Abstract
When an ultra-high-speed train moves into a tunnel, a pressure wave is generated and propagates in the tunnel. At a side branch of the tunnel, a part of the pressure wave enters into the branch and discharges from its portal as a booming noise. In this study, we propose measures to suppress the booming noise and also the ventilation wind noise for the side branch in the Chuo-Shinkansen. First, to reduce the ventilation noise, we expand the cross-section of the side branch to slower the flow inside and install a flow outlet with guide vanes to flatten the velocity profile. The flow in the outlet is numerically simulated, and the result shows that the ventilation noise can be reduced below the standard level with these measures. The expansion of the side branch, however, increases the booming noise, and a conventional porous absorber is not sufficient to suppress it. Thus, we utilize the ventilation facilities including a ventilation fan and a silencer along with a porous absorber as measures to reduce the booming noise. The propagation of a pressure wave through the side branch with these measures is experimentally and numerically studied, and the result shows that the booming noise can be reduced to less than the standard noise level.
