Designing a floating floor

Folks, I'm gonna build a properly floating floor for my two rehearsal room ive built in the 2nd floor of my building and that I previously mentioned the flanking problem I had with them. I managed to find neoprene/rubber pads designed for floating systems. Their data sheets show me the ammount of weight they take in order to compress a certain %. So with some math, I know for a fact how much weight that pad must receive to compress the amount of mm i need. With some research, I found 10%-15% should be okay. So, My plan is to sum all the static weight (the layers of mass, the average people on it, equipment, drumkit, etc) and divide that by the amount of weight I want my pads to take, that will give me the number of pads I need to purchase. That calculation is for an equal amount of weight distributed across the room for each pad. Now, should I take into consideration where the drumkit will be put for example and distribute more weight underneath that section? Or placed equally should do fine? The main plan here is to put these pads, fill everything with 20mm rockwool and add 1 sheet of 20mm MDF on top. I cannot add more mass because my ceiling is very low already. This floating floor will be decoupled from the inner walls The goal is to gain 3db of sound isolation to the outside because we are over by 3db by the local regulation in order to get our permit to work as a rehearsal space. So you be aware of the problem, the sound coming from the 2nd floor (where the rooms are) are gettin into the first floor and and also the floor is vibrating the whole structure, so its cancellating the 2 leaf system so to speak.

Rod just posted a comment on a floating type floor that has been around this forum for a few years, it might be an option if you have not considered it yet. viewtopic.php?f=2&t=13845 Good luck, Brien

Thanks Brien, My design is basically the same, except these spring pads will be taking the load and providing the amount of compression in order to decouple Maybe Rod could chime in here and give me his advice about my design

Could you just build a floor for the drums and a small platform for the bass amp? That would save the height? I have no idea about your questions though :roll:

Hey Lil I guess not.... My thinking is that the airbone sound is making the structure (floor) vibrate as well. so its not only a flanking thing. So floating the whole floor could absorb some airbone as well and obviously the direct transmission

I've been pounding my head on this subject my self this week. Currently building 3 rehearsal rooms on different floors. My initial idea was to floot the top floor which will also houses a CR. Been testing with some material and wasn't satisfied with any of'm Used bonded-foam (about 60kg/m3) which needed atleast 3x12,5mm GB / MDF layers to have about 5-10% of compressing. Second I tested sheets of 48kg/m3 wool, it needed atleat 2x12,5mm sheets of GB /MDF to have it compressed a bit. I didn't scatter the sheets, it was one big layer. Another thing I noticed where the edges, they will be very unstable. And since it's very common to put your amps on the edges of a rehearsal room (the rooms are small/mid sized) it will, euh, suck. Another thing I didn't like was the height this will eat up. It takes about 10cm of total space, which I don't have a lot of (vertically). So, as mentioned by Lilly, I'm thinking of skipping the whole "floating" floor and only float the sources (drums, amps etc) using mobile decouplers (same principle as the floors but on wheels this time :), atleast for the amps). I have never floated a complete floor so I don't have any experience with it. Rod mentioned he got good results with a 5cm sheet of wool adding 2 layers of wood on top. (assuming about 700kg/m3) Have you tested anything yet, JB ? I'm just curious...

I hear you. Well, this acoustic company who also did the noise testing for us, recommended these spring pads. http://www.dbaingenieria.cl/modelo-ts.pdf The good thing about these things is that I know how much weight the can take in order to compress and do the calculations for my needs. that was the main point about floating floors on this forum, that you reall dont know how many pads you need, or how much weight they need in order to compress properly. well i got all that information. so. i think it should work...or not lol I guess i'll have to give it a try, move on, and post the results One question tho, what about 2 layers of 1/2" plywood instead of 1 x 20mm mdf ?

The other main and more important point is can your structure take the additional weight. You should have someone supply you with a deadload weight amount that your structure can be loaded to. Then you would need to calculate the additional weight you are attempting to place on this structure and have that checked as well. It is one of many factors.

jbassino wrote:

I managed to find neoprene/rubber pads designed for floating systems. Their data sheets show me the ammount of weight they take in order to compress a certain %. So with some math, I know for a fact how much weight that pad must receive to compress the amount of mm i need. With some research, I found 10%-15% should be okay. So you be aware of the problem, the sound coming from the 2nd floor (where the rooms are) are gettin into the first floor and and also the floor is vibrating the whole structure, so its cancellating the 2 leaf system so to speak.

Do not overlook the often forgotten MAM resonance of the floating floor. This frequency is usually in the upper low end (100-150 Hz) and the isolation of the floor is reduced significantly at this point. Andre

Andre, You mean I can actually make it worse? All I need is extra 3db isolation. and remember the band is playing directly on the 2nd floor 180mm concrete floor

jbassino wrote:

One question tho, what about 2 layers of 1/2" plywood instead of 1 x 20mm mdf ?

Doesn't matter.. it's not about the material of even the props of material (width, mass etc). It's the amount of mass needed to compress the floor. If it takes 2x 1/2" PW or 20mm MDF, that's what it is then.

I guess you are right!

jbassino wrote:

Andre, You mean I can actually make it worse? All I need is extra 3db isolation. and remember the band is playing directly on the 2nd floor 180mm concrete floor

Yes, the isolation will be reduced at the MAM resonance frequency. The (obviously simple) trick is calculate the resonance frequency and design the floor so that the frequency is at least 1/2 octave below the lowest frequency you want to isolate. Andre

I see The thing is, I cant really see how it can be even worse, because when a band is playing, the floor is vibrating SO MUCH that is shorting the whole MAM system anyway. All the existing brickwall walls are vibrating, so its really a mess

Hey Javier, just dropped in here on the forum to see how your build is going. Too much other stuff going on for me right now to post here regularly, but I wanted to make a suggestion here: why don't you at least try Lilith's decoupling suggestion, partially? with a "quick and dirty" riser that will at least give you an idea. Easy and cheap to do, for a quick test: Place a thick layer of rock wool (5cm thick at least, more if you can) spread over a 4'x8' section of the floor, in that far corner where you normally have your drums set up. Place a full sheet of really thick plywood or MDF (19mm or more) over the rock wool, just resting on top of it, taking care that it does not touching the walls. Set up your drum kit / bass amp / whatever on top of that, bash away as hard as you can, and test for vibrations, sound levels, etc. My guess is that you'll see a fairly decent reduction in vibration. Will it be 3dB? Maybe. You might be lucky. I think we tend to underestimate just how much impact sound gets into floor from the drum kit itself, the bass amp, etc. Sure, airborne is a still a major issue, but impact is a biggie too and risers can help there. This might not get you as much as you need, but it's worth a try! For the cost of a bag of rockwool and a sheet of plywood, you'll at least get an idea of whether or not a proper well-built drum riser would work for you. If you want me to come over with my sound level meter when you are ready to test, just let me know. I could drop by next week, if you want. - Stuart -