Barrier materials furnished under this specification are intended for application to plane and curved ship structures and machinery surfaces in order to attenuate airborne noise. Type I barrier material (see 1.2) is primarily used as the top or middle layer of thermal, acoustic, or fire insulation materials which are attached to the deck, bulkhead, overhead, ducting, or machinery casing surfaces. Standard application details are contained in Naval Sea Systems Command (NAVSEA) drawings 804-5773931 and 804-5773932. The type II barrier material (see 1.2) is intended as a middle layer (sandwich) component of composite treatments, and uses an insulation material for the lower layer and a faced panel or metal sheathing as the upper layer. Type II barrier material is used when Coast Guard approval is required. Type I and type II barrier materials are specified in sizes that are convenient and economical for shipboard installation. The barrier materials are cut and fit to irregular shapes and the sizes are selected to minimize waste and allow handling by installation personnel.