Calculation Method of Transmission Loss of Dissipative Silencers with Arrayed Elements
Using Belov formula to calculate the transmission loss of dissipative silencers with arrayed elements has large errors.To improve the accuracy of the calculation,the calculation model of the transmission loss(TL)for the arrayed elements silencer is developed following these steps:(1)Dividing the silencer into corner,edge and interior units.The TL of each basic unit is calculated by Belov formula.(2)Assuming that the sound energy is uniformly distributed in the inlet of the silencer,the sound power at the outlet of each basic unit is determined according to the sound power at the inlet and the TL of each basic unit.(3)The theoretical value of transmission loss TLt is obtained based on the total sound power at the inlet and outlet of the arrayed elements silencer.(4)With 11 425 Pa∙s/m2 as the reference value of flow resistance,the simulated value of transmission loss of the silencer with porous sound absorbing material,TLs,is obtained by the finite element method.The ratio of simulated TL to theoretical TL,K1=TLs/TLt is obtained.(5)The ratio between the TLs of silencers using porous sound absorbing material with different flow resistances and that with a reference flow resistance,K2,is determined by simulation.The fitting function K2(σ)of K2 vs.the flow resistance σ is obtained.(6)The calculation model of the TL,TL=TLt∙K1∙K2(σ),for the arrayed elements dissipative silencer is established.The measurement results show that the absolute error between the TLs calculated by this model and measured value is less than 2 dB,and the relative error is less than 10%at each 1/1 octave band.The calculation model is suitable for calculating the TL of arrayed elements dissipative silencers which have different structures and sizes and use sound absorbing materials with different flow resistances.
acousticsarrayed elementsdissipative silencerstransmission losscalculation modelBelov formula
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