| 摘要 |
A noise attenuation panel used to attenuate noise in aircraft engines includes a cellular core and a facing sheet formed with an array of holes. The holes are laser drilled to provide: (i) hole size variation over the facing sheet; (ii) non-circular hole cross section; (iii) polygonal hole cross section; (iv) hole locations not contiguous with walls of the cellular core; and (v) inclined holes passing through the facing sheet in a direction inclined to the normal to the facing sheet.
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