I currently live in a 40 year old particially renovated apartment building converted into condo units. An extension was added to the end of the building. I share two common walls with my neighbors. I can hear their conversations, music, tv and shower. I have lost faith in hiring contractors. I also have one bedroom closet on an exterior wall that emits cold air in the winter. My clothes are cold. Can I insulate this closet wall? Can I open up the common walls and put up sound barrier dry wall and insulation to keep the noise level down? Is this a project I can do myself? My unit is approximately 1500 square feet.

My neighbors are not overtly noisy. The barrier is so thin that I can hear them close their kitchen cabinets. This is very embarrassing when I have overnight or weekend guests.