When I was a teenager, I worked in the cafeteria of a hospital. All of the cardboard cartons that the eggs came in like these:https://superiorenterprise.com/store...ed=1&Itemid=53 were saved for one of the doctors, who was soundproofing his media room. He said it was the best soundproofing, and all he had to do was attach the cartons to the walls and ceiling. I'm not sure if he painted them later.