Coefficients for MDF

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Coefficients for MDF

Postby Jas » Thu Feb 26, 2004 2:17 am

I was wondering if anyone has (or knows where to get) Absorption coefficients and/or NRC's for MDF board. I am designing a room at the moment and can't find any info for this material other than its average density. -Which helps but no cigar!

I am also wondering why so many people tend to use multiple plasterboard layers for lining control room/studio walls/ceiling? Seems to me that mass laws apply in blocking sound, and as most wallboard is not very heavy...?? Before investigating alot of other studios, I had always thought multiple layers of varying density paticle board,chip board, MDF, soundboard, canite etc. was used (other than masonary) and would probably offer better isolation (at equivalent thickness to plasterboard) -Maybe flatter freq response too.
I'd be very interested to here some thoughts on this.
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Postby Eric.Desart » Thu Feb 26, 2004 8:39 am

Hello Jas,,

Read Scott's Faq first to get an overall view.

If I'm right then MDF is this type of dense particle board isn't it?
The absorption is negligible.

Panels, if they show absorption, than this is mainly caused by the fact that they are mounted on a cavity. Than they start reacting as panel absorbers.

Gysumboard is good for soundblocking.
In fact drywalls as standard used are ideal.
Improving them is mainly obtained by increasing cavity, and adding layers.

But first check Scott's Faq's.

Warm regards and
WELCOME to the group.
Eric
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Postby Scott R. Foster » Thu Feb 26, 2004 1:13 pm

Eric:

MDF = Meduim Density Fiberboard - quite heavy [if someone has the spec please post].

There is also HDF [high density fiberboard] which I have seen used in custom cabinent installs.

Jas:

In general drywall is easy to cut and install and the methods of installation are well understood by many craftsmen so finding someone who will do a good job for a reasonable price is usually very easy to do. Drywall works well as a isolative partition panel, and is very cheap per unit mass. There is rarely anything you can do with a reasonably designed partition wall that will give you a better return on time/money than another layer of drywall.

The big exception I would note is that of opting to build a masonry wall instead of a framed structure covered by panels - grout filled concrete block is a great way to go - and might be cost superior to a high TL framed wall design under consideration once all in costs are measured.

Good Luck
SRF
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Postby Savant » Thu Feb 26, 2004 2:14 pm

An exhaustive search of my references turned up nothing on the absorption of MDF. (Which probably doesn't matter. Since it's at least 3x more dense than plywood, it probably won't absorb much of anything by itself. On studs, you'd likely get something nominal at the low end.)

FWIW, I weighed a sample of 1/2" thick MDF here at the office: 45 lb/ft³ = about 721 kg/m³.
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Postby Paul Woodlock » Thu Feb 26, 2004 2:37 pm

Greetings

Also.. When cutting MDF. WEAR A MASK. The fibres are dangerous.


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Postby Ido » Fri Feb 27, 2004 6:33 pm

< FWIW, I weighed a sample of 1/2" thick MDF here at the office: 45 lb/ft³ = about 721 kg/m³. >




Greetings Jeff and all,
I remember from somewhere MDF = about 900 kg/m³.
This makes sense to me cause some plywoods come as ~ 700, and the bugger MDF is heavier/denser.
Oh, MDF doesn't like water (I do).
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Postby Savant » Fri Feb 27, 2004 8:21 pm

Ido,

That's just the weight of a piece I had here in the office. I'm sure YMMV = Your MDF May Vary! :-)
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Postby Ido » Fri Feb 27, 2004 9:23 pm

yeah, I just "searched', and it goes from about 600-900. cheers, Ido
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Postby Andrew Steel » Fri Feb 27, 2004 11:22 pm

I measured many pieces that were 3mm thick and got an average of 2.51kg/m^2. I use this to calculate for up to 18mm thick i.e. 12mm = 10.04kg/m^2 and I usually get the measured response close to predicted. Here it comes in 3, 6,12 and 18mm thick sheets commonly.

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Postby Ido » Sat Feb 28, 2004 1:19 pm

Yeah, your local stuff is ~ 840 kg per cubic meter,
and as Jeff said, Y Mdf M V.
I think our local MDF is same, also comes max 18 mm.
Ido
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Postby Eric.Desart » Sat Feb 28, 2004 3:03 pm

Jas,

If you get confused.

All this doesn't matter.
Whatever construction panel the absorption is insignificant......

It can become significant if used on a cavity, but then it's more a panel trap like behavior.
A few exceptions are construction panel with very low density feeling fibrous. But even then be careful.

You all caused Jas not to search only for MDF anymore, but for MDF in all kinds of densities.

:):):)

The same not me:)
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Postby giles » Mon Mar 01, 2004 12:14 pm

there are sites that give density tables for mdf; i used them when i was studying; i'll look around for you;
mdf = medium density
hdf = high density (hardboard)
ldf = low density (chipboard)
the safety concerns are more to do with the binding agents than the wood fibres;
these boards used to be bound with urea formaldehyde glues which are highly toxic when in dust form; most european countries have banned these adhesives & you can specify a UF free product.
one of the problems of measuring mdf density is that there is a significant difference in density between the faces of the board & the centre.
a more useful (&cheaper) product is OSB panel you can get this off the shelf with T&G edges so you can achieve very good seals over large areas & it has a higher linear rigidity than mdf which bends very easily.
G
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more mdf trivia

Postby giles » Mon Mar 01, 2004 3:45 pm

for the record you can get MDF up to at least 50mm thick and i believe up to 100mm. sheets are often bonded together to create volume; the reason the density difference between edge and core is significant is that it means a 6mm board is heavier per cubic unit than a 50mm board; if you had a cubic metre stack of 6mm boards next to a cubic metre stack of 50mm boards the 6mm stack would be heavier.
black MDF is much harder with superior lateral rigidity & has a more even density; it's extremely beautiful & can look like polished slate but it costs a lot more.
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Coefficients for MDF

Postby Jas » Fri Mar 05, 2004 1:30 am

Thanks for the replies everyone.

So what does it all mean Basil?

Since posting, I have found specs on most sorts of particle board. Weight is an important factor when comparisons are made for use in wall lining. Normal plaster board comes in at about 6.5 kg m2 (10mm)
The heaviest fire rated plaster board is about 13.5 kg m2 (16mm) - nice and heavey but quite a bit more expensive. (intrestingly has fibreglass in it) - There are lots of thicknesses and densities in between. As a few of you have correctly mentioned, Standard MDF ranges from 700 to 900 kg m3. It gets lighter per m3 as it increases in thickness. 25 to 35mm MDF is about 18 kg m2. Heavier than normal dry wall but lighter than the heavier types, though at 25mm is more rigid. Lower density particle boards like 22mm chipboard flooring is about 15kg m2. In my neighborhood, CSR make a "Soundcheck" plasterboard which is 13kg m2 at only 13mm thick....extremely heavey! - more expensive again but almost the same weight as two layers of normal 10mm stuff. -This would be a good option if you were paying for installation as the cost hanging and finishing drywall is usually more than the drywall itself.
In the end it comes down to cost, available space and level of isolation required. Ideally you would have a combination of all of the above.
-BTW I still can't find anyone who has got NRC's or at least STC rated particle boards. I think it would be interesting to see how it compares to drywall at different frequencies so we could estimate the isolation of a multi-layer wall. I'm sure someone must have looked into this before!?
Maybe its not worth investigating?

Cheers[/i]
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Postby Bob » Fri Mar 05, 2004 1:52 am

Hi Jas:

For the past several months the good people here and elsewhere have been banging on my thick skull the concept that gypsum/drywall/sheetrock (same thing) is the cheapest and easiest way to achieve proven sound isolation.
You can use anything you want of course, but apparently it will either be more expensive, or work less well, or both. At the very least it's risky. The concept is that people have been using gypsum and RC and insulation because it's the cheapest thing that works the best for walls and ceilings, and occasionally in floors and in doors. If there were something that worked cheaper or better, well they'd be using it. (Although for the cost is no object croud there's words like: concrete, ICW little springs, RSIC, and of course Sylomer, and really big springs.)

As for the absorbtion of a wall system, well apparently that's extremely complicated (sort of a sum of a large number of sub-systems).

For a completely unrelated story of the heroes of "well, this ought to work" please enjoy the somewhat disgusting QuickTime movie http://rezrov.perp.com/whale/whale-hi.mov
Regards
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Postby Paul Woodlock » Fri Mar 05, 2004 3:26 am

Now here's a Tip......


I'm using MDF as the penultimate inner layer of my inner room. ( the other 4 layers being drywall of course )

Reason. I can screw things to the walls and ceiling... ANYWHERE!!! :) :)


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Coefficients for MDF

Postby Jas » Fri Mar 05, 2004 4:31 am

Now thats an idea!





Nice one Paul
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Postby giles » Fri Mar 05, 2004 5:52 am

the most important factor in the equation is what do you want to achieve? people build studios for different reasons and in very different circumstances; this has a bearing on the degree of sound control you need to achieve; some people are trying to stop sound coming in for others the problem is sound going out.
cost plays a major part but the other important thing is the final aesthetic if your going to spend a lot of your time in a space it has to feel good; for me hitlers bunker wouldn't achieve that & so i've gone to more trouble & expense to have a window, for example.
the thing about gyproc is that you can finish it very well & make large surfaces that in the end look continuous, joining other panels is not so easy; usually with panelled walls instead of trying to join the panels designers deliberately leave a 3 - 5 mm gap between the panels. labour costs are the biggest expense & gyproc is quick to install as cutting and shaping doesn't involve sawing or milling & doesn't produce much dust & it's much cheaper. on one of my walls where i want particular isolation from my nieghbours i used edge jointed osb boards laid horizontally first & then gyproc vertically on top. you also need less framing with this system .
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Postby Andrew Steel » Fri Mar 05, 2004 10:29 pm

MDF shriks a tiny bit over time too. If you make plastered type joins, you might firn some cracks later.
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