The unique nose of the Shinkansen 500 bullet train prevents sonic booms whenever it exits a tunnel. It was designed based on the shape of a kingfisher’s beak, which allows it to hit the water at high speed with very little splash. – WTF Fun Facts
Source: https://earthsky.org/earth/sunni-robertson-on-how-a-kingfisher-inspired-a-bullet-train
THE shrinkage also doesn’t travel at the speed of sound and can’t break the sound barrier ( no sonic boom). I’ve ridden the train several times, 280-320 mph is the best it does.