Could someone help out interpreting material's gas flow properties

[andy3]

thx guys. I want the air into the corner (Various reasons). Thanks anyway. you rock!

[localhost127]

^^^^

[KeeZ22]

Hi to all ,

I took my time to read this thread as i tryed to get informed to others but no results so i decided to post my thoughts here.

I am from East Europe and im building bass traps / apsorbers for my home room.
I found this two types of rock wool in my nearest building material supplyer.

Now there are few things i cant connect ,everybody is writing about density and all ,and i dont know what density should be.

Take a look at this two parameters at pictures i posted . ( Rd m2K/W and "lamda" d W/mK )

What is the density ,how are theese two products in relation of the things you have been saying ,like something with 58 kg/m3 or 100kg/m3.

Thank you in advance ,looking foward to get a reply..

Cheers

[DanDan]

For acoustics the data we would like is Gas Flow Resistivity. However, these materials are used as thermal insulation in the real world. So they don't show GFR or even Density sometimes.
I can't even read the small print on those photos. Look up the manufacturers Data sheets or ask them about density.
703 is about 50KG per Cubic Metre. 705 is about 100KG.

Things don't need to be exact at all.
DD

[KeeZ22]

Thank you for a fast reply.

True ,but it also says it is in use for thermal insulation and acoustic as well ,

Looks like i should really do that ,again if any of you guys can explain and compare my data from those 2 pics i uploaded to like 703 and 705 i would be glad

Wonder what settings of rockwool would be allright for mic screen purpose ? hm

[sentient]

Originally Posted by KeeZ22

... if any of you guys can explain and compare my data from those 2 pics i uploaded to like 703 and 705...

Looks like we're neighbours (I'm from Romania)

First of all, hello everyone. I'm new here. Really helpful forum.



As it has been stated above, gas flow resistivity is the most important factor when it comes to sound absorption.

The densities are for those products are:

ROCKWOOL STEPROCK - C 120 KG/M3 meant for floor insulation - reduces impact noise (footsteps, etc.)

According to the graphs below, air flow resistivity should be 70.000 MKS Rayls/m = 70.000 KPa.s/m2 roughly equivalent to OC 705 96 kg/m3 glass wool.

ROCKWOOL MULTIROCK - C 28 KG/M3 meant for general thermal insulation

According to the graphs below, air flow resistivity should be 8.000 MKS Rayls/m = 8.000 KPa.s/m2 roughly equivalent to a lower-density OC 701 - should be 18 kg/m3.


Owens Corning 700 Series specific density and air flow resistance. Density is taken from data sheets. I copied the Air flow resistance from one of Avare's posts dating back to 2008, when he mailed Owens Corning asking for the information. So It's not published official information (from what I gather, NASA measured the 703 to be 24.000 MKS Rayls/m)

OC 701 1.5 pcf = 24 kg/m3 = 8.000 MKS Rayls/m = 8.000 K Pa.s/m2
OC 703 3.0 pcf = 48 kg/m3 = 16.000 MKS Rayls/m = 16.000 K Pa.s/m2
OC 705 6.0 pcf = 96 kg/m3 = 30.000 MKS Rayls/m = 30.000 K Pa.s/m2
OC 707 7.0 pcf = 112 kg/m3

As a general rule of the thumb, in East Europe, Rockwool has the following system for describing density:

ROCKWOOL AIRROCK LD LOW DENSITY - 40 kg/m3 - roughly equivalent to OC 701 or 711
ROCKWOOL AIRROCK ND NORMAL DENSITY- 50 kg/m3 - roughly equivalent to OC 702
ROCKWOOL AIRROCK HD HIGH DENSITY - 70 kg/m3 - roughly equivalent to OC 703
ROCKWOOL AIRROCK XD EXTREME DENSITY- 90 kg/m3 - roughly equivalent to OC 704

All of these equivalents are based on the two graphs below. Please correct me if I'm wrong.
The examples above are referring to a "general building" product, but I suspect it's mostly the same as the better-known Rockwool RW series, measured in Bob Gold's Absorption Coefficients Table

Rockwool RWA45 = 45 kg/m3
Rockwool RW3 = 60 kg/m3
Rockwool RW5 = 100 kg/m3
Rockwool RW6 = 140 kg/m3


Quoting Scott R. Foster:
"...rockwool requires a higher density because of the nature of the material. Generally you could expect similar acoustic performance with a panel about 50% denser in grade [this would approximately match the gas flow properties of 703] which works out to about 5 lbs. per cubic foot or about 60 kg/m3. But even at this density rockwool has inferior handling properties to 703 and yields a heavier panel [no biggy for a hang forget application, but if portability matters this is a flaw]."

Quoting Andre Vare:
"Rockwool is broady equivalent at slightly denser at around 48 kg/m^3 fiberglas at 64 kg/m^3. the relationship acoustically is not linear."


Some useful graphs - I thing I saw them posted somewhere on the forum before, sorry for the redundancy but I believe they're important:



Source: Rockwool Marine & Offshore Acoustic Manual - Highly recommended reading



Source: Building Acoustics, author Tor Erik Vigran

[DanDan]

Here's a very well written post from Hannes.
Note however he uses 16000 for OC703, while NASA regarded it as 27,000.
He then regards 705 as 45000, which ties in with NASA if one were to guess, but does not tie in with OC published 30000 or the 70000 from the graphs.
So, perhaps most of the confusion is to do with OC's released figures.

http://www.gearslutz.com/board/6328646-post88.html


The graphs show a fairly linear relationship, I expect that is a prediction, not a set of measured results.

Common Gas Flow Resistivity numbers.


Here's a load of published GFRs. Common Gas Flow Resistivity numbers.

I was thinking about compiling all the say 50KG products to see what the range of GFR's is.

I suspect it is surprisingly broad.



DD

[andrebrito]

Hello,

In Europe you can find rockwool from 20 or 30 kg/m3 up to 150-200 kg/m3

[RScott]

Sorry to add an air gap to this wonderfully dense thread -- I really appreciate all the info being shared here. My head hurts in a good way! And Andre, I also appreciate your sigs!