| 摘要 |
PROBLEM TO BE SOLVED: To further reduce noise from an engine by reducing resonance sound in addition to sound absorption by an acoustic material. SOLUTION: A cover body 10 has a through-hole 12 passing through the top side and rear faces thereof at a portion opposed to a resonance space 3 generating resonance sound, and the opening of the through-hole 12 is closed by an acoustic material layer 11. Thereby, since a part of the resonance space 3 is opened, resonance sound generating in the space 3 can be reduced.
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