It seems that when they carved out this guest unit they failed to insulate the walls. I've read up on spray foam insulation, adding drywall over existing drywall with green glue in between.

Both sound like quite a project for a lay person. Although, I do have a friend in construction who has agreed to help with another layer of drywall. I am just not sure what will add maximum sound barrier.

**Do I need to drywall the closet ceiling too since it's the closet through which I hear the most noise.** (*Help! It's like living in the same room with the tenants in the main house*).