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PostPosted: Mon Aug 11, 2003 8:15 pm 
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I found more Owens Corning measurements.
I formatted/sorted them and did some additional calculations to show some points.
The numbers speak for themselves.

Owens Corning 701, 703, 705
Thickness: 1", 2", 3", 4" and one 6"
All Measurements mounting direct to reflective background (no cavity).

SORTED PER DENSITY VERSUS THICKNESS
Freq: 125, 250, 500, 1000, 2000, 4000 Hz

1 inch
OC 701 · 1.0" · 0.17 · 0.33 · 0.64 · 0.83 · 0.90 · 0.92
OC 703 · 1.0" · 0.11 · 0.28 · 0.68 · 0.90 · 0.93 · 0.96
OC 705 · 1.0" · 0.02 · 0.27 · 0.63 · 0.85 · 0.93 · 0.95

2 inch
OC 701 · 2.0" · 0.22 · 0.67 · 0.98 · 1.02 · 0.98 · 1.00
OC 703 · 2.0" · 0.22 · 0.82 · 1.21 · 1.10 · 1.02 · 1.05
OC 703 · 2.0" · 0.17 · 0.86 · 1.14 · 1.07 · 1.02 · 0.98
OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.99 · 0.99
OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.98 · 0.98

3 inch
OC 701 · 3.0" · 0.43 · 1.17 · 1.26 · 1.09 · 1.03 · 1.04
OC 703 · 3.0" · 0.53 · 1.19 · 1.21 · 1.08 · 1.01 · 1.04
OC 705 · 3.0" · 0.54 · 1.12 · 1.23 · 1.07 · 1.01 · 1.05

4 inch
OC 701 · 4.0" · 0.73 · 1.29 · 1.22 · 1.06 · 1.00 · 0.97
OC 703 · 4.0" · 0.84 · 1.24 · 1.24 · 1.08 · 1.00 · 0.97
OC 705 · 4.0" · 0.75 · 1.19 · 1.17 · 1.05 · 0.97 · 0.98

6 inch
OC 703 · 6.0" · 1.19 · 1.21 · 1.13 · 1.05 · 1.04 · 1.04


SORTED PER THICKNESS VERSUS DENSITY
Freq: 125, 250, 500, 1000, 2000, 4000 Hz

Owens Corning 701... 24 kg/m^3 - 1.5 pcf
OC 701 · 1.0" · 0.17 · 0.33 · 0.64 · 0.83 · 0.90 · 0.92
OC 701 · 2.0" · 0.22 · 0.67 · 0.98 · 1.02 · 0.98 · 1.00
OC 701 · 3.0" · 0.43 · 1.17 · 1.26 · 1.09 · 1.03 · 1.04
OC 701 · 4.0" · 0.73 · 1.29 · 1.22 · 1.06 · 1.00 · 0.97

Owens Corning 703 ... 48 kg/m^3 - 3 pcf
OC 703 · 1.0" · 0.11 · 0.28 · 0.68 · 0.90 · 0.93 · 0.96
OC 703 · 2.0" · 0.22 · 0.82 · 1.21 · 1.10 · 1.02 · 1.05
OC 703 · 2.0" · 0.17 · 0.86 · 1.14 · 1.07 · 1.02 · 0.98
OC 703 · 3.0" · 0.53 · 1.19 · 1.21 · 1.08 · 1.01 · 1.04
OC 703 · 4.0" · 0.84 · 1.24 · 1.24 · 1.08 · 1.00 · 0.97
OC 703 · 6.0" · 1.19 · 1.21 · 1.13 · 1.05 · 1.04 · 1.04

Owens Corning 705 ... 96 kg/m^3 - 6 pcf
OC 705 · 1.0" · 0.02 · 0.27 · 0.63 · 0.85 · 0.93 · 0.95
OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.99 · 0.99
OC 705 · 2.0" · 0.16 · 0.71 · 1.02 · 1.01 · 0.98 · 0.98
OC 705 · 3.0" · 0.54 · 1.12 · 1.23 · 1.07 · 1.01 · 1.05
OC 705 · 4.0" · 0.75 · 1.19 · 1.17 · 1.05 · 0.97 · 0.98


ABSORPTION VALUES VERSUS MATERIAL THICKNESS AS % OF WAVELENGTH.
Compare column 3 , giving the material thickness as a % of the wavelength, with the corresponding absorption in Column 2.
You can compare them with the Engineering rules given before.
It's clear that the traditional 1/4 wavelenght (25%) approach does NOT apply.
This approach only relates to PLAIN waves at STRAIGHT incidence for DISCRETE frequencies:

The picture below shows a theoretical simulation of the above described 1/4 wave approach (copyright).

OC 701 · 1.0" · 25.4 mm
0125 Hz · 0.17 · 000.9%
0250 Hz · 0.33 · 001.8%
0500 Hz · 0.64 · 003.7%
1000 Hz · 0.83 · 007.4%
2000 Hz · 0.90 · 014.8%
4000 Hz · 0.92 · 029.6%

OC 701 · 2.0" · 50.8 mm
0125 Hz · 0.22 · 001.8%
0250 Hz · 0.67 · 003.7%
0500 Hz · 0.98 · 007.4%
1000 Hz · 1.02 · 014.8%
2000 Hz · 0.98 · 029.6%
4000 Hz · 1.00 · 059.2%

OC 701 · 3.0" · 76.2 mm
0125 Hz · 0.43 · 002.8%
0250 Hz · 1.17 · 005.5%
0500 Hz · 1.26 · 011.1%
1000 Hz · 1.09 · 022.2%
2000 Hz · 1.03 · 044.4%
4000 Hz · 1.04 · 088.8%

OC 701 · 4.0" · 101.6 mm
0125 Hz · 0.73 · 003.7%
0250 Hz · 1.29 · 007.4%
0500 Hz · 1.22 · 014.8%
1000 Hz · 1.06 · 029.6%
2000 Hz · 1.00 · 059.2%
4000 Hz · 0.97 · 118.4%

OC 703 · 1.0" · 25.4 mm
0125 Hz · 0.11 · 000.9%
0250 Hz · 0.28 · 001.8%
0500 Hz · 0.68 · 003.7%
1000 Hz · 0.90 · 007.4%
2000 Hz · 0.93 · 014.8%
4000 Hz · 0.96 · 029.6%

OC 703 · 2.0" · 50.8 mm
0125 Hz · 0.22 · 001.8%
0250 Hz · 0.82 · 003.7%
0500 Hz · 1.21 · 007.4%
1000 Hz · 1.10 · 014.8%
2000 Hz · 1.02 · 029.6%
4000 Hz · 1.05 · 059.2%

OC 703 · 2.0" · 50.8 mm
0125 Hz · 0.17 · 001.8%
0250 Hz · 0.86 · 003.7%
0500 Hz · 1.14 · 007.4%
1000 Hz · 1.07 · 014.8%
2000 Hz · 1.02 · 029.6%
4000 Hz · 0.98 · 059.2%

OC 703 · 3.0" · 76.2 mm
0125 Hz · 0.53 · 002.8%
0250 Hz · 1.19 · 005.5%
0500 Hz · 1.21 · 011.1%
1000 Hz · 1.08 · 022.2%
2000 Hz · 1.01 · 044.4%
4000 Hz · 1.04 · 088.8%

OC 703 · 4.0" · 101.6 mm
0125 Hz · 0.84 · 003.7%
0250 Hz · 1.24 · 007.4%
0500 Hz · 1.24 · 014.8%
1000 Hz · 1.08 · 029.6%
2000 Hz · 1.00 · 059.2%
4000 Hz · 0.97 · 118.4%

OC 703 · 6.0" · 152.4 mm
0125 Hz · 1.19 · 005.5%
0250 Hz · 1.21 · 011.1%
0500 Hz · 1.13 · 022.2%
1000 Hz · 1.05 · 044.4%
2000 Hz · 1.04 · 088.8%
4000 Hz · 1.04 · 177.6%

OC 705 · 1.0" · 25.4 mm
0125 Hz · 0.02 · 000.9%
0250 Hz · 0.27 · 001.8%
0500 Hz · 0.63 · 003.7%
1000 Hz · 0.85 · 007.4%
2000 Hz · 0.93 · 014.8%
4000 Hz · 0.95 · 029.6%

OC 705 · 2.0" · 50.8 mm
0125 Hz · 0.16 · 001.8%
0250 Hz · 0.71 · 003.7%
0500 Hz · 1.02 · 007.4%
1000 Hz · 1.01 · 014.8%
2000 Hz · 0.99 · 029.6%
4000 Hz · 0.99 · 059.2%

OC 705 · 2.0" · 50.8 mm
0125 Hz · 0.16 · 001.8%
0250 Hz · 0.71 · 003.7%
0500 Hz · 1.02 · 007.4%
1000 Hz · 1.01 · 014.8%
2000 Hz · 0.98 · 029.6%
4000 Hz · 0.98 · 059.2%

OC 705 · 3.0" · 76.2 mm
0125 Hz · 0.54 · 002.8%
0250 Hz · 1.12 · 005.5%
0500 Hz · 1.23 · 011.1%
1000 Hz · 1.07 · 022.2%
2000 Hz · 1.01 · 044.4%
4000 Hz · 1.05 · 088.8%

OC 705 · 4.0" · 101.6 mm
0125 Hz · 0.75 · 003.7%
0250 Hz · 1.19 · 007.4%
0500 Hz · 1.17 · 014.8%
1000 Hz · 1.05 · 029.6%
2000 Hz · 0.97 · 059.2%
4000 Hz · 0.98 · 118.4%

Some additional comments:

If interested:
I measured here different densities of glassfiber in an acoustic laboratory (plain boards without special facing).
In the range to ca 6 pcf (Isover glassfiber boards), I measured improvement unto 32 to 35 kg/m³ (2 to 2.2 pcf) which should equal about the OC 702 (but I couldn't find measurements of the OC 702). Only this can differ a bit by brand (production method).

Absorption is mainly defined by entrance impedance and gasflow resistance and the behavior of a complex soundfield. As such one will measure different values in function of angle of incidence and the fact if one measure pure tones (sinuswaves) or broadband noise.

The relation with mass (density) is only true in as far this mass goes hand in hand with the previous described properties.
So this can be true, partly true or untrue but is wrong to state as a defining property for absorption.
Melamine foam with a density of only 0.55 to 0.70 pcf has rather surprising absorption properties.
So it's the cellular structure which mainly defines those properties.

For straight incidence, increasing density can help, but for grazing/angled incidence lowering the density is often the way to go.
Do not assume that a backwall is necessary only straight incidence. A sound field is a bit more complex. A lot of the velocity of the air particles happens in the neighborhoud almost parallel and at any angle to the wall.

Best regards
Eric


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PostPosted: Mon Aug 11, 2003 11:51 pm 
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Thanks Eric, good to see you floating around still

Bryan Giles


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PostPosted: Tue Aug 12, 2003 12:35 am 
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Great info. Now what about prices! That would help.

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PostPosted: Tue Aug 12, 2003 3:16 am 
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check you local supplier

My Supplier quoted me .75 sq.ft. for 703 unfaced. which yeilds the lower LF #'s

Bryan Giles

Calling OC's Toll free number will help. I called and they had a local supplier call me back within 24 hours


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PostPosted: Wed Aug 13, 2003 1:54 am 
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giles117 wrote:
Thanks Eric, good to see you floating around still

Bryan Giles


:oops: :oops: :oops: :P
Thanks,

I thought it could be useful (to be honest entered it in 3 groups, once made was easy to copy).


About prices of mineral wool:
With exception of local market situations (certain types are more standard than others).

One pays for wool in function of the amount of spinned fibre.
So the cost is directly linear related to the density.

However due to handling, packaging and transport this becomes more expensive relative to the amount of fibre. So this disrupts this linearity.

As such a 703 will cost somewhat less than double the 701, and the 705 somewhat less than double the 703.

Regards Eric

Simplified:
Fibre is spinned at a constant rate.
To make higher densities or larger thicknesses, one slows down the subsequent production chain (weaving, backing etc).


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PostPosted: Wed Aug 13, 2003 2:26 am 
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Eric, thanks for the link - been following it (with occasional comments) over on RO, but appreciate your posting it here too.

I kind of intuitively knew how they got the different densities, since I work in a heavy manufacturing situation (Process Instrumentation & Control, rare metals manufacture) but it's good to verify, plus others without similar background may not have had any idea how this is accomplished.

To your knowledge, has anyone ever tried to "sculpt" rigid fiberglas (cut "V" grooves in it) in order to compare to the "scupted" foams for grazing incidence measurements? I've not seen anything along these lines, kind of curious whether it would be a good thing or not. It certainly would be a messy operation... Steve

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PostPosted: Wed Aug 13, 2003 2:43 am 
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I use Roxul AFB Mineral wool. They are over the border in Canada. My supplier is about 30 minutes from me. I believe I get the prices I get because they are so close to each other.

.25/sq ft 2"
.35/sq ft 4"
.16/sq ft 1"

Bryan Giles

A bundle of 18 1" 2x4 sheets runs me about $16.00

A bundle of 4 4" sx4 sheets runs me about $11.00


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PostPosted: Wed Aug 13, 2003 3:17 am 
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Hello Steve

knightfly wrote:
Eric, thanks for the link - been following it (with occasional comments) over on RO, but appreciate your posting it here too.

To your knowledge, has anyone ever tried to "sculpt" rigid fiberglas (cut "V" grooves in it) in order to compare to the "scupted" foams for grazing incidence measurements? I've not seen anything along these lines, kind of curious whether it would be a good thing or not. It certainly would be a messy operation... Steve


Sculpting wool is standard for anechoic room wedges (they excist in all kinds of shapes). However the acoustic effect is extremely minor and only meant to obtain the extreme stringent specs for anechoic rooms. In practice this is hardly measurable (they are measured in extreme large impedance tubes.

A second area where sculted wool is used is as filling for perforated steel ceilings (to fill those profiles, following this shape).

In general sculpting wool should mainly have acoustic disadvantages.
Sculpting has only effect when the sculting becomes large versus the wavelength. This means that for the low frequencies, the disadvantage of removing wool by the sculpture is much more bad than any gain one could have (even for traveling waves this sculpture is seen as ca plain material).

For foam it has some sense, since the traditional acoustic polyether and polyester foams have an higher entrance impedance than wool (more surface reflection). As such profiling foam mainly compensates (mids and highs) for the less good material properties, at the expense of low frequent absorption (removed material). The better the basic material (as wool) the less effect this sculpture has, only leaving the disadvantages.

In fact this commercial sculpting of foam is derived from the first wedges ever installed in Germany (Herz institute) think somewhere in the 40ies (have exact data somewhere).
It's a bit the magic (+ huge PR budgets) which keeps it alive.
In the industry lots of acoustic foam is used for technical applications, but in 99 % this is plain flat foam. This market is MUCH larger than for the sculpted foam, only unknown in the studio world.

With Melamine which has different properties this sculpting becomes bad or less desirable. Problem for the producers: how to explain/sell that to potential customers.
Therefore you'll notice that lots of producers will still use pyramides with Melamine, but make the sculpture much less high (base versus sculpture changes in favour of base).

Best regards
Eric


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PostPosted: Wed Aug 13, 2003 6:07 am 
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Hi Eric & Steve
Quote:
In the industry lots of acoustic foam is used for technical applications, but in 99 % this is plain flat foam. This market is MUCH larger than for the sculpted foam, only unknown in the studio world.

Exactly ! Few months ago i check with BASF about their BASOTECT, i think is kind of melamine and u know how they sell this thing...... they sell by each container, frist i was thinking to use them to replace 703, but can't affort to buy a container of foam, now i am trying to buy them through some building contractor ! but can't find yet ! Anyway do u think i can susitule the glass fiber with Basotect ? and heard that a company made a metal penal trap with this foam as damper, are they good for studio use ?
Thanx


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PostPosted: Wed Aug 13, 2003 7:54 am 
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hi feni,

Basotect is the BASF name for Melamine Resin foam which is a patented BASF product.

All other Melamine foam used world-wide either comes directly from BASF or is produced under BASF license.
You find it under lots of names as Willtec etc.

To find a supplier it's easier that you give your location.
Maybe somebody can help you.

But in general, rockwool or glassfiber is still a lot cheaper. so why should you choose Melamine?
There are of course valid reasons, but standard glassfiber or rockwool is very hard to beat.

Eric
PS: it's not surprising that you can't buy minor quantities at BASF itself.


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PostPosted: Wed Aug 13, 2003 2:23 pm 
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Hi Eric
Thanx for the reply !
My location is HongKong, i did contact BASF HK/China but they don't have supplier infor for me, any accoustic matrial is not easy to find here ! or very expansive, even 703. u can only get 2" 703 so i have to stack them together if i want to make a 4" boardband module, but with yr infor now i am quite happy to know that just 2" 703 can do more than i knew before.
There are 2 main reason i want to use non- fiberglass product beause... Reason 1- i have a very very sensitive skin, my arms turn red every time i touch them !......... Reason 2 - space for experiment is very limit in my place, most of the work is inside my apartment, my wife wants to kill me every time i cut the glass fiber ! So if melamine can replace 703 in terms of accoustical usage, i rather pay a bit ( just a bit ) more for it ! on the others hand i may save money on housing the 703. Eric ! what do u think ? is it worth for me to keep on seaching for basotect supplier ?
Thanx ! and hope u understand my english !
Feni


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PostPosted: Wed Aug 13, 2003 6:28 pm 
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Hello feni,

Find it difficult to compare prices for you. That's more defined by local market situations.

Maybe you can find coton wool, ployester or polyether (as in matraces) foam?

From an acoustic point of view, Melamine is about as good as wool, say a little bit less good. It's acoustically certainly a valid alternative.

From the point of view of fire properties, within the foam world, it's the best alternative around.

It's difficult to rate the different solutions for you without knowing the cost.
Here the basic Melamine will be 2,5 to 3 times more expensive than a valid naked glassfiber alternative (but that depends on density).

Best regards
Eric


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PostPosted: Wed Aug 13, 2003 7:48 pm 
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OK so I can get this straight. The number like 703 does not apply to the actual thickness of the material, just the model? Like 703 is 3" and 705 is 5" thick? I want 4" boards.

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PostPosted: Wed Aug 13, 2003 8:37 pm 
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Thanx again Eric

Quote:
Find it difficult to compare prices for you. That's more defined by local market situations.

Yes ! fully understandable, if a different about, 2.5 to 3 times, i think, at least it worth for a try !
Now i am looking at the Borchure they sent to me, The CSR & CBA seem very interesting to me ( i think u did read it ! right ! ). They claim that A CBA ( product using Basotect with metal sheet ) " with thickness of 25cm which in the frz. range from 30Hz upwards allows the maintenance of free accoustic field conditions even in relatively small rooms." Do u think it's possible ??
honestly don't quite understand what means " Free accoustic Field" in this situation !
But why on the DIN 52215 & DIN 52212 graph, they don't look very impressive, especially on the LOW (125Hz) side, may be i don't fully understand the DIN system or comparing in a wrong concept !

Quote:
Maybe you can find coton wool, ployester or polyether (as in matraces) foam?

Infect i did try! after i saw a foam corner trap made with ployester, claimed that it can go down to 45hz ( anyone try this ? ), badly it cost 3 to 4 times more if ship from England.
Anyway all i found locally were closed cell foam. many supplier even don't know their product are close or open cell. i sound like a idiot to talk with them (or may be i was), :( So after all this disappointing search, i forced to use glassfiber together with my skin problems !

Quote:
From an acoustic point of view, Melamine is about as good as wool, say a little bit less good. It's acoustically certainly a valid alternative.
From the point of view of fire properties, within the foam world, it's the best alternative around.

Glad to know that !
thanx Eric !
i have to reset my english system inside my head for awhile and will come back to u and others great members here later ! Ciao !


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PostPosted: Wed Aug 13, 2003 9:46 pm 
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feni

You're welcome.
You ask a lot of details with very specific end-product codes.

If you have links it's always easier to check what exactly you're talking about.

The question is not necessarilly. Is this a good absorber (you can make panel/membrane absorbers in lots of ways), but what do you need.

You'll notice in the group that Helmholtz slat resonators are used a lot.

To check if you have open cell foam, just blow trough it. If you get a blown-up red head while trying it's closed cell foam. :lol:

Regards
Eric[/url]


Last edited by Eric_Desart on Thu Aug 14, 2003 1:41 am, edited 1 time in total.

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