| 摘要 |
PURPOSE: To reduce noises generated in an engine room of a construction machine without affecting taking-in of cooling wind. CONSTITUTION: Stacked ducts 30, 32 are arranged on a take-in port and a discharge port 16 for cooling wind. A total amount of the cooling wind is taken in through the stacked ducts 30, 32, or discharged therefrom. The stacked ducts 30, 32 are divided into four small ducts 30a to 30d. The longest small duct 30a and the shortest small duct 30d have the length ratio such that a phase difference ofλ0/2 is formed whereλ0 is wavelength of frequency of noise to be reduced. Adjacent small ducts have lengths differentiated from each other byλ0/20.
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