We are getting ready to install a home theater in an unfinished area in our basement. We're trying to find an effective way to keep the theater sound in the theater and not in the rest of the house. We are getting ready to stub in the room and would be appreciative for any ideas. Weather-stripping, caulking and tight construction is used to block the path of the sound transmission. For example, solid core doors should be used instead of hollow core doors.
Hard surfaces tend to bounce the sound off the surface.
By using carpet, cork board, drapes and other soft surfaces on the inside of the soundprooofed room, some of the sound can absorbed. Professional sound studios are very carefully designed and very expensive to build. With some planning you should be able to accomplish good results for reasonable costs. But the devil is in the details. It is out of print and in the public domain.