In the last days I was discussing my studio floor design and my experience in the 7 rehearsal rooms I build teach me more things that I could never think.
My floors were builded by 100 x 50 mm pine joists and two plies of particleboard on top. 4 of them were filled with sand 2 wtih low density fiberglass and one of them with medium density rockwool.
the four filled with sand have no problems, but the low density filled rooms have resonance on 200 Hz aprox.
I think the medium density rockwool room has resonance too. So, the SAE site joists floor maybe works on isolation but has a lot of resonance in low frecuencies.
has somebody any experience with this kind of floating floor??
• How thick are the neoprene pads?
• What is the "durometer" hardness rating of the neoprene?
• How far apart - measured center-to-center - are the neoprene pads along the joists?
• How far apart - measured center-to-center - are the joists?
---lovecow--- It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. - Mahatma Gandhi
Simply based on the wood framing and layering supported by the neoprene, you should get adequate isolation above about 40 Hz or so. (Rough calcs - exact would require a lot more detailed information that we need not get into here.)
As for resonance, filling the cavities with soft or not-soft (e.g., sand) material should minimize much of any resonance you would otherwise experience.
Finally, the layers themselves will have panel resonances. These are most often damped with some sort of "constrained layer" between the sheets of plywood. This can be glue, mass-loaded vinyl (MLV), or some other thin resilient material. When building floated floors, we often find this the most difficult resonance issue to tackle. We use our "SheetBlok" material to damp panel resonances and add significant mass to the floor. This has the added bonus of lowering the effective frequency of the floated floor by a few Hertz.
First, did you glue the two plywood layers together, or screw them...or both?
Second, if you did not include glue, can you remove the top layer and glue it, or add an MLV layer? Alternatively, can you glue a third layer of plywood, or add it with an MLV barrier between?
---lovecow--- It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. - Mahatma Gandhi
Simply based on the wood framing and layering supported by the neoprene, you should get adequate isolation above about 40 Hz or so. (Rough calcs - exact would require a lot more detailed information that we need not get into here.)
Isolation is not the problem, resonance is the problem. Sand is better than rockwool. Rockwool hasn't enough density for isolate the resonance.
First, did you glue the two plywood layers together, or screw them...or both?
layers are screwed
We use a glued thin PVC layer over the two layers.[/quote]
hugo_inside wrote:Isolation is not the problem, resonance is the problem. Sand is better than rockwool. Rockwool hasn't enough density for isolate the resonance.
What density? We typically use 8 lb/ft³ = ~130 kg/m³. This density often helps minimize resonance issues. As I mentioned, the resonances we typically experience with the type of construction you have shown and described, and using Rockwool, are resonances with the panels themselves.
We use a glued thin PVC layer over the two layers.
And did this help, or are you still experiencing the 200 Hz thing in these floors? If so, perhaps the density of the Rockwool is too low? This could make sense since it seems that you aren't having the same problem with the floors that have sand?
---lovecow--- It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. - Mahatma Gandhi
130 kg/m3 doubles the rockwool density I use. But is better than sand? I only have resonance in low density rockwool floors. Perhaps I should used more density rockwool.
But what can I do? Remove floor panel and fill with sand? Use amps stands? Bass amps make vibrate the floor and feet too
hugo_inside wrote:130 kg/m3 doubles the rockwool density I use. But is better than sand?
I don't know. I have never compared the two. I suspect their effects would be similar, possibly with the sand being the better of the two? But I really couldn't say for certain.
I only have resonance in low density rockwool floors. Perhaps I should used more density rockwool.
But what can I do? Remove floor panel and fill with sand? Use amps stands? Bass amps make vibrate the floor and feet too
If you haven't had a problem with sand versus Rockwool, I would say pulling up the floor and redoing the insulation is worth considering. How feasible it is or isn't is completely up to you. I suspect that's a big undertaking though, no?
As for "amp stands," something like our GRAMMA can certainly reduce low/mid frequency energy transmission into your floor. However, whether or not it will solve this particular problem is not guaranteed. I can reasonably suspect that GRAMMAs would help. How much is difficult to say from afar...
---lovecow--- It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. - Mahatma Gandhi
you can't have a mass-air-mass resonance where there is no air, so the sand eliminates that problem.
if you can give the exact makeup of the floor (how many layers, of what material) and how large the airpsace, and what the bottom layer is (earth? slab?) then it would be interesting to see what the predicted resonance for this cavity is.
neoprene thickness/hardness won't tell you the mass-air-mass resonance frequency. neoprene affects the frequency somewhat but the mass per area of the floor and the airspace are i think the main factor.
the type of insulation does not have too much effect on the resonance. it certainly will not change the frequency, it might make it a little louder or quieter but it will still be there.
this is what i've read, take it for what it's worth
The bottom layer is 150 mm concrete slab aprox. But the problem is the low density rockwool used to damp any resonance. As Rod Gervais said I built a big drum head.
I'll try to record with large diaphragm mic a band rehearsing in a resonant room. Then I try to post the recording for you can hear it.
upon further thinking it seems that lovecow's estimate is probably right on, not because of the thickness or hardness of the rubber but the basics of the construction you describe, a couple of layers of wood and a few inches of airspace will give a resonance frequency in that range more or less.
for example 1 1/2 incehs of wood (53 pounds/cubic foot) with 4 inches air over a slab give about 40hz
sorry i don't know where your 200hz is coming from
unless the stiffness of the rubber is driving the frequency up more than i ever imagined possible? i think (i'm a little fuzzy on this so ... ) that the frequency of the system is determined by the frequency of the STIFFEST spring. if your floors were very underweighted then could they vibrate on the rubber at this freq?? maybe
sorry i don't know where your 200hz is coming from
I try to explain. I don't make any mesurement with adecuate material. I just only play keyboard and the note A3 and closer notes sound more much louder than the others. Maybe room modes acts in this frecuency.
Room sizes are: 3 x 5 x 2'60 meters. Could that problem be caused by modes??
But if floor is not the problem? Vibrations could be damped glueing the two plies?
Dan Fitzpatrick wrote:just out of curiosity, how far did your neoprene pads compress with your construction completed.
Based on the information we have about the construction materials, the type of neoprene used, the spacings, etc., I calculated a static deflection of around 0.05". This sounds about right to me and it jives with similar products from companies like Mason Industries. It's not much deflection, but it certainly should be enough to get as much as 80% reduction at 40 Hz. In theory...
---lovecow--- It is easy enough to be friendly to one's friends. But to befriend the one who regards himself as your enemy is the quintessence of true religion. - Mahatma Gandhi
it seems that lovecow's estimate is probably right on, not because of the thickness or hardness of the rubber but the basics of the construction you describe, a couple of layers of wood and a few inches of airspace will give a resonance frequency in that range more or less.
) that the frequency of the system is determined by the frequency of the STIFFEST spring. if your floors were very underweighted then could they vibrate on the rubber at this freq?? maybe
