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Hello,

I post exceptionally because drummer from France I can hardly find advice for my sound insulation project. I intend to order the products below and do myself the work with a friend specializing in partitions. Already well advanced in my head and on paper, I have only 1 question. If you had a contact who knows these topics well it would be great to be able to ask him his opinion. I take any last advice to realize well this studio "box in the box", ground, walls, and ceiling based on mass-spring- mass. Here is the plan and the details of my play and my question, or rather seeking advice, is on the balance of these walls:

Does the ratio of rockwool vs masses seem balanced? (Or if it would take more mass or on the contrary more rockwool?)

Note that this apartment is in the basement, no neighbors below or on the sides (left, right, front, behind), but above only and the ceiling height is 2.15 m.

I will use rockwool 70 kg/m3, and that the heavy mass makes about 5 kg/m2 for 2.5mm, or in 5 mm 7.5 kg/m3, or in 10 mm 10kg/m3.

ba13 and ba18 are plates of plaster 13 and 18 cm thick.

(The details concerning the electticity, the light, are regulated, so I do not approach them)

- Floor : Because of this lack of ceiling height, but also because I have no neighbors below, I intend to do the ground quite simply: 5 mm (minimum) heavy mass on the entire surface floor + floating floor 14 mm = 1.9 cm. I know that my floor should not touch the walls (separation of a few mm) to separate, do not create bridges phonic.

- Wall A (where there is the door 82 mm/-50dB): ba 13 mm + heavy mass 20 mm (glued to ba13) + wood frame (100 mm depth) + in the frame rockwool 100 mm + empty air 10 mm + ba 18 mm + heavy mass 20 mm + acoustic Ba 13 mm = 19.4 cm (thicker wall because it looks on the rest of the apartment, and not on the load-bearing wall).

- Wall B (on very thick load-bearing wall): wood frame 100 mm + in the rock wool frame 100 mm + Ba 18 mm + heavy mass 10 mm + ba 13 mm acoustic = 14.1 cm.

- Wall C: Ba 13 mm + heavy mass 10 mm (glued to ba 13) + wood frame 70 mm + in the rockwool frame 70 mm + ba 18 mm + heavy mass 10 mm + ba 13 mm = 13.4 cm.

- Wall D (on thick bearing wall which gives on cellars): As wall B.

- Ceiling: Glue heavy weight to the original ceiling. But before fixing the acoustics shroud (sustainers) in which we enter the lines (rods) to create a frame to put over the rock wool, and screw to the frame of the heavy mass previously glued to the ba13. Total: 20 or 22 cm.

(Note that some rubber bands will be used mainly on the ground so that the wood frame does not touch the ground, so to separate, do not create sound bridges between the tiles and the walls. They will be useful in general construction everywhere necessary if it will break any bridge possible phonic between two "hard" materials.)

Best regards.

(Here are the products used) :

[/url]https://www.amazon.fr/dp/B000SKWD8Y/?tag=r06fa-20[/URL]

[/url]https://www.acoustique-studio.com/sustainer-p25-10-pieces-c2x9061918[/URL]

[/url]https://www.leroymerlin.fr/v3/p/produits/plaque-diamant-phonik-nf-m1-2-5-x-1-2-m-ba13-entraxe-60-cm-e59741[/URL]

[/url]https://www.leroymerlin.fr/v3/p/produits/20pan-lr-120x60-ep15-rocksolexpert-r-35-e163073[/URL]

[/url]https://www.leroymerlin.fr/v3/p/produits/laine-de-roche-ballot-de-4-panneaux-rockwool-l-1-35-x-l-0-6-m-ep-75-mm-r-2-25-kr-e1501880044[/URL]

[/url]https://www.leroymerlin.fr/v3/p/produits/3-panneaux-en-laine-de-roche-rockplus-rockwool-1-35x0-6m-ep-100mm-r-3-e162966[/URL]

Then one of the following 3 heavy masses (must recompare, there are the data sheets) :

[/url]https://www.audiophonics.fr/fr/amortissants/pinta-amortson-bi5a-phd-amortissant-bitume-auto-adhesif-400x500mm-p-5187.html[/URL]

[/url]https://www.audiophonics.fr/fr/amortissants/stuffson-5k-amortissement-polymere-adhesif-500x600mm-03m-p-10698.html[/URL]

[/url]https://www.pierreetsol.com/vente/isolation-acoustique/2537-insulmass-masse-lourde-acoustique-insulco-9145385944301.html[/URL]

Comments

kmetal Sun, 05/05/2019 - 16:01

Im not sure if your using the rockwool to treat the sound of the inside of the room, or if your implying it has a significant effect on the isolation.

You dont need to float a floor. At ground level the existing slab is your best source of isolation.

For walls and ceiling, you either use a new set of wood frames, or RISC-1 clips/hat channel, to create your room-in-room. These are the only two methods that will reliably help isolate the SPLs drums generate.

For mass, standard 5/8" drywall, with optional green glue, are what to use.

Standard fluffy insulation is best for wall cavities.

Rockwool is useful for bass trapping. Rigid fiberglass/rockwool useful for acoustic absorber panels. How much depends on the size of the room. General figures are 20-30% of the surfaces covered with mid-high absorbers, and 40-60% treated with bass trapping.

When talking things like floating floors which dont work except for highly specific and expensive cases, or mass loaded vynal sheets, which are difficult to install and much more expensive than standard wall sheathing, the waters become murky and expensive.

The methods described in Rod Gervias's book "home studio, build it like the pros", is tried and true, cost effective, and widely used in the best of the best commercial studios, home studios, and everything in between. Ive used his methods in several large and small studio builds.

jerem1 Tue, 05/07/2019 - 05:32

Thank you very much kmetal and sorry for the late.

Thank you for that information for the floor. Indeed I was not sure that for the floor it was so easy. I am happy to know that i don't need to build a structure. I heard as you that an american sound engineer, Jonn Sayers, said (if i am not wrong), that in apartment is in the basement, with no neighbors below, it's not mandatory to build a floor with the system mass-spring- mass (like the walls). But is it sure for you ? So if i understand i juste need to put my parquet, floating floor on my actual floor tile ? And no heavy mass like a minimum 2.5 mm in between ?

Yes or the Rockwool i heard also that it is not so much for insulation but for the low frequencies. But i don't know if 70mm rockwool and 100mm for Wall A is enough for my 10m2 room playing drum. In general i don't know if the walls i described seems ok for a 10m2 drum room. But you said that the rockwool need to be around 40-60% for treating bass trapping, and thank you also for that information, it seems that my walls (if i am not wrong) have indeed 40 or 50% of rockwool.

Yes the would be a wood frame or metal as you said. I heard wood can be a little bit better for acoustic than metal but maybe it's not significant.

Thanks a lot.

Kurt Foster Tue, 05/07/2019 - 07:35

be sure to test the concrete floor for moisture content. any flooring specialist wil know how to do this. if there is too much moisture in the concrete any floor tiles / materials will not adhere properly.

kmetal Tue, 05/07/2019 - 14:36

jerem1, post: 460938, member: 51587 wrote: I heard as you that an american sound engineer, Jonn Sayers, said (if i am not wrong), that in apartment is in the basement, with no neighbors below, it's not mandatory to build a floor with the system mass-spring- mass (like the walls). But is it sure for you ? So if i understand i juste need to put my parquet, floating floor on my actual floor tile ? And no heavy mass like a minimum 2.5 mm in between ?

John Sayers is a well regarded acoustician and audio engineer from Australia. For your flooring, there is no need to do anything as far as adding mass. Assuming proper humidity, install your floor covering using standard methods directly on the exist floor. This will probably involve some sort of underlayment in between the tile flooring and new floor covering.

jerem1, post: 460938, member: 51587 wrote: Yes the would be a wood frame or metal as you said. I heard wood can be a little bit better for acoustic than metal but maybe it's not significant.

Wood offers the significant advantage if being able to hold more layers of drywall, and support the weight of a ceiling. It also blocks low frequencies better. Steel has an advantage of being fire proof, and wont twist in high moisture areas.

kmetal Tue, 05/07/2019 - 16:20

For placement of rockwool-

Assuming this room is not used for mixing, just tracking, heres what id generally do.

Cover most of the ceiling with absorption, since low ceiling's reflections are generally not useful.

Id cover the walls behind and to the side of the drum kit, almost completely.

Once you get into the open area of the room id distribute the absorbers more sparsely, treating spots here and there. The goal here being to help tame unruly ambience, flutter, and pings. We want to eliminate interfereing reflections from getting back into the mics near the kit.

This orientation of your absorption, allows for nice tight, punchy, and clear closer micing of the kit, and more open and ambient sound for the more distant mics.

jerem1 Wed, 05/08/2019 - 04:19

Thank you very much for those details and so sorry to ask.

- I noticed that difference between metal and wood. There is not so much humidity so i will go for wood if possible (i will see with the guy that help me what he can do do, prefer) both are ok for me.

- For the floor that was i wanted to do, putting some heavy mass (5kg/m3) in between the actual floor tile and the floating floor. I am just hesitant putting a thickness of 2.5mm, 5mm, or 10mm heavy mass ?

- Ceiling : Yes the rockwool will be the main thing. But insulation, soundproofing is very important for the ceiling because the only neighbors are at the floor upstairs, and i know that for insulation, soundproofing, mass is also very important. So i wanted to do : Glued some heavy mass to the original ceiling, and before fixing rubber/metal acoustic sustainers in which we enter the lines, rods, to create a frame to put all over the rockwool, and finally closing with screwing to the frame the ba13 previously glued to heavy mass. Total: 20 or 22 cm. Exactely : 10mm heavy mass glued on the actual roof + 170 mm rockwool + 10mm heavy mass glued to ba 13mm = 20.3 cm. Do you think it's ok for my drums (soundproofing, acoustic insulation) and there is enough rockwool as you mentioned ? Note that the actual ceiling between me and the neighbors is around 20 cm plaster i think, so i need to isolate well.

- And yes, after insulation, i will do an acoustic treatment inside the room (bass traps, foam...).

Best regards.

kmetal Wed, 05/08/2019 - 07:27

jerem1, post: 460948, member: 51587 wrote: For the floor that was i wanted to do, putting some heavy mass (5kg/m3) in between the actual floor tile and the floating floor. I am just hesitant putting a thickness of 2.5mm, 5mm, or 10mm heavy mass ?

There is no need for more mass on the floor. The concrete slab has tile on it which is heavy, and is insulated by earth (dirt) this is about as good as it gets from an isolation perspective. So your floor is the strongest link in the chain of your build. The walls or ceiling wont meet or exceed the isolation value of the floor.

What you may want to do is use some self leveling concrete, a skimcoat, just to fill in the gaps on the tile/grout, to have a smooth surface to apply the new floor covering to. Id only do this if it was deemed necessary by the floor installer.

jerem1, post: 460948, member: 51587 wrote: Ceiling : Yes the rockwool will be the main thing. But insulation, soundproofing is very important for the ceiling because the only neighbors are at the floor upstairs, and i know that for insulation, soundproofing, mass is also very important. So i wanted to do : Glued some heavy mass to the original ceiling, and before fixing rubber/metal acoustic sustainers in which we enter the lines, rods, to create a frame to put all over the rockwool, and finally closing with screwing to the frame the ba13 previously glued to heavy mass. Total: 20 or 22 cm. Exactely : 10mm heavy mass glued on the actual roof + 170 mm rockwool + 10mm heavy mass glued to ba 13mm = 20.3 cm. Do you think it's ok for my drums (soundproofing, acoustic insulation) and there is enough rockwool as you mentioned ? Note that the actual ceiling between me and the neighbors is around 20 cm plaster i think, so i need to isolate well.

You likely need to remove the existing ceiling drywall, and apply drywall inbetween the framing studs. You can re-use the drywall you remove and pack it in the bays.

This is outlined in build it like the pros, the book you should have ordered by now.

If you leave the drywall as is you create whats known as a "3 leaf" system which makes isolation worse. You want Room in a room. A three leaf system is like a room in a room in a room.

Your proposed setup would have three leafs- 1. Flooring above 2. Drywall on ceiling 3. New ceiling on channel.

When you remove the drywall on the ceiling and pack it in tbe bays, attached to the upstairs flooring, you eliminate one of the leafs.

Ditto for the walls.

For drums isolation id be considering a minimum of 3 layers of mass in the bays, 3 layers on the new isolation framing. Adding green glue in the isolation layers will be very useful.

Even with all that your still looking at sound bleeding upstairs and it depends how pateint your neighbors are. If there watching tv then the noise you make probably wont bug them much. If they're quietly reading then it might.

Since three layers of drywall is the max the RISC-1 clips can hold, and those clips hold the most of any clip/channel system i know, three layers and glue is your limit. After that, you would need a new wood framed ceiling resting in your new walls, which would hold significantly more layers.

They do have heavy duty clip/hanger systems, but they are significantly expensive compared to a new wood framed system.

I urge you to take a step back, get the book, and re-evaluate your plan. You want to make your mistakes on paper where it doesnt effect your bank account.

Youve got to test your drums with a DB meter, and see what the readings are 1 meter from the kit, in your bedroom, outside the studio (outdoors), and upstairs if your neighbors will let.

The readings from your bedroom will be a good estimate of upstairs readings.

A jazz drummer would play in the high 90s DB, where rock/pop/metal 110db+.

Given the time and expense of your project, and the fact that it involves neighbors which could be a different set of folks in a year or two, its absolutely critical your plan facilitates your isolation requirements.

I appreciate the amount of work youve done so far, it shows you have the potential to get it right, but youve got to re-evaluate and alter your plan if you want it to work.

Particularly the ceiling.

For walls you want- studio wall and foundation wall only. This means if your careful, you can re-use the existing framing for your studio walls, and the drywall for adding mass to the ceiling bays.

There is a science to studio design, and an art to project planning and budgeting, which have to have synergy, or you end up with an expensive mistake, or unfinished money pit.

Im glad to help here, but its beyond the scope of this forum to recite the priniciples and designs in the book(s). The best thing is to use it as a common reference, and fill in here whats unclear to you, or unique to your case.

I dont have any financial benefit from the book. I bought my copy in 2006. It led me down a decade of research and studio builds.

jerem1 Wed, 05/08/2019 - 09:55

Thank you for the book i found it (it's not easy for me in english even with google translator, but i will do my best to read it before doing anything).

The neighbors are very nice, it's an office (nobody en the evening and week end) and some noise at the day because they move, they work. But i want to do my best for them and me.

Here is a video if it can help of the room but it's in french if it helps : https://streamable.com/klfdk

- For the floor i have no problem of understanding, i understand perfectly that i don't need to put heavy mass before the floating floor and i wanted to put 5 mm or 10mm but now i'm reassured and i will also save space, but to tell you the truth i am still hesitant, tempted to put only a very little 2.5mm or 3mm heavy pas, or nothing to follow exactly your opinion. I don't think ot can be a problem to put that very thin layer of heavy mass. Hope it's not a big problem, because i don't why, maybe in further to have a flat and just a little dumping surface.

-Also thank you for the Risk-1 i will see with the guy help me, but to separate the wood frame from the ba13 to avoid creating sound bridges i thought more rise use simply that product : https://www.amazon.fr/dp/B00MGCRUI0/?tag=r06fa-20

But the Risk-1 seems very good, i will see for it (i'm quite sure there isn't it in France, i will see, or command it and the guy help me understand it).

- For the ceiling I am sorry but something is not clear for me or for you but i hope i expressed myself enough well to be understood, or maybe i can't understand everything.

In what i described it's only a "2 leaf" system because i just glue to the actual roof some heavy mass (so we have here the first mass) after it's 170 mm spring, and after we close with the last mass (heavy mass glued to ba13). So we have mass-spring-mass system with 2 leaf of mass (1 at the beginning, one at the end). Except if you consider the spring as a leaf but for me it is just the spring, necessary for the mass-spring-mass system and the drying wall where there is the rockwool is not called a leaf. A leaf is in my opinion one the masse. So i heard it's not good indeed to have 3 layers of mass but in my plan there is only 2 layer of mass : the actual ceiling just glued to a 5mm layer of heavy mass, after there is the spring of rockwool, and to finish the second layer of mass just constituted by some mass glued to ba13.

And note that for me the flooring above, the flooring of my neighbors is some parquet. So the parquet+the 20cm plaster ceiling between us and i + the heavy mass i glued to this ceiling constitued a single peace of mass in the systeme mass-spring-mass.

I did not understood this : " You likely need to remove the existing ceiling drywall, and apply drywall in between the framing studs. You can re-use the drywall you remove and pack it in the bays" and this "When you remove the drywall on the ceiling and pack it in tbe bays, attached to the upstairs flooring, you eliminate one of the leafs."

I'm also not sure to understand when you said : "For drums isolation id be considering a minimum of 3 layers of mass in the bays, 3 layers on the new isolation framing." You mean that for the heavy mass on my walls and ceiling, instead of having 10mm of heavy mass consisting by 2 layers of 5mm heavy mass, it's better to have mutiple layers of 2.5 or 3 mm heavy mass ?

If you can do simply draw on a paper there is no better way in think to understand. I am so sorry to ask but the roof seems the main "problem" and i noted that you did not said anything about my walls simulation, so maybe it's sound ok for you for that walls.

- To finish I understood all the rest of you message.

Again i am so sorry to disturb with that project and thank you very much kmetal for your helps and advice, i have at least advanced on some points.

jerem1 Wed, 05/08/2019 - 10:01

Thank you for the book i found it (it's not easy for me in english even with google translator, but i will do my best to read it before doing anything).

The neighbors are very nice, it's an office (nobody en the evening and week end) and some noise at the day because they move, they work. But i want to do my best for them and me.

Here is a video if it can help of the room but it's in french if it helps : https://streamable.com/klfdk

- For the floor i have no problem of understanding, i understand perfectly that i don't need to put heavy mass before the floating floor and i wanted to put 5 mm or 10mm but now i'm reassured and i will also save space, but to tell you the truth i am still hesitant, tempted to put only a very little 2.5mm or 3mm heavy pas, or nothing to follow exactly your opinion. I don't think it can be a problem to put that very thin layer of heavy mass. Hope it's not a big problem, because i don't why, maybe in further to have a flat and just a little dumping surface.

- Also thank you for the Risk-1 i will see with the guy help me, but to separate the wood frame from the ba13 to avoid creating sound bridges i thought more rise use simply that product : https://www.amazon.fr/dp/B00MGCRUI0/?tag=r06fa-20

But the Risk-1 seems very good, i will see for it (i'm quite sure there isn't it in France, i will see, or command it and the guy help me understand it).

- For the roof it's a little bit more complicated because for me in what i described it's only a "2 leaf" system because i just glue to the actual roof some heavy mass (so we have here the first mass) after it's 170 mm spring, and after we close with the last mass (heavy mass glued to ba13). So we have mass-spring-mass system with 2 leaf of mass (1 at the beginning, one at the end). Except if you consider the spring as a leaf but for me it is just the spring, necessary for the mass-spring-mass system and the drying wall where there is the rockwool is not called a leaf. A leaf is in my opinion one the masse. So i heard it's not good indeed to have 3 layers of mass but in my plan there is only 2 layer of mass : the actual ceiling just glued to a 5mm layer of heavy mass, after there is the spring of rockwool, and to finish the second layer of mass just constituted by some mass glued to ba13.

And note that for me the flooring above, the flooring of my neighbors is some parquet. So the parquet+the 20cm plaster ceiling between us and i + the heavy mass i glued to this ceiling constitute a single peace of mass in the system mass-spring-mass.

I think indeed if you read closely again my plan for the ceiling and what i just said above in that post, you will see that my ceiling plan is really more close of that system "STC 63" in that image than anything else : https://recording.org/attachments/imgext-gif.18991/

And also like that double leaf here : https://recording.org/attachments/images-jpeg.18992/

Il will do also in few minutes a draw to describe the ceiling ( i thought it was described well).

I did not understood this : " You likely need to remove the existing ceiling drywall, and apply drywall in between the framing studs. You can re-use the drywall you remove and pack it in the bays" and this "When you remove the drywall on the ceiling and pack it in the bays, attached to the upstairs flooring, you eliminate one of the leafs."

I'm also not sure to understand when you said : "For drums isolation id be considering a minimum of 3 layers of mass in the bays, 3 layers on the new isolation framing." You mean that for the heavy mass on my walls and ceiling, instead of having 10mm of heavy mass consisting by 2 layers of 5mm heavy mass, it's better to have multiple layers of 2.5 or 3 mm heavy mass ?

If you can do simply draw on a paper there is no better way in think to understand. I am so sorry to ask but the roof seems the main "problem" and i noted that you did not said anything about my walls simulation, so maybe it's sound ok for you for that walls.

- To finish I understood all the rest of you message.

Again i am so sorry to disturb with that project and thank you for your help and advice, i have at least advanced on some points.

jerem1 Wed, 05/08/2019 - 11:10

Here are the draws.

I think i understood why you saif 3 leaf, because on all the walls there is a leaf of ba18 plaster and ba13 plaster. But it is not 2 leaf, because there not spring in between. For me and i heard that exactly the "sandwich" i need to do to create mass, ba18 + heavy mass + ba13 are one mass, glued each one to another like one piece.

And it's even more revealing for the ceiling because there is no at all ba18.

http://zupimages.net/viewer.php?id=19/19/p65d.jpg

http://zupimages.net/viewer.php?id=19/19/tyxw.jpg

http://zupimages.net/viewer.php?id=19/19/fdp5.jpg

kmetal Thu, 05/09/2019 - 08:15

jerem1, post: 460953, member: 51587 wrote: For the floor i have no problem of understanding, i understand perfectly that i don't need to put heavy mass before the floating floor and i wanted to put 5 mm or 10mm but now i'm reassured and i will also save space, but to tell you the truth i am still hesitant, tempted to put only a very little 2.5mm or 3mm heavy pas, or nothing to follow exactly your opinion. I don't think ot can be a problem to put that very thin layer of heavy mass. Hope it's not a big problem, because i don't why, maybe in further to have a flat and just a little dumping surface.

Glad to assist you. Theres no reason based on physics to do this. Your floor is the most massive part of your studio already. Mass is pounds per sqaure foot over here, im guessing kilograms per meter over there?

Either way your floor mass exceeds what your planning on your walls and ceiling by quite a bit.

Avatar/The Powerstation, a famous world class, New York City, USA, studio built there rooms directly on a slab on earth (dirt), just like your studio. They added no mass between the slab and the wood floor covering.

Do as you want but know theres no improvement to be made by adding mass to the floor. Theres no acoustics pro, or physicist who would tell you otherwise.

jerem1, post: 460953, member: 51587 wrote: I'm also not sure to understand when you said : "For drums isolation id be considering a minimum of 3 layers of mass in the bays, 3 layers on the new isolation framing." You mean that for the heavy mass on my walls and ceiling, instead of having 10mm of heavy mass consisting by 2 layers of 5mm heavy mass, it's better to have mutiple layers of 2.5 or 3 mm heavy mass ?

Mass is mass so from that perpective 10mm, 2x5mm, and 4x2.5mm is equal assuming it weighs the same.

The advantage to multiple layers is the ability to add Green Glue in between the layers to increase isolation.

For "in between the bays" -

When you remove the drywall on the ceiling, youll expose the ceiling framing joists. The space between those joists is reffered to as "a bay". This is where you'll commonly find insulation. What you do is remove the insulation, and fasten drywall strips (mass) to the studio side of whats the flooring upstairs. You add drywall to the underside of the upstaris flooring.

There are great illustrations in the book. Ill see if i can find a picture in the meantime.

Why your ceiling is 3 leafs.

Leaf 1- upstairs flooring

Leaf 2- existing drywall downstairs ceiling

Leaf 3- your new drywall attach to the clips.

So its mass-air-mass-spring-mass.

When you remove the existing drywall on the ceiling you then have a proper 2 leaf system with the clips and new drywall installed.

As far as that isolation tape, ive never used it. Its not required when using risc-1.

jerem1 Thu, 05/09/2019 - 10:42

Thank you again very much.

For the floor, i think, and read you again, and you convinced me more. But i understand more why i wanted that thin layer of heavy mass : In my mind the problem is not the mass on the floor, you're totally right, there is earth under, and even more materials (it's a classic building in Paris) under that the floor tile. So the problem for sure you're right there is no problem of mass, but maybe a problem of "acoustic", "reflections" with the floor tile himself ? Indeed for me, in my mind, it's a tough and rough material (and i will be just under a thin 1.4mm parquet), so for me, a though and rough material like squares of floor tile are not a good thing for acoustic, not isolation, but quality sound acoustic, reflections, "treatment", etc.... That's why i wanted to put something more "elastic" in between. So in a pure question of mass i understand totally what you said and you convinced me, but if we think more about "treatment", sound reflection, acoustics qualities, i thought that squares of floor tiles are bad, baddest as heavy mass. So i was not clear in the purpose of that thin layer of heavy mass on the ground. But if you understand me and tell me again that i am wrong (and why) on that point, so not isolation, but acoustic but acoustic qualities, reflection, etc... i will go you way, i will put the wood floating floor directly on the floor tile. Sorry to ask, talk, but i just had that thought, i understood more precisely why i wanted that layer of mass.

For the multiple layers i totally understood what you said. But are you sure the green glue has a significant action on isolation ? I did not knew that. I thought it was just a glue but a little bit better than other for acoustic and that was really not significant in the total balance sheet of such a structure. And also i wanted more going on layers of 5.4 mm (it's the maximum in France) than little layers of 2.5 because i thought that it gonna be easier to glue one to each other pieces of 5.4 mm than pieces of 2.5 in further to maintain, keep up the structure. But if you tell me that that green glue is so important that it's better to put thinner layers that thicker, i will go for it (but it still a bigger problem to glue every thing, and more glue used also).

Now i understand what ares bays and about removing drywall to make it better with filling the bays with mass, add drywall in bays, and after rockwool. It's a great idea but i can't do this legally, i can't touch that ceiling because it's an apartment in a building in co-ownership (the only thing that separates me from the neighbors above, is that 20cm layer of plaster and their floating floor). The idea is perfect and i
am really tempted to do it but it's more work and especially risky works, and not legal (i can do it technically and the week end nobody see it and i'am sure nobody will see it (if i do it the week-end) and even it's better for everybody. Maybe i can ask but it's very complicated and long if i ask the co-ownership. I will widely prefergoing on the idea of fixing first of all heavy mass on that ceiling, going as i described but if there is a better solution (without touching that ceiling) i'll take it, go for it.

Again that's what i see for the ceiling : Glued some heavy mass to the original ceiling, and before fixing rubber/metal acoustic sustainers in which we enter the lines, rods, to create a frame to put all over the rockwool, and finally closing with screwing to the frame the ba13 previously glued to heavy mass. Total: 20 or 22 cm. Exactely : 10mm heavy mass glued on the actual roof + 170 mm rockwool + 10mm heavy mass glued to ba 13mm = 20.3 cm.

So for the Risk-1 i can't really use it because of what i said i have no access at the joists (because of the co-ownership settlement). I will go the classic way : sustainers in which we enter the lines, rods, to create a frame to put all over the rockwool, and finally closing with screwing, clipping to the frame the ba13 previously glued to heavy mass.

And i think understood also why you say it'a 3 leaf : neighbors parquet (basically) is mass ; joists/empty bays (spring) ; actual plaster + my glued heavy mass (mass) ; my rockwoolspring) ; and i close (like one piece, leaf) with the ba18/heavy mass/ba13 sandwich (mass). And you said : leaf 1 upstairs flooring ; Leaf 2- existing drywall downstairs ceiling (plaster) ; and my ba13/heavymass/ba 18 "sandwich piece" attach to the clips. So yes it's 3 leaf if regard things like this.

But for me (i hope i a not wrong) the leaf 1 upstairs flooring and Leaf 2- existing drywall downstairs ceiling (plaster) are just one leaf. I say this for many reasons : the floor of my neighbors is very poor (it's Paris, old building of the end of the 19 century, 1880 exactly) i hear them very well walking on the parquet. The ceiling of the neighbors is consisting parquet with under like 5 cm plates of wood, a little air indeed, and directly they full the bays with plaster. So basically you have 6 or 7 cm wood (parquet + plates of wood under the parquet, 5 cm of mix air and plaster (it's doing like waves of plaster the electrician told me) and to finish 10 cm of full plaster. But as we see the air is not very important and above there is only 5 or 6 cm of wood plates, parquet, that's why i am not sure we can talk of layers of "mass" for the wood there is above that thin layer of air. The plaster (with the mass i'm gonna put) is in my mind the real, the main layer of "mass", and the little air and wood above are to thin to be consider as something significant in the structure. Isn't it ?

I just had the information by the electrician. I thought there was no air, that everything was full of plaster. So indeed it like 2 leaf and with my my ba13/heavymass/ba 18 "sandwich piece" attach to the clips it's gonna be 3 leaf. :cry:

I don't know what to do. I asked the electrician to send me a draw of the ceiling, because he saw it entirely, because the last owner has dug illegally to put some lights in the bays) and the electrician had to fill it.

I'll send you a draw of the entire ceiling as soon as possible. I think, i wait for the draw of the electrician, it's very thin layer of air, so for me all that ceiling can be a little bit like one piece, one leaf.

We are close to found a solution for that ceiling, the last thing to see (it's seems i guess quite clear for floor and the walls isn't it ?).

thanks very much again.