As a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel and generates a pulse wave, which causes an imp...
As a railway train enters a tunnel at high speed, a compression wave is formed in front of the train and propagates along the tunnel. The compression wave subsequently emerges from the exit of the tunnel and generates a pulse wave, which causes an impulsive noise. In order to clarify the acoustic characteristics of the noises, in the present study experiment was carried out by using the pulse waves emitted from an open end of a shock tube. Various pulse waves were obtained by controlling the compression wave formed in the tube. The results show that as the compression wave formed at tunnel exit becomes strong, the pulse wave emitted propagates with strong directional characteristics forward the axial direction of the tube, and that attenuation of the pulse wave propagating a ground surface can be reasonably predicted by a linear acoustic theory. Furthermore, the impulsive noise at far-field from the tube exit results in a sound level reduction of 6dB with a doubling of the propagating distance.