This specification describes the construction and installation of standard reference specimens for quality control of laboratory sound transmission loss measurements. The reference specimen is composed of framed steel panels. The required materials for fabrication and installation are as follows: galvanized sheets, frame, and panels. Four kinds of installation may be done: Installation A using a single layer reference specimen, Installation B using double layer reference specimen with a common plate, Installation C using double layer reference specimen with separate plates-empty cavity, and Installation D using double layer reference specimen with separate plates and added layer of sound-absorbing material in the cavity.