"Sill Seal" used in studio construction?

Dr. J · Post by **Dr. J** » Mon Jun 16, 2003 7:38 am

Has anyone used the product "Sill Seal" in the construction
of any of their studio walls?

I was thinking of running Sill Seal under the wall plates on the floor,
and on the the top between the ceiling to increase insolation.
Much like the neoprene or rubber idea on floating floors.
Reason is, my ceiling is only 7'2" tall, so I am crammed, with not
much for options.

Thanks for replies or ideas,
J

knightfly · Post by **knightfly** » Tue Jun 17, 2003 10:13 am

J, love to comment (can you tell?) if I knew WTF you were referring to - it always helps if you can post a link or pic when asking about trade name stuff - it's a big world out there, and things every Aussie knows about I have no clue - things I consider "standard" , people in Reykjavik (sp?) never HEARD of -

Love to see a link or pic, or at least a thorough description... Steve

Michael Jones · Post by **Michael Jones** » Tue Jun 17, 2003 1:46 pm

I think the Dr. is talking about this stuff.

Michael Jones · Post by **Michael Jones** » Tue Jun 17, 2003 1:49 pm

Its used under the base plate in a wall (particularly on exterior walls) to eliminate any air gaps between the base plate and the concrete foundation.

I actually used 2 layers of it. It might aid in isolation. I dunno. It "squashes" down pretty flat once the wall is loaded though. Its primary purpose is to eliminate any possible space for air to leak out, making your HVAC more efficient. Here, its required by code.

You can just make out a thin pink line in the photo.
(I intend to caulk that seam too.)

knightfly · Post by **knightfly** » Tue Jun 17, 2003 6:12 pm

Cool Michael, thanks - all that type of thing is CLOSED cell foam, which is what's needed for sealing and probably helps in de-coupling walls from floors. It wouldn't be worth ANYTHING for acoustic treatment, same as the "rigid FOAM" sold by Home Depot and others... Steve

Michael Jones · Post by **Michael Jones** » Wed Jun 18, 2003 3:16 pm

Steve - the stuff is only 5 1/2" wide. How could it possibly be used in any way for acoustic treatment? I mean, I know its no good for that, but, can you get closed cell foam wider than 5 1/2"? I guess that's what I'm asking....

Just curious.

But, so.... you think it would aid in isolation? Thats cool if it does, 'cause, umm.... I put it under the interior walls too.

knightfly · Post by **knightfly** » Thu Jun 19, 2003 9:32 am

Michael, I was kinda half-joking about the acoustical treatment comment, just noting the similarity of materials more than anything.

About the only place I could think of that a person might consider using the Sill Seal stuff that way, would be as surround inside a double wall/double window (around the window) and that would be a BAD idea. You'd want something a lot more absorbent, like either OPEN cell foam, homosote, 703/705, etc -

And yeah, bedding your walls with a couple layers of the stuff should work pretty well... Steve

Post by **John Sayers** » Thu Jun 19, 2003 10:14 am

i though that stuff was there to create a vapour barrier between the concrete floor and the timber frame. We run similar stuff under window sills for water barrier and where timber joins concrete.

cheers
john

knightfly · Post by **knightfly** » Thu Jun 19, 2003 10:49 am

Yeah, John it's good for that too.

Closed cell - heat insulation, acoustic SEAL, vibration damping, vapor barrier

Open cell - acoustic absorption, dish washing sponges :=)

Dr. J · Post by **Dr. J** » Thu Jun 19, 2003 4:00 pm

Thanks for the replies guys.
I guess what I'm trying to acheive is a barrier between the bottom plate
of my wall, and the concrete floor to decrease sound transmission.
I guess like a poor man's floating floor- exept the walls would float on
a doubled layer of sill seal (or something else?).

The problem is, my ceiling is so low (7'2") that I can't float the floor
or hang the ceiling, so I figure I'm left with trying to make the walls
and the ceiling "float" on something absorbant.

If anyone has suggestions I'm all ears.

Thanks,
J

knightfly · Post by **knightfly** » Thu Jun 19, 2003 6:37 pm

J, in which direction do you need the MOST Transmission Loss? And what's your ceiling like? Do you have any drawings posted that I've missed ?

I know 7 foot ceilings is a tough one, but there are things than can help - it's just hard to figure out on verbal descriptions... Steve

Eric_Desart · Post by **Eric_Desart** » Thu Jun 19, 2003 10:17 pm

Hello Steve, Dr.J.

Just some minor things. (little time to go in-depth next week).
Decoupling in the studio world must be one of the most abused and misunderstood words and/or concepts in acoustics.

Look at:
http://www.earsc.com/pdfs/engineering/i ... epaper.pdf

At the bottom I entered one of there pictures (credit not mine, but E;A.R.'s)

What you see at the resonance frequency is that the decoupler acts as an amplifier rather than an attenuator.
In orther words doing decoupling wrong can introduce a problem rather than solving one.
I've seen numerous messages in groups, where I'm sure that the posters were introducing a problem, which wasn't one before.

So, or you calculate decoupling, understanding what is happening, which is related to load versus spring properties of the material, or you don't.
So it's not the question, which is the perfect material (which indeed is an important parameter) but how to apply it in your specific circumstances.
Therefor the excat load and properties of the material must be known.

For linear springs (as helical springs) it's rather easy to check since there a linear relation between the compression of the spring and the resonance frequency.
the formula:
fo = 15.8 / sqrt (imprint of spring in mm).
However synthetic materials react non-linear and must be checked.

Basically if you just want to isolate your wall from the floor, someting as vilt, or low density open foam is OK, even when it' gets pressed together.
As such you use it as damping (meanly influence on high frequencies). and as edge absorber (as an attenuating ventilation splitter silencer).
Once you try to do it better, by using higher thicknesses hoping it will really decouple than it just becomes dangerous if applied wrongly.

If you look at the picture you'll notice that it is in fact a vertical flipped isolation curve of a cavity wall, which in principle works exactly similar (air is a spring as well). You can interpret the 1 horizontal line as the mass-law, and the deviation versus this neutral line (this 1 equals 100% is no decoupling, no amplication = 10 log (1) = 0 dB) as the effect a cavity wall brings compared to the mass law.
Note: this is not an accidental similarity. It explains the main physical basics of a cavity wall.
So when you reverse it, one notice the nonchalance often decoupling is handled (more like if it feels soft and/or elastic it should be good). This is not caused by the users but by the companies selling this material as a side product, I assume often even unaware about the physics behind it.

Doing decoupling wrong can be compared with building a cavity wall with 1/2" boards on each site with a cavity of only few mm (fractional inches) creating a dip in insulation at the mass-spring-mass resonance. And this dip can be interpreted as an amplification of the sound transmission compared to the same wall, with the same mass, build as a single leaf system without cavity.

Kind regards
Eric

Eric_Desart · Post by **Eric_Desart** » Thu Jun 19, 2003 10:36 pm

One more thing,

The shown material is polyethyleen foam which is indeed used for cheap floating floor systems (and thermal purposes of couse which is mean target).
This material gets it resistance by the enclosed air bubles (Is closed cell foam). The material itself has no resistance.
So it acts as the tires of a car.
Under dynamic load this air will escape, just as the air of bycicle tires does.
This is no material to use for demanding applications.

Eric

AndrewMc · Post by **AndrewMc** » Fri Jun 20, 2003 3:33 am

Hi Eric - great post

On the chart - what is the frequency ratio?

If I understand correctly - this means that at some frequencies the isolation is not isolation at all - the product amplifies movement with rubber & silicone being particulary prone to this.

In my situation - the 2 walls both sit on a common concrete slab. The outside wall does not have any isolation or sill seal under the wood footer. It's just caulked along the edge. For the inside wall what would you recommend to put under the footer 2by4?

Eric_Desart · Post by **Eric_Desart** » Fri Jun 20, 2003 4:52 am

Hello Andrew,

I checked the thread, couldn't find your name. So I don't know your construction (maybe I missed somewhat, somewhere in another thread)

I can only get the feel for something if I have a clear picture of the exact build up of a construction.
If it's a room in a room, the outer shell is also part of the construction (even when seemingly nowhere in direct contact).
If it is drywall ......, if it is ?????....
I can't try to list all possible occurences.

So limit myself for now to the principle part.
The frequency ratio is the frequency versus the resonance frequency here noted as 1 (reference).
This resonance frequency is defined by the the (dynamic) load versus the (dynamic) stiffness of the spring. So this depends on the specifics of the application.

Don't mind the names silicone or rubber. Meant is materials with low internal damping. E.g. for a helical or other steel spring this amplification is even worse. E.A.R. sets those materials versus one of their own products in this picture.

One can easily recognize materials with high or low internal damping.
Let some silicone dry and drop it on the floor: it bounces back = low internal damping = the energy is stored in the material and given back. Take plumbers mastic or children's clay, drop it on the floor and it drops dead = high internal damping = the energy is disipated in the material itself.

In principle:
The lower the internal damping of a spring the better the decoupling in the isolation area, but the higher the amplification at the resonance frequency. And vice versa.

Gas or oil dampers on a car are used to damp the resonance frequency of the spring system, or your car should jump of the road.
So this is a perfect balanced system between damping and spring system.
But however perfect the gas or oil damper diminishes the decoupling of the spring system in the isolation area. However perfect the system is a compromize.

Best regards
Eric