Hi,
there are different products of rockwool (e.g. sonorock, floorrock).
What product is suitable for what application?
Rockwool is cheaper than fiberglas for me.
They don't print any density or absorbtion coefficient on their data sheets.
For instance, is a sheet of 30mm-floorrock usable as bass hanger?
Thomas
Rockwool
Originally posted at johnlsayers.com, topic 13875.
floorrock is high density stuff.
xtreme compressed.
i would say it's not that good for bass hangers.
try to find weichfaserdämmplatten and use sonorock.
i think this is what john always suggests.
somewhere in the acoustics forum is a great thread about bass hangers i think
it was this thread
carsten
Im glad to had someone on the telefon from rockwool that could give some more specific answers. At first rockwool does not measure any absorbtion coefficents like ovens corning or other manufactures of fiberglas did. floorrock has 100kg/m³ sonorock has 30kg/m³ flexirock has 60kg/m³ But he suggested http://produktwegweiser-rocknavi.rockwool.de/media/67995/1.308.3%20raf.pdf. Doesn't look that nice to me. Greetings Thomasfloorrock is high density stuff. xtreme compressed. i would say it's not that good for bass hangers. try to find weichfaserdämmplatten and use sonorock. i think this is what john always suggests.
Normal recommendation here is for 48 kg/m³, so based on that the "Flexirock" product seems to be the closest match, at 60kg/m³. That should probably do the job reasonably well. IMHO
- Stuart -
Hi,
but flexirock is doubled expensive. Sonorock is around 40 Euros/m³, flexirock 80 Euros/m³.
Will Sonorock (30kg/m³) work for absorber panels and "super chunks"?
Thomas
yes, that will work too. You see density isn't the most important factor in building a good absorber, it's generly the depth that will have the most significant impact.
48kg/m3 is most recommended since it has best overall absorption but it isn't a strickt rule.
If you go supperchunk, assuming you want a low-end absorber, make it as thick/deep as you can affort (in a corner, 50x50cm wide will do already) Put a "filter" in front to keep it from sucking too much high frq as well. Read the board and you'll understand.
check viewtopic.php?f=10&t=12321
Put another way...allowing a lighter density material (say, batts of rockwool) to occupied more space will give better absorbtion figures than higher density using less space.
True! But speaking of picky ( :) ), there's also the issue of diminishing returns: once the density gets too low, it stops being effective. Just as when the density gets too high.allowing a lighter density material (say, batts of rockwool) to occupied more space will give better absorbtion figures than higher density using less space.
Hope this helps
In recent discussions with Dr. Peter D’Antonio, he said the following: For optimal absorption, a porous absorber should offer a surface impedance with a lowfl ow resistivity, which matches that of air to remove refl ections, while offering a high internal acoustic attenuation. When attempting to control refl ections with a single density material, it is fair to say that thin fi berglass panels should not be used, and in my view lower density is preferred over higher density. In addition, thicker panels and a rear air cavity both contribute to extending the absorption to lower frequencies. When it comes to sound absorption, it could be useful to ask what is used in anechoic chambers, where the goal is complete elimination of sound above a certain “cut-off” frequency. In traditional designs, the wedge-shaped absorbers must be at least 1/4-wavelength long at the lowest frequency of interest. In good chambers, this is typically 3 to 4 ft (0.9 to 1.2 m). The material used in these wedges is usually compressed glass fi ber with a density of about 3 pcf (48 kg/m3). According to one study, that density appears to have been a choice of convenience (structural rigidity and particle shedding considerations) because a lowerdensity material (1.1 pcf, 18 kg/m3) was closer to the acoustical target performance (Koidan et al., 1972). Rasmussen (1972) describes an anechoic chamber constructed of suspended cubes, somewhat randomly arranged with small (2-in., 50 mm) low-density (1.9 pcf, 30 kg/m3) cubes farthest from the wall and progressively larger, denser cubes placed closer to the wall, with the inner layer being Acoustical Performances of Some Common Materials 6 to 7.5 pcf (100–120 kg/m3) stacked against the wall. It apparently worked superbly. In summary, all of this suggests that the surface of the absorbing material— the interface with the sound fi eld—should have relatively low density and that to achieve performance at lower frequencies, one may need to seriously consider how much real estate can be devoted to the task because materials that work well have appreciable thickness.