The laws of Physics no longer apply!

[princeplanet]

OK, now that I have your attention , I have recently engaged consultancy for my studio build from someone who claims to have built more studios than anyone living. Further, upon investigation, his CV stacks up, and includes TV stations, radio stations, auditoriums, post houses as well as recording studios of all sizes. The dude is a heavy weight, and his designs and advice is almost impossible to dismiss.

... Except for the fact that his methods turn much of the accepted practice in Studio building upside down!!!

What could be so controversial, you say? OK, let me start by saying that after consulting with several other designers and engineers, it became apparent that in order to achieve desired attenuation of drums and bass through a floor (125mm concrete) so I don't disturb office neighbours beneath me, I needed 100mm floated concrete over a 100mm insulation filled gap supported by carefully engineered rubber or spring mounts.

On top of this floated floor would be walls and ceiling of around 80kg/m2.
Mass / Spring / Mass. All the books, all the historical tests and data, all the forum experts, and all the experienced studio designers, all agree this is unavoidable if you want anything near the 70 db transmission loss down needed.

Enter the the old school guru, who turns up his nose at all this overkill nonsense. ""You simply do not need that much mass, it's all BS! " He says. And what replaces Mass? Much larger gaps? No,you don't need 100mm gaps, 20mm is enough! ...

So what's his secret? Well, basically, it all about Stiffness. Yep, we know that stiffness has always been considered important for low frequencies, but we have been taught that only for LF below the resonant frequency of the cavity system, or the fmam.

Concrete? No, particle board! 1 x 19mm and 1 x 25mm. For floor, walls and ceiling. 60mm air gap for the floor, and 20mm air gap for walls and ceiling. Insulation density of 60kg/m3. Are you worried about resonances ? No, the insulation gets rid of it. 600mm centres? No! 450mm (more stiff!).

What if the room does not effectively isolate drums or bass after it has been built?
Vey unlikely he says, but in an extreme case, you would simply add another floating floor on top of the first one. 2 piggy backed identical cavities? 3 leaf effect? Nope. What about the isolation mounts deflection, all the extra weight of the added floating floor will surely flatten out the mounts so they no longer float?
No problem if you use the right kind of rubber...



... I know... that's how I reacted too. Problem is, he's been designing places for 40 years, ONE THOUSAND of them! No failures. I rang up a number of them. All owners expressed reverence and awe. "Just do what he says" they all said.

So, suddenly I'm in a parallel universe, or a Twilight Zone episode. A new time and place where the laws of Physics as I knew them no longer apply.

Test data? No, he hasn't bothered. His work is his proof.

Too good to be true? Well, you tell me! Does anyone have any thoughts about this "Stiffness" first approach?

[Paulus87]

I have to say, it seems counterintuitive, very heavy and limp if possible with large insulated air gaps has always been the traditional and proven way of constructing. The complete opposite of what you describe. But, the more you know the less you know...

Who am I to say it’s BS? I am continuously being surprised by acoustics.

The only question I have is, who are you talking about?

I can think of a couple who it might be, but even that would surprise me.

I guess you’re not going to tell us, are you...

Paul

[princeplanet]

The only question I have is, who are you talking about?

I can think of a couple who it might be, but even that would surprise me.

I guess you’re not going to tell us, are you...

Paul

No, I really think it would be poor form, but rest assured, this person really does exist, along with his stated claims.

[Paulus87]

The only question I have is, who are you talking about?

I can think of a couple who it might be, but even that would surprise me.

I guess you’re not going to tell us, are you...

Paul

No, I really think it would be poor form, but rest assured, this person really does exist, along with his stated claims.

It sounds to me like the person in question would have a very laissez-faire attitude to all of this and wouldn’t be bothered by you revealing him... after all, surely the whole point of your post is to help the community?

If we cannot even take a look at his work or contact him ourselves then there is really no benefit in you posting about this as we are required to take your word for it.


Thanks for flirting with us anyhow...

Paul

[DanDan]

The Behringer of Acousticians?

[Paulus87]

So, since you asked for our thoughts, here’s my thoughts from the info you’ve shared...

19mm and 25mm particle board - that’s already a huge amount of mass, is that per leaf or is this 19mm on the one and 25mm on the other?

What size studs? I’m going to guess at least 6x2 since he’s going for stiffness, plus 450mm o.c. Well again, that is a huge amount of added mass just from the studs there, especially as there’s more studs than normal. Studs have way more mass than drywall. So, add that to the already heavy particle board and you’ll end up with very beefy walls indeed.

That will certainly helps compensate the lack of apparent air gap, but I wonder, is he defining the air gap between the two sets of framing or between the panels? 20mm between the framing would be about normal in most scenarios.

If he’s talking about between panels then that is very unusual, since how would he achieve only a 20mm air gap between the panels if the studs take up about 300mm alone?

Something doesn’t add up from the info you’ve given us...

If I’ve misunderstood then please clarify as I am interested.

Paul

[princeplanet]

So, since you asked for our thoughts, here’s my thoughts from the info you’ve shared...

19mm and 25mm particle board - that’s already a huge amount of mass, is that per leaf or is this 19mm on the one and 25mm on the other?

What size studs? I’m going to guess at least 6x2 since he’s going for stiffness, plus 450mm o.c. Well again, that is a huge amount of added mass just from the studs there, especially as there’s more studs than normal. Studs have way more mass than drywall. So, add that to the already heavy particle board and you’ll end up with very beefy walls indeed.

That will certainly helps compensate the lack of apparent air gap, but I wonder, is he defining the air gap between the two sets of framing or between the panels? 20mm between the framing would be about normal in most scenarios.

If he’s talking about between panels then that is very unusual, since how would he achieve only a 20mm air gap between the panels if the studs take up about 300mm alone?

Something doesn’t add up from the info you’ve given us...

If I’ve misunderstood then please clarify as I am interested.

Paul

20mm between panels, or between frames? Yes, I can see how my info was confusing, perhaps I've been a little confused myself because I was talking to him about inside out walls- which could have as little as 20mm gap, but now that I think about it, I'm sure he must have meant 20mm between frames ! As for the 2 layers , they were to form one panel. I think it comes to around 33 kg/m2. For studs I'm assuming 4 x 2, but was hoping to be allowed 3 x 2 to save a little space...

[Paulus87]

So, since you asked for our thoughts, here’s my thoughts from the info you’ve shared...

19mm and 25mm particle board - that’s already a huge amount of mass, is that per leaf or is this 19mm on the one and 25mm on the other?

What size studs? I’m going to guess at least 6x2 since he’s going for stiffness, plus 450mm o.c. Well again, that is a huge amount of added mass just from the studs there, especially as there’s more studs than normal. Studs have way more mass than drywall. So, add that to the already heavy particle board and you’ll end up with very beefy walls indeed.

That will certainly helps compensate the lack of apparent air gap, but I wonder, is he defining the air gap between the two sets of framing or between the panels? 20mm between the framing would be about normal in most scenarios.

If he’s talking about between panels then that is very unusual, since how would he achieve only a 20mm air gap between the panels if the studs take up about 300mm alone?

Something doesn’t add up from the info you’ve given us...

If I’ve misunderstood then please clarify as I am interested.

Paul

20mm between panels, or between frames? Yes, I can see how my info was confusing, perhaps I've been a little confused myself because I was talking to him about inside out walls- which could have as little as 20mm gap, but now that I think about it, I'm sure he must have meant 20mm between frames ! As for the 2 layers , they were to form one panel. I think it comes to around 33 kg/m2. For studs I'm assuming 4 x 2, but was hoping to be allowed 3 x 2 to save a little space...

I see.

Yes 19mm+25mm of chipboard per leaf = 33kg/m2 per leaf, which is a lot! Plus the studs 450mm o.c.

The standard 2x15mm drywall is only ~22-24kg/m2 plus studs 600mm o.c.

In an 8' wall with 600mm centres you would need 5 studs, if 450mm centres you would need 7 studs.

So, his assembly has way more mass than typical assemblies used round here.

Regarding the air gap, well even if he did understand you and was talking about inside out walls then he still must have been talking about the gap between the framing because the outer wall would still need to be a non-inside out wall otherwise the insulation and framing would be exposed to the weather. So that means, with 4x2 framing with 20mm between the frames the total air gap would be 110mm. But, I'm going to bet he's talking about traditional, non-inside out assemblies which would mean a total air gap of 200mm for 4x2 framing or 6x2 would 314mm. As most professional studios are higher than 3m, it means he should be using 6x2 framing for the walls.

If you plug 33kg/m2 per leaf with 6x2 timber and total air gap of 20mm between the framing into Gregwor's TL calculator then you end up with this:

WallAssembly.png

Bearing in mind this doesn't take into account the mass from the studs, so you could expect even better real life results with the same assembly.

It has 56.62db of TL @20hz, but your requirement of 70db of TL for bass and drums would almost be met if we assume the lowest frequency you need to isolate down to doesn't go below 31.5hz - you'd be 10db short. But, add the mass of the studs into the equation and perhaps you'd reach it. The thing with low frequency when you get down that low is that it is far less noticeable than low mids, so the need for extreme isolation below about 40hz is not that important in my opinion.

If we look at the STC rating of the assembly then it very easily reaches the required 70db of sound reduction.

All this to say, there is no magic involved, no defying the laws of physics, it seems he just builds heavier and stiffer than "normal" walls.

I still want to know who he is though, so I can check out some of his studios!

Paul

[princeplanet]

So, since you asked for our thoughts, here’s my thoughts from the info you’ve shared...

19mm and 25mm particle board - that’s already a huge amount of mass, is that per leaf or is this 19mm on the one and 25mm on the other?

What size studs? I’m going to guess at least 6x2 since he’s going for stiffness, plus 450mm o.c. Well again, that is a huge amount of added mass just from the studs there, especially as there’s more studs than normal. Studs have way more mass than drywall. So, add that to the already heavy particle board and you’ll end up with very beefy walls indeed.

That will certainly helps compensate the lack of apparent air gap, but I wonder, is he defining the air gap between the two sets of framing or between the panels? 20mm between the framing would be about normal in most scenarios.

If he’s talking about between panels then that is very unusual, since how would he achieve only a 20mm air gap between the panels if the studs take up about 300mm alone?

Something doesn’t add up from the info you’ve given us...

If I’ve misunderstood then please clarify as I am interested.

Paul

20mm between panels, or between frames? Yes, I can see how my info was confusing, perhaps I've been a little confused myself because I was talking to him about inside out walls- which could have as little as 20mm gap, but now that I think about it, I'm sure he must have meant 20mm between frames ! As for the 2 layers , they were to form one panel. I think it comes to around 33 kg/m2. For studs I'm assuming 4 x 2, but was hoping to be allowed 3 x 2 to save a little space...

I see.

Yes 19mm+25mm of chipboard per leaf = 33kg/m2 per leaf, which is a lot! Plus the studs 450mm o.c.

The standard 2x15mm drywall is only ~22-24kg/m2 plus studs 600mm o.c.

In an 8' wall with 600mm centres you would need 5 studs, if 450mm centres you would need 7 studs.

So, his assembly has way more mass than typical assemblies used round here.

Regarding the air gap, well even if he did understand you and was talking about inside out walls then he still must have been talking about the gap between the framing because the outer wall would still need to be a non-inside out wall otherwise the insulation and framing would be exposed to the weather. So that means, with 4x2 framing with 20mm between the frames the total air gap would be 110mm. But, I'm going to bet he's talking about traditional, non-inside out assemblies which would mean a total air gap of 200mm for 4x2 framing or 6x2 would 314mm. As most professional studios are higher than 3m, it means he should be using 6x2 framing for the walls.

If you plug 33kg/m2 per leaf with 6x2 timber and total air gap of 20mm between the framing into Gregwor's TL calculator then you end up with this:

WallAssembly.png

Bearing in mind this doesn't take into account the mass from the studs, so you could expect even better real life results with the same assembly.

It has 56.62db of TL @20hz, but your requirement of 70db of TL for bass and drums would almost be met if we assume the lowest frequency you need to isolate down to doesn't go below 31.5hz - you'd be 10db short. But, add the mass of the studs into the equation and perhaps you'd reach it. The thing with low frequency when you get down that low is that it is far less noticeable than low mids, so the need for extreme isolation below about 40hz is not that important in my opinion.

If we look at the STC rating of the assembly then it very easily reaches the required 70db of sound reduction.

All this to say, there is no magic involved, no defying the laws of physics, it seems he just builds heavier and stiffer than "normal" walls.

I still want to know who he is though, so I can check out some of his studios!

Paul

Paul, I should remind you that I'm far more interested in the T/L through the floor. There will be no noise sensitive neighbours on the same level as myself.
I understand that low frequency sound through the walls still pose problem through the floor, especially as the outer leaf is only 27 kg/m2, but I'm more concerned with the direct transfer of sound through the floor. Many say 250kg/m2 above an insulation filled 100mm gap is what is required for my rooms, so 33 kg/m2 with 60 mm gap sounds unlikely... What do we think a second floating floor on top of the first floating floor made the same way would achieve through the floor?

I agree that 70hz to 200 hz seems more difficult to attenuate through walls and floors, so I'm worried about the fmam falling in the range...

And if it means that much to you, I might see if I can PM you the name of out mystery man

[Paulus87]

As you can see, if that level of isolation is possible with those materials then by using bigger joists and a bigger air gap (60mm between frames) you can achieve even higher transmission loss. I think it will be more than enough and you’ll be satisfied with the level of isolation achieved with such an assembly for the floor.

I suspect if you were to build another floating floor on top then your very low frequency isolation will suffer but your mids will become even more isolated. That’s a guess.

And yes, please do pm me the designer, would love to check out his designs!

Paul