| 摘要 |
PURPOSE: To obtain high sound absorption performance not only in the low frequency region but also in the medium and high frequency regions by installing a sound absorbing material in the inside of an extended part. CONSTITUTION: A sound absorbing duct structure 1 is provided with a section (expanded duct) expanded in its inside diameter to a duct (basic duct) having the circular section, square section, ellipsoidal section, etc., as a basic. The inside diameter of the extended duct is preferably within the range of 1.1 to 5 times the inside diameter of the basic duct, and the length of the extended duct in its longitudinal direction is preferably within the range of 1 to 200cm. The sound absorbing material 2, which is a fiber assemblage, is installed on one or more part in the inside of the extended duct. The sound absorbing material 2 is preferably the fiber assemblage constituted of short fibers and/or long fibers having an average diameter within the range of 0.1 to 60μm. Further, the surface density of the sound absorbing material 2 molded in the above- mentioned manner is preferably within the range of 50 to 4000g/m<2> . |
