It was called the bullet train because it was rounded in front, but every time it went into a tunnel it would build up a pressure wave, and then it would create like a sonic boom when it exited.
之所以叫子弹列车 是因为车头是圆的 但每次驶进山洞时 就会产生一股压力波 驶出山洞时就会发出音爆巨响