Abstract: Method and apparatus for a reinforced skin structure such as an aircraft fuselage which has reduced interior cabin noise. The reinforced skin structure according to the present invention, includes a frame assembly which has a plurality of spaced apart frame members and an outer skin mounted on the frame assembly. A plurality of inner panels, which generally defines an interior compartment, are incorporated within the skin structure. Each of the inner panels is typically supported in a spaced apart fashion from the frame members. A septum is disposed between the outer skin and at least some of the plurality of inner panels. The septum acts to provide an air barrier and increases the air resonant frequency of the cavity between the outer skin and the inner panels. A layer of insulation is placed on the inner side of the septum removing the need to place insulation against the outer skin.