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Absorbent structure for attenuating noise particular by a rotor-generator noise, and a rotor duct including such a structure

Image Number 4 for United States Patent #7779965.

An absorbent structure for reducing the propagation of soundwaves emitted by noisy devices such as rotors or motors, the structure includes a rigid partition (1), at least one porous wall (4), and separator elements (2) for placing the porous wall (4) at a determined distance from the rigid partition (1), defining cavities (3) of a height h1 between the porous wall (4) and the rigid partition (1), the height h1 being determined to obtain maximum absorption of a given frequency of the emitted soundwaves, wherein includes additional absorption elements for obtaining maximum absorption of at least one additional frequency of the emitted soundwave.

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