| 摘要 |
A sound barrier comprises a substantially periodic array of structures disposed in a first medium having a first density, the structures being made of a second medium having a second density different from the first density, wherein one of the first and second media is a porous medium other than a porous metal, the porous medium having a porosity of at least about 0.02, and wherein the other of the first and second media is a viscoelastic or elastic medium.
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