This Matt Risinger video shows the results -- six months later -- of an interior remodeling job. Matt applied soundproofing to a master bedroom that's back-to-back with a bathroom. Result: You can't hear the radio playing in the bathroom, even though it's close to the headboard of the bed on the other side of the wall. NOTE: I think the wall also has insulation and Homasote in it.
information and simple solutions for people with neighbor noise.