Patent ID: 7484592

Claim:
An acoustic attenuation panel, comprising at least one layer of cellular structure flanked on a first side by a resistive layer composed of at least one porous layer and at least one perforated structural layer, and on a second opposing side, by a layer forming a total reflector, said at least one perforated structural layer is pierced with identical non circular holes each having a largest dimension and a smallest dimension along respectively two perpendicular axes, said holes are aligned in at least a direction of their elongation, the largest dimension of the holes is parallel to a direction of main forces to be resisted, a material of said at least one perforated structural layer is a composite material comprising mineral or organic fibers that are natural or synthetic, and impregnated with a polymerized thermosetting or thermoplastic resin, the material of the at least one perforated structural layer comprising unidirectional fibers parallel to the largest dimension of the holes or one or more cloths, whose weft or warp threads are disposed respectively along the largest dimension and the smallest dimension of said holes.