My back and knees can’t take concrete so a few work really well instead of a creepier.
They also work for sound. I rigged up a sort of sound booth and the blankets went a long way to solve the acoustics problem in the room.
I’m a hi-fi hobbyist. I was planning on putting in a lot of 2’x4’ roxul (rockwool) stiff panels for sound deadening, but these may be a very cheap alternative. Both would end up with the same covering treatment.