This is not necessarily true for the isolation of structure-borne sound, where an increase in mass may have little or no effect on the isolation performance of a system. The use of a resilient channel system for the installation of a gypsum board ceiling can have similar effects of improved airborne and structure-borne sound isolation. The improved performance due to the use of mineral wool in a stud or joist cavity is also dependent on the other components of the partition assembly and the type of sound source. Cavity insulation works best in combination with decoupling. Channels has a synergistic effect greater than the sum of both treatments individually.
Air is the basic medium of acoustic transmission.
If air transmission is eliminated, then the passage of airborne sound is also eliminated, e.g., through use of acoustic sealant. All changes made after the original design is completed should be viewed with suspicion. These changes, which may seem minor, may completely nullify the sound performance of the original design. We recently were involved in the design of a multi-story apartment building. Our design was based on using light-gauge metal studs with multiple layers of gypsum board and sound attenuation blankets in each stud cavity, a nominal 50 STC design.