Cellular sound insulation structure including a diaphragm provided with a tube configured to treat different acoustic frequencies, method for manufacturing such a cellular sound insulation structure, and associated tool
A cellular sound insulation structure and associated aircraft, a cell of which is provided with a diaphragm which includes a membrane having at least one orifice passing through a thickness of the membrane, and at least one tube surmounting the orifice and extending from a face of the membrane into one compartment of the cell, the tube comprising a free end, forming an acoustic outlet, which is positioned at a distance (p) from the base cross section of the cell. Also, a method for manufacturing such a cellular sound insulation structure, as well as to a tool for inserting a diaphragm into a cell. Such a cellular structure makes it possible to treat a wider acoustic frequency spectrum, and its acoustic dimensioning as well as its manufacture are simplified.
1. A cellular sound insulation structure comprising:
a plurality of cells, each cell of the plurality of cells having a base cross section of arbitrary shape and a height extending between a first side and a second side, each cell of the plurality of cells being juxtaposed along two orthogonal directions relative to at least two cells of the plurality of cells,
wherein each cell of the plurality of cells comprises a diaphragm, the diaphragm comprising
a membrane dividing the cell into two compartments along the height, the membrane comprising at least one orifice passing through a thickness of the membrane and an outer peripheral edge fixed to an internal wall of the cell, and
at least one tube enclosing the at least one orifice and extending from a face of the membrane into one of the two compartments, the tube comprising a free end, forming an acoustic outlet, which is positioned at a distance from the base cross section,
wherein the membrane is folded such that the outer peripheral edge of the membrane is located along the height between the orifice and one of the first and second sides.
2. The cellular sound insulation structure according to claim 1 , wherein a distance between the acoustic outlet and the base cross section of the cell is between 20% and 80% of a height of the cell.
3. The cellular sound insulation structure according to claim 1 , wherein the acoustic outlet of the tube comprises at least one of the at least one orifice, microperforations or a woven zone.
4. The cellular sound insulation structure according to claim 1 , wherein the membrane comprises at least one corrugation.
5. The cellular sound insulation structure according to claim 1 , further comprising a resistive sheet covering the cell on the first side and a closure sheet covering the cell on the second side, the closure sheet being perforated.
6. An aircraft comprising at least one propulsion unit comprising a nacelle, the nacelle comprising an air intake having an acoustic panel, the acoustic panel having a cellular sound insulation structure according to claim 1 , of which an acoustic skin comprises a resistive sheet and a rear skin, configured to ensure structural strength of the acoustic panel, comprises a closure sheet.
7. A cellular sound insulation structure comprising:
at least one cell having a base cross section of arbitrary shape and a height,
wherein the cell comprises a diaphragm, the diaphragm comprising
a membrane dividing the cell into two compartments along the height, the membrane comprising at least one orifice passing through a thickness of the membrane and an outer peripheral edge fixed to an internal wall of the cell, and
at least one tube enclosing the at least one orifice and extending from a face of the membrane into one of the two compartments, the tube comprising a free end, forming an acoustic outlet, which is positioned at a distance from the base cross section,
wherein the membrane comprises at least one corrugation positioned between the outer peripheral edge and the at least one tube, the at least one corrugation configured to allow extension of the membrane from a resting position.