The kingfisher’s beak turns out to be supremely efficient at crossing the air-water interface with the minimum amount of turbulence, thus making the bird more successful at catching fish by surprise.
Obviously the train does not dive into water, but it has many tunnels to pass through.
Tunnels tend to create an air-air interface between the inside and the outside, which, when crossed, generates turbulence and noise.
The efficiency of the design has enables engineers to create a train that is the most silent of its kind.
Mother Nature is indeed science and technology's first teacher!