As far as I understand, mineral-fiber ("rockwool") and acoustic form perform similar roles: sound absorption, or reducing echo.

The fact that both exist and are for sale imply there's a trade-off going on between these two technologies.

What are the differences?

  • Possible options: price, overall effectiveness, effectiveness in different frequencies, aesthetics, ease of application, flammability.
    – iLikeDirt
    Feb 12, 2015 at 19:02
  • I would look into their actual R-Value. I suspect one better insulates against temperature, and the other sound absorption. Feb 12, 2015 at 19:35

2 Answers 2


Yes, as general concepts, both can be used for noise absorption but that doesn't mean they work the same way. They can have potentially different absorption levels; different targeted frequencies; different form factors; different areas of use.

This page tallies up the absorption coefficients of hundreds of products: http://www.bobgolds.com/AbsorptionCoefficients.htm

Note how there are wildly differing values based on type, thickness, and even specific frequencies. If you have a serious spike at 500Hz and only have 1" of space to work with and it's a curved area, then you'll want to find a material or product that is flexible and works well at that frequency. Add in factors such as if the product will be visible or not; enclosed or not; and such, and you find a massive amount of variability.

So in the end, why are they both in the market? Because they serve different specific purposes within the subset of acoustic control.

  • Impressive resource... Feb 12, 2015 at 23:44

Depending on what you mean by acoustic foam (spray foam or egg-crate type sheets) they are different products meant for different applications with some overlap in function.

Rockwool is batt insulation product made to be installed within walls or other structures. It provides good insulation that is not affected by moisture and is not a food source for pests. It's density compared to other types of in-wall insulation make it good at reducing sound transmission through it compared to other types of batt insulation.

Acoustical foam sheets, the egg-crate or other bumpy surface types are meant to be applied on top of a surface. In addition to limiting sound transmission they also absorb and disperse sound so you don't get echos.

Acoustical foam spray type goes inside a wall and has insulating and air sealing properties as any spray foam insulation does but claims to have better sound proofing qualities.

How much sound proofing and at what frequencies vary by product as the R-Value. You should check the manufacturer's websites for the specs and find the combination of specs that is most suitable to your situation.

  • There are types of rigid rockwool boards specifically made for soundproofing, not just insulation.
    – iLikeDirt
    Feb 12, 2015 at 20:38

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