Patent ID: 7779965

Claim:
An absorbent structure for reducing the propagation of soundwaves emitted by noisy devices, the structure comprising: a rigid partition, at least one porous wall, separator means for placing the porous wall at a determined distance from the rigid partition, defining cavities of a height h 1 between said porous wall and said rigid partition, said height h 1 being determined so as to obtain maximum absorption of the emitted soundwaves at a given basic frequency F 1 , and additional absorption means for obtaining maximum absorption of the emitted soundwaves at at least one additional basic frequency Fi, i being an integer greater than or equal to 2, wherein the at least one porous wall comprises at least a first layer constituted by a fine-mesh screen, and at least one second layer constituted by a fiber felt, wherein the additional absorption means comprise an alternation of cavities of height h 1 , and additional cavities of height h 3 , said height h 3 being less than the height h 1 , and wherein the additional cavities are made by depositing an absorbent material on the rigid partition in some of the cavities of height h 1 .