Sound absorbers for airframe components

An airframe component of an aircraft, the airframe component comprising:

• a skin defining an aerodynamic surface;
• a closing rib supporting the skin, the closing rib comprising perforations extending through a thickness of the closing rib for permitting passage of sound waves therethrough, the closing rib having a C-channel configuration;
• and
• a boundary surface spaced apart from the closing rib, the boundary surface and the closing rib at least partially defining a cavity in the airframe component for attenuating some of the sound entering the cavity via the perforations in the closing rib.

An airframe component of an aircraft, the airframe component comprising:

• a skin defining an aerodynamic surface having a side edge;
• and
• a close-out plate disposed at or adjacent the side edge of the aerodynamic surface, the close-out plate having a front side exposed to an ambient environment outside of the airframe component and a back side, the close-out plate comprising perforations extending through a thickness of the close-out plate for permitting passage of sound waves therethrough;
• and
• a rib supporting the skin, the rib comprising a boundary surface spaced apart from the close-out plate, the boundary surface and the back side of the close-out plate at least partially defining a cavity in the airframe component for attenuating some of the sound waves entering the cavity via the perforations in the close-out plate, the rib having a C-channel configuration.