A system for dampening noise generated by a gas turbine engine is disclosed. In various embodiments, the system includes a fan exit guide vane having a leading edge, a trailing edge and a pocket that extends in a chordwise direction between the leading edge and the trailing edge; and an acoustic panel configured to be received within the pocket, the acoustic panel including a back sheet, a face sheet and a core disposed between the back sheet and the face sheet, the core having a first cavity extending between a first wall and a second wall and a second cavity disposed within the first cavity.