Weight is effective in reducing sound transmission. Concrete, Concrete block filled with sand, brick are heavy and effective sound reducers. Resilient clips or strips are effective. Mount gypsum wall board and ceiling board on these. They are springy and disipate sound energy when sound hits the board material.
Discontinuity is useful.
Two stud walls side by side with an air space between the studs is better than a single wall of the same thickness and weight. The sound travels easily throught studs but jumps the air space between them less efficiently. Caulk all the corners, vertical, horizontal, ceiling and floor otherwise sound passes through the cracks and by-passes the wall system. Soft insulation used by itself is not efficient in reducing the transmission of sound since it is easily by-passed by sound going through the studs. I wouldn't bother using it unless you use it in conjunction with resilient clips or in a double wall system.