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Rigid glasswool with appropriate GFR but too high density?
Old 7th May 2019
  #1
Rigid glasswool with appropriate GFR but too high density?

I'm getting more and more into acoustics, but am still very green. The Master Handbook of Acoustics is on its way to me as I write this, but a quick reply to my question in bold below would be much appreciated!

There are many threads pertaining to GFR vs. density and I have checked a few of them but have yet to find one that talks about what seems to be an odd combination of GFR and density in some rigid insulation pieces I've got:

GFR = 25 kPa, density = 113 (!) kg/dm3

These pieces (or slabs, they're just 2 cm thick) are made to be used as soundproofing in a floating floor, if my understanding is correct. I got them a long time ago when I was just starting out with acoustic treatment and was looking for rigid slabs. This was the only type I found at the time.

I am wondering whether these might be effective as bass traps or if they are so dense they would actually start to work more like a wall. Also wondering if treating "secondary" areas on the side walls with these would work decently or if they are too dense to absorb mid and high frequencies. The room isn't very wide, so slim absorbers on the sides would be nice. I am anticipating to use more typical insulation for the RFZ absorbers, though. By the way, I have 20 of these 120x60x2 cm pieces.

As a side note, I have been trying to find the GFR values for the types of absorption I've used so far (a couple different kinds of Rockwool and Glava), but very often these values are not specified. Any chance of a master list of GFR and density values for specific products?
Old 12th May 2019
  #2
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Quote:
Originally Posted by thermal View Post

GFR = 25 kPa, density = 113 (!) kg/dm3

?
hello,

113 kg/dm3 = 0.113 kg/m3

There are something wrong in the number you gave.

A gfr of 25 KPa.s/m2 equal to a density between 62 an 75 kg/m3.
Old 13th May 2019
  #3
Quote:
Originally Posted by dinococcus View Post
hello,

113 kg/dm3 = 0.113 kg/m3

There are something wrong in the number you gave.

A gfr of 25 KPa.s/m2 equal to a density between 62 an 75 kg/m3.
Thanks for the reply! I am sorry, thought I wrote kg/m3...I calculated 113 kg/m3. Very heavy compressed glass wool. This is the product: https://www.gaus.no/produkter/425486...20x570x1200mm/
Old 13th May 2019
  #4
Lives for gear
Quote:
Originally Posted by thermal View Post
Thanks for the reply! I am sorry, thought I wrote kg/m3...I calculated 113 kg/m3. Very heavy compressed glass wool. This is the product: https://www.gaus.no/produkter/425486...20x570x1200mm/
did you confuse "load resistance" 25 KN/m² with the GFR ?


At my knowledge you can not have a density of 113 Kg/m3 with a gfr of 25000 rayles.
Old 15th May 2019
  #5
Quote:
Originally Posted by dinococcus View Post
did you confuse "load resistance" 25 KN/m² with the GFR ?


At my knowledge you can not have a density of 113 Kg/m3 with a gfr of 25000 rayles.
I think you are right...I read somewhere to look for "strømningsmotstand" (which I now believe is the correct Norwegian word for GFR) or "trykkfasthet" (load resistance). Found a spec sheet that said 25 Pa and thought that was the GFR. Of course, it would have been 25,000 Pa and not just 25...doh!

So actually I have no clue what the GFR is. Probably way too high then! Thanks for your help Dino :-)
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