As tunnel boom can be a major disturbance to residents near the mouth of the tunnel; reducing it is a major challenge for trains such as Japan's Shinkansen and the French TGV.
As tunnel boom can be a major disturbance to residents near the mouth of the tunnel and when a train passes through mountain valleys where the sound can echo throughout the area. Reducing it is a major challenge for trains such as Japan's Shinkansen and the French TGV.