Soundproofing wood shed... worth the effort and cost?

Chris del Camino

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Jul 20, 2020
Location
San Diego, CA
Hi folks! New to forum here. Before I begin, please know I've searched forums & threads far and wide on the topic of soundproofing sheds but just had some questions I've never seen fully answered, as well as having bought and read the Gervais build-your-own-studio book.

I've got a 12' x 10' x 10' gable roof wooden shed, elevated a few inches off ground. I'm moving to the location where it's installed, not there currently. I'll outline my basic soundproofing plan before my questions:

- Acoustic sealant to all crevices/corners before adding drywall
- CO 703 (or 705?) sound batt between studs
- RSIC-1 clips + hat channels (studs are 22.5" apart)
- 5/8" drywall
- ISO-step layer on floor + carpet tiles
- Adding lots of sound traps/treatment (a bunch RealTraps actually)

I fully understand that my only real option inside of the room, for treatment, is to deaden as much as possible, and that bass response/resonance in the room will render critical listening impossible/useless. That's OK with me. I'll rent a mixing studio when I need to mix.

My goal is to reduce sound escaping so that neighbors can't hear me practice sax / sing / bump music (if some bass gets out, that's not a huge concern). Also, reduce incoming noise so that rustling leaves and bird chirps don't affect my daily voiceover work (I also do sax recording).

Questions:

1. Main question: Can I skip drywalling the ceiling? I fully expect this would reduce sound proofing, but wouldn't noise escaping from the roof be better than noise escaping from the walls? Or what I just put sound batt between the studs on roof at the very least? Or is hanging decoupled drywall only worth it on EVERY wall/surface?
2. Is the above plan the best bang-for-your-buck soundproofing? I was debating using Green Glue and adding another layer of drywall (or just adding another layer of drywall and saving the $500+ of Green Glue) but I feel that may be overkill
3. There are two vents at the apex of the gable roof on each side. Slit-vents.. will these totally screw my soundproofing? Can I just place sound batt against them? Wasn't planning on an A/C system if I can get by using a fan/duct combo from one of these vents, possibly (it's in NorCal, doesn't get super hot but for a few days each summer)
4. The double doors are huge (64"), but that wall is facing into the yard of the home I'll be living at. Considering creating a 64" x 60" (or however large) "plug" for that door using 2-by-4's, sound batt and plywood on each side (or sheetrock?), which I could put into place when I'm inside (is there a better plan even at the sacrifice of less sound blocking? Like simple windstops/weather stripping + curtains?

Again, sorry if some of y'all have commented/advised on this before, I really have scoured videos/the web and just haven't found a solid answer for these questions above.. any tips/tricks/hints greatly greatly appreciated!
 

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kmetal

Kyle P. Gushue
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Joined
Jul 21, 2009
Location
Boston, Massachusetts
Hi Chris welcome to RO!

Alot comes down to budget, and expectations. Best bet is to use a sound meter about 3ft away from you, and test how loud your are. An RTA app will show you at what frequencies.

Then look up the IR-761 test data paper


https://www.google.com/url?sa=t&source=web&rct=j&url=https://nrc-publications.canada.ca/eng/view/fulltext/?id=04ac8069-a5d2-4038-8787-da064b073e7f&ved=2ahUKEwjcs-Gk_NzqAhWGmXIEHVXQA5YQFjAAegQIAxAB&usg=AOvVaw1Fwk6YyStmgaqR5TL3p9Ux&cshid=1595287410191

This has test data for like 300 assemblies. It will show you what you need for for level of db and frequency content.

You will probably need to call the town hall to see what the noise ordinances are. This way you can be in accordance to the law at the property line.

I've got a 12' x 10' x 10' gable roof wooden shed, elevated a few inches off the ground.

This is a problem, because sound is going to bleed out the floor. You would have to match the mass of the walls and ceiling on the floor. It gets further complicated because the decoupling you would use on the walls aids isolation. So you would need enough mass to compesate for that decoupling.

So the best option is to design to the weakest link. This means make the floor as strong as the walls acoustically, or make the walls as strong as the floor can be.

One option could be to use a layer of self leveling concrete to mass up the floor.

- Acoustic sealant to all crevices/corners before adding drywall
- CO 703 (or 705?) sound batt between studs
- RSIC-1 clips + hat channels (studs are 22.5" apart)
- 5/8" drywall
- ISO-step layer on floor + carpet tiles
- Adding lots of sound traps/treatment (a bunch RealTraps actually)

Use non hardening silicone or butyl caulking, its cheaper than "acoustic caulking" generally, and equally good performance wise.

Use standard "fluffy" insulation for wall cavities, or whichever is cheapest. No need for anything special between the studs.

Risc1 clips are a good option. You would want more than a single layer of 5/8" drywall. 2 would be the minimum on each side of the assembly.

Assuming you can't modify the outside of the shed with more layers of sheathing, you would have to add mass to the inside, in between the wall bays, as Rod diagrams in the book.

1. Main question: Can I skip drywalling the ceiling? I fully expect this would reduce sound proofing, but wouldn't noise escaping from the roof be better than noise escaping from the walls? Or what I just put sound batt between the studs on roof at the very least? Or is hanging decoupled drywall only worth it on EVERY wall/surface?

Your assembly is strong as the weakest link. Any (or a very large portion) of the sound your decoupled walls contain within the shed, will pour out the top, the path of least resistance.

A sound batt is good for 2db or so of isolation. Basically nill.

2. Is the above plan the best bang-for-your-buck soundproofing? I was debating using Green Glue and adding another layer of drywall (or just adding another layer of drywall and saving the $500+ of Green Glue) but I feel that may be overkill

No. Green glue might be useful, it depends on the range of frequencies your trying to isolate. Green glue is roughly equal to 4x layers of drywall, but 4x layers of drywall is more effective at isolating low frequencies by roughly an octave.

3. There are two vents at the apex of the gable roof on each side. Slit-vents.. will these totally screw my soundproofing? Can I just place sound batt against them? Wasn't planning on an A/C system if I can get by using a fan/duct combo from one of these vents, possibly (it's in NorCal, doesn't get super hot but for a few days each summer)

You could use one vent for fresh air exachange. Or block the vent with mass. Your going to need ventilation for the roof, rod describes this in the chapter where he discusses a garage design. You also need fresh air intake because your room will be airtight. A mini split and hrv unit are typical quiet systems for small rooms. Mitsubishi makes a mini split AC/heater that runs at 19db.

Remember your gear will kick a surprising amount of heat, and so will you when playing. And with air tight, double walls, and insulation inside the studio for acoustic treatment you will have a super insulated structure.

Rod describes how to calculate for this in the hvac section.

You could do a thru wall ac, which handles fresh air, and just make a little doorway for it so you can have isolation when not cooling the room.

4. The double doors are huge (64"), but that wall is facing into the yard of the home I'll be living at. Considering creating a 64" x 60" (or however large) "plug" for that door using 2-by-4's, sound batt and plywood on each side (or sheetrock?), which I could put into place when I'm inside (is there a better plan even at the sacrifice of less sound blocking? Like simple windstops/weather stripping + curtains?

You want to match the mass of the doors to the mass of the walls.

You would also need a plug for the window.
 

paulears

Well-Known Member
Joined
Feb 7, 2014
Location
Lowestoft - UK
Always worth checking the concrete before you put lots of weight on its edges. Shed base groundwork is often high on stone and low on concrete, and crumbles. With soundproofing it's mass doing the work. There is no point doing walls without the ceiling, because that's an easy path out. If the walls and floor are a good barrier to the enemy trying to escape, it will take the easy route. They prevent transmission, the energy in the room they would have worked on will take the easy option. If you have a great studio and open the door to the outside world, then you get the level of sound through that doorway. Some will still get reduced by the absorption inside, but open that door and it happily escapes. I'm personally not that certain green glue is as magical as the specs suggest. Two similar studios with similar size and design, one with and one without green glue between two layers of plasterboard, and i'm struggling to hear it's benefit in real terms. My view could perhaps be coloured by the fact it's expensive and horrible stuff, and in American size tubes which don't fit most British guns, and having one tube get jammed and exploded covering me head to foot in the damn stuff. You also get through such a lot of it. If you want the shed to be effective, do all the walls, AND the ceiling.
 

kmetal

Kyle P. Gushue
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Jul 21, 2009
Location
Boston, Massachusetts
Two similar studios with similar size and design, one with and one without green glue between two layers of plasterboard, and i'm struggling to hear it's benefit in real terms.

There's no reason to doubt the test data it works as the data shows. The issue with green glue is it doesn't lower the resonant frequency of the walls assembly. So its effect in low frequencies isn't as good as equivalent layers of drywall. At other parts of the spectrum its equal to 2x layers of drywall, but for the cost of a single layer. At least in America in the mid 2012's. I haven't checked the prices recently.

I believe there have been 2 formulations of green glue. Its possible you used it in its first iteration which i *think* performed differently and/or cost more.

If bass isn't the main concern here gg might be a beneficial path to take.
 

paulears

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Feb 7, 2014
Location
Lowestoft - UK
In the UK, a tube of green glue is twice the price of one sheet of drywall. I'm not sure, but the green glue added very little I could hear (not measure, of course) to the construction's performance. Of course that's the problem with a studio build. You have no way to measure with and without for a design that won't be repeated. Walls and ceiling were all layered and green glued on this project as the budget was there, and I got somewhat underwhelmed by the difference between my studio rebuild without green glue, and the similar sized one with. The specs and the reviews suggested more, I expected more, and the two studios both have very low leakage. Two layers of plasterboard here is around £15 (2 x 8x4 sheets) The recommendations for green glue are two tubes per 8x4 sheet. so that pushes the £15 to £45 - per 8x4 area. The UK is of course a bit odd. Plasterboard, what is drywall in the US actually comes in metric sizes - 1200 x 2400, a tiny but smaller than 8x4 - 600 centres. Bizarrely plywood and MDF come in real 8x4 sheets, but have metric thickness. We're weird!

The extra spent on green glue I'm struggling with. Personal opinion, not actual data of course. The adverts on the sales sites say things like.
The result is dramatic - just one layer of Green Glue Noiseproofing Compound in between two sheets of drywall can eliminate up to 90 percent of noise, even at low frequencies.
That suggests real improvement I simply did not hear in practice, and on the latest build, I took extreme care to seal every potential weak point, even trying a new idea to seal the tops of the wall to ceiling joint where there are potential weak spots where boards need to be cut. The cross joists were put on top of a layer of 18mm plasterboard that was sat on top of the walls, and glued completely around the perimeter, so the joint between the wall and ceiling was absolutely airtight. In my previous builds I put a smoke machine inside the studio space before adding the extra layers, and then checking for gaps - which you can see the smoke seep through. The wall to ceiling joint in the past was always the weak link, and much time and effort went into sealing, but surface sealing is still weak for sound, if OK for for stopping little leaks. The two layers of plasterboard were then added in the normal way, with the green glue.

It's perfectly good, insulation wise, and outside level is tiny, and mainly right at the bottom - but I didn't get the expected result. It's subjective, of course, but perhaps I expect more for the money spent. My new idea did cost a little more because the ceiling timber size had to go up to cope with the extra weight of the MDF/PB/PB, but still was pricey due to the huge amount of glue you get through. AND it's disgusting stuff.

I wonder if anyone has ever built a test room? 4 sheets of plasterboard on stud work with a ceiling, and then added extra layers with a sound source inside, and measure it. That would be really interesting single skin, measure. add another skin, measure - then take it off again and add green glue, measure. Could be an interesting project?
 

kmetal

Kyle P. Gushue
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Jul 21, 2009
Location
Boston, Massachusetts
There's no reason to doubt the test data its reliable.

One place that i find well suited for GG is in situations where the structure cant handle the weight of additional drywall, and isolation must be maximized. Like when using risc1 clips that support a max of 3x layers of dw, and more isolation would be required. GG doesn't add significant weight to the assembly.

The best way to buy GG is in 5 gal buckets, not the tubes.

Id be interested to do a cost anylisis. Its important to differentiate between diy and hired out when considering this. Since a hired job would charge more tape/mud each layer, than to install GG when hanging the drywall.

I think that is where the equalizer is. The cost of installing and taping 4x layers of drywall vs 2 with gg.

At 16$ per tube it costs about the same as a sheet of 5/8 drywall around New England which is 14$. This doesn't include shipping/delivery.

I haven't seen any test data on true double wall assemblies and i feel this is where the biggest gap in LF isolation will reside. But even on a single wall the gg published test data shows 4x dw layers ahead at 80hz and one would expect that trend to continue below 80hz.

I think GG gets used based on advertising more than it is necessary. If your considering 4x layers of dw and that is what meets your requirements gg can be a good alternative. Otherwise i find mass is the besr bang for the buck.

Lol Paul id probably toss the gg in the trash if i got it all over myseld like you did! Argh!
 

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paulears

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Lowestoft - UK
Ha! yes - the plunger on the tube jammed, and it got given a lot of heaving, and then it slipped sideways, the moving part blew out and what a mess.

I like the points you've made - I'm just not sure in my mind if the claims stack up? Nobody else finds them suspicious - so I guess it's just me.
 

Kurt Foster

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Jul 2, 2002
Location
77 Sunset Lane.
Ha! yes - the plunger on the tube jammed, and it got given a lot of heaving, and then it slipped sideways, the moving part blew out and what a mess.

I like the points you've made - I'm just not sure in my mind if the claims stack up? Nobody else finds them suspicious - so I guess it's just me.

 

Chris del Camino

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Jul 20, 2020
Location
San Diego, CA
Thanks for all the responses! And yep Kyle, bass isn't the main concern; I know it's hard to trap and control. And a low bass rumble escaping is way less concerning than the bright, loud tone of my sax.. Lowest note on an alto saxophone is, I believe ~140 hz... if I can reduce frequencies above that as much as possible as well as a human voice singing or doing voiceover, that'd be my top priority.

As per Kyle's link, I went and checked that list of the sound transmission ratings of many types of assemblies... I didn't find one specific to what my potential assembly would do. Since it's a shed, the "outer wall" would be: outer veneer + pressboard, with 2x4" studs inside.. so I'd be adding decoupling clips/hat channels and 2 layers of 5/8" drywall BUT.. what I'm sensing is even that is not worth completing because the outer wall isn't also drywall. My main concern is wasting money, i.e., if moving ahead is a total waste of soundproofing efforts, but if, say, having wood/pressboard outers + double drywall inners gets me 50-80% of the soundproofing effects of having a double-layer drywall outer AND inner wall, then I'd likely just move ahead and construct in that way. Not sure how else I could move forward otherwise.. I mean, I could attach drywall externally, from the outside of the building, to the walls?

As for how to approach the floor.. self-leveling cement might be the way to go? But to mass match, I'm not sure how I'd factor in for the decoupled nature of the double walls I plan on installing.. Some initial calculations:

Each 4'x8' piece of 5/8” drywall is 32 sq ft @ 75 lbs..
For doubled up drywall, we get 150 lbs..

Long walls of the shed are 10’ x 12’ = 120 sq ft, so that’s 562 lbs of drywall per long wall..

The floor is 10 x 12 so I'd want to then at least match 562 lbs of concrete.. about 11 x 50-lb tubs of the stuff hah :) but if decoupling is in essence "adding mass" to the walls, then it might be the case that I'd have to multiply that amount by some factor.. so if it's a factor of 2-3 or more, I'd begin to wonder how many lbs per square foot this structure could support...
 

paulears

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Feb 7, 2014
Location
Lowestoft - UK
The project just completed was going to use strip and isolation clips but the problem with these is they eat up space. Use them in your shed, and you have what? 3" studs, then another 2" of strip and clip, maybe even 2.5", then your layers - that's quite a lot of lost space. We went to direct fixing on the stud walls, which we sat on 12.5mm neoprene strip, maximising the room space.
 

Kurt Foster

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Jul 2, 2002
Location
77 Sunset Lane.
bass transmission is the concern when decoupling. i doubt your sax or even bump music is going to be that much of an issue especially if there's a bit of distance between buildings. put up some insulation and mass on the walls, ceiling and the floor and make sure it's air tight. then address ventilation. that will suffice for VO and sax recording and will mostly attenuate anything else without breaking the bank.
 

cyrano

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Brussels
I've talked about the numbers published by Green Glue with two people that are into acoustics professionally. One was a uni lector, the other one is a friend who measures loudspeaker cabinets, studios and even big sports arenas. Both agreed it's simply a marketing scheme. Not eve a clever one, for that matter.
 

Chris del Camino

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San Diego, CA
Cool. Yeah something had me thinking, "gee it's only a $3k shed, all this soundproofing and treatment is looking like $4k, more than the shed itself." It seems like for my purposes even having resilient channels may be overkill, especially if I don't have full control over the wall assembly or the space to sacrifice 4-8" per wall...

When I initially added up numbers I thought, "I bet I could better spend $600 somewhere else than on this glue which isn't actually even glue" ... I could easily see going for all the tricks and utilizing all the crazy marketed materials and spending more than the cost of the shed itself. I suppose what I'm getting at is, I'd rather "go all the way" at some point in the future when I'd have full control over the build of the space itself, as well as a bigger, more acoustically viable space of over 2500 cu feet.

For this shed it looks like I'm then leaning toward no decoupling of walls, just sealing the hell out of it, adding sound batt and throwing up double drywall layers and creating plugs for the windows/door/vents and adding mass to the floor equal to the mass per sq ft of the walls.
 

kmetal

Kyle P. Gushue
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Joined
Jul 21, 2009
Location
Boston, Massachusetts
Thanks for all the responses! And yep Kyle, bass isn't the main concern; I know it's hard to trap and control. And a low bass rumble escaping is way less concerning than the bright, loud tone of my sax.. Lowest note on an alto saxophone is, I believe ~140 hz... if I can reduce frequencies above that as much as possible as well as a human voice singing or doing voiceover, that'd be my top priority.

As per Kyle's link, I went and checked that list of the sound transmission ratings of many types of assemblies... I didn't find one specific to what my potential assembly would do. Since it's a shed, the "outer wall" would be: outer veneer + pressboard, with 2x4" studs inside.. so I'd be adding decoupling clips/hat channels and 2 layers of 5/8" drywall BUT.. what I'm sensing is even that is not worth completing because the outer wall isn't also drywall. My main concern is wasting money, i.e., if moving ahead is a total waste of soundproofing efforts, but if, say, having wood/pressboard outers + double drywall inners gets me 50-80% of the soundproofing effects of having a double-layer drywall outer AND inner wall, then I'd likely just move ahead and construct in that way. Not sure how else I could move forward otherwise.. I mean, I could attach drywall externally, from the outside of the building, to the walls?

As for how to approach the floor.. self-leveling cement might be the way to go? But to mass match, I'm not sure how I'd factor in for the decoupled nature of the double walls I plan on installing.. Some initial calculations:

Each 4'x8' piece of 5/8” drywall is 32 sq ft @ 75 lbs..
For doubled up drywall, we get 150 lbs..

Long walls of the shed are 10’ x 12’ = 120 sq ft, so that’s 562 lbs of drywall per long wall..

The floor is 10 x 12 so I'd want to then at least match 562 lbs of concrete.. about 11 x 50-lb tubs of the stuff hah :) but if decoupling is in essence "adding mass" to the walls, then it might be the case that I'd have to multiply that amount by some factor.. so if it's a factor of 2-3 or more, I'd begin to wonder how many lbs per square foot this structure could support...

Its important to test how loud your sax, vox, and speakers are. A db meter app with RTA will get you in the ballpark. Down to 80hz is concern for vocals, 40 or lower for music. Bass will be a concern with music, tho you do have a volume knob. That testing is what tells you how much isolation you need. Then you decide what you can afford. No guesswork required.

As far as pressboard. 3/4" OSB is about the same as a sheet of 5/8 dw, 1/2" osb a litte less. So you've got about the equivalent of a single layer of 5/8.

Since the air gap between double walls creates additional isolation than just the mass, it would require extra mass to compensate on the floor. So you'd calculate your walls with a basic MAM calculator, or use available test data. Then calculate the floor with a calculator for that, or use available test data. I believe the IRC has floor data.

The closest to a rule of thumb is the "mass law". 6db of attenuation for each doubling of mass.

So leys say you get 12db of attenuation from double walls or clips, which is about what you get.

You then take the mass of the walls, and apply it to the floor. Say 1" of concrete for example. You then double to 2", for 6db, double that for the next 6db, for 4" total.

This is an overly simplistic way too look at it since the airgap works differently than pure mass, but the db's line up in the ballpark.

In reality you would match the floor up so its isolation values, and its resonances line up. So its got equal isolation at various frequencies.

This is where id call Rod Gervais for assistance before committing to anything.

Cool. Yeah something had me thinking, "gee it's only a $3k shed, all this soundproofing and treatment is looking like $4k, more than the shed itself." It seems like for my purposes even having resilient channels may be overkill, especially if I don't have full control over the wall assembly or the space to sacrifice 4-8" per wall...

When I initially added up numbers I thought, "I bet I could better spend $600 somewhere else than on this glue which isn't actually even glue" ... I could easily see going for all the tricks and utilizing all the crazy marketed materials and spending more than the cost of the shed itself. I suppose what I'm getting at is, I'd rather "go all the way" at some point in the future when I'd have full control over the build of the space itself, as well as a bigger, more acoustically viable space of over 2500 cu feet.

For this shed it looks like I'm then leaning toward no decoupling of walls, just sealing the hell out of it, adding sound batt and throwing up double drywall layers and creating plugs for the windows/door/vents and adding mass to the floor equal to the mass per sq ft of the walls.

One thing i would consider is adding a layer of drywall between the stud bays. This gives you a psuedo double layer (6db gain) on the outer layer. Doubling the inner layer gives you another 6db. So you have essentially standard wall 35db, plus 12db, so 47db in the vocal/sax range. If your singing/playing at 90db, then your 43db ouside the shed. 30db is a whisper, so your 12db louder than that, ie twice as loud.

You could alternatively look at clips/channel with a single layer of drywall and see what the specs show. You could save some $ and labour possibly. Whisper clips are the most budget friendly clips.

You have the floor to contend with either way. You could maybe add some mass and trim to the bottom of the outside of the shed, "a skirt", to help seal in sound, and add another layer of flooring to get 6db gain there. This is probably the best that can be done without a lot of work.

I would design to the weakest link ie the floor, since there is significant diminishing returns when some things have much higher TL than others. Its a waste to gave 80db walls and a 60db floor or ceiling.

Either way, i hope this helps you make a cost efficient solution, and one that suits the purpose. Studio construction is expensive enough, no need to add unnecessary cost to things.

3-5x is not uncommon for studio construction relative to standard construction. So a 3k shed is a 12-15k studio. No wonder so many great rooms closed.
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts
The project just completed was going to use strip and isolation clips but the problem with these is they eat up space. Use them in your shed, and you have what? 3" studs, then another 2" of strip and clip, maybe even 2.5", then your layers - that's quite a lot of lost space. We went to direct fixing on the stud walls, which we sat on 12.5mm neoprene strip, maximising the room space.

5" of wall space for 12db is decent compared to the alternatives. Taking a 12ft room to 11.5 isn't horrible in my book. Ceilings are on area where an inch or two can violate code. But otherwise if 5" makes a significant difference, the room was compromised to begin with, and i wouldn't blame the clips. Conversely and extra 5" wound not improve things to any great degree.

Ive never seen test data for those strips, when i looked some months back. That led me to believe they are innefective, or at best un-proven. Did you get data?

bass transmission is the concern when decoupling. i doubt your sax or even bump music is going to be that much of an issue especially if there's a bit of distance between buildings. put up some insulation and mass on the walls, ceiling and the floor and make sure it's air tight. then address ventilation. that will suffice for VO and sax recording and will mostly attenuate anything else without breaking the bank.

Yes distance is a good thing as you know, 6db for every doubling of distance in a free feild (inverse square law) is our friend.

Plus the neigbors walls are good for 30-35db most likely. So it comes down to noise ordnance compliance at the property line generally.

Tho my mesa boogie full stack was audible from my basement to the neigbors basement 15ft or so away. I suspect the windows to be the culprit since our two Foundations and regular walls spaced an inch off, and 15ft of earth, is a damn good isolator.

That said i was a little surprised it was audible.

I've talked about the numbers published by Green Glue with two people that are into acoustics professionally. One was a uni lector, the other one is a friend who measures loudspeaker cabinets, studios and even big sports arenas. Both agreed it's simply a marketing scheme. Not eve a clever one, for that matter.

How did they disprove the test data, which was done at a credible lab? I would love to see it.

Acoustics can be counterintuitive and subjective sometimes. That's why data is king, whenever available.

Rod Gervias, and others agree it works as advertised. Tho Rod will acknowledge its not suitable for every situation, however where it is suitable, its acoustically effective and can be cost effective too.

https://www.gearslutz.com/board/showpost.php?p=5621087&postcount=74
 

kmetal

Kyle P. Gushue
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Joined
Jul 21, 2009
Location
Boston, Massachusetts

Kurt this guy sells stuff, ive seen his videos they can be misleading.

First he uses absorbsion coefficients. This is the acoustical absorption, no the TL. Nobody is using drywall for an acoustic absorber. The nrc IRC-761 tests show TL at a series of frequencies. This is not the same as a coefficient, which shows how much energy a surface reflects or absorbs, not how many db of isolation. Dbs, and absorption coefficients are not interchangeable.

If a thick concrete slab has a coefficient of like .03 at 125hz, does that mean its not am effective isolation material? It means its reflecting most of the 125hz back into the room. Its a frequency response rating, not a transmission loss (isolation) rating. The logic (or rather lack of logic) presented in this video would lead someone into thinking thick masonry is Worse, than 3/8 plywood. Completely wrong.

Second, nobody in their right mind uses 3/8 veneered plywood as a mass layer. Common is OSB 1/2", 3/4", and 5/8 drywall which are all similar in cost and performance. 5/8 dw is often the best bang for the buck. Using osb as the first layer can add structural integrity to a wall system, and make it easier to hang stuff from the wall as opposed to a wall composed completely of drywall.

The video takes unrealistic materials, and unsuitable data, and misleads people. Noticw he shows no test data of a wall assembly 3/8 veneered plywood. Its not readily available because it doesn't work well for isolation.

The national council of research in canada, tested over 300 assemblies, non included 3/8 plywood.

This guy just fooled people into 6-8x the cost of 5/8 drywall. What's better for isolation, 6x layers 5/8 drywall, or 1x layer of 3/8 veneer plywood?

Isolating sheathing mostly boils down to mass. More mass, better isolation. Use the cheapest mass available.

Further in the 70's and 60's you were far more likely to see wooden slats/strips, usually pine, or perforated mdf/plywood, as a finish material. Motown, and the Powerstation come to mind.

If 3/8 plywood was used, it was likely as a surface for a tuned membrane trap, which is an air spring absorber, with a gap and possibly insulation in the cavity. Its not little to do with the absorption characteristics of the wood itself. Its about the air gap, and flexibility of the wood.

The guy is a fraud.

Acoustics is full of people selling products and services, as well as opinions and myths. This further reinforces my point that data is king. Good data and the proper data for the particular interest is paramount. Otherwise you've got people spending 60$ on a sheet of mass thats not close to as effective as a 12$ sheet of drywall. 6x the cost, and about half as effective.

This guy should sell bridges.
 

kmetal

Kyle P. Gushue
Well-Known Member
Joined
Jul 21, 2009
Location
Boston, Massachusetts

Paul this is false. The graph i linked clearly shows the effect of GG, and i noted low frequencies is not its strong suit, but it clearly has some effect.

2nd. Green glue is not an adhesive. It is a constrained layer damper- ie it never fully hardens, and it doesn't glue anything, you still need screws. By never fully hardening, it can absorb and disperse energy.

Regular construction adhesive that this fool perscribes makes wall assemblies WORSE!!! Not better. It makes them worse than no adhesive at all!

As Rod eloquently puts it.

https://www.gearslutz.com/board/showpost.php?p=4954941&postcount=22
 

Kurt Foster

Well-Known Member
Joined
Jul 2, 2002
Location
77 Sunset Lane.
Paul this is false. The graph i linked clearly shows the effect of GG, and i noted low frequencies is not its strong suit, but it clearly has some effect.

2nd. Green glue is not an adhesive. It is a constrained layer damper- ie it never fully hardens, and it doesn't glue anything, you still need screws. By never fully hardening, it can absorb and disperse energy.

Regular construction adhesive that this fool perscribes makes wall assemblies WORSE!!! Not better. It makes them worse than no adhesive at all!

As Rod eloquently puts it.

https://www.gearslutz.com/board/showpost.php?p=4954941&postcount=22

i don't know that i would call him a fool. ... he explains further here

https://www.acousticfields.com/use-drywall-green-glue-room-acoustics/
 
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