A method of manufacturing an acoustic structure is disclosed. An adhesive material and a septum forming material may be deposited on a first honeycomb ribbon. A second honeycomb ribbon may be adhered to the adhesive material and the septum forming material. The first honeycomb ribbon and the second honeycomb ribbon may be expanded to form a honeycomb structure. The septum forming material may stretch or expand to form a septum cap in a cell of the honeycomb structure. The septum forming material may be inherently porous, and/or the septum cap may be cured in order to introduce pores into the septum cap.