Research On Sound Absorbing Material And Simulation Method Of Transmission Loss Of Splitter Silencer

Splitter silencer is a kind of dissipative silencer,widely used in various types of industrial equipment to reduce noise,such as fans with large capacity,air compressor,air conditioning,cooling towers,ect.The splitter silencer generally has a large cross-sectional area of inlet and outlet,the cut-off frequency of the plane wave at the import and export is low,and the number of high-order modes is large,which makes the accurate prediction of the transmission loss of the splitter silencer become more complicated.In order to improve the efficiency and prediction accuracy of the acoustic performance analysis of the splitter silencer,this paper studied the acoustic characteristics of the sound absorption material and the simulation method of the transmission loss of splitter silencer.Firstly,the glass wool and the face structure of the splitter silencer are studied.The calculation method of the vertical incidence of the absorption coefficient of the glass wool and the perforated plate are given.The influence of the perforated plate on the sound absorption of the porous material is analyzed.Simulation and impedance analysis methods were used to verify the results of the analysis and the model used.It is proposed to simulate the transmission loss of the splitter silencer by using the duct acoustic modal boundary condition and AML property in the finite element module of LMS Virtual.lab.Compared with the traditional simulation method,the result is the same when the plane wave is at the inlet and outlet of the dissipative muffler.When the high-order modal wave appears at the inlet and outlet,the traditional simulation mode fails,and the transmission loss of the muffler can be calculated by the duct acoustic mode method.And the duct acoustic modal method was used to simulate the splitter silencer studied in this paper,the influences of the flow resistance and the length of the silencer on the transmission loss were analyzed.Finally,the insertion loss of the splitter silencer was measured at the pipeline muffler laboratory of Beihai Research Station,Institute of Acoustics,Chinese Academy of Sciences.Under the premise that the difference between the transmission loss and the insertion loss is not significant,the insertion loss of the experimental measurement is compared with the simulation of the transmission loss.The experimental results are in good agreement with the simulation results in this paper,which proves that the transmission error of the splitter silencer can be predicted quickly and accurately by using the duct acoustic mode method.