have already done the work for you, and figured out ratios of dimensions (height : length : width) that happen to produce good spread, so you'll sometimes see people here referring to "Sepmeyer's best ratio" or "Louden's third ratio", or things like that. But you don't need to worry too much about those names: the truth is that there are many good ratios, and the differences between a good Bolt ratio and a good Boner ratio is not worth arguing about, unless you like splitting hairs.

If you really want to get yourself totally confused about this whole "room ratio" thing, then here's a little light bedtime reading for you:

http://forum.studiotips.com/viewtopic.php?t=684

That's probably the best thread on the entire internet about room ratios. And as Eric says, the idea is not so much to hit a "perfect ratio" (there is no such thing!), but rather just to stay away from the bad ones, and get close to one of the good ones. You don't need to go nuts about sliding walls around in increments of 1/64"! Just get close, and you'll be fine.

Another tool that helps to see how smooth the spread is, is something called the Bonello diagram. Bonello was another researcher who noticed that if each 1/3 octave on the scale has MORE modes than the next lowest 1/3 octave, then that usually indicates a good spread. So if you graph how many modes are in each 1/3 octave, then you should see a smoothly rising exponential curve. Of the curve has kinks in it, or is uneven, then that's not a good ratio.

for mixing is it preferable to have the monitors on the long or short wall?

Speakers on the short wall, facing down the long axis of the room. That means that the round trio for sound waves is as long as possible, as they leave the speaker, head for the rear wall, bounce and then get back to your head. That's one of the goals: to make that path as long as possible, so the waves don't arrive until after 20 ms has elapsed, and even then at -20dB.

How do we go about making the front and back asymmetrical?

Generally the front is more reflective and the rear is more absorptive. If you choose to splay your side walls (angle them) then the front should be narrower and the rear wider. But that takes up some extra space, and your room is already small, so splayed walls might not be a good idea for you.

We had a plumber move all the pipes he could within reason/budget. The ones that are left are 1 inch high copper lines and only in a few places. We are planning to use the isolation clips on the joists anyway, and those clips with the hat channel are taller than that 1 inch pipe.

Well, yes, but if the pipes were not in the way then you could gain all that lost space: You can also mount the clips to wooden blocks attached to the SIDE of the joists, and positioned a little higher, such that the hat channel ends up just a fraction below the joists: So you save the thickness of the clips...

Or you could build your ceiling on a joist frame that rests on your inner leaf walls (no clips, no channel), in which case the drywall itself can start just a fraction of an inch below the joists, gaining you even more space (especially if there is enough space up there ti interleave the new joists between the old, or if not then build inside-out). And if you combine that with fiber-cement board (instead of drywall) then you can gain another few precious fractions of an inch. And if you also use the "beef up between the joists" technique for the INNER leaf, there's another little bit.

But you can only do that if you get the plumber back in: all he has to ti is drill holes in the joists (in the middle of the joists, of course! Not close to the top or bottom edge) and re-route the pipes through those holes, leaving nothing at all below the joists. You could even make the most of the opportunity to beef up the sub-floor above you while he has the pipes out...

So the gypsum board would sit just below those few copper pipes... which adds up to 6'11 ceiling height (or slightly less) based on my calculations (I could be wrong).

I bet you can gain as much as two inches, using the above methods!

Also, don't forget that those pipes are NOT outside of you isolation system: they are INSIDE, in the air gap, so they will not be isolated from the rooms. Water running in those pipes might be audible inside the rooms. Also "water hammer" will be heard, for sure.

Wow - I need to read about this technique!

The basic concept is easy: For the inner leaf, just put the drywall on the "wrong" side of the studs. The side that faces AWAY from the room. In other words, when you stand in a finished (but untreated) inside-out room, you see the studs with the drywall attached on the far side.

- Stuart -

[missmoo]

Wow - again your insights are extremely helpful. I have some more research to do now...

There's still one important question that I accidentally buried in my last post (messed up formatting) that I would love advice on:

My big worry is soundproofing around that PVC pipe in the picture. Based on our current layout, the wall should be coming up right in the joist space here - so that the PVC pipe is "outside" the sound room. This is detail 2 and this is where I thought about nailers to bridge between the joists? But I am not sure how to soundproof the wall given that we are not finishing the other space. Should we be using nailers there to bridge between the joists? How do we make that wall air tight, particularly where it meets the unfinished ceiling on the outside of the room? If the pictures and this description makes no sense, please let me know and I'll clarify.

Also - you mentioned in one post that we could use two sliding glass doors (I think). I'm curious - why is a sliding glass door any better than a window for soundproofing? You had mentioned that a window wouldn't be sealed so it wouldn't be soundproofed... wouldn't we have the problem with a sliding glass door? A good friend of mine has a studio and he used two sliding glass doors in the doorway of his vocal booth... maybe he messed up some other aspect of the soundproofing, but man you can hear that band in the vocal booth like there are not even any doors there. Do two layers of sliding glass doors provide as much mass/airtightness/soundproofing as a one very solid and properly sealed door?

Thanks!

[Soundman2020]

I'm curious - why is a sliding glass door any better than a window for soundproofing?

It's neither better nor worse, if sealed the same way. It's the seal that matters, not the glass.

You had mentioned that a window wouldn't be sealed so it wouldn't be soundproofed... wouldn't we have the problem with a sliding glass door? A good friend of mine has a studio and he used two sliding glass doors in the doorway of his vocal booth... maybe he messed up some other aspect of the soundproofing, but man you can hear that band in the vocal booth like there are not even any doors there.

That's because he did not do it correctly! His doors are not acoustic rated sliding doors. The glass is most likely not laminated, is too thin, and the panes are too close together. The frames are probably also not heavy enough and rigid enough, and I can guarantee you that the seals around those doors are totally unsuitable, if indeed there are any seals. If you just buy a couple of normal sliding glass doors form Home Depot, then yes, you certainly will get the result you describe above, since such doors are not designed not intended for acoustic applications. Acoustic sliding doors should have heavy frames fitted with thick laminate glass, the rollers and tracks should be heavy duty to take the large weight, and most important of all, the seals must be up to the job: there must be at least two independent seals around the entire perimeter of the door, and they must seal the door totally air-tight when it is closed. Of course, all of that makes the door rather expensive, but if you need isolation then that's the way to go.

Do two layers of sliding glass doors provide as much mass/airtightness/soundproofing as a one very solid and properly sealed door?

They can do, if built right. If the surface density of the glass in each door is roughly the same as the surface density of the rest of the leaf, and the gap between the glass panes is at least as great as the gap between the leaves, and the seals are really good, then yes, the glass doors can provide every bit as much isolation as a single door, or maybe even better.

so that the PVC pipe is "outside" the sound room.

If it is outside both leaves, then there should be no problem. If it is in between the leaves, then you would have a problem.

However, Detail 2 seems to show that the upper layer of drywall on the ceiling seems to be flanking to the outer leaf of the wall and also the outer leaf ceiling, through the top plate. So that needs to be fixed. As long as the place where the pipe runs is totally outside of the studio, then you should be OK.

- Stuart -

[missmoo]

And so, after life got in the way for a while, we are back to making the studio happen..We have gone through some cost checking and have a couple of updates to fill in - as well as follow up questions.

1. Flooring -
The existing concrete floor is uneven and the surface creates a lot of dust. We checked in to refinishing the floor - a thin overcoat to level the floor, professional polish and seal it. The cost was about $8/sf - which would eat in to our budget significantly. We are now looking in a more DIY option of a microtopping and sealing with an polyurthane sealer. We just want to make sure we end up with a surface that gets us an acoustic seal at the base of our walls.

2. Detail 2 - You mentioned flanking of the drywall. Can you clarify what this means and how we would fix this? Is it just in the way the drywall is detailed?

Detail 2 - Also, instead of getting a plumber in to relocate the copper pipes (expensive) is there any way to seal around the pipe so that is passes from between the leaves in the ceiling (between the drywall at the ceiling and the drywall mounted to the underside of the floor above) and through the wall detailed in Detail 2? Hmmm...just wondering.

3. Sliding doors - We checked in to getting sliding doors. Acoustic sliding doors are expensive. We can get one in the wall between the sound room and the hang out room. Is one enough or do we need 2?

Thanks again for all your help!

[Soundman2020]

2. Detail 2 - You mentioned flanking of the drywall. Can you clarify what this means and how we would fix this? Is it just in the way the drywall is detailed?

"Flanking" just means that there is a hard mechanical path that sound waves (vibrations) can traverse to get from the inner leaf to the outer leaf. On your "Detail 2" diagram, roughly in the middle is something called "New nailer" running between two joists. The inner-leaf drywall and the top plate of the inner-leaf wall both seem to be in direct contact with that, and therefore you have flanking paths. That should be corrected, so that there is no physical connection at all between inner leaf and outer leaf. They must be independent:

3. Sliding doors - We checked in to getting sliding doors. Acoustic sliding doors are expensive.

Yup! They sure are.

We can get one in the wall between the sound room and the hang out room. Is one enough or do we need 2?

If you only have one then you are relying on mass law along to isolate your room. Mass law is not your friend. You would need very heavy glass if you do that. Two doors provides the full MSM system that you need to get good isolation, but of course it doubles the cost. So the question is: Do you really NEED sliding glass doors there? Maybe a pair of ordinary hinged doors would work just fine? You can put glass in hinged doors if you want, so sight lines should not be an issue.

- Stuart -

[missmoo]

Thank you again for your response. We really appreciate the help!

We will look in to some more door options.

We had a structural engineer over yesterday to check out the existing structure and the advise us as to how many layers of drywall we can handle with this existing structure. So we will be revising those details when we hear back.

We are also looking in to getting a good seal at the outer leaf. We are concerned about this where the sound walls run perpendicular to the joist cavities. For example, at the exterior foundation wall ( See Detail 1_rev 1 below) as well as the opposite wall between the music room and the unfinished utility space (See Detail 4_1 below). The drywall will have to be notched around every joist. I was wondering about using spray foam insulation in these areas to insulate and seal? I read in some other posts about you cautioning folks about using the spray foam and the potential to create the flanking. In Detail 4_1 we were looking in to using the inside out wall at the outside of the music room. Our dimensions here are set by the air space required around our existing furnace. But I also thought that the inside out wall could provide a good fence for the spray foam to be on the outside of the wall, so that it is visible from the unfinished laundry room (See Elevation 1_1 below).

Would spray foam also work to seal around any pipes that pass from the air gap in the ceiling and then pass through the outer leaf to the unfinished space? We have several situations where a pipe will pass through the outer leaf, in to the air space between the leaves and then pass through the outer leaf again. These pipes never penetrate the inner leaf. Unfortunately, we don't have the budget to relocate all these pipes. Do you advise wrapping these pipes, using spray foam, etc.?

Thanks again for all your help.

[Soundman2020]

We are also looking in to getting a good seal at the outer leaf. We are concerned about this where the sound walls run perpendicular to the joist cavities. For example, at the exterior foundation wall ( See Detail 1_rev 1 below) as well as the opposite wall between the music room and the unfinished utility space (See Detail 4_1 below). The drywall will have to be notched around every joist. I was wondering about using spray foam insulation in these areas to insulate and seal?

Acoustic sealant (also called "acoustic caulk") is what you need for that. Spray foam does not have enough mass to provide the seal that you need, and most types of spray foam also dry rigid and brittle. You need stuff that stays flexible, soft and rubbery forever, even when it is fully cured. There are several companies that manufacture acoustic sealant.

Would spray foam also work to seal around any pipes that pass from the air gap in the ceiling and then pass through the outer leaf to the unfinished space?

Same thing: acoustic caulk is the answer. Just leave a small gap around the edge of the joist or pipe as you put the drywall in place, then fill that with backer rod and acoustic caulk.

We have several situations where a pipe will pass through the outer leaf, in to the air space between the leaves and then pass through the outer leaf again. These pipes never penetrate the inner leaf. Unfortunately, we don't have the budget to relocate all these pipes. Do you advise wrapping these pipes, using spray foam, etc.?

It would be good to wrap them with pipe insulation, yes. If you need very high levels of isolation, another possibility might be to build a "soffit" around them, with drywall and fill that with insulation.

- Stuart -

[missmoo]

Thanks again Stuart. Very much appreciated.

What is your opinion of a double door assembly on the isolated walls vs. a single solid core door with sheet lead?

[Soundman2020]

What is your opinion of a double door assembly on the isolated walls vs. a single solid core door with sheet lead?

Both will work fine, but the single door with lead is going to be VERY heavy, which makes it hard to mount, and hard to adjust. You need very tough hinges and extra bracing in your framing to be able to carry the weight of a super-door. On the other hand, two doors means twice as much work...

So there are advantages and disadvantages. Personally, I think I'd go with two doors in most cases.


- Stuart -