We did this at our previous townhouse bedroom. We added a second wall about 15 inches from first one. In between the walls we installed acoustic insulation that hangs off metal strips designed not to transmit sounds. You can Google it. We found the acoustic materials from a warehouse in Vienna. We paid handyman $600 to build the wall & hang the insulation. That blocked all noises coming through the bedroom wall.Anonymous wrote:We had soundproofing done in the house we rented. I do not know what it cost the owners, but it really helped. Essentially, they added a layer of wall and put something inbetween the old wall and new wall. It moved the wall about 2-3 inches in. Definitely helped with the sound, although not completely.