Acoustic structures for a gas turbine engine are disclosed. In various embodiments, the acoustic structures comprise a panel in the form of a cellular structure having a plurality of cells; and a housing configured to house the cellular structure, the housing including a first rail configured for attachment to a static structure within the gas turbine engine and a second rail configured for attachment to the static structure. In various embodiments, the acoustic structures comprise a liner in the form of a non-segmented or two-piece structure configured to extend about the inner barrel of a nacelle structure. The disclosed panels and liners are configured to maximize the operational area of the acoustic structures by eliminating obstructions from adjacent flow paths.