Which acoustic panels absorb the most noise?
Some of the most absorptive panels types available are those composed of carbon loaded glass wool.
The scientific parameter in acoustics which deals with the sound absorption capacity of a material is NRC- Noise Reduction Coefficient.
Its value ranges from 0 to 1 where 0 is no sound absorption at all (completely sound reflecting like glass, concrete) and 1 is all the sound incident on the material surface is absorbed (like perfect black body in lighting).
So ask any manufacturer or vendor for the NRC value, which is a number between 0 & 1 (eg-0.2, 0.66, 0.95, and 0.36). Higher the number higher is the sound absorption capacity of that material and vice versa.