System and method for noise suppression
Systems and methods for noise suppression are disclosed herein. In one embodiment, an acoustic structure has a core that includes a plurality of cells. Each of the plurality of cells includes one or more engaging structures for positioning a septum relative to the cell. The acoustic structure further includes a plurality of septums positioned relative to the plurality of cells.
1. An acoustic structure comprising:
a first sheet;
a second sheet;
a core comprising a plurality of cells, wherein each of the plurality of cells is defined by walls, at least one of the walls having an opening, the opening having a closed perimeter disposed entirely in the wall for positioning a septum relative to the cell, at least a portion of the core being disposed between the first and second sheets; and
a plurality of septums positioned relative to the plurality of cells.
2. The acoustic structure of claim 1 , wherein at least one of the first and second sheets is perforated.
3. The acoustic structure of claim 1 , wherein a cross-section of the core comprises a plurality of hexagons.
4. The acoustic structure of claim 1 , wherein the opening has a circular shape.
5. The acoustic structure of claim 1 , wherein each of the plurality of cells comprises a surface engaged with a surface of the plurality of septum.
6. The acoustic structure of claim 1 further comprising an adhesive disposed around an inner perimeter of at least one of the plurality of cells.
7. The acoustic structure of claim 1 , wherein the opening is sized and shaped so as to bias at least one of the plurality of septums in a direction.
8. The acoustic structure of claim 1 , wherein the first sheet is spaced from the second sheet by a constant offset.
9. The acoustic structure of claim 1 , wherein each of the plurality of septums comprises one or more engaging structures for interacting with the opening.
10. The acoustic structure of claim 9 , wherein the one or more engaging structures of the septums include a protrusion, at least a portion of one of the protrusions extending into at least a portion of the opening.
11. A method of manufacturing an acoustic structure, the method comprising:
providing a core comprising a plurality of cells, wherein at least one of the plurality of cells is defined by walls, at least one of the walls having an opening, the opening having a closed inner surface for positioning a septum relative to the cell;
inserting a septum having at least one engaging structure into at least one of the plurality of cells, the engaging structure of the septum abutting the opening of the cell;
bending the at least one engaging structure while the septum is being inserted into the at least one of the plurality of cells;
affixing a first sheet to one end of the core; and
affixing a second sheet to the other end of the core.
12. The method of claim 11 further comprising applying an adhesive to at least a portion of the inserted septum.
13. The method of claim 11 , wherein at least one of the first and second sheets is perforated.
14. A nacelle for housing a noise source, the nacelle comprising:
an acoustic structure including at least one cell having an inner surface and at least one septum, the inner surface having an opening with a closed shape disposed entirely in the wall, and a portion of the at least one septum engaging the opening in the inner surface.
15. The nacelle of claim 14 wherein the acoustic structure is disposed in a wall of the nacelle.
16. The nacelle of claim 15 , wherein the at least one cell includes a first end and a second end, and the acoustic structure comprises a first sheet affixed to the first end of the cell and a second sheet affixed to the second end of the cell, wherein at least one of the first and second sheets is perforated.
17. The nacelle of claim 15 , wherein the acoustic structure includes a plurality of cells and each cell has an inner surface including an opening with a closed shape and a portion of the at least one septum engaging the opening in the inner surface.
18. The nacelle of claim 15 , wherein the acoustic structure forms at least a portion of a cylindrical shape which surrounds at least a portion of the noise source.
19. The nacelle of claim 15 , wherein the acoustic structure comprises a perforated layer, at least a portion of the perforated layer being disposed between the noise source and the at least one cell to attenuate noise from the noise source.
20. The nacelle of claim 15 , wherein the noise source is an aircraft turbine engine.
21. The method of claim 11 further comprising bending the engaging structure so that the engaging structure abuts the opening of the cell.
22. The method of claim 11 , wherein the engaging structure regains enough of its original shape after being inserted into the at least one of the plurality of cells to abut the opening of the cell.
23. The method of claim 11 , wherein the septum is inserted in a first direction and the engaging structure bends in a second direction opposite to the first direction.
24. The method of claim 11 , wherein the engaging structure undergoes elastic deformation while the septum is being inserted into the at least one of the plurality of cells.
25. The method of claim 24 , wherein the elastic deformation is due to a bending force applied by the at least one of the plurality of cells to the engaging structure.