| 摘要 |
PROBLEM TO BE SOLVED: To provide a lightweight noise reduction structure of an engine undercover superior in sound insulation and gas permeability. SOLUTION: The noise reduction structure of the engine undercover 20 comprises a through hole 21 formed on the engine undercover 20, and a space 24 formed on a peripheral face 29 of the through hole 21 and opened for the through hole 21. A sound wave passing through the through hole can be effectively attenuated by interference with a diffracted wave R2 via the space 24 and a direct wave R1 not via the space 24. COPYRIGHT: (C)2004,JPO
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