초록
Lower tunnels and concrete based tracks are introduced to newly constructed metro lines to reduce the construction and track maintenance fees. But such a lower tunnel together with concrete based track causes higher interior noise of metro trains. It is required that the trains should not only be a transportation media but also be comfortable. So, to lower the metro train's interior noise level, design was made to increase the transmission loss per sectional part. Through such a design, it is expected that about 7 dB(A) of noise level will be reduced compared to that of the conventional train.