Railway noise reduction effect by absorption of tunnel entrance hood

It is considered that railway-noise of Shinkansen wayside tunnel entrance could be increased generally due to a influence of reflection noise from within a tunnel. So, the reflected sound from within a tunnel might not be reduced sufficiently only with the countermeasures against direct sound such as sound barrier. Therefore, to reduce the reflected sound from within a tunnel, we have constructed to install the acoustic absorbent material of inside whole surface a tunnel entrance hood. It was confirmed the result that wayside noise reduction effect due to absorption of tunnel entrance hood was 4dB at the most. In this paper, the quantitative result of noise reduction effect due to absorption of tunnel entrance hood is reported.