A method of producing an acoustic panel suitable for performing acoustic control of jet engine noise, the method comprising the steps of: - conforming a sheet of thermoplastic paper into rows (622, 624, 626) that each comprise a three dimensional shape, - transforming the sheet into a multi-celled core by: - identifying fold lines separating the rows, - folding the sheet at the fold lines (630, 640) in a pleat fold, thereby uniting upper surfaces (621, 623) of adjacent rows (622, 624) and uniting lower surfaces (625, 627) of adjacent rows (624, 626) in the sheet, and - compressing the rows (622, 624, 626) of the folded sheet together in the presence of heat causing adjacent rows (622, 624, 626) to fuse together into hexagonal cells, each cell including a double wall defining a single side, - heating core and pressing double walls resulting in double walls plastically deforming and integrating into each other to create core as a singly integral shape comprising unified, seamless walls of thermoplastic material, - applying a backing sheet to the core; - applying a facesheet to a surface of the core that includes openings able to direct a portion of airflow across the facesheet into the cells, preferably wherein the facesheet comprises a thermoplastic material; and wherein applying the facesheet comprises: ∼ fusing the facesheet to the surface via the application of heat and pressure, - and the method preferably further comprising the step of inserting a septum into each of the cells. - conforming a sheet of thermoplastic paper into rows (622, 624, 626) that each comprise a three dimensional shape, - transforming the sheet into a multi-celled core by: - identifying fold lines separating the rows, - folding the sheet at the fold lines (630, 640) in a pleat fold, thereby uniting upper surfaces (621, 623) of adjacent rows (622, 624) and uniting lower surfaces (625, 627) of adjacent rows (624, 626) in the sheet, and - compressing the rows (622, 624, 626) of the folded sheet together in the presence of heat causing adjacent rows (622, 624, 626) to fuse together into hexagonal cells, each cell including a double wall defining a single side, - heating core and pressing double walls resulting in double walls plastically deforming and integrating into each other to create core as a singly integral shape comprising unified, seamless walls of thermoplastic material, - applying a backing sheet to the core; - applying a facesheet to a surface of the core that includes openings able to direct a portion of airflow across the facesheet into the cells, preferably wherein the facesheet comprises a thermoplastic material; and wherein applying the facesheet comprises: ∼ fusing the facesheet to the surface via the application of heat and pressure, - identifying fold lines separating the rows, - folding the sheet at the fold lines (630, 640) in a pleat fold, thereby uniting upper surfaces (621, 623) of adjacent rows (622, 624) and uniting lower surfaces (625, 627) of adjacent rows (624, 626) in the sheet, and - compressing the rows (622, 624, 626) of the folded sheet together in the presence of heat causing adjacent rows (622, 624, 626) to fuse together into hexagonal cells, each cell including a double wall defining a single side, - heating core and pressing double walls resulting in double walls plastically deforming and integrating into each other to create core as a singly integral shape comprising unified, seamless walls of thermoplastic material, - applying a backing sheet to the core; - applying a facesheet to a surface of the core that includes openings able to direct a portion of airflow across the facesheet into the cells, preferably wherein the facesheet comprises a thermoplastic material; and wherein applying the facesheet comprises: ∼ fusing the facesheet to the surface via the application of heat and pressure, - and the method preferably further comprising the step of inserting a septum into each of the cells.