TM Soundproofing The Triple Leaf Effect

The Triple Leaf Effect

During your research on the topic of soundproofing, you may have come across commentary on "triple leaf walls". In this article we will take a look at what a triple leaf wall is, and why they are very undesirable for any sound isolation application.

What is a triple leaf wall?

A triple leaf wall is a wall with 2 air cavities, and not just one. Similarly, a quadruple leaf wall would be a wall with 3 air cavities. A leaf in a wall is a solid layer like drywall and a triple leaf wall has 3 leaves, etc. Like this:

Here we see single leaf (no air cavity), double leaf (like most walls), triple leaf and quadruple leaf constructions. It is important to remember that if you use 2 layers of drywall directly against each other, it still only counts as one leaf because there is no air cavity between the layers. In the sketch below we show again single through quadruple leaf walls, but this time they all have the same number of drywall layers.

Why is a triple leaf wall a bad thing?

It is not illogical to presume that the quadruple leaf wall above would have the best sound isolation. After all, the sound has to go through a

Solid mass & air space & solid mass & air space & solid mass & air space & solid mass.

That quadruple leaf wall is decoupled 3 times over! While in a double leaf wall, it has to make it through only one air space, and in a single leaf wall there is no air space at all.

While this makes sense, it is very false, especially at low frequencies. To understand why this is, we have to take a look at how decoupling works. Decoupling isn't effective at all frequencies. If you take two layers of drywall, and separate them with an air space, it does not improve things at all frequencies. The air in the cavity acts like a spring, and creates a resonance. Only well above this resonance do things improve (but then they improve very nicely indeed). This graph should make the point:

Effect of Decoupling a Solid Mass

What you see is the sound-stopping power of the wall, in decibels, at different frequencies. This is called "transmission loss". While this data is hypothetical, this is what occurs in real walls, the decoupling has a large positive effect at high frequencies, but a negative effect around the resonance.

Resonance must be as low in frequency as possible

To attain good low frequency performance, this resonance must be as low in frequency as possible – otherwise the weak point of your wall will fall at an unfavorable location, and low frequency noise will have little trouble passing through the wall.

The goal of any decoupled wall should be to drive resonance down in frequency. To do this you have to
1. Add mass to one or both sides of the wall
2. Increase the depth of the air cavity
3. Add insulation (if you don't have insulation)

Triple leaves are bad because for a given amount of mass and space,they always have a higher resonance point than a double leaf wall.

One of the criteria that were given above for getting a low resonance point & and good low frequency performance was a deep air space, with a lot of mass on either side.

The double leaf wall might have an air cavity depth of 8, but for the same overall net wall depth, the triple leaf walls cavity will be just half that, and the quadruple leaf's cavities will be only 1/3 of the depth of the double leaf wall.

To make matters worse, each leaf in the double leaf wall is very heavy, but each leaf in the quadruple leaf wall is far lighter & half the mass. This will cause resonance to go up in frequency even more, and low frequency performance will be badly degraded.

To further complicate things, a triple or quadruple leaf wall may exhibit more than one low frequency resonance and if one is bad, then two or more are surely even worse.

Finally, the resonance behavior of multiple leaf walls isn't simple or entirely predictable, and may be more severe than with a double leaf wall.

Next, let's take a look at just how bad triple leaf walls can perform relative to their double leaf counterparts.

These are tests TLF-95-107a (double leaf) and TLF-95-153a (triple leaf), taken from IR-811, a document published by the National Research Council of Canada. This data is copyright NRC Canada and shared with permission.

The difference here is stunning to say the least. It is even more remarkable when you consider that the same type of construction, and same type and amount of materials were used in each case.

Double leaf & resilient channel on joists, one big air space

Triple leaf & resilient channel between drywall layers, small air space

The STC values shown above are from a series of tests run by Owens Corning in 1972 at Geiger and Hamme laboratories. While STC doesn't tell the entire story, the point is clearly made.

Summary:

Triple leaf (or quadruple or higher # of leaf) constructions should be avoided like the plague. You will always get a lower level of sound isolation, and this loss may be most severe where you need performance the most, low frequencies.

Click here to return to our Acoustic and Sound Proofing homepage.

Customers Questions and Answers

1) Will: Hi, I am in the process of building a studio for a youth project and we are in a room which has a neighbouring stud wall. In other words, the wall between us and the room next door is a stud wall. It is one frame with one sheet of plasterboard either side. We are going to build a room within a room but we are not allowed to remove the plasterboard from our side. This means we will have a triple leaf effect. Is there anything we can do to reduce this? Many thanks for your help. Will.

Trademark Soundproofing Reply: Hi Will, The deeper the air space between the boards the less of an effect the triple leaf will have. So when framing your new wall move it in as far as possible and put boards on the inside only that should create enough air space for you.

2) Brian: We are renovating a bed/bathroom loud outside voices the concern. The Ext. wood stud wall will have 2.5'' spray foam in a 3.7'' stud bay then MLV applied,then RC channel,then 5/8 drywall. will this create a triple leaf effect?

Trademark Soundproofing Reply:

Hi Brian, As the MLV is a limp material you should not have much of a triple leaf issue there.

3) Brian: Neighboring unit in townhouse complex wants to upgrade her bathroom which is adjacent to our master bedroom. Currently we hear noise that we would rather not hear coming through the adjoining wall. Accodrding to the structural drawings, the shared wall is symetriical, consisting of: 5/8" gypsum, 3.5" space with acoustical insullation, 2 sheets 5/8" gypsum in the middle, 3.5" space with acoustical insullation and 5/8" gypsum. Contractor is proposing to put 1/2" QuietRock over neighbors gypsum using Green Glue. He is suggesting that he needs to use a different thickness of QuietRock than the gypsum in order for the QuietRock to work effectively. There is a significant difference in sound transmission going to 5/8" QuietRock. Can you advise, given what the wall consists of now, whether using 1/2" versus 5/8" QuietRock would be recommended to have best success for reducing sound transmission? Thanks.

Trademark Soundproofing Reply: A heavier wall is better than a thinner wall. So 5/8" is better than 1/2" however it is a very very slight difference.

4) Brian: Thanks for the reply. Follow-up question. What do you mean by "slight difference"? According to the QuietRock website 1/2" versus 5/8" QuietRock can result in 47-52 STC versus 52-74 STC respectively which is a big difference at the high end. Is there any rationale for using 1/2" instead of 5/8" in the described situation (5/8" gypsum, 3.5" space with acoustical insulation, 2 sheets 5/8" gypsum in the middle, 3.5" space with acoustical insulation and 5/8" gypsum); wood frame construction? Is there any concern for a "triple leaf effect"? The contractor conveyed that placing 5/8" QuietRock on 5/8" gypsum would be a problem for sound transmission, that you needed to use a different thickness of QuietRock overtop gypsum. Any truth to this? Thanks, Brian

Trademark Soundproofing Reply:

Hi Brian, In lab testing when using 2 layers of half inch vs 5/8 with the Green Glue I have not seen it to be more than 1-2 STC points difference. when using a pre damped panel like you mention, the 1/2" is really 2 quarter inch layers which may account for the bigger difference you see there. You can check with the company that produces the pre damped panels as to the results.

5) Herb: I've used your process of adding another layer of drywall to my ceiling with a generous coating of the green glue between. For whatever reason I seem to be hearing way more vibrational noise and conversations are clearer now from upstairs. Also there was rockwool insulation blown Ito the ceilling prior to the new drywall being added. It was completed last week . Can you shed some light on this epic fail? While reading your FAQs someone asked about using foam insulation between their walls. Your reply was that the foam insulation would adhere to the two pieces of drywall and ineffect make them one making it easier for sound vibrations to make it through. That seems very much like what's happening t the project I just finished. I will never sleep again and I am so disappointed! Help!

Trademark Soundproofing Reply: Hi Herb. That is very interesting as just adding a 2nd layer of drywall should reduce your noise to some degree. There are many different factors that can effect the sound transfer including the exact work that was done there and what the construction of existing walls and ceilings are etc. Try to contact the company that you purchased the product from to see if they can help you. Also give the GG at least 30 days to cure, especially if you used a "generous" amount. Thank You

6) curtis: in layman's terms what does single stud STC value of 37 vs quiet clip and GG STC value of 63 mean. Can I still hear normal talking, TV and radio on the other side of wall, or percentage wise how much of it is now "blocked"?

Trademark Soundproofing Reply: Hi Curtis. STC 37 you will still hear conversations. STC over 60 is luxury and you should not hear much unless it is very very loud.

7) Greg G: Hi. I have a 2 by 4 wall with fiberglass insulation. Between apartments. I can modify one wall. Would another layer of drywall ( what kind ) clips and green glue be my best option. Not sure of the combination here? Do you have a schematic?Thanks-----Greg

Trademark Soundproofing Reply:

Hi Greg, Yes that would be your best option. Remove the existing drywall, apply clips, channels, 2 layers of half inch drywall with GG. Seal with acoustical caulk and putty pads. You can read more details here soundproofing existing walls article.

8) Greg: I all ready have a finished wall I am working with, ( plastered and painted about two years old ). My thought was to either use the clips on the existing wall and another layer of drywall on the clips or use the green glue on the existing wall and then another layer of drywall. 1. can I use green glue over the plastered and painted wall ? Will it adhere ? 2. Are the clips attached to the existing wall and then drywall on them an option ? 3. Between the two if either is appropriate what would the difference in sould reduction be ? 4. Would cement board give more sound deadining ? Thanks , hope this clarifies my situation. -------- Greg

Trademark Soundproofing Reply:

We do not recommend adding clips and channels over existing walls due to the triple leaf effect. You can add another layer of drywall with Green Glue over your existing painted wall. You have to screw the new layer back to the studs as the GG is not meant to be used as an adhesive. Drywall should be as effective as Cement board. Thank You

9) Karen: In trying to avoid the triple leaf affect how far away should I build a second wall from the adjoining office wall. I am next to a bar with the subwoofer on our adjacent wall.

Trademark Soundproofing Reply: Hi Karen, As long as you can remove the drywall between the new wall and the old one then any amount of distance will be beneficial. If you cannot remove the drywall in between than we suggest a space of at least 6 inches.

10) Abraham: I am trying to sound proof a room that is 6 x 11, so it can be used as a studio. There are already two sheets of 5/8's drywall on the walls and ceilings. Would I be better off using green glue and another piece of 5/8's drywall or using 1/2 inch homasote and 5/8's drywall, or building additional walls for a decoupling effect. I am looking to block out the general noise of the house: Tv's, radios, washing machine, the kids playing etc... What do tou think?

Trademark Soundproofing Reply:

Hi Abraham, If there is insulation in your walls than I think adding another layer of 5/8 drywall with Green Glue should be enough. If there is no insulation then you should consider removing your wall adding insulation and at that point you can decouple your wall with resilient sound clips, channels and finish with double layer of drywall and Green Glue.

11) Karina: Hi, I have problems with sound transmission through walls/pipes in wall, and maybe some resonating in my room. So, I am wondering how would I figure out what kind of walls are between me and my side neighbor? I think the walls are hollow inside (they sound so) but how do I figure out if there are 3 drywall pieces between me and neighbor (bad triple leaf), or just 2 drywall pieces, or cement plus drywall on each side? I cannot tear down existing walls, don't have any approvals. If I hire a contractor to just green glue +mlv another layer of drywall on top of my room wall can that make the situation worse (if I don't know what's between me and neighbor)? Thank you, Karina

Trademark Soundproofing Reply: Hi Karina, You can try obtaining the original construction plans from the builder otherwise you would need to make a hole in your wall. Adding more drywall with Green Glue to your existing wall or adding MLV will only make it better.

12) Ed C: Trying to reduce sound emission from vacuum pumps under a table which will have sheet metal panels boxing in the space under the table. We are thinking of using a 2" layer of Owens Corning 705 against the panels and then hang 1/8" MLV in front of the 705 - sound hits the MLV first .....or....should we attach the MLV-PSA directly to the metal [to create a CLD, Dynamat type product??] and have the 705 as the first acoustic layer

Trademark Soundproofing Reply: Hi Ed, I would attach the MLV directly to the metal and have the 705 absorb the sound first.

13) Bob: Turning 120 year old house into two apartments,(upstairs and down).I plan on stripping the 1x6 t&g off ceiling and floor leaving me with full 2"x8" joist on 19" centers. For the floor 3/4 t&g osb green glue 1/2" osb. Ceiling hat channel and two layers drywall with gg in between. Insulation in cavity. (1)Is it best to to completly or partially fill with insulation. (2) I would like to add several can lights. Is there a good way to sound proof them. (MDF box gg and drywall on the inside glued to ceiling and not touching joist?). It's going to be a lot of work so any advice to get it right the first time would be appreciated. Thanks Bob

Trademark Soundproofing Reply:

Hi Bob, Minimum of 6 inch insulation, no problem with fully filling the cavity. Your idea of building boxes around the cans is a good one. Lately we have been advising customers to use flat LED lights that have the same look as recessed lights, those just use a a standard electric box which can be treated by using an acoustical putty pad.

14) Jo: Hi, I inadvertently created a triple leaf (maybe quadruple) wall before reading this article and learning about them. My wall assembly is as follows: drywall, 2x6 studs (filled with insulation), plywood, 2" air space (between the 2 wall assemblies), 2x4 studs, drywall, RC channel, drywall. What can I do to remedy this situation? I'd hate to tear down the drywall and redo since I just had it put up. Will filling the entire cavity (2" air space + 2x4 studs) with blown in insulation help?

Trademark Soundproofing Reply: At this point I would just leave it and see the results. It is still a good wall for many frequencies and you may be OK.

15) jason: I have a new build home (still in the framing stage, 2x6 studs) which is within 30 feet of a train. the train blows its horn right at the house. for insulation I plan on 2" of sprayed in polyurethane foam and then 4" fiberglass rolled in insulation. next I was going to put sound clips and two layers 5/8" drywall. I would also like to use the mass vinyl product either between the two sheets of drywall or on the studs. or would green glue be better? I am willing to build ANY type of configuration that you would recommend.

Trademark Soundproofing Reply:

Hi Jason, You are better off using the green glue between the layers of drywall. If you would like to add mass loaded vinyl in the nix than you should install it on the channel before adding the first layer of drywall. (you can also add it to the studs before applying the clips as there is no serious issue of the triple leaf with the mass loaded vinyl as it is a limp material). We do not recommend spray foam for soundproofing purposes.

16) Joel: Question: I have a finished basement ceiling with sheetrock, then glue up ceiling tiles fixed to the sheetrock. I'd like to add another layer of sheetrock for sound blocking purposes. Would the ceiling tiles qualify as an air cavity, in which case I would be creating a triple leaf? Or, would they qualify as a layer of somewhat rigid material? I'm trying to figure out if I should remove the ceiling tiles, or leave them in between two layers of sheetrock. Thanks in advance!

Trademark Soundproofing Reply:

Hi Joel, those are somewhat rigid and you can leave them in place if it involves a lot of work to remove them. You may want to consider removing them if you would like to apply Green Glue damping compound between the new layer of drywall and the existing one as that would boost the soundproofing significantly.

17) dougald: I have an existing ceiling. I plan to decouple with clips and add 2 layers of 1/2 drywall with green glue in between. What can I expect?

Trademark Soundproofing Reply: A very big difference over what you have now. Be sure that you install insulation in the ceiling as well. Also keep in mind that any recessed lights or HVAC vents will compromise the soundproofing.

18) Cole M: I have one reservation about clips; Since the Res-channel just snaps into the clips by compressing the flanges together, I think of this as structurally weak, especially for ceilings. If the weight of the drywall is pulling on the middle of the channel/hat-track, that would mean bowing in the middle, basically reversing the process fo snapping the channel in, where the flanges could conceivably slip out of the clips, and result in a falling drywall ceiling? Any known instances of this ever happening, or is this clip system immune to such a scenario?

Trademark Soundproofing Reply: As long as you stick to the layout design and do not exceed recommended clip and channel spacing you should not have any issues.

19) Ted: Our community is renovating an old movie theater, the downstairs (theater 1) is done and we are in the process of doing the upstairs (theater 2) The rear wall of theater 1 has speakers on it and the upper 12' of it is theater 2 front wall. If we install another wall of 2x4 studs with fiberglass insulation fastened only at the top and bottom and covered with drywall on the theater 2 side, will a 6" dead air space be enough to not worry about the triple leaf effect?

Trademark Soundproofing Reply: Hi Ted. You should be OK as far as the triple leaf. However you may still have an issue with sound coming through the floor. You should treat the floor of theater 2 as well.

20) Ted: Thanks for your response, so if we use a layer of MLV on the floor, would it be best to put it down first and set the vertical wall on top of it?

Trademark Soundproofing Reply: Yes. However even if you do the wall first it will be fine.

21) Joe: I have one connecting wall,in a townhouse, with an elderly neighbor who plays her TV at a very high volume. The wall appears to be drywall on each side with fiberglass insulation between. My plan is to install 5/8 drywall over the existing drywall using Green Glue and GG Sealant (no clips). My contractor recommends drilling holes in the existing drywall and filling the space between with Great Stuff insulating sealant (which dries hard). Here are my questions please. 1. Is using Great Stuff a bad idea? 2. Is 5/8 drywall ok or should we use Quiet Rock?

Trademark Soundproofing Reply: If you have insulation in the walls already, drilling and trying to add some more will not help. 5/8 with Green Glue is fine, no need to use pre damped panels.

22) Sally: I live in a mobile home and am doing a bedroom exterior wall to soundproof, to the best of my ability, the sound of a very loud truck next door with dual mufflers, that actually sound like has no mufflers! First, I'm downsizing my window as the windows are old and that contributes to the loud issue. This truck goes off at 4:00 in the morning and idles for a good 10 minutes, so I need my sleep! the project plan is to do what is called a 'staggered wall' which I know you're familiar with; insulating Safe N Sound in the first set of studs and R19 in the second set of studs using the acoustic caulk in all possible places on these studs and then install 5/8" drywall. Since my bed is up against an interior wall, we are also doing that wall with Safe N Sound and taking the R19 all the way over to the opposite wall...these three walls make a U shape so to speak. How do you think this will work for the muffler? New carpeting comes next, so should I put a heavy duty MLV before padding is installed? I wish there was some kind of sound deadening padding! I would buy that! Expense is not object when this has been at the expense of my sleep!!!!!

Trademark Soundproofing Reply:

Sorry to hear that. Your plan is a good one. There is a good carpet undelayment which you can find here soundproof carpet underlayment.

I would also suggest that you purchase our highly rated soundproof window panel.

23) Marc I: I am told there is a "party wall" which goes all the way up thru the attic between our bedroom and our townhouse neighbor. This sounds like a triple leaf effect. We are disturbed by the neighbor's voice, low frequency talking. What benefit can we expect with GG and 5/8" drywall?

Trademark Soundproofing Reply: The Green Glue will have a very big effect on cutting down low frequency sound however you have to treat the wall and the whole in the attic (provided that it goes to the roof and is sealed there). Alternatively you can treat your wall and ceiling.

24) Fernendo: Following up on Joe?s question, so quiet rock is not that much better than gypsum, then? So in between 2 floors that have : carpet subfloor 12 inch joists ( about 8 inches of cellulose insulation which I added and it help some but disapointed because I was expecting more soundprofing from that) then 1 layer of 1/2 inch sheet rock, what should I expect from adding another layer of sheetrock to downstairs ceiling with gglue?And should I go 1/2 inch or 5/8? Thanks in advance and I learned more about soundproofing in this q&a than all the other confusing info out there , so Thanks again!

Trademark Soundproofing Reply:

QR is better vs plain gypsum. My response was when using Green Glue your OK with using plain gypsum in place of Green Glue together with QR. You will gain additional reduction in talking, music etc airborne sound, hard to put a number on it as there are many variables dependent on your construction). You will not gain as much for footfall sound as that would require you to decouple your ceiling. If footfall noise is your concern than you should consider using the carpet underlayment as padding underneath the carpet on the floor. The heavier the drywall the better. So 5/8 is better than 1/2, however the difference is minimal so if you want to go with 1/2" you will be fine. Thank you for your feedback.

25) Sally: What thickness would you recommend for the floor mat? At some point I would think thickness wouldn't even matter so what is the best? The floor is chip board or whatever they call the board that has all the scraps glued together. And right now, I don't know if I'll go with regulary plywood or treated plywood as a second layer, so with that second layer would I need a big thickness? And would I still need a carpet pad over that? This outline for the carpet underlay on the website looks live overkill, but you tell me the best solution of thickness accourding to my outlined plans: existing flooring > green glue > another layer of flooring > matt. Shouldn't this be enough?

Trademark Soundproofing Reply:

Half inch or 5/8 is enough for the 2nd layer of sub floor. If you will be using the Green Glue Damping in between than you can get away with a thick padding under the carpet. The premium carpet underlayment is great and I wouldn't call it overkill when it comes to footfall noise which can be very difficult to eliminate.

26) Andy: I have a 15'x20' summerhouse constructed from 2" thick interlocked planks which have an additional 1" of solid board foam insulation and a final 1/2" sheet of sheetrock. I plan to create a room within a room sitting with a 1" air gap inside the existing structure (1/2" sheetrock) using 4x2 studs, 4" rock wool, 2x 1/2" sheetrock with GG damping between. I have some fibreglass insulation from another job that I was going to use to fill the air gap. Given that the existing external wall has no air gap (as the insulation is solid foam) am I creating a triple leaf effect and does my solution sound workable? Thank you

Trademark Soundproofing Reply: Hi Andy. Unfortunately the board foam will not prevent the triple leaf as the sheetrock can still vibrate independently. Nevertheless your solution is workable and should give you good results.

27) Mark: Hi there - fantastic site you have here. I have 4" stud in an attic space with rockwool packed in and 1/2" fireboard over that. Over the fireboard is 1/2 rubber matting and then 1/4" 54oz felt. (I can not get to the back side of the 4"stud to add additional board. All edges are sealed with fire grade foam. I am planning on adding an additional 2" stud wall, again filled with rockwool then adding acoustic hats and a final 1/2" board. There will be a 2" air gap between the two stud walls. I do not have much additional space to play with and wonder if you have any further suggestions that I could use to modify the second stud wall? Laine.

Trademark Soundproofing Reply:

Thank you. Add a 2nd layer of 1/2" board with the Green Glue Damping Compound in between.

28) Joshua: Great article! I have a finished room in which I am going to build a home theater. I'm in a condo. I wanted to add another studded wall, R-13 insulation, 2 layers of drywall w/ GG. Then I read about triple leaf effect. I really do not want to tear up the existing drywall to eliminate this effect, so what would be better: double stud wall with triple leaf effect or simply adding two layers of drywall with GG to the existing wall (for a total of 3 layers of drywall on interior side)?

Trademark Soundproofing Reply: The double stud wall will be better for the general soundproofing.

29) Joshua: How much better? I couldn't find any data to make a comparison on 3 layers of drywall with GG between each layer. I'm trying to weigh the cost/work to performamce ratio since I'll be installing myself and not through a contractor.

Trademark Soundproofing Reply:

We don't have testing to compare the 2 so we would not be able to give you an exact number. Usually a 3rd layer of drywall with Green Glue Noiseproofing Compound adds an additional 4 STC points (9 points for the 2nd layer) while proper decoupling can add up to 15 points.

30) Ross: I'm finally getting around to finishing my basement in my new home. It has iJoist which are engineered joist. Previously I have placed drywall resting on the top of the bottom flange. Like it says in this article: https://www.apawood.org/i-joist-fire-assemblies. If the basement is finished with drywall on the ceiling over the existing drywall that is resting on the flange, will the sound proofing be better or worse than if I removed the drywall panel and then drywalled the ceiling? The panels are resting on the flange and are not screwed or glued down.

Trademark Soundproofing Reply: That little air gap will create a triple leaf effect. In your case where it is not much labor to remove I would suggest you remove it and screw it to the bottom of the flange so that the 2nd layer of drywall sits right on the first one.

31) Jack: Hello! I have 4"wall filled with insulation plus 5/8" drywall on both sides.If I'll add 2" semi ridgit insulation on side that will helps to reduce noise from my Neighbor?

Trademark Soundproofing Reply:

It will help somewhat. You would achieve much better results if you add a 2nd layer of drywall with Green Glue Damping Compound in between.

32) Gideon: Hi, great site, thanks so much!! My questions it: Which side of the wall should the decoupling clips / 2 layers of gypsum with GG be placed? Would it be best to put them in my own bedroom (where I want to reduce noise) or on the other side of the wall (the noisy side) For reference, the wall would be: 2 layers of 13mm gypsum, 90mm timber with fibreglass insulation, sound isolation clips + resilient channel, 2 layers of 13mm gypsum with Green Glue. Thanks!

Trademark Soundproofing Reply: Hi Gideon. If possible it is best to put on the noisy side.

33) Ryan W: Hi! I'm ready to convert a garage into a full mixing studio by using the room within a room method. From the outside in, there is 1/2in plywood with 2x4 studs, then another set of 2x4 studs (3 inches apart) with 2 layers of 5/8 drywall with green glue between layers. My question is that 2 of the 4 walls are exterior walls and I obviously want a thermal break using insulation but also reduce sound. I love spray foam as it totally seals the exterior wall cavity but don?t want it to hurt the sound attenuation. I was hoping to put unfaced r13 fiberglass insulation in the exterior wall cavity and put 1in insulation board (to fully seal for heat loss) over that. Then on the inner wall use faced r13 fiberglass. I?m just worried about the triple leaf effect, thank you!

Trademark Soundproofing Reply: Hi Ryan. The foam board should not cause any triple leaf effect issues. If you would like to leave it out than spray foam the exterior walls and leave room for some fiberglass and add fiberglass insulation the the interior walls.