Does two 2"layers of absorbent = one 4" layer?

[cct]

I'm thinking to make some absorbent panels and I find materials in 2", 4", 6" thicknesses. If I only purchase 2" material, and make a 4" (or 6" or 8") panel by stacking layers of the 2" material, does the stack act the same as a single layer of thicker material? It certainly seems to me that it would. Doing this could allow me to place a higher quantity order for only 2" material that might be filled by a commercial distributor of building materials (e.g. Rockwool).

 

[Chrispy]

I doubt stacking could be adverse. You're overthinking it

 

[antcollinet]

If I only purchase 2" material, and make a 4" (or 6" or 8") panel by stacking layers of the 2" material, does the stack act the same as a single layer of thicker material?

Yes.

 

[LesterNZ]

Thicker gets you lower freq absorbtion. And an air space between layered materials also helps. Check the DIY posts on absorbers - bass traps etc.
Good luck.

 

[skankhobag]

A little known fact is that having acoustic foam slightly away from the wall actually increases its effectiveness. Having your two layers an inch or two apart is going make them a hair more effective, too.

 

[Chrispy]

I haven't checked, but what is more cost effective would be a major consideration here. Is buying the generally insufficient on its own 2" cheaper than just buying the 4" in same l/w needed? Some other factor involved? Seems if you can actually make the 2" more effective with a gap between layers, tho I imagine building framing for that might be a bigger pain....

 

[BillH]

Yes they are the same but…
Don’t put a thick layer of glue to hold them together. The glue will dry and harden forming a partial reflector between them.
Just keep the surface area of any adhesive small compared to the total surface area or don’t form a continuous film and it will be fine.

 

[Chrispy]

Yes they are the same but…
Don’t put a thick layer of glue to hold them together. The glue will dry and harden forming a partial reflector between them.
Just keep the surface area of any adhesive small compared to the total surface area or don’t form a continuous film and it will be fine.

Wonder if there's significant differences to be had with various suitable aerosol adhesives in terms of any sort of forming any formidable layer.....but shouldn't be hard to not use adhesives otoh.

 

[BillH]

Wonder if there's significant differences to be had with various suitable aerosol adhesives in terms of any sort of forming any formidable layer.....but shouldn't be hard to not use adhesives otoh.

I suspect you would have to lay it on pretty thick to create a problem - like a complete film of wood glue…

 

[cct]

I found a local building materials supplier with a lot of Rockwool AFB material, 1.5" thickness. Good price, and I can pickup so no shipping charge. Then I will stack the 1.5" layers to make panels in multiples of that thickness, so 6" or 9" for bass traps.