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A propfan assembly includes a plurality of blades that each include an internal cavity containing a noise attenuation structure. Acoustic energy is communicated to the internal cavity through a plurality of openings in the blade surfaces. The cavities include features for attenuating noise energy to

A propfan assembly includes a plurality of blades that each include an internal cavity containing a noise attenuation structure. Acoustic energy is communicated to the internal cavity through a plurality of openings in the blade surfaces. The cavities include features for attenuating noise energy to reduce generation of noise emitted from the propfan assembly.

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1. A propfan assembly comprising: a plurality of blades;at least one inner cavity within each of the plurality of blades, wherein the at least one inner cavity extends longitudinally a length greater than a thickness of a corresponding one of the plurality of blades;a plurality of openings within ea

1. A propfan assembly comprising: a plurality of blades;at least one inner cavity within each of the plurality of blades, wherein the at least one inner cavity extends longitudinally a length greater than a thickness of a corresponding one of the plurality of blades;a plurality of openings within each of the plurality of blades for communicating noise energy with the at least one inner cavity; anda noise attenuation structure disposed within the inner cavity. 2. The assembly as recited in claim 1, wherein the plurality of openings are disposed on at least one of a pressure side and a suction side of each of the plurality of blades. 3. The assembly as recited in claim 1, wherein each of the plurality openings comprises an area determined to limit disruption of airflow over each of the plurality of blades. 4. The assembly as recited in claim 1, wherein the inner cavity includes a length that corresponds with a frequency of noise to be attenuated. 5. The assembly as recited in claim 1, wherein the noise attenuation structure comprises a honeycomb structure. 6. The assembly as recited in claim 1, including a plurality of inner cavities within each of the plurality of blades. 7. A blade configured for rotation about an axis for a propfan assembly comprising: an internal cavity disposed within the blade, wherein the internal cavity extends longitudinally a length greater than a thickness of the blade,a plurality of openings within the blade that communicate noise energy with the internal cavity; anda noise attenuation structure disposed within the internal cavity. 8. The assembly as recited in claim 7, wherein the noise attenuation structure includes a honeycomb structure disposed within the internal cavity. 9. The assembly as recited in claim 7, wherein the plurality of openings comprise openings of an area determined to limit disruption of airflow over the blade. 10. The assembly as recited in claim 7, wherein the internal cavity includes a length corresponding with a desired noise frequency. 11. The assembly as recited in claim 7, wherein the plurality of openings are disposed on at least one of the pressure and suction sides of blade structure.