| 摘要 |
PURPOSE:To built a silencer in light weight and eliminate low frequency band of noise by providing such a noise absorbing structure that a noise absorbing material is attached on the internal surface of a duct, and a hollow cylindrical body with a closed end is installed in the duct with the closed end facing the air flow. CONSTITUTION:A noise absorbing structure 1 is built in such a manner that a noise absorbing material 4 is attached on the inner surface of a duct 2 and a hollow cylindrical body 3 with a closed end is installed in the duct 2. The cylindrical body 3 is arranged with the closed end facing the air flow in the duct, adequately located at a position, where the distance between the inner wall of the duct and the cylindrical body is uniform, and supported by stays 5 in the up and down and right and left directions. The hollow cylindrical body 3 can be made of a thin steel plate, and the closed end preferably has a nearly hemispheric shape. When the closed end is flat, the noise eliminating effect may decrease. In the case the sectional area at the open end of the cylindrical body is about half of the sectional area of the duct, the maximum noise eliminating effect can be achieved, and little difference in noise elimination effect may occur even when the sectional area is gradually reduced from the open end to the closed end. For the noise absorbing material attached on the inner wall of the duct, such inorganic fiber as glass wool, rock wool and asbestos and organic fiber are applicable, however, inorganic fiber is preferable. |
