Hey,
the following will help finding any data around:
There is norm which explicitly defines a Echo-Room and therefore lets you find a
Attenuation coefficient for any material: "DIN EN ISO 354"
The Room:
Information about the Room:
German:
Hallraum - Wikipedia,
translated to english
English:
Echo Chamber
Just google for any material, add "DIN EN ISO 354" and "pdf"
Google Search Query A Sample PDF of a company that does those tests officially and independent
Attenuation coefficient for 160mm Thermo Hemp -
this one:
...
1,00 until 200Hz
0,85 until 100Hz
It comes from Mother Earth.
For our Bass Trapps, we use big jute sacks filled with straw, hemp and wood chips to fill up the volume, framed.
Our wide band absorbers are two 14mm hemp segments = 28mm depth, build up in a wooden frame for different absorbtion sufrace sizes.
Also Helmholtz resonators can be build with those material.
MDF wood is cheap
We don't really need any foam, folks.
greetz,
ebon