A new private message reply from Gerry Lemay.
HI Zhao,
Normally, a low density glass wool material is laid inside the walls in most wall designs. In the US we call this fiberglass batting. I assume that’s what you meant by “cotton”? Cotton would be a bad choice as it is prone to mold unless specifically treated.
I hope that helps!
Gerry
Original message by Zhao WenJie
About the sound insulation of Av room
Sir:
Whether soundproof cotton should be added inside soundproof wall ?