Multi-pore expansion noise silencer

The utility model relates to a porous diffusion muffler which is used for muffling the noise of a pneumatic machine. The utility model is characterized in that the muffling element is installed on the inner side wall of a casing, a metal net is installed on the inner side wall of the muffling element, and a filtering cloth is arranged between the muffling element and the metal net. The side wall of the casing is porous, and the casing is connected by screws. After the compressed air gets into the utility model, the expansion and depressurization of the compressed air is realized firstly; next, the sound absorption of the compressed air is realized by the muffling element; last, the compressed air is exhausted from the utility model by making use of the exhaust vent of the side wall of the casing. The utility model has the advantages of good muffling effect, simple structure, good mechanical property and good corrosion-resisting property. The muffling element of the utility model can be changed at any moment as required.