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ABSTRACTKey words: tunnel noise, normal mode solution, boundary element method
.Noise propagating in a tunnel is investigated by both theoretical analysis an
d boundary element computation in this study. Because sound wave varies rapidl
y right at the outlet of the tunnel the analysis of sound field near the tunne
l outlet becomes the main subject of this study. Following form the developmen
t of three-dimensional sound wave equation then to the derivation of three-dim
ensional sound wave equation inside a circular pipe and finally to the achieve
ment of axi-symmetric solution based on the normal mode method, the theoretica
l investigation is conducted. On the other hand, because of the superiority of
boundary element method in handling sound wave problem and also due to the we
ll-behaved character of this method for inner field problem, boundary element
method is used as the numerical approach in this study.The convergence of the
analytical solution and the accuracy of two kinds of numerical approach are te
sted for different pipe-radius /wavelength ratio and large-pipe-radius/small-p
ipe-radius ratio. Finally, the boundary element method applying approximated r
adiation condition is used to similar the tunnel noise field. And hopefully th
is can serve as a reference to tunnel noise remedy.
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