According to the frequency spectrum characteristic data obtained from the actual test of various kinds of industrial fan operation site noise sources, the main basis for the design of sound absorption body and fluid channel is to determine how much noise reduction is needed in which frequency spectrum range. At the same time, narrow rectangular channel with large sound-absorbing material veneer is adopted to enhance the absorption effect. In addition, when the noise source of the fan is at the maximum noise level, its spectrum value is often more than one, and the requirements of noise reduction amount for different frequency bands are also different. For this reason, the series of duct mufflers and blower and induced draft fan mufflers are impedance acoustic flow type, adopting the resistance structure which can absorb and eliminate the high and medium frequency noise, and the anti structure which plays the role of noise elimination and noise reduction for medium and low frequency noise. At the same time, two kinds of sound absorption and silencing areas, high frequency and low frequency, are used in the resistance channel to maximize the noise elimination frequency band and achieve good noise elimination Noise reduction effect.