A panel for attenuating sound, comprising: a first skin, a second skin and a core between and connected to the first skin and the second skin, the core including a corrugated body, a first sidewall and a second sidewall; the corrugated body including a plurality of corrugations configured from at least a plurality of baffles and a plurality of septums, each of the corrugations including a respective one of the baffles and a respective one of the septums; wherein the panel extends longitudinally along a longitudinal axis, and laterally along a lateral axis; wherein a first cavity extends along the lateral axis within the core from a first of the baffles to a first of the septums, the first cavity extends along the longitudinal axis within the core from the first sidewall to the second sidewall, and the first cavity is fluidly coupled with a passage through a first portion of the first skin; and wherein the first portion of the first skin, the first sidewall and the second sidewall are collectively at least partially formed by a single ply of material; characterised in that: the single ply of material comprises a plurality of adjacent segments; wherein each of the segments comprises: a rectangular base at least partially forming the first portion of the first skin; a plurality of adjacent first triangular projections on a first side of the rectangular base; and a plurality of adjacent second triangular projections on a second side opposite the first side of the rectangular base; and wherein, for a first of the plurality of segments, each peak of the first triangular projections of the first of the plurality of segments is connected to a corresponding peak of the second triangular projections of an adjacent one of the plurality of segments such that each of the first triangular projections of the first of the plurality of segments respectively overlaps the corresponding one of the plurality of the second triangular projections of the adjacent one of the plurality of segments; and wherein the rectangular bases collectively at least partially define the first skin. a first skin, a second skin and a core between and connected to the first skin and the second skin, the core including a corrugated body, a first sidewall and a second sidewall; the corrugated body including a plurality of corrugations configured from at least a plurality of baffles and a plurality of septums, each of the corrugations including a respective one of the baffles and a respective one of the septums; wherein the panel extends longitudinally along a longitudinal axis, and laterally along a lateral axis; wherein a first cavity extends along the lateral axis within the core from a first of the baffles to a first of the septums, the first cavity extends along the longitudinal axis within the core from the first sidewall to the second sidewall, and the first cavity is fluidly coupled with a passage through a first portion of the first skin; and wherein the first portion of the first skin, the first sidewall and the second sidewall are collectively at least partially formed by a single ply of material; characterised in that: the single ply of material comprises a plurality of adjacent segments; wherein each of the segments comprises: a rectangular base at least partially forming the first portion of the first skin; a plurality of adjacent first triangular projections on a first side of the rectangular base; and a plurality of adjacent second triangular projections on a second side opposite the first side of the rectangular base; and wherein, for a first of the plurality of segments, each peak of the first triangular projections of the first of the plurality of segments is connected to a corresponding peak of the second triangular projections of an adjacent one of the plurality of segments such that each of the first triangular projections of the first of the plurality of segments respectively overlaps the corresponding one of the plurality of the second triangular projections of the adjacent one of the plurality of segments; and wherein the rectangular bases collectively at least partially define the first skin. the single ply of material comprises a plurality of adjacent segments; wherein each of the segments comprises: a rectangular base at least partially forming the first portion of the first skin; a plurality of adjacent first triangular projections on a first side of the rectangular base; and a plurality of adjacent second triangular projections on a second side opposite the first side of the rectangular base; and a rectangular base at least partially forming the first portion of the first skin; a plurality of adjacent first triangular projections on a first side of the rectangular base; and a plurality of adjacent second triangular projections on a second side opposite the first side of the rectangular base; and wherein, for a first of the plurality of segments, each peak of the first triangular projections of the first of the plurality of segments is connected to a corresponding peak of the second triangular projections of an adjacent one of the plurality of segments such that each of the first triangular projections of the first of the plurality of segments respectively overlaps the corresponding one of the plurality of the second triangular projections of the adjacent one of the plurality of segments; and wherein the rectangular bases collectively at least partially define the first skin.