Laminated floor underlayment and the 3rd leaf effect

[studio kaze]

Hi,

I'm on the 3rd floor of a 12 floors concrete building and needed to isolate from the impact sounds coming from all around.
The ceiling is done ( 2 layers of gypsums/mason springs/...)

For the floor we have 2" of Roxul Rockboard and 2 sheets of 3/4 OSB on top.
construction glue and nail gunned.
Backer rod, acoustic caulking all round,..

From a quick research putting an underlayment between the OSB sheets and a 12cm Laminated floor might create a 3rd leaf effect
and create a higher resonnance (less mass to the floor )

any comments/ experience with this ?
if i dont put an underlayment, will my laminate floor squeak ?

should i screw the laminated floor a little ?

Thanks,
Kaze

[Soundman2020]

Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things!

For the floor we have 2" of Roxul Rockboard and 2 sheets of 3/4 OSB on top.
construction glue and nail gunned.

You should probably read this thread, carefully:
http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173
.

What you did there will basically make no difference at all if it is not suitably decoupled from the concrete floor with a proper MSM system that is correctly tuned. You didn't mention any tuned resilient layers in there, so I'm assuming that you laid that directly on the original concrete floor. Assuming that the concrete is maybe 8" thick, the surface density of that is around 450 kg/m2. Two sheets of 3/4 OSB has a surface density of about 24 kg/m2. You therefore increased the mass by a factor of 0.05. According to mass law, the difference is imperceptible.

But anyway, to answer your question:

From a quick research putting an underlayment between the OSB sheets and a 12cm Laminated floor might create a 3rd leaf effect and create a higher resonnance

No it won't create a 3-leaf effect: Firstly, because you don't have a two-leaf system to start with, and secondly because even if you did have one the mass and resilience of the laminate flooring are very small with respect to the mass of the rest of the system. You always need underlay for laminate flooring, and the majority of underlays are simple closed-cell foams with no trapped air, so little likelihood of creating an air resonant system.

(less mass to the floor )

I'm not sure what you mean by that: How could adding mass to the floor make it less massive? That doesn't make any sense.

if i dont put an underlayment, will my laminate floor squeak ?

Yes. Even worse, it will crack sooner or later. The underlay is part of the laminate system. If you leave that out, you void your guarantee, the manufacturer will not be responsible for any problems with your floor.

should i screw the laminated floor a little ?

Never. That would certainly cause it to crack, warp, ripple, distort, or fail in other ways. Only install it the exact way the manufacturer tells you to install it.

Finally, you only mentioned your inner-leaf ceiling and floor: you did not mention how you did your inner-leaf walls, which obviously must have been put in place before you did the floor: How did you build the inner-leaf walls, and how did you handle the joints between the inner-leaf walls and the ceiling, and also between the floor and the inner-leaf walls?


- Stuart -

[studio kaze]

Hi Stuart,

Thanks for your comments.

First,
i'm gonna start a thread about the studio in the acoustic section when we start to send pink noise in there but i wanted this thread to be a place where people can find useful info on this type of floor matched with a Laminated floor on top.

You say 'What you did there will basically make no difference at all if it is not suitably decoupled from the concrete floor with a proper MSM system that is correctly tuned'
A reminder here that i'm talking about impact sound from the concrete and not air borne isolation from underneath.
i understand that the inner layer needs to be in a state where it acts as a spring and not get too compressed.

I'm sorry to say but there's a room 10' away from my room and he basicly had the same walls (that was done before i added more mass to my inner leaf), the same ceiling system and the same floor system as i have now but done more quickly/poorly, worst acoustic caulking, and when we did some real live impact sound testing, it was not scientific, just a couple of iphone 4 calibrated together with the same app in the each room and i went on the same floor and above us and hit with a regular hammer and a rubber hammer 5 times in a row at 6 places in all on concrete.
A friend in each room.
Nothing scientific but still an interesting test to do.
His room was getting always around 12-17dbs less from impact sounds. So that ceiling and floor clearly does make a difference isolating from impact sounds in this building.
and that amount is pretty much what i'm trying to cut from impact sounds.
i have peaks of maybe 47dbs from impact sound when it gets very loud (construction guys drilling in the concrete etc)
At least a couple of very respected acousticians did recommend this type of floor here or on GS it as an option on concrete floor for impact sound.
Regupol was an good/interesting option but very hard and expensive to get here, only sold as a massive roll and i already had all that Rockboard 40.
And something to remember is that often impact sounds are in the higher Freqs as oppose to air borne where the battle is often in the bass freqs. So the Rockboard 40 probably also works by absorbing too (highs-mids).

I actually didnt thing about creating another leaf effect until i read it on this site, if i remember well.
i'll need to research where i read that when i have some time.
But nobody comments on it, so i was skeptical, and wanted more people to pitch in...



" How could adding mass to the floor make it less massive? That doesn't make any sense."

Here i was talking about the resonnance of the top layer (2 X 3/4 OSB) that is i'm pretty sure to a certain extend floating on the Rockboard 40.

i have the impression that if a foam is in between the top layer (2 X 3/4 OSB) and the 12cm laminated flooring it wont have the same resonance (wood together-mass) (probably because as a musician i also see that as a major marimba note somehow) but i could definitely be wrong like that person posting somewhere on an acoutic forum and that is why i'm posting here.
To learn.

Thanks i' guess i'll put something in between because i dont want it to squeak.

Kaze

[Soundman2020]

There is an announcement at the top of the forum about what to do to assure getting as many responses as possible.
The announcement leads to this post (click here). Actually, several people, who are experts on this forum, will most likely not reply if you don't do what is written in that post. Many others who are very helpful, will most likely not reply out of respect for the moderators' wishes.

[studio kaze]

you wanted more infos

the room is now 32.5 x 23.9 x 9.9

The concrete on the building floors is 12''

the steel studs of the walls are resting on a resilient rubbers all around.
Not thick enough to my taste but it was there before i came in.

outer
5/8" Drywall
5/8" Drywall
Steel Studs/safe n sound
1" Gab
Steel Studs/safe n sound
5/8" Drywall
5/8" Drywall
5/8" Drywall
5/8" Drywall

we added 2 for a total of 4 layers of 5/8'' Drywall to the inner leaf
Taped both layers and caulked with Big stretch

inner and outer walls were connected by the air ducts.
So we took those out and got a duct specialist to build ducts with flexible sections that goes between the walls to decouple them.

build some baffles from MDF 3/4 + insulated them with 1'' brown duct insulation and suspended them from small mason neoprene hangers.
These works but not perfect at the moment.
we still have to caulk the outer wall / duct joint
and put grills
and the floor caulking is not finished
so i dont worry about that for now.
hopefullly that will help
what i see coming in now is mostly 40-60hz
we killed a lot of 120hz

The ceiling is a grid hangin' from 35 x W30-N hangers.
2 layers of 5/8" both taped.
about 2' filled with pink stuff on top
caulked

i have the half of 2 20"x20'' structural beams in the middel on the side of the room.
An acoustician told me not to worry about those
because the weight of 9 floors was weighting on those beams
but i could definitely hear more impact sound coming off those beams than from the 4 x 5/8'' inner wall resting on not so thick rubber,
at least the double
so we covered those beams with a frame resting regupol (easy to buy if for a small quantity),
stuffed with safe n sound
covered with 2 layers of 5/8''.
caulked

the 2 heavy doors are great but were not on there yet
i like Rod's idea with the car trunk rubber for the seal

budget ?
sold my B15n last week
definitely busted

[Soundman2020]

You might find this thread interesting: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20358

It's not exactly the same case you are asking about, but it is very similar. For the same reasons outlined in that thread, the effect in your case (if any) would be tiny, imperceptible, and basically non-existent.


- Stuart -

[studio kaze]

quite similar
very informative and helpful what you posted over there.

i bought some underlay with pretty good reviews this afternoon
i'll try that

thank you Stuart !