Only in the highs and at what frequency I am not sure. If you have slap eco go for it. But honestly most treatments should be broad band at least 6’ think. You can heavily treat a room without it being too dead. The key is to treat the full spectrum and not just nuke the highs. Under 60hz is very hard to treat and that is where subs and room correction come in IMO.
Wool Blankets as Room treatment
Just noticed Pendelton has some really nice wool blankets that can be hung on the wall. They even sell the fixturing. I would assume the wool blanked would have some beneficial properties for a blank wall?