Auralex U Boats, Do they really work?

[AnAverageJoe]

How's it going guys, I'm getting ready to raise my floor with 2x4s and I was wondering, if it was a good idea to get U Boats from auralex. Do they really work?

[nosebleedaudio]

Yes they work, have used them and other's just like them with very good results.

[AnAverageJoe]

Originally Posted by nosebleedaudio

Yes they work, have used them and other's just like them with very good results.

Ok So They are workth getting?, What material do you you use to dampen the hollow sound in between your 2x4 spaces? If thats what you use.

[DSD_Mastering]

I used them under my control room floor. I filled the cavities with R-22 rockwool and sand. Works perfectly

Regards,
Bruce

[nosebleedaudio]

I used 3/4" plywood and 3/4" MDF on top of that with nothing in between.
Bat insulation would work but may not be required.
I had the 2 layers glued with wood glue, very solid feeling and no noise.
In the main studio I built the finished layer was a tongue and groove solid wood.
I would not use sand for several reasons, your choice..

[AnAverageJoe]

Originally Posted by DSD_Mastering

I used them under my control room floor. I filled the cavities with R-22 rockwool and sand. Works perfectly

Regards,
Bruce

Cool, as long as it sounds solid and not hollow. Where did you get your R-22 rockwool from?

[AnAverageJoe]

Originally Posted by nosebleedaudio

I used 3/4" plywood and 3/4" MDF on top of that with nothing in between.
Bat insulation would work but may not be required.
I had the 2 layers glued with wood glue, very solid feeling and no noise.
In the main studio I built the finished layer was a tongue and groove solid wood.
I would not use sand for several reasons, your choice..

What is bat insulation? Do you think I should use 3/4 plywood one the top of my frame?

[nosebleedaudio]

Batt insulation, the pink stuff. But if you may have a moisture problem I would not use it.
It only adds a very little to the STC rating.

[AnAverageJoe]

Originally Posted by nosebleedaudio

Batt insulation, the pink stuff. But if you may have a moisture problem I would not use it.
It only adds a very little to the STC rating.

What do you mean by STC rating?

[DSD_Mastering]

Originally Posted by AnAverageJoe

What do you mean by STC rating?

Sound Transmission Class - It's the amount of sound attenuation between 125hz and 4000hz. We know that these frequencies are easy to tame and the bass is what is the hardest.

We sealed the cement slab, put down a heavy mil vapor barrier, used the U-boats under the joists and filled the cavities with conduit, sand and rockwool. We then put down 2 layers of 3/4" hardwood sheets at 90 degree offset with green glue in between. On top of that was 1/4" rigid fiberglass and then a floating laminate 3/4" Bellawood flooring.

We got the "Roxul" rockwool at R-Factor in Woodinville, Wa We used 250 bags!

Regards,
Bruce

[AnAverageJoe]

The way I'm going to do it is similar to this picture.

[AnAverageJoe]

Originally Posted by nosebleedaudio

Yes they work, have used them and other's just like them with very good results.

Mike, What other options are they besides the U boats?

[uiiok]

Hey you might want to check out the John Slyer Studio Design Forum. Here is a relevant link on floating floors.

Recording Studio Design :: View topic - Is a Floating Floor Right For You? Answer: Probably NOT.

[AnAverageJoe]

Originally Posted by uiiok

Hey you might want to check out the John Slyer Studio Design Forum. Here is a relevant link on floating floors.

Recording Studio Design :: View topic - Is a Floating Floor Right For You? Answer: Probably NOT.

Thanks I'll take a look

[nosebleedaudio]

I agree and disagree with the link.
Have seen where a floating floor is overkill, and where it WAS required.
Have seen at a local University who did NOT have a floating floor and could hear people walking around the building...and it was a concrete floor...
A floating floor also produces a perfect place for conduit ect for wires ect.
Even if the slab is concrete I have seen many times it is NOT the ultimate mass some think.
And a little common sense and experience goes a long way.

[Eric Desart]

AnAverageJoe

The problem with the U boats of Auralex is that they give no technical data.
An U boat is an elastic decoupler with a handy U shape to keep it in place.
Auralex gives no technical information whatsoever about dynamic stiffness making it not possible to calculate whatever.

Possible alternatives are CDM, Sylomer, Kinetics stuff and lots if others.

A good floating floor should be around 10 Hz MSM (mass-spring-mass) (lower is better) and not exceed around 16 Hz.

This value for +/- linear springs (the elastic U-boats or any alternative for that matter) is directly related with the deflection of the elastic material under static load.
Hence even without knowing the dynamic stiffness or the physical principles you can test and measure this yourself.

You have a good floating floor if your deflection is around 2 to 3 mm under static load.
Hence ANY elastic material can only be judged within a total construction taking top and floor mass into acount.
The same material can result in a bad or a perfect floor.

You can influence this deflection by in- or decreasing the number of U boats per surface unit, or by in- or decreasing the mass of the top floor.

The relation between MSM and deflection can be rather exact calculated from:

In metric

d = (15.8/fo)^2
fo = 15.8/sqrt(d)
where >>>
d = defection in mm
fo = MSM (mass-spring-mass resonance in Hz)

In Imperial

d = (3.13502/fo)^2
fo = 3.13502/sqrt(d)
where >>>
d = defection in inches
fo = MSM (mass-spring-mass resonance in Hz)

Hence you can easily see that the mass of this top floor, and the spread of the pads or U-boats is very defining.
The basic idea of ANY decoupler is to load them to the maximum technical allowed static load.
Underloading a decoupler will give the false feel of additional safety and more stability, but will cause loss in acoustic decoupling quality which should be avoided if possible.

A rough rule of thumb, in order not to overload such materials is that the deflection should not exceed ca 10% of the initial material thickness. But this can depends a bit on the type of material, the edge factor and so on. E.g. the standard sylomer types will be somewhat less, rubbers can be somewhat more. Best of course is that the supplier provides useful data to work with.
There are 2 main types: compressible decouplers (volume material decreases under load = foam or fibre like stuff) and deformable decouplers (the volume does not decreases or hardly, but the material deforms expanding sideways = rubber like stuff). This latter type doesn't work anymore when you prevent them to expand sideways under load.

Another good rule of thumb is making the top floor as heavy as possible.
That way the relative comparison of temperary loads as e.g. people become less defining.
The more spare (relatively) you have to foresee in order to cover these temperary loads the higher the MSM will become when these loads aren't present + are standard too high (since underloaded) on these spots where such loads aren't present.

I CERTAINLY should put mineral wool (fiberglass or rockwool with low density in that cavity since it does influence STC rather strongly (certainly with a light topfloor). And it also helps to diminish a drumskin effect of such a floor.
If hygro-thermal problems should be involved that's more a matter of the correct use of a good vapour barrier (dampscreen).
A further good improvement is the use of Green Glue which diminishes flanking extremely, makes that floor more dead (drumskin effect) and additionally increases TL somewhat.

About the John Sayers topic I agree with nosebleedaudio.
That topic arose strongly in function of typical drywall separations in a studio setup, where they meant that it has no sense to additionally strengten a link in a chain when the overall TL is defined by the TL of the walls anyhow.

Real high insulations need very low MSMs and can't be obtained with such applications, needing very large deflections.

[jwl]

AnAverageJoe,

Listen to Eric Desart on this. He is quite right, Auralex makes these convenient products which could be great, but they don't supply the technical data that is NECESSARY to make them work properly.

The idea is this: the floor has to float properly. In order to do so, the mass of everything floating has to be precisely calculated, so that the U-boats compress the proper amount. If there is too much weight, the U-boats will "bottom out" and offer no springiness at all, therefore it is not floating. If there is not enough weight, then the U-boats won't begin to operate as a spring, and therefore it is not floating.

From the John L Sayers thread linked above (written by Sharward):

Imagine putting a 15 pound weight on a spring that "bottoms out" at 10 pounds. The spring is completely compressed. The weight is unable to bounce on this overloaded spring, and therefore is not isolated from the surface below.

The same holds true of a lighter weight upon a heavier grade spring. Imagine a 10 pound weight on a spring that does not begin to compress until the weight reaches 15 pounds. The weight is too light to cause the spring to compress, so it too is unable to bounce, and is therefore again not isolated from the surface below.

So yes, even if you determine that floating your floor is necessary (DO THE RESEARCH on this to be sure), then you need to do some math to figure out how many U-boats (or whatever other products) you need for your room. And Auralex does not provide this information. I wish they did, as the U-boats do look like a nice convenient product for builders.

[AnAverageJoe]

Great LOL I read these posts after I ordered them, good thing I only ordered 5 to start off with lol. I'm ready for them to, I just built the floor joists a couple hours ago. BTW Thanks Eric and JWL.