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PostPosted: Wed Jul 05, 2017 3:42 am 
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Joined: Wed Jul 05, 2017 3:30 am
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Location: Bedfordshire, UK
Hi all,

so im trying to stop as much sound as i can from leaking out of a small bedroom studio, inparticular the low end frequencies through the floor in to the linving room downstairs and ultimately my neighbors too.

I am thinking of doing a room within a room and a floating floor.

Watching youtube videos, i am planning the following for the floor...

3 layers of 15mm neoprene rubber sheeting straight on to the floorboards
then build the new floating floor frame ontop using 2x4 wood
then fill in all gaps using rockwool 45kg/m3 density (i think)
then reinforce it with some steal strips
then add the new hardwood floor
then add carpet underlay and a new carpet

the rubber alone looks like it will cost over £1000 as i need 3 layers to fill a 6m2 room.

Is there any advice from experience as to whether this will work or not before i splash some serious cash?

I am not a professional sound engineer so apologies if i respond with any newbie questions!

Thanks again,

Mario De Rosa


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PostPosted: Wed Jul 05, 2017 4:51 am 
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Location: Santiago, Chile
Hi. Please read the forum rules for posting (click here). You seem to be missing a couple of things! :)

About floating floors: Before you do anything else, read this thread: viewtopic.php?f=2&t=8173

Quote:
Watching youtube videos, . . .
Bad idea! There's a huge amount of YouTube videos from people trying to build home studios, that clearly don't understand even the most basic concepts of sound and acoustics. If you see a video of someone trying to "float" a studio floor using rubber pads, wood framing, and sheets of plywood, turn and run. Fast.

After you read the above thread, come back here and read the rest of this thread....

...

.......

.....


Ok, you came back, after reading the above threads?.... Here's why it is impossible to successfully float a studio floor using light-weight deck on rubber pads, if you want high isolation across the complete musical spectrum: . . . it's also the part that the purveyors of "plywood deck floated on our magic rubber pucks" don't tell you.

Here's how it goes... First, take a look at this graph that explains the problem in simple terms:

Attachment:
resonant-frequency-of-floating-floor-by-mass-and-gap-Graph---GOOD!!!.-S02.jpg


That shows how much mass you need on your floor, and how much air gap you need under it, to get the right resonant frequency. What I mean by "right resonant frequency" is simply the one that will allow your floor to actually isolate! Your floor is a resonant system. It will resonate naturally at a certain frequency that is governed by the mass (weight) of the final floor, and the depth of the air cavity under it. At that frequency, and for one octave above it, the floor will NOT isolate. In fact, not only does it not isolate, it can potentially amplify sounds at that frequency. And because this problem extends to one octave higher, obviously you want your floor's resonant frequency to be at least one octave lower than the lowest frequency you need to isolate. So if you need to isolate kick drums, which are often tuned around 80 Hz, then your floor should be tuned no higher than 40 Hz, which is one octave lower. If you want to isolate bass guitar, which easily goes down to 36 Hz (5 string bass), then you'd need to tune your floor no higher than 18 Hz. Let's assume this is the case, and now we can look at the graph.

The graph shows the frequency up the left hand side. You need something at 18 Hz, so draw an imaginary line across the graph a bit less than 20 Hz. You can now see that no matter how deep your air cavity is, the top two dashed lines are no use: you can never get a low enough frequency if your floor only weighs 5 PSF (pound per square foot) or 10 PSF. Not possible. However, at 30 PSF it is possible (the dotted line, third from the top): it looks like you would need to have an air cavity that is at least 4.5 inches deep, so you can't do it with 2x4's, as they are only 3.5" deep. You'll need to use 2x6's (which are 5.5" deep). Your other option is to go with an even heavier floor: the bottom curve on the graph, labeled 60 psf (solid line, not dashed). With that option, you can get a frequency of 18 Hz. with a cavity about 2" deep, so you could use 2x4s there.

So those are your options: you can build up your floating floor on 2x4s with a 60 PSF floor, or 2x6s with a 30 PSF floor.

So that brings up the question: What would you need to do, to get a 60 PSF floor? Well, let's consider OSB: the density of OSB is roughly 610 kg/m3, which works out to about 3.2 PSF for every inch of thickness. So to get 60 PSF using OSB board, you'd need to make it about 19 inches thick! :shock: In other words, you'd need to have 31 layers of 5/8" OSB on your floor, to get enough mass. :!: But if you wanted to go with the 30 PSF option, you'd "only" need 16 layers of OSB to get there....

As you can see, it is physically impossible to float a light-weight deck consisting of just a couple of sheets of OSB on 2x4 studs. If you did that, the resonant frequency would be around 42 Hz, so the floor would amplify kicks, toms, bass guitar, electric guitar, and keyboards! It would only isolate from about 84 Hz upwards.

So how do you get such a high mass? If you can't do it with OSB, then what do you need? Simple: Concrete. The density of concrete is around 2400 kg/m3, which is roughly 12 PSF for each inch of thickness. So a concrete slab just 3 inches thick (36 PSF) would let you do it with a 3.5" cavity, and if you went up to 5" thick concrete slab, you could do it on a 1.5" air cavity.

That's the plain, hard, cold facts. You cannot float a light-weight deck and expect to get good isolation for low frequencies. The laws of physics prevent it.

Now, all of the above assumes that the "deck" is fully isolated from the underlying subfloor, and that the only "spring" in there, is the air in the cavity. In real life, that is not possible: you need some type of resilient mounting to decouple the deck: it might be rubber pads, or metal springs, or something else, but there has to be something that disconnects the deck from the subfloor, mechanically. Which makes things worse! That rubber or metal spring works in parallel with the air spring, and that REDUCES the total "springiness". So you actually need a deeper cavity to get the same frequency...

Now for the kicker that really dooms this whole light-weight deck concept: Whatever it is that you use as the spring to decouple the deck (rubber, metal springs, snake oil), you have to ensure that it will will float! If you put too much weight on a spring, then you flatten it out completely, and it is not "springy" any more: it bottoms out, and does not float. On the other hand, if you don't put enough weight on it, it is also not "springy"! It "tops out" and does not float. So you have to ensure that you put the right amount of weight on each spring, such that it has the optimal amount of compression, and really does float. For each type of spring, there are tables and equations that allow you to do that, but for most springs, you need to compress it about 10 to 25% to make it "float". Less that 10% "tops out" and more than 25% "bottoms out" (the actual numbers vary widely, per product).

Great So let's go back to the light-weight deck (pretending that the above graph does not exist, and imagining that it might be possible to magically get the right frequency with just two layers of OSB). We already know that two layers of OSB weighs about 6 pounds per square foot, so let's say we do some calculations for magical rubber pads, made of purest snake oil and pixie dust, and arrive at the conclusion that we need four pads of two square inches each for every square foot of floor, and with a load of 6 PSF, that will float just fine, with exactly 15% compression. Great! Amazing! The floor floats! ... Until you stand on it.... :shock: Assuming you weigh about 180 pounds, and that your weight will be spread across four square feet of floor, just by stepping on that floor you increase the loading from 6 PSF to 51 PSF :shock: Gulp! I think you see where this is going.... You just flattened your rubber pads into oblivion! They are now squashed flat, and don't float.

So you think creatively, and decide that you don't need the floor to float when you are not in the room, it only has to float when you ARE in there, so you re-design it to float when the load is 51 PSF. Fantastic! Wonderful! It floats! .... until you bring in your guitar, amp, a couple of pizzas and a crate of beer... now the load is 65 PSF, and the floor doesn't float....

So you wrack your brains, and re-design the rubber pads yet again, so they float at 65 PSF.... But then you invite your buddy over to join you for a jamming session, and he brings his girlfriend, another amp, more pizza, and a suitcase, since he's going to stay the night.... and now you have a load of 90 PSF....

OK, so I'm exaggerating a bit here, but I can keep on adding scenarios here, such as the desk, chair, couch, your DAW, other gear, etc. etc., ... however, you can see the problem: The load on a light-weight deck varies so enormously that it just is not practical. But with a concrete deck, that has a much, much higher density, this is not a problem. Putting all that extra load on the floor, or taking it off, only changes the total mass by a few percent, and the floor still floats: the springs are still inside their optimal range.

So that's the issue. Floating a light-weight floor is not a viable solution. You need huge mass to float a floor successfully. It is certainly possible to float a floor, and companies like Mason Industries make devices to do that, but it only works with very high mass for the floor deck, such as 3 or 4 inches of solid concrete.

There's another option here, which is even better: build your inner-leaf walls on top of the floor! In that case, the entire room is floated. The calculations for the springs are a bit more complicated like that, but the total floated mass is even greater, so variations from people standing on the floor and moving gear in and out are even lower, as a percentage of the total floated mass. That's a lot more expensive, of course, and more complex, but if you really do have a need for extra high isolation, that's as good as it gets.



So now lets apply all that you learned above, to the plan you proposed:

Quote:
3 layers of 15mm neoprene rubber sheeting straight on to the floorboards
What is the resilience of that rubber, how much does it need to be compressed in order to float, and what loading would you need to put on it to keep it within its correct range? In other words, how many kilograms of mass er square meter would you need in order to ensure that the floor actually does float?

Quote:
then build the new floating floor frame ontop using 2x4 wood
How heavy is that wood? What is the surface area of that wood, that would be applying pressure to the rubber? Is that enough to make the rubber float?

Quote:
then fill in all gaps using rockwool 45kg/m3 density
Why did you choose mineral wool, and why did you choose that density? What is the gas flow resistivity of that product, in MKS Rayls? Does that provide suitable damping for the predicted resonances that will be happening in the floor cavity? What air temperature and air pressure and air humidity did you use when you did those calculations?

Quote:
then reinforce it with some steal strips
Why? For what purpose? How heavy are those steel strips? Did you take those into account when you did the calculations for the mass that will be loading the rubber?

Quote:
then add the new hardwood floor
How thick? What mass? How much total mass do you now have on the floor? If you divide that by the surface area that you calculated for the part of your framing that will be causing the rubber to deflect, does that produce the correct surface density (pressure) to correctly compress the rubber with that resilience such that it is within the optimal range? What will be the resonant frequency of that system? Is that at least one octave lower than the lowest frequency you need to isolate?

Quote:
then add carpet underlay and a new carpet
:shock: Why carpet? Are you not aware that carpet does the exact opposite of what small rooms need, acoustically? Small rooms need a lot of bass trapping (the smaller the room is, the more it needs), some controlled absorption in the mid range on a descending curve (more at low mids, less at high mids), and little to no absorption in the high end. Carpet does the exact opposite: It sucks out all of the high end wonderfully, absorbs some of the mid range randomly on an ascending curve, and does nothing at all to the low end. So not only is it useless, it actually makes things worse. Carpet will make your room sound dull, boomy, muddy, and dry. It will suck out your crash and ride, wreak havoc on the hi-hat and some of the snare, trash the toms, and make the kick sound like a wet cardboard box inside a concrete pipe....

Control rooms need to have neutral acoustics. Take a look at ITU BS.1116-2 to get an idea of how tight a control room needs to be kept, acoustically. It is flat impossible to achieve that with carpet.

Quote:
the rubber alone looks like it will cost over £1000 as i need 3 layers to fill a 6m2 room.
Why do you think you need to cover the entire floor, and why do you think you need three layers? Even if there were some magical method to make light-weight floating floors work, you would ONLY need rubber under the framing, and even then you would only need small rubber pads at intervals. If you tried putting rubber over the entire floor, it will most certainly not float.

Also, if you did cover your entire floor with 45mm of Neoprene, and considering that Neoprene has a density of roughly 1230 kg/m3, you would be adding a load of 1230 * 0.045 * 6 = 332 kg of load to your floor, plus the framing, plus the hardwood deck, plus nails, plus caulk, plus the steel, .... probably something like 600 or 700 kg in total.... did you check with a qualified structural engineer to make sure your floor will not collapse under that huge extra load? That's almost as much as a small car... do you think that your floor will be able to support the weight of car?

Quote:
Is there any advice from experience as to whether this will work or not before i splash some serious cash?
Save your money! You'd be totally wasting it. Firstly, as you can see above, it is not possible to successfully float a light-weight floor using rubber pads. Second, even if it could work, your existing floor is very likely unable to support the weight, and will fail. And thirdly (the "really bad news" part): it is usually not possible at all to isolate a studio on an upper floor. The reasons for that categorical statement are the same as above: isolation requires large amounts of mass, and most typical houses do not have the structural integrity to support that mass. The only exception is for those cases where the building already has plenty of extra live load and dead load capability, or where the owner is willing and able to invest the large amount of money needed to reinforce the building structure sufficiently, and also is able to correctly design and calculate the parameters needed to make the floor float, with the correct resonant characteristics, and provide the needed amount of isolation at the right frequencies.

Sorry to be the bearer of bad news, but if you need good isolation, (you didn't say how much you need.....), unless you have a substantial budget and are willing to do all of the above, it just isn't feasible.

- Stuart -

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I want this studio to amaze people. "That'll do" doesn't amaze people.


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PostPosted: Tue Jul 18, 2017 9:36 am 
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Joined: Wed Jul 05, 2017 3:30 am
Posts: 3
Location: Bedfordshire, UK
Hi, Stuart thanks for that explanation. For some reason i dont see the graph... can you repost it? I have read your post and it definately has made me reconsider.

Firstly all my suggestions of how i was to implement it was taken from a youtube video which, now im glad i came to this forum to understand it is clearly not possible (for me).

So my second option would be my Outside Garage. It needs renovating... so with some effort and careful calculations i could float an inner room... it could be a project i would invest in.

As you can tell i am a complete novice at this. The Garage has a concrete floor, would it need a floating floor? Is the concrete dense enough to need a seperate floating conrete floor and air gap? And the walls look like a single layer of brick... how would i ensure that the inner isolated wall could resonate?

I have a pair of Mackie 824 studio monitors that literally shake my house at only half the volume. There are settings at the back that allow me to cut the low's but i need to hear the low's so thats not an option for me.

So if I was to look at tuning to 18Hz as i do wish to try and isolate as much as possible, how thick would the walls have to be and also how about the volume of the signal how does that come in to play when calculating the mass required to achieve 18Hz?

and then also the Windows and doors, is it just about making sure they are as dense as possible?

thanks for all your information so far and apologies for the delay in my response!

Mario


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PostPosted: Tue Jul 18, 2017 9:51 am 
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Joined: Wed Jul 05, 2017 3:30 am
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Location: Bedfordshire, UK
So after reading the forum rules i will read some more of the older posts and then post a little more detail about my project... and i have filled in my location in my profile :)


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