A turbofan engine is provided. The turbofan engine includes a fan comprising a plurality of fan blades; and a nacelle that circumferentially surrounds the fan, the nacelle comprising an annular wall having an exterior surface and an interior surface, the exterior surface comprising a first exterior portion, and the interior surface comprising a first interior portion, wherein a first exterior portion is formed of a first structure defining an exterior surface porosity, and wherein a first interior portion is formed of a second structure defining an interior surface porosity.