An acoustic liner and a method of attenuating noise are provided. The acoustic liner includes a face sheet, a back sheet spaced from the face sheet, and a core layer extending between the face sheet and the back sheet. The core layer includes a plurality of resonant cells, each resonant cell including at least one cell wall coupled to the back sheet along a cell wall base edge. The at least one cell wall extends from the back sheet at an angle toward the face sheet. The at least one cell wall further coupled to the face sheet along a cell wall top edge. The resonant cell is formed in a predetermined shape and contains a volume in a space defined by the at least one cell wall, the back sheet, and the face sheet. The cell wall base edge length is greater than the cell wall top edge length.