A panel for attenuating noise includes a porous first skin, a second skin, and a core connected between the porous first skin and the second skin. The core includes a corrugated body and a stringer body. The corrugated body includes a plurality of corrugations configured from at least a plurality of baffles and a plurality of porous septums. Each of the corrugations includes a respective one of the baffles and a respective one of the porous septums. A first of the corrugations forms a first channel that extends laterally between and longitudinally along a first of the baffles and a first of the porous septums. The stringer body includes a plurality of sidewalls arranged longitudinally along the first channel. Each of the sidewalls is disposed within the first channel and configured to fluidly isolate longitudinally adjacent portions of the first channel from one another.