To easily and positively mount the structure of an noise absorbing member in the inside of a box shaped body such as an air cleaner and the like without using any complex pressing plate.

The plural number of noise absorbing bodies 15a in which each porous absorbing material such as non-woven fabric, glass wool, foamed resin and the like is formed into a block shape, are disposed at specified intervals, and each absorbing body 15a is enclosed with a skin body 15b thin in thickness, and made out of non- woven fabric so as to allow each fused flange part 15c in a specified width to be formed up around each absorbing body 15a. A fixing through hole is provided for the specified position of each flange part 15c, a washer 16 is disposed over to each through hole so as to be fixed thereto, each absorbing body 15a is provided so as to be adhered to the inner surfaces of three directional walls with exception of the top of a bottom wall for a body 11 and an entrance pipe 11a, and the through hole of each flange part 15c is allowed to coincide with each mounting hole over the wall surface of the body 11. Each inhibiting fixture F formed out of a fastening top 18 having split leg pieces 18b, and of a push pin 17, is inserted in the through holes from the outside so as to allow each absorbing member 15 to be firmly fixed to the inner surface of the body using each push pin 17 and the split leg pieces 18b.