I actually ended up building a "floating floor" after all - but instead of the U-boats ... a material called sylodon
That material would do something useful, if you were using it in the way outlined in the data sheet: to reduce the transmission of impact vibration. For example, if you had a noisy mechanical pump that was causing the floor to vibrate, you could, indeed, use some pads of that material, carefully cut to the correct dimensions for the problematic frequency of the pump vibration, and that really would help to reduce the amount of vibration transmitted into the floor. If that's what you want to achieve, then that will work. But that is not the way you are using it! You are using it to support a "floating floor", and light-weight "floating floors" just do not work, regardless of how you "float" them. I'm sorry to be the bearer of bad news, but there is no magical material or method that will cause a light-weight floor deck to float.
I wrote an article about that a couple of years ago:
What is a floating floor? How to do it wrong, and how to do it right:The issue is that a "floating floor" is not related at all to isolating the vibration from a piece of machinery. They are two very different things. With a piece of machinery sitting on an isolation pad, there is no isolation of
airborne sound, only "structure-borne" sound, but with a proper floating floor in a studio, the goal is to isolate the airborne sound as well. If you only need to isolate vibration from an instrument, such as a piano, drum kit, or bass guitar amp, then Glenn's "riser" design is excellent! That will, indeed, provide really good
vibration isolation, as has been shown by forum members who have actually built them and tested them. But airborne sound is somthing else, and that's the issue I talk about in the article above: you cannot achieve that up to studio standards with a light-weight (low mass) deck resting on resilient pads. That's the problem. Take a look at the graphs and explanations in that article, to get a better idea of why it does not work.
OK, I should clarify that: it's not that it won't work at all, but rather it won't work for low frequencies. If you want to build such a floor to isolate the sound of people speaking or singing, or the sound of an acoustic guitar, or a violin, or even a trumpet, or the sound of someone playing their radio loud, or their TV, or vacuum cleaner, then you could probably do that successfully with the method you mention. But that is not the case for a studio, where you need to isolate low frequencies (drums, bass guitars, keyboards, growling electric guitars, etc.). That's a different scenario, and light-weight floating floor just is not capable of doing it.
The problem, as I mention in that article, is that low frequencies are the hardest to isolate, and the resonant system of the floating floor needs to be tuned low enough to isolate all of those frequencies. Tuning the resonant frequency low enough needs a LOT of mass: More mass than you can get from a few sheets of drywall and MDF. The equations are in that article, so you can calculate for yourself just how many sheets of drywall you would need. I think you'll be surprised!
Here's something else I wrote about floating floors in home studios:
Floating your floor: How and why... and why not. It was built using aprox. 80 sylodyn blocks (each block is cut to 85x45x12,5 mm)
This might seem like a strange question, but... Why? Why did you cut them to that size? Who did the math for you, to calculate that those specific dimensions will give your floor a resonant frequency below 15 Hz? (I'm just using that as an example frequency, since that's about the upper limit for what would be a usable system in a studio floor: most studios need much lower frequencies...) And what load factor was used to calculate those pad dimensions? In other words, how much must the complete floor weigh in order to produce the correct deflection in those resilient blocks? Did you check that your sandwich of MDF and drywall actually does provide the correct weight? The problem here is that of you put too much weight on those blocks, such that they are defected beyond their operating range, then the floor is not floating any more: it is directly connected to the underlying subfloor. And if you did not put enough weight on them, then they are not floating at all! In that case, they also act as solid connectors between your "floating" deck and the subfloor below. The floor only "floats" properly when the resilient pads are compressed (deflected) just the right amount, to produce the correct resonant conditions. There is a range of possible deflections for most resilient materials, and in general it is better to compress them close to the upper limit of that range (higher mass), but you have to be careful to not exceed the maximum mass. And that's yet another problem for light-weight "floating floors". Assuming someone did the math, and that the pads are deflected correctly from the weight of the floor itself.... what happens when you stand on that floor? You are than adding a lot of extra mass at one point, very likely causing one of the pads to deflect too much, beyond its range, and thus destroying the "float".
Now, maybe the weight of a person really was taken into account for your floor design (ask the person who did the aluclations nad told you to cut the pads to that size), but how about with
two people? Or three? Or a desk with gear on it? Or a drum kit? Or a piano? There is no way that a floor using those pads can be designed to handle a wide variation of loads. Either it will "top out" when there is not enough load on it (and thus it will not isolate), or it will "bottom out" when there is too much load on it (and thus it will not isolate). It will only isolate when the deflection of the pads is within the manufacturers' design range. The only way that such a floor can always float, is if the load does not change ever. In other words, you don't ever put in furniture or equipment or instruments or people that would over-deflect the pads, and you don't ever take out furniture or equipment or instruments or people that would get to the point where the pads are "under-deflected". And with a light weight floor deck, such as you show, that is indeed a big problem. There just isn't much mass in the floor deck itself, so adding the weight of a single person can easily cause a large change in the loading on the pads: there is a large percentage increase in the surface mass at the location where the person is standing. With a properly built studio floor, that is not the case, since the deck is extremely massive already, so adding the weight of people or equipment does not change the loading by a substantial amount. But with a light-weight floor deck, that is a problem.
The "sandwich" consists of sylodyn blocks, rockwool, 73x48mm wood beams, 22mm standard floor chipboard, two layers of 10mm fiber gypsym - which has more mass than normal gypsym and also isolation properties.
OK. And what is the total surface density of that sandwich? In other words, how many kilograms per square meter? And what load does that place on the sylodyn blocks? Is that enough to produce the required deflection, as per the data sheet?
I'm also considering the use mass loaded vinyl as an extra safe measure.
If you did that, how much extra mass would it add to the floor? What would the loading on the resilient blocks be then? Would that then go over the limit (putting too much mass on the floor), and cause the blocks to be deflected beyond their useful range? What would the resonant frequency of the floor then be, if you did add the MLV, and it was still in the range?
Please do take a look at those two articles I linked above, so you can better understand the issues.
This is why I recommend Glenn's plan as the best alternative: it is not a true floating floor in the sense of a proper studio floor with high mass and springs, but it DOES do the job of isolating vibration and even reducing airborne sound quote a bit (if you do the entire floor like that). It its also
really hard to overload! You would need very huge weight on it to cause defection beyond the range where it usefully isolates vibration. Even with a dozen layers of drywall, it still would do the job that Glenn designed it to do. But it still would not be a floating floor, in the true sense.
So, what you have there will very probably isolate just fine for the mid range and high range of the spectrum, but it will not isolated will for frequencies lower than about twice the resonant frequency, whatever that is. Ask the person who did he calculations to show them to you, so you can see what the real resonant frequency of your floor is. Multiply that number by two, and that is the lowest frequency that you can expect good isolation for. Maybe that is good enough for you, if you don't plan to have drums and bass guitar music in your room, nor other low-frequency sound. Only you can determine that, by testing to see how much isolation you are getting under real conditions: in other words, get a friend to bring along a drum kit, set it up on that floor, and play it at typical performance levels (usually around 115 dBC), then go measure and listen in the rooms down below you, and around you, and see if the isolation you are getting is "enough". As Jennifer pointed out, you might have very tolerant neighbors who really don't mind... or perhaps not!
I hope that the current floor construction will work for the piano as it is now.
How much does the piano weigh? Did the person who did the calculations for your floor take into account the weight of the piano? Does it push the loading too high, beyond the resign range of those resilient blocks? Ask the person who did the calculations to show you where he took that into consideration, to check that the pads are not overloaded.
and I have more or less made peace with the fact that my mixing position will be sub-optimal
Sometimes you just have to do h best you can, within the limitations that are available to you! n your case, the biggest issue will be lack of symmetry. Your desk is not on the room center-line, so your speakers are not the same distance from the side walls (the left speaker is tight up against the left wall, while the right speaker is far away from the right wall), and in addition the acoustic loading on the two speakers will be very different: the left one is in a "tri-corner", created by the two walls and the desk, while the right one is basically out in the open, with just a desk under it (and a small section of front wall, but negligible). As long as you are aware of the phsyco-acoustic issues this asymmetric situation will creats for you, and know how to deal with them in your head, then you should be OK. It might be possible to compensate slightly with very careful digital tuning, but I'm not sure you could get very far with that.
One alternative might be to turn the room orientation around: Put the speakers at the other end of the room, with the desk centered left-to-right: There's the problem of the door, of course, but you might consider replacing that inner-leaf hinged door with a sliding door: That would be the best possible situation, I think. Considerably better than the layout you show.
I have really tried to ask for advice from the people I know and have gotten in contact with, but there doesn't seem to be many experts on the field of studio building in my city/country.
You are not alone! Unfortunately, that is very common in many cities and countries. That's one of the reasons I created this forum: to give ordinary musicians and engineers the information that can help them build their own rooms. But even then, it often isn't enough. Designing a studio is much more than just reading about it, as you already discovered! It's not as simple as it looks, and there are quite a few websites on the internet that talk about it, but actually give terrible advice, that makes no sense and has no basis in acoustic theory. So you are not alone at all in that sense. Fortunately, you did find the forum, and hopefully it has helped you!
To conserve as much of the space as possible, especially room width, I've built the floor/walls aprox. 3 cm away from the outer surfaces. My impression/hope has been that the most important thing is that there's an air gap.
For isolation, what matters is the resonant frequency of he wall system, which is governed by the air gap and also by the mass (surface density) of the two leaves. There are equations for calculating that, to find out if your resonant frequency is low enough. The basic rule is that more mass = lower resonant frequency, and more air gap = lower resonant frequency. It's important to understand that the term "air gap" refers to the entire cavity between the outer leaf and inner leaf, not just the distance between the frames. In other words, if you were small enough t stand inside the wall, and could stretch out a tape measure across the cavity, you would measure the distance between actual drywall surface on one side, and the drywall surface on the other side, ignoring any framing or insulation. That's the number you need. And that needs to be at least 10cm. More is better, and ideally that should be 15cm or even 20 (if you need high isolation for low-frequency sounds), but 10cm is the minimum. If the gap is smaller than that, then the resonant frequency will likely be too high, no matter how much mass you put on the leaves. It is important to do the math.
Right now I'm considering to cover all of the walls with insulation and fabric, but at the same time I would also like to preserve room width as mentioned above. Any ideas here?
Your room is very small, so it will need a lot of treatment. Much more then a larger room would need. In any control room, the most critical wall is the "back" wall (at the opposite end from the speakers): That will need very deep treatment. You will need abundant bass trapping in there, but you have to be careful to also account for the high end: Bass traps also "suck out" way too much of the high end, so you need to take precautions to prevent that. One common option is to cover the front surface of the bass traps with something reflective, such as thick plastic sheeting, wood slats, panels, etc. But once again, that has to be done in the right way, to affect the right frequencies.
A common mistake in home studios is treat all the walls exactly the same, but that always ends up making the room sound terrible: because it only affects one frequency range! Instead, each wall and each part of the ceiling needs to have the correct treatment for that location. So the ceiling above the mix position will need a cloud, and in your case it will need to be very thick, and very steeply angled: perhaps even hard-backed. Your rear wall will need 100% deep, thick absorption all the all across it, combined with bass trapping in the corners, and the side walls will need broadband absorbers at the first reflection points. In your case, that's a major challenge, because of he asymmetric mix position. That is going to be tough to figure out!
But that's the basic approach you wold need. However, before you do any of that, you should first test the response of the empty room, like this:
How to calibrate and use REW to test and tune your room acoustics...I would suggest doing some testing or estimating, to first define a goal for isolation: in other words, how many decibels of isolation you would need. That will help you define things like the materials to us to build your studio, and the dimensions of those materials.
Yes, I will do some measurements in the near future.
It's a it late for that now! You already built the room, so there's no need to define the goals any more. Your isolation will be whatever it is from the construction you already did, and cannot be changed at this point. You can't change that, unless you modify the floor and walls that you already built. The best you can do now, is to just test it to see if it is enough for your purposes. As I mentioned above, you could do that by getting someone to play the drums in your room at normal levels (around 115 dBC), then listen and measure how loud that is in the other locations around your studio. That way, at least you will know loud your neighbors will be hearing your sessions. It would be good to do that anyway, so you are aware of it, and can plan your sessions for the times of day when you would be least annoying: hopefully, when the neighbors are not even at home!
Here's one other article that you might find interesting, adding to what Glenn, Starlight, and Jennifer said about isolation and STC ratings:
Why STC is not a good way of measuring studio isolation.- Stuart -
I only just saw it now, still awaiting approval... I do hope you see this, and it is still useful for you!
