| 摘要 |
The disclosure is directed broadly to a thin metal sheet containing a multitude of small openings therethrough. Typically, the sheet will contain at least 400 openings per square inch with the openings having an average cross-sectional area of from about 0.0005 to about 0.005 square inch. The sheets are used to overlay a series of perpendicularly aligned walls which define air chamber(s) behind the sheet. Sound waves pass through the porous sheet and are absorbed in the air chamber(s).
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