The noise level of the generator set is generally 94dB, which is installed in the machine room with smooth four sides. The noise level in the machine room can reach 103~105dB. Therefore, the surrounding walls and ceilings of the machine room are used as sound absorbers to absorb some of the sound energy and reduce the reverberation sound generated by the reflection of sound waves. When the sound waves are incident on porous materials, the air movement of small holes or fibers can be aroused, The air close to the hole wall or fiber surface will produce viscosity due to the influence of the hole wall, which will cause the friction between the sound wave and the porous material to convert the sound energy into heat energy, thus obtaining attenuation