Multi-degree of freedom acoustic panel

1. An acoustic panel, comprising:

a first skin, a second skin and a cellular core vertically between and connected to the first skin and the second skin, the cellular core comprising a plurality of cavities, a plurality of sidewalls and a plurality of septums;

each of the plurality of cavities extending vertically through the cellular core between the first skin and the second skin, and each of the plurality of cavities extending laterally within the cellular core between a respective laterally adjacent pair of the plurality of sidewalls;

each of the plurality of septums vertically dividing a respective one of the plurality of cavities into a set of fluidly coupled sub-cavities;

a set of the plurality of septums formed by a ply of folded material; and

each of the set of the plurality of septums having a four-sided polygonal shape when viewed in a plane that is parallel to the first skin;

the plurality of sidewalls comprising a first sidewall and a second sidewall;

the plurality of cavities comprising a first cavity that extends laterally between the first sidewall and the second sidewall;

the plurality of septums comprising a first septum within the first cavity;

the ply of folded material forming the first septum;

the first sidewall comprising a second ply of material;

the second sidewall comprising a third ply of material; and

the first sidewall further comprising a first portion of the ply of folded material.

2. The acoustic panel of claim 1 , wherein the four-sided polygonal shape is a square.

3. The acoustic panel of claim 1 , wherein the set of the plurality of septums are arranged in a longitudinal extending array.

4. The acoustic panel of claim 1 , wherein the second sidewall further comprises a second portion of the ply of folded material.

5. The acoustic panel of claim 4 , wherein the first portion has a first vertical height, and the second portion has a second vertical height that is different from the first vertical height.

6. The acoustic panel of claim 4 , wherein the first portion vertically contacts the second skin, and the second portion does not contact the second skin.

7. The acoustic panel of claim 1 , wherein the first portion vertically contacts the second skin.

8. The acoustic panel of claim 1 , wherein the ply of folded material comprises metal.

9. The acoustic panel of claim 1 , wherein the ply of folded material comprises polymer.

10. The acoustic panel of claim 1 , wherein the ply of folded material comprises fiber-reinforced composite.

11. The acoustic panel of claim 1 , wherein the ply of folded material comprises woven fiber mesh.

12. The acoustic panel of claim 1 , wherein the first skin is a perforated first skin.

13. The acoustic panel of claim 1 , wherein a second set of the plurality of septums are formed by a second ply of folded material, and the second set of the plurality of septums is laterally adjacent the set of the plurality of septums.

14. The acoustic panel of claim 1 , wherein the first septum comprises a second portion of the ply of folded material and a third portion of the ply of folded material that overlaps and lays against the second portion of the ply of folded material.

15. An acoustic panel, comprising:

a first skin, a second skin and a cellular core vertically between and connected to the first skin and the second skin, the cellular core comprising a plurality of cavities, a plurality of sidewalls and a plurality of septums;

each of the plurality of cavities extending vertically through the cellular core between the first skin and the second skin, and each of the plurality of cavities extending laterally within the cellular core between a respective laterally adjacent pair of the plurality of sidewalls;

each of the plurality of septums vertically dividing a respective one of the plurality of cavities into a set of fluidly coupled sub-cavities;

the plurality of sidewalls comprising a first sidewall and a second sidewall;

a first sidewall segment of the first sidewall connected to a second sidewall segment of the first sidewall the at a first peak;

a first sidewall segment of the second sidewall connected to a second sidewall segment of the second sidewall the at a second peak, and the second peak aligned with and meeting the first peak at an interface between the first sidewall and the second sidewall;

the plurality of cavities comprising a first cavity that extends laterally between the first sidewall and the second sidewall;

the plurality of septums comprising a first septum within the first cavity;

wherein a ply of folded material forms at least the first septum and a portion of the first sidewall; and

the ply of folded material contacts the second skin at an interface between the first sidewall and the second skin, and is separated from the second skin at an interface between the second sidewall and the second skin.

16. The acoustic panel of claim 15 , wherein the ply of folded material further forms a portion of the second sidewall.

17. An acoustic panel, comprising:

a first skin, a second skin and a cellular core vertically between and connected to the first skin and the second skin, the cellular core comprising a plurality of cavities, a plurality of sidewalls and a plurality of septums;

each of the plurality of cavities extending vertically through the cellular core between the first skin and the second skin, and each of the plurality of cavities extending laterally within the cellular core between a respective laterally adjacent pair of the plurality of sidewalls;

each of the plurality of septums vertically dividing a respective one of the plurality of cavities into a set of fluidly coupled sub-cavities, and each of the plurality of septums vertically separated from the first skin and the second skin; and

a set of the plurality of septums formed by a ply of folded material;

wherein the plurality of septums comprises a first septum; and

wherein the first septum comprises a first portion of the ply of folded material and a second portion of the ply of folded material that lays against the first portion of the ply of folded material.

18. The acoustic panel of claim 1 , wherein

the first septum is vertically displaced from the first skin by a non-zero first distance; and

the first septum is vertically displaced from the second skin by a non-zero second distance.

19. The acoustic panel of claim 1 , wherein the first sidewall includes a plurality of corrugations arranged in an end-to-end longitudinally extending array.

20. The acoustic panel of claim 1 , wherein

the first sidewall comprises a first corrugation with a first peak; and

the second sidewall comprises a second corrugation with a second peak that is aligned with and connected to the first peak.