R/E/P > Acoustics in Motion

small floating room, with a light weight concrete floor

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http://recforums.prosoundweb.com/index.php/t/32439/0/ (previous thread)

After all the information and all the reactions on this forum I first decided to stop with the project because of the difficulties and the limitations of the building. But after a visit from the neighbour during a recording session of a cagon I have to go on with the project.

First I spoke with the constructor of the building, he is prepared to check my final design to be shure that the building can handle the weight of the construction. He also confirmed me that it wouldn't’t be a problem to hang the ceiling to the floor of the second-floor. So that’s good news to reduce the weight J.

I will hang the ceiling with, clips like the isohangers, 2 layers of drywall, and a layer of glass-wool between the existing ceiling and the drywall.

The floating floor will be made of regufoam benches/pads. Merford calculated the amount and type of regufoam that has to be used for the weight of the construction.(I also had grate advice from Alara-Lukagro, with kidpads) There should be 1/8m2  of foam under each m2. I was wondering what would be the best way to spread the weight, long small benches or pads, on the net I see both. In this design I go for the benches cause it is easyer to work with.

The benches will be 5cm wide and 3.7 cm height, , with a layer of obs on it, the total height of this will be 3.7 cm + 1.8= 5.5 between the benches there will be a thin layer of +/- 3.5 cm rock-wool/glass-wool. On the obs I will put lewis-board, with 5 cm light concrete(1700 kg/ m3). The floor will be on whole floor, to spread the weight over a  as big possible surface. There will be a gap of 5 cm around the floating floor with a layer of glass-wool.

The wall will be made of metal studs, with 2 layers of drywall and the gap between the existing wall(25 cm concrete) will be stuffed with 14 cm of glass-wool.


Static weight   120,45 kg m2
dynamic weight    33,34 kg m2
Total weight   153,79 kg m2

I draw some pictures of the construction in excel, I will scan them tomorrow and Will post them.

I'm looking forward to your reactions, i think that this is the best that can be done within the limitations of the building.

Best regards,


It did take a while, but here are the files. I'm looking forward for your advice en comments.

Best regards,


And the other file, with my ideas for the best way to spread the weight, i think v3 is the best.

Best regards,


Thomas Jouanjean:
What's the natural frequency of the Regufoam under this load? Is it low enough? (<10hz?)

You likely need to vent the air cavity under the floor more than that. What's the floor self-resonant frequency with the current air gaps?

Hi Thomas,

It is calculated with the regufoam 150, it is in its dynamic range between 0.010 N/mm and 0.015 N/mm, my total weight will be 0,012395154N/mm2 max. There will be 1/8 m2 regufoam at every m2.

The natural frequency of the regufoam, will be about 7hz by the 5cm and 9hz by 3.7 cm thick regufoam.

Do you mean with"You likely need to vent the air cavity under the floor more than that" that the airgap has to be bigger between the existing floor and the floating floor? how be has the airgab to be, I'will isolate it with rockwool

How do you calculate the floor's self resonant frequency?


Best regards,



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