Townhouse Rehearsal Space Design

[jdrews]

I am planning on building a band rehearsal space in an unfinished portion of my townhouse basement. It was built around 2005. The basement walls are (I think) 10" thick poured concrete and the floors are truss joists that span from wall to wall. The concrete slab is isolated from the walls by expansion board. There are units on both sides. For typical everyday noise, the construction is sufficient. I rarely hear my neighbors. But a loud stereo could probably be heard even from basement to basement (probably flanking through the floor joists more than through the concrete walls.) My intent is to create a space where a relatively loud rock band (guitar, bass drums) could play without disturbing the neighbors. I'm less concerned about sound transmission throughout the house (unit) itself, but that would be ideal as well.

I have a plan, but there are some concerns and questions about details. I'm going to describe my plan, and let people tell me where I could improve, do without, or do differently. My biggest fear is that I will dump a lot of money and effort into this, and realize that it's not as quiet as I anticipated, or that I should have done something else to an area that is now closed off. What I have now, I've estimated will cost me about $2500-3000 in materials. I would like to keep it in that range.

I plan to build a stand-alone room within the unfinished space shown in the attached photos. The only attachment will be to the concrete slab. Walls and ceiling will be 2x4 wood framing, 16" OC, the cheapest fiberglass batt insulation, two layers of 5/8" drywall with green glue between drywall layers. There will be at least a 2" gap between exiting and new construction. Two of the walls will be quite far from existing walls (6'-0"+).

Now the details/questions:

1. Doors: Because of the space I'll need three doors. Two standard 30-32 inch doors, and one double door to mirror the 48" door that is currently in place. I was planning on using solid core exterior doors from a big box store, but the double door is harder to find. Are there any suggestions for cheap doors that would be good for this?

2. Existing space treatment: I feel like something needs to be done to at least the existing ceiling before beginning the room. It is completely unfinished and terrible as far as sound transmission goes. I was going to put insulation and draywall at the bottom chord of the truss joists but then I read about triple leaf effect. So would it be better to glue pieces of drywall to the subfloor instead? That's more difficult. Would insulation be necessary? Based on other threads here, it would seem that since I'm already adding insulation to the new wall, additional insulation would be negligible. That's counter-intuitive to me. Is there anything else that I could do to the existing space before building the room to help improve the isolation?

3. Existing Ducts: The room will not be touching the overhead ducts directly, but I'm still concerned about bass vibrating them and causing sound to travel throughout the house. What is a good way to prevent that? Should I wrap them with something as a dampener?

4. Ventilation: I intend to run one inlet and one return duct. I guess I'll build a baffle box for each, or just wind some flex duct in the truss space. My concern here is how stuffy the room will get when the furnace is not running since it will be nearly air tight. Will having the ducts be sufficient for health safety and comfort, even when not running the fan to circulate air? Is there anything else I need to consider regarding ventilation?

5. Decoupling: The one decoupling problem with my plan is the slab. it is technically decoupled from the exterior walls, BUT the room will be fastened to the slab which is fastened to other interior framing (the finished portion of the basement) which is attached to the floor joists which is attached the walls and other units. It's a rather long and probably poor flanking path, but I wonder if it's worth setting the new framing on rubber strips or something. I have some rubber base molding I am considering running beneath the sole plate of the new room. Is that worth the trouble? Is there a better material for the job?

6. Receptacles: I am planning to use the putty backers AND caulk the from of each receptacle. Is that sufficient? Too much?

7. Caulking/sealing: I plan to use typical silicone caulk for the corners at the drywall, at the gap between the drywall and the slab, and around doors and everything else. Is this ok, or would it make a significant difference to use an acoustical sealant?

Am I on the right track? Is my goal reasonably attainable given my plan, or should I rethink this entirely?

I appreciate any advice. Thanks!

[jdrews]

Since I'm not getting any response, maybe i'll try asking an individual question. It seems like the main wall system separating the units will be quite good (two layers of 5/8" drywall with GG, an insulated 2x4 stud cavity, a 2" air gap, and a 10" thick poured concrete wall). The weak point is at the top of this wall. The truss joists sit on top of the concrete wall. There is no rim joist. So there is an opening between each joist where you can see the area separation wall (2x1" thick drywall fire wall). This is a thick wall but much less STL than the concrete wall, so It's a weak point. My plan is to fill those areas with layers of drywall. But I'm wondering, is it worth while since there will be a flanking path through the joists themselves which short circuit the drywall?

[Soundman2020]

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

Sorry about the lack of response, but I've been on vacations the last couple of weeks, and out of touch: no internet! Beautiful...

Anyway:

The basement walls are (I think) 10" thick poured concrete

Excellent! That's a good start for isolation.

and the floors are truss joists that span from wall to wall.

You mean the floor above you, or your own floor? If it's a basement, I'd assume that your floor is slab on grade?

My biggest fear is that I will dump a lot of money and effort into this, and realize that it's not as quiet as I anticipated,

Welcome to the world of studio design! That's a very common fear... and the solution is to design every last detail up front, carefully, with full understanding of what each part does... before you ever buy even a single stud or nail. Planning is the key to getting it right.

What I have now, I've estimated will cost me about $2500-3000 in materials. I would like to keep it in that range.

If that is only for the actual building materials for isolating the room, then you might be able to stretch it, but don't forget that you¿ll also need to budget for the HVAC system, electrical system, and the acoustic treatment inside the finished room.

Walls and ceiling will be 2x4 wood framing, 16" OC,

24" OC is cheaper (less materials) and slightly better acoustically.

the cheapest fiberglass batt insulation

Don't go for "cheapest". Instead, go for "lowest cost that does the job effectively". The insulation that goes inside the wall cavity is part of the tuned MSM system. It has to be the correct type and density to do its job, which is to act as acoustic damping on the various types of resonance going on inside the wall.

two layers of 5/8" drywall with green glue between drywall layers

While that would be great, I don't think your budget will stretch to Green Glue. Get a quote from them, and take into account that you need two to three complete tubes for each panel of drywall....

There will be at least a 2" gap between exiting and new construction.

Careful with terminology! "Gap" can mean many things. What you want is at least 4" of air space across the wall cavity, between the surface of the outer leaf and the surface of the inner leaf. That entire gap should then be filled with insulation, but it is still considered "air gap" because insulation is mostly air anyway. But 4" might not be enough: you have to do the math to make sure that the MSM resonant frequency will be low enough to meet your goals, and that the entire system will provide the level of isolation that you want.

1. Doors: Because of the space I'll need three doors.

I guess that the two 32" doors go back-to-back at some point, but you didn't post the plans for your room, so it's hard to figure out what you have in mind...

and one double door to mirror the 48" door that is currently in place. I was planning on using solid core exterior doors from a big box store, but the double door is harder to find. Are there any suggestions for cheap doors that would be good for this?

There's a reason why you very seldom see double doors in studios: They are notoriously hard to get a good seal on, and without a good seal, there is no isolation. Double doors that can be used in studios do not come close to meeting your objective of "cheap". You could blow your entire budget on a good set of acoustic rated double-doors- So I'd suggest rethinking that plan: If that were my place, I'd swap the existing 48" door for a single 36" or 38", frame and drywall the empty bit left over, then mirror that door on the inner leaf.

2. Existing space treatment: I feel like something needs to be done to at least the existing ceiling before beginning the room. It is completely unfinished and terrible as far as sound transmission goes. I was going to put insulation and draywall at the bottom chord of the truss joists but then I read about triple leaf effect. So would it be better to glue pieces of drywall to the subfloor instead?

You have the right idea there, but the method is a bit different. What you are doing is often referred to as "beefing up": you are adding mass to the existing outer leaf. The normal way to do that is to cut pieces of 5/8" drywall to fit in each stud bay up there, hold it in place with cleats nailed sideways into the studs, and carefully caulk all the way around the edges. Also use caulk to seal any gaps, cracks, small holes, o anything else up there. Your goal is to make that floor above you fully air-tight, and to have consistent mass all across it (constant surface density). Depending on what is up there already, you might need more than one layer of drywall to get there. But you also have to take care to not overload the existing structure: you'll need a structural engineer to tell you how much extra load you can add safely.

Would insulation be necessary? Based on other threads here, it would seem that since I'm already adding insulation to the new wall, additional insulation would be negligible. That's counter-intuitive to me.

Your intuition is correct! Once you have beefed up the floor above you, then you do indeed need to put insulation up there too. The insulation here serves the same purpose as in the walls: it acts as damping on the multiple acoustics stuff going on inside. The more insulation you put in, the better it gets. Not because the insulation absorbs the sound passing through the walls (that's the normal way that people think about it, but that effect is minor), but rather because it is an integral part of the whole MSM system. It does the exact same job as what the shock absorbers on your car do. Without those, even though you still have the suspension springs attached to your wheels, the ride is terrible. Without insulation, even though you still have the air gap between the two leaves, the isolation is terrible. Insulation = shock absorber. It can add anywhere between 5 and 16 dB of isolation to your walls. So use the right type, and put in as much as you can without compressing it.

3. Existing Ducts: The room will not be touching the overhead ducts directly, but I'm still concerned about bass vibrating them and causing sound to travel throughout the house. What is a good way to prevent that? Should I wrap them with something as a dampener?

The best way to deal with that is to build soffits around those ducts, with framing and drywall, and also with insulation inside. Yes, that does create a 3-leaf system, but it's still the best way to do it at low cost.

4. Ventilation: I intend to run one inlet and one return duct. I guess I'll build a baffle box for each,

Right! Except that you need two silencer boxes on each duct, if you want high levels of isolation. One box goes on the outer-leaf penetration, and the other on the inner-leaf penetration. If you don't need high isolation, then you can get away with just one, if you do it carefully.

or just wind some flex duct in the truss space.

Only if you don't need good isolation...

My concern here is how stuffy the room will get when the furnace is not running since it will be nearly air tight. Will having the ducts be sufficient for health safety and comfort, even when not running the fan to circulate air?

Why would you turn the fan off? It doesn't draw much power, so you an leave it on permanently. Your fan is independent of the furnace fan...

Is there anything else I need to consider regarding ventilation?

Yes: Room changes per hour, occupation, sensible heat, latent heat, flow volume (CFM), flow velocity (fpm), duct size, silencer cross section, baffles, static pressure. Those ate the biggies.

5. Decoupling: The one decoupling problem with my plan is the slab. it is technically decoupled from the exterior walls, BUT the room will be fastened to the slab which is fastened to other interior framing (the finished portion of the basement) which is attached to the floor joists which is attached the walls and other units. It's a rather long and probably poor flanking path, but I wonder if it's worth setting the new framing on rubber strips or something.

You can if you want, but you probably don't need to unless you have a need for high levels of isolation. Floating your walls is just as complicated as floating a floor, and just as hard to get right. And just as easy to get wrong! There's a lot of math and assumptions that go into that, so unless you understand how to calculate the amount of deflection percentage you'll need for the exact type and thickness of rubber you are using, in order to get the resonant frequency down to at least one octave below the lowest frequency that you need to isolate, then you won't get anywhere! Your chances of getting it right by pure luck are about as good as your chances of winning the state lottery in all fifty states on the same day... without buying any tickets!

I have some rubber base molding I am considering running beneath the sole plate of the new room. Is that worth the trouble? Is there a better material for the job?

This thread (link below) is all about floating floors, but the same applies to walls:

http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

6. Receptacles: I am planning to use the putty backers AND caulk the from of each receptacle. Is that sufficient? Too much?

A MUCH better plan is to not cut any holes at all in your isolation shell! Just one small hole to bring in the main power feed through suitable conduit, then distribute from that point using surface-mount electrical system.

7. Caulking/sealing: I plan to use typical silicone caulk for the corners at the drywall, at the gap between the drywall and the slab, and around doors and everything else. Is this ok, or would it make a significant difference to use an acoustical sealant?

Acoustic caulk is better, of course, but ordinary caulk works well too. Just make sure you get the type that never sets hard: it remains soft, flexible and pliable forever. Get a good quality one that sticks like crazy, and don't use the transparent type: it is lower density. Use the colored type (any color: white, grey, brown, black, whatever: just not transparent).

Am I on the right track? Is my goal reasonably attainable given my plan, or should I rethink this entirely?

Well, you didn't actually define your goal! The most important goal is the number of decibels that you need to isolate. That's the key to designing any isolation system. So you should figure out that number first, then check on construction methods and materials that will give you that amount of isolation, and within your budget.

the main wall system separating the units will be quite good (two layers of 5/8" drywall with GG, an insulated 2x4 stud cavity, a 2" air gap

Careful there... If you have 2x4 studs and a 2 inch framing gap, and are using conventional construction, then you have a 5-1/2" air gap...

The weak point is at the top of this wall. ... My plan is to fill those areas with layers of drywall. But I'm wondering, is it worth while since there will be a flanking path through the joists themselves which short circuit the drywall?

That entire wall, and the roof above, are all one single component: They are your outer leaf. so anything you do to seal them up and increase the mass is good. Once that is complete, then you build the new inner-leaf walls, with the new inner-leaf ceiling resting on them, also as a single unit, but with no connection to the outer leaf (except the floor). In other words, the existing structure plus your beefing up and sealing is one unit, and the new room (stud framing with drywall on only one side) is another unit. As long as these two "units" are decoupled from each other (no mechanical connections) then you are OK. So your plan of beefing up and sealing that weak section above the concrete walls is excellent, since it creates a better outer leaf, with more consistent mass and a more complete hermetic seal.

- Stuart -

[jdrews]

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

Sorry about the lack of response, but I've been on vacations the last couple of weeks, and out of touch: no internet! Beautiful...

Anyway:

Thanks for taking the time to respond. I very much appreciate your advice. My comments are in red.

The basement walls are (I think) 10" thick poured concrete

Excellent! That's a good start for isolation.

and the floors are truss joists that span from wall to wall.

You mean the floor above you, or your own floor? If it's a basement, I'd assume that your floor is slab on grade?

Correct. The basement floor is concrete slab on grade, the first floor is truss joist.

My biggest fear is that I will dump a lot of money and effort into this, and realize that it's not as quiet as I anticipated,

Welcome to the world of studio design! That's a very common fear... and the solution is to design every last detail up front, carefully, with full understanding of what each part does... before you ever buy even a single stud or nail. Planning is the key to getting it right.

What I have now, I've estimated will cost me about $2500-3000 in materials. I would like to keep it in that range.

If that is only for the actual building materials for isolating the room, then you might be able to stretch it, but don't forget that you¿ll also need to budget for the HVAC system, electrical system, and the acoustic treatment inside the finished room.

Walls and ceiling will be 2x4 wood framing, 16" OC,

24" OC is cheaper (less materials) and slightly better acoustically.

the cheapest fiberglass batt insulation

Don't go for "cheapest". Instead, go for "lowest cost that does the job effectively". The insulation that goes inside the wall cavity is part of the tuned MSM system. It has to be the correct type and density to do its job, which is to act as acoustic damping on the various types of resonance going on inside the wall.

two layers of 5/8" drywall with green glue between drywall layers

While that would be great, I don't think your budget will stretch to Green Glue. Get a quote from them, and take into account that you need two to three complete tubes for each panel of drywall....

My above estimate is based on all the building materials required to complete the room. It takes into account two layers of drywall with 2 tubes of greenglue for each panel. This is the bulk of the cost. The electrical and mechanical are minimal for what I intend to do. [It's not a large room.

There will be at least a 2" gap between exiting and new construction.

Careful with terminology! "Gap" can mean many things. What you want is at least 4" of air space across the wall cavity, between the surface of the outer leaf and the surface of the inner leaf. That entire gap should then be filled with insulation, but it is still considered "air gap" because insulation is mostly air anyway. But 4" might not be enough: you have to do the math to make sure that the MSM resonant frequency will be low enough to meet your goals, and that the entire system will provide the level of isolation that you want.

I should clarify: There is a 2" space between the new inner stud wall and existing outer stud wall or concrete wall. The air space is actually much larger when the stud cavity is taken into consideration. 5.5" at one concrete wall, 9" where there is a double stud wall, and the other walls are a great distance from existing walls (3-10 feet).

1. Doors: Because of the space I'll need three doors.

I guess that the two 32" doors go back-to-back at some point, but you didn't post the plans for your room, so it's hard to figure out what you have in mind...

and one double door to mirror the 48" door that is currently in place. I was planning on using solid core exterior doors from a big box store, but the double door is harder to find. Are there any suggestions for cheap doors that would be good for this?

There's a reason why you very seldom see double doors in studios: They are notoriously hard to get a good seal on, and without a good seal, there is no isolation. Double doors that can be used in studios do not come close to meeting your objective of "cheap". You could blow your entire budget on a good set of acoustic rated double-doors- So I'd suggest rethinking that plan: If that were my place, I'd swap the existing 48" door for a single 36" or 38", frame and drywall the empty bit left over, then mirror that door on the inner leaf.

There is a PDF attachment in my original post that shows a floor plan. The two 32" doors i mention are separate openings which are necessary because of the layout. I need access to both unfinished areas that will be separated by the furnace and water heater. I am not using a double door for those, because they are opening up to what is the equivalent to a large air space (mechanical/storage rooms) that do not need noise reduction themselves.

2. Existing space treatment: I feel like something needs to be done to at least the existing ceiling before beginning the room. It is completely unfinished and terrible as far as sound transmission goes. I was going to put insulation and draywall at the bottom chord of the truss joists but then I read about triple leaf effect. So would it be better to glue pieces of drywall to the subfloor instead?

You have the right idea there, but the method is a bit different. What you are doing is often referred to as "beefing up": you are adding mass to the existing outer leaf. The normal way to do that is to cut pieces of 5/8" drywall to fit in each stud bay up there, hold it in place with cleats nailed sideways into the studs, and carefully caulk all the way around the edges. Also use caulk to seal any gaps, cracks, small holes, o anything else up there. Your goal is to make that floor above you fully air-tight, and to have consistent mass all across it (constant surface density). Depending on what is up there already, you might need more than one layer of drywall to get there. But you also have to take care to not overload the existing structure: you'll need a structural engineer to tell you how much extra load you can add safely.

I'm afraid adding mass to the ceiling outer leaf is going to be very challenging, making it airtight is nearly impossible, given the ducting, wiring, piping, penetrations, etc. I wonder how effective the mass would be if it is not air tight, and not necessarily covering the entire exposed ceiling. I'm not concerned about the capacity of the floor. I am a structural engineer, and these trusses have plenty of extra capacity.

Would insulation be necessary? Based on other threads here, it would seem that since I'm already adding insulation to the new wall, additional insulation would be negligible. That's counter-intuitive to me.

Your intuition is correct! Once you have beefed up the floor above you, then you do indeed need to put insulation up there too. The insulation here serves the same purpose as in the walls: it acts as damping on the multiple acoustics stuff going on inside. The more insulation you put in, the better it gets. Not because the insulation absorbs the sound passing through the walls (that's the normal way that people think about it, but that effect is minor), but rather because it is an integral part of the whole MSM system. It does the exact same job as what the shock absorbers on your car do. Without those, even though you still have the suspension springs attached to your wheels, the ride is terrible. Without insulation, even though you still have the air gap between the two leaves, the isolation is terrible. Insulation = shock absorber. It can add anywhere between 5 and 16 dB of isolation to your walls. So use the right type, and put in as much as you can without compressing it.

That is easy enough to add

3. Existing Ducts: The room will not be touching the overhead ducts directly, but I'm still concerned about bass vibrating them and causing sound to travel throughout the house. What is a good way to prevent that? Should I wrap them with something as a dampener?

The best way to deal with that is to build soffits around those ducts, with framing and drywall, and also with insulation inside. Yes, that does create a 3-leaf system, but it's still the best way to do it at low cost.

That seems doable. I'm also considering wrapping the ducts with FatMat to dampen them. The actual furnace itself and the larger plenums will be more difficult to tame since they are adjacent to the room and cannot be enclosed much more than they already will be.

4. Ventilation: I intend to run one inlet and one return duct. I guess I'll build a baffle box for each,

Right! Except that you need two silencer boxes on each duct, if you want high levels of isolation. One box goes on the outer-leaf penetration, and the other on the inner-leaf penetration. If you don't need high isolation, then you can get away with just one, if you do it carefully.

or just wind some flex duct in the truss space.

Only if you don't need good isolation...

My concern here is how stuffy the room will get when the furnace is not running since it will be nearly air tight. Will having the ducts be sufficient for health safety and comfort, even when not running the fan to circulate air?

Why would you turn the fan off? It doesn't draw much power, so you an leave it on permanently. Your fan is independent of the furnace fan...

I think i'll wind some flex duct from the supply into a baffle box built onto the inner structure. I'll do the same for both supply and return. And add an inline fan to the return side to help circulate air when the furnace is not running. Another concern is it getting to hot being that the temperature of the room has no impact on the thermostat, there is no equalization with the rest of the house, and the supply is right off the main branch. I might put a damper that switches the supply air to draw air directly from the unfinished mechanical room space if it gets too warm.

Is there anything else I need to consider regarding ventilation?

Yes: Room changes per hour, occupation, sensible heat, latent heat, flow volume (CFM), flow velocity (fpm), duct size, silencer cross section, baffles, static pressure. Those ate the biggies.

This is a small room that will only be used for casual practicing with 1-4 people. More than likely it will end of being used as a kids play room, or a guest bedroom.

5. Decoupling: The one decoupling problem with my plan is the slab. it is technically decoupled from the exterior walls, BUT the room will be fastened to the slab which is fastened to other interior framing (the finished portion of the basement) which is attached to the floor joists which is attached the walls and other units. It's a rather long and probably poor flanking path, but I wonder if it's worth setting the new framing on rubber strips or something.

You can if you want, but you probably don't need to unless you have a need for high levels of isolation. Floating your walls is just as complicated as floating a floor, and just as hard to get right. And just as easy to get wrong! There's a lot of math and assumptions that go into that, so unless you understand how to calculate the amount of deflection percentage you'll need for the exact type and thickness of rubber you are using, in order to get the resonant frequency down to at least one octave below the lowest frequency that you need to isolate, then you won't get anywhere! Your chances of getting it right by pure luck are about as good as your chances of winning the state lottery in all fifty states on the same day... without buying any tickets!

I have some rubber base molding I am considering running beneath the sole plate of the new room. Is that worth the trouble? Is there a better material for the job?

This thread (link below) is all about floating floors, but the same applies to walls:

http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

That's true. It's probably not worth the trouble in my case.

6. Receptacles: I am planning to use the putty backers AND caulk the from of each receptacle. Is that sufficient? Too much?

A MUCH better plan is to not cut any holes at all in your isolation shell! Just one small hole to bring in the main power feed through suitable conduit, then distribute from that point using surface-mount electrical system.

That would be ideal for sound control. However since it will probably end up being used for other purposes, II would rather not use surface mounted conduit for aesthetic purposes.

7. Caulking/sealing: I plan to use typical silicone caulk for the corners at the drywall, at the gap between the drywall and the slab, and around doors and everything else. Is this ok, or would it make a significant difference to use an acoustical sealant?

Acoustic caulk is better, of course, but ordinary caulk works well too. Just make sure you get the type that never sets hard: it remains soft, flexible and pliable forever. Get a good quality one that sticks like crazy, and don't use the transparent type: it is lower density. Use the colored type (any color: white, grey, brown, black, whatever: just not transparent).

Am I on the right track? Is my goal reasonably attainable given my plan, or should I rethink this entirely?

Well, you didn't actually define your goal! The most important goal is the number of decibels that you need to isolate. That's the key to designing any isolation system. So you should figure out that number first, then check on construction methods and materials that will give you that amount of isolation, and within your budget.

The loudest condition the space will see is a 4 piece rock band with acoustic drums, a couple smaller guitar amps, bass and vocals through a PA. I've seen estimate at around 110db, but my concern is mostly with the low frequencies from the bass and kick drum. I know those are going to be the most difficult to contain.

the main wall system separating the units will be quite good (two layers of 5/8" drywall with GG, an insulated 2x4 stud cavity, a 2" air gap

Careful there... If you have 2x4 studs and a 2 inch framing gap, and are using conventional construction, then you have a 5-1/2" air gap...

The weak point is at the top of this wall. ... My plan is to fill those areas with layers of drywall. But I'm wondering, is it worth while since there will be a flanking path through the joists themselves which short circuit the drywall?

That entire wall, and the roof above, are all one single component: They are your outer leaf. so anything you do to seal them up and increase the mass is good. Once that is complete, then you build the new inner-leaf walls, with the new inner-leaf ceiling resting on them, also as a single unit, but with no connection to the outer leaf (except the floor). In other words, the existing structure plus your beefing up and sealing is one unit, and the new room (stud framing with drywall on only one side) is another unit. As long as these two "units" are decoupled from each other (no mechanical connections) then you are OK. So your plan of beefing up and sealing that weak section above the concrete walls is excellent, since it creates a better outer leaf, with more consistent mass and a more complete hermetic seal.

This might be the complicated part. This link shows a similar detail to what I have: http://goo.gl/4MlH8v. The the right side of page 10. THe only difference is that I have trusses instead of 2x10's so there is no rim joist closing it off. So I can touch the drywall (2x1"thick) in between truss joists. That needs to be sealed off and mass added.

[Soundman2020]

My above estimate is based on all the building materials required to complete the room. It takes into account two layers of drywall with 2 tubes of greenglue for each panel. This is the bulk of the cost. The electrical and mechanical are minimal for what I intend to do. It's not a large room.

Your estimate includes studs, insulation, nails, and acoustic caulk too? You are going to need a ton of caulk, and it isn't cheap. Good insulation isn't cheap either, for the amount you need in a studio.

I am not using a double door for those, because they are opening up to what is the equivalent to a large air space (mechanical/storage rooms) that do not need noise reduction themselves.

You seem to be misunderstanding the physics behind the way that MSM systems work for isolation. An MSM wall is a resonant system that is tuned to a specific fundamental resonant frequency, and provides excellent isolation for sounds on opposite sides of the entire wall, for all frequencies that are higher than about twice resonant frequency. But it provides practically no isolation for sound sources that are inside the resonant cavity, between the two leaves of the wall. What your diagram shows is that you have a furnace, a water heater, a drain pipe, and and stairwell inside your wall cavity, so will you get no isolation for those as they are planned right now. Your furnace sounds will be clearly audible inside the studio, as well the sound of people on the stairs, and the sounds of your studio will take that route up the stairs into the rest of the house. In order to isolate your room properly, you have to complete the MSM system such that there are two complete leaves around the room, separating it from the rest of the world. Right now, that is only happening on two sides of your room. You need to complete it for the other sides as well, where the furnace, storage, and stairs are. And that automatically requires that you have back-to-back doors in the locations where you are only showing single doors right now. If you don't do that, you don't get isolation for the entire room. MSM is a compete system, and it is tuned. If you don't do what is needed to tune it, then it doesn't work at all, and the entire room remains non-isolated.

I'm afraid adding mass to the ceiling outer leaf is going to be very challenging, making it airtight is nearly impossible, given the ducting, wiring, piping, penetrations, etc. I wonder how effective the mass would be if it is not air tight, and not necessarily covering the entire exposed ceiling

That's often the case in basements. The only other option is to create a three-leaf system, which will work too, but unfortunately it will eat into your room height a bit.

The actual furnace itself and the larger plenums will be more difficult to tame since they are adjacent to the room and cannot be enclosed much more than they already will be.

Once you complete the MSM system as I outlined above, the furnace itself will be on the other side of a fully decoupled two-leaf MSM wall, so it won't be causing any issues inside your room. It will be inaudible, if the MSM is tuned right and the wall is built right.

From the photos you posted, it also looks like it won't be too hard to soffit in the ducts. Once again, it will eat into your room height a bit, but with careful framing that only needs to happen in some places.

That would be ideal for sound control. However since it will probably end up being used for other purposes, II would rather not use surface mounted conduit for aesthetic purposes.

Maybe you aren't getting what I mean by "surface mount" systems. They can look really nice, and are commonly used in open-plan offices these days. Here are some examples:

http://www.export.legrand.com/EN/dlp-wa ... ng_95.html

http://www.calcentron.com/Pages/fram-tr ... aceway.htm

The loudest condition the space will see is a 4 piece rock band with acoustic drums, a couple smaller guitar amps, bass and vocals through a PA. I've seen estimate at around 110db

Probably a bit higher: more like 115 to 120, if the drummer is a bit heavy-handed and the bass player like it loud. The drum kit alone can hot 115 dB, without too much trouble.

but my concern is mostly with the low frequencies from the bass and kick drum. I know those are going to be the most difficult to contain.

Right. Lower frequencies are much harder to isolate than higher frequencies.

So assuming 115 dB in your room, how quiet do you need that to be outside the room? That's the key question. The difference between that and 115 dB is how much isolation you need. A typical house wall gets you around 30 dB, and what you are proposing right now would get you around 35 to 40. If you complete the MSM system properly and do the other stuff I have outlined, you would be getting around 50 dB of isolation or so, which is about as good as you can expect from a home studio in a basement. So your 115 dB peaks inside the room would be heard at about 60 to 65 just outside the wall, and decreasing with distance. Provided that there is no structural flanking, and no leakage into the HVAC system, then you'd likely be getting around 40 to 50 in the rest of the house. Is that quite enough?

- Stuart -

[jdrews]

Thanks for the response. You make good points that I need to consider a bit more carefully.

I do understand the basic physics behind the double MDM system. I realize it is not ideal to have the furnace and stairs in the wall cavity. I'm not concerned with keeping noise from the stairs and furnace out of the room. I'm only concerned with keeping noise out. And although I want some minimization to the rest of the house, my main concern is keeping noise out of the adjacent units. So although there will be some bleed into the rest of the house through the HVAC system, ultimately the outer wall of the system is the concrete/2" drywall separation wall. If I had enough room I'd put build the second leaf next to the first all the way around, but that would get tight.

So really the wall system between my music and the neighbors would be two layers of 5/8" with GG on wood framing, insulation in the cavity, varying cavity depth, and then 10" concrete wall (or the bigger concern, at he top of the wall 2" drywall). I don't know what the neighbors have on the other side of the separation walls. Probably finished, if that helps at all. I think the weakest point may be where the 2" drywall rests on the concrete wall. That may need to be sealed better than it already is, and it's difficult to access.

I would like to be able to play music without the neighbors hearing anything. That's probably not realistic. I would settle for them not hearing enough to annoy them while doing other things like watching TV.