Patent ID: 7735600

Claim:
An acoustic panel for an engine nacelle inlet, the panel having a first end and a second end, and comprising: a layered, integral structure comprising, in order: (a) a perforated film extending from the first end to the second end; (b) a sound attenuating core comprising a first honeycomb material extending from the first end to the second end; and (c) a structural layer comprising a second honeycomb material having a higher density than the first honeycomb material, the second honeycomb material extending from the first end to the second end, wherein the second end is in contact with the first end, and wherein the second honeycomb material further comprises a region with through-holes adapted for receiving fasteners configured to engage structure of an engine nacelle, wherein the through-holes extend through the structural layer, but do not extend through the sound attenuating core and do not penetrate the perforated film, such that an outer surface of the perforated film is smooth and free of discontinuities and projections into an airflow path.