求助：消声器问题
求助：消声器问题用SYSNOISE做消声器传递损失分析，DBEM、IBEM、FEM都试过了，可结果就是和理论求解不一样，趋势差不多，最小传损处也一样，可峰值差了近两倍，而且在300Hz以下也不一致，到底是什么原因啊，我做的就是一个简单的一个扩张腔的消声器。
FEM轴对称：
OptionFEM Frequency Fluid Return
Import Mesh Format NASTRAN File femaxi.DAT Return
AxiSymmetry Return
Set 1 Name "inlet"
Face 54
Return
Set 2 Name "outlet"
Face 59
Return
Material Fluid
Name 'air'
Sound 3.4000e+002Rho 1.2250e+000
Elements All
Return
Boundary VelocityReal -1 Imag 0
Faces Set 1
Return
Boundary AdmittanceReal 2.401e-3 Imag 0
Faces Set 2
Return
SolveFrequency 50 To 3000 LinStep 50 Return
Combine
Read Node 11 Pressure Return
Amplitude
Read Node 1 Pressure Return
Read Node 1 VelocityVector 0 1 0 Return
Constant Real 416.5 Imag 0
Multiply
Add
Constant Real 2 Imag 0
Divide
Amplitude
Divide
Log10
Constant Real 20 Imag 0
Multiply
Write Table 1 name tl Return
Return
BEM:
Import Mesh Format NASTRAN File BEM.DAT Return
Check Mesh Merge Return
Material Fluid
Name 'air'
Sound Real 3.4000e+02Rho Real 1.2250e+00
Return
Boundary VelocityReal 1 Imag 0
Elements X=0.06
Return
Boundary ImpedanceReal 416.5 Imag 0
Elements X=-0.06
Return
SOLVE
Frequency 50 to 3000 linstep 50
return
import point format nastran file point.dat return
postrocess
points all
frequency 50 to 3000 linstep 50
Near 2
Far 5
Quadrature 2 2 1
Save Results Step 1
Return
Return
combine
read point 176 pressure return
amplitude
read point 92 pressure return
amplitude
divide
amplitude
log10
constant real 20 imag 0
multiply
return
最后得出的传递损失曲线比理论值大了两倍左右。
急切需要得到帮助 ，谢谢各位了。
附图中的结果是我除了2以后得出的。 怎么没人帮忙呀
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