The use of sealant materials to improve interior acoustics has increased significantly in todays automobiles. One such application is to use expandable sealant materials in rails, pillars, and cavities to reduce noise propagation. However, there is no standardized method for evaluating the acoustical performance of these materials. This paper reviews the basics of noise control engineering and discusses a proposed laboratory based test methodology that has been developed for properly evaluating the acoustical performance or expandable sealant materials. The test method is intended to simulate actual applications so that different materials can be evaluated to achieve optimum acoustical performance within a channel representing the rails or pillars in automobiles.