| 摘要 |
PROBLEM TO BE SOLVED: To reduce sound pressure of a comparatively low frequency region made impossible to be reduced by only a sound absorbing material, in an air intake duct 1 causing air flow sound as a problem. SOLUTION: In this air intake duct 1 made of synthetic resin, an extension part 14 expanded upward is provided in a part of the air intake duct 1, and an intermediate wall 16 for partitioning between the extension part 14 and a main air intake passage 10 is provided. The intermediate wall 16 is provided with a plurality of slits 17. In a space in the extension part 14, a sound absorbing material layer 18 made of foamed polyurethane, etc. is provided along an inner wall surface of an upper part wall 14a, and the sound absorbing material layer 18 is away from the intermediate wall 16. A space layer 19 is remained between a surface of the sound absorbing layer 18 and the intermediate wall 16. The space layer 19 functions as a kind of resonator in addition to a sound absorbing action of the sound absorbing layer 18 to reduce sound pressure of a specified frequency. COPYRIGHT: (C)2010,JPO&INPIT
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