How kingfisher inspired bullet trains?

Bullet trains in Japan used to make a loud boom sound when they traveled through tunnels. A bird-watching engineer was able to fix the problem after he was inspired by a kingfisher.
Sinan Tolukan

The Japanese Shinkansen bullet trains are a miracle of modern engineering. Despite being able to travel at speeds of up to 200 miles per hour (320 kph), they have also proved incredibly safe over their 50-year-plus history. But the early trains came with one major problem: they created sonic booms when they left tunnels. The sound was so loud, it was like standing in a room with a constantly running washing machine! 

Not ideal for local residents, to say the least. Something had to be done, not only for the residents' sanity but also for their hearing. The first issue was determining why the trains were creating this loud boom. Japanese engineers soon discovered it was due to a phenomenon called “tunnel boom.” This is caused by the train pushing air through an enclosed space, like a tunnel, and building up an air pressure wave until it reaches the end of the tunnel. When the train exits the tunnel, just like a bullet from a gun, it generates sound waves of over 70 decibels over an area more than 1,312 feet (400 meters) away in all directions. 

Next, engineers scratched their heads to find a solution. Slowing down the trains or avoiding tunnels was not an option, but, as it turned out, nature might have already solved their dilemma. Over millions of years, nature has tried out many different ways for animals to use their bodies to solve problems. The bird’s wing, the human eye, and the plant’s leaf are all examples of life “finding a way.”

And, in the case of the “tunnel boom,” nature was, once again, leagues ahead of human beings. Enter the mighty kingfisher.  A small fish-eating bird, the kingfisher hunts its prey by turning itself into a high-speed fishing spear. From a raised perch, this little bird can leap, fall, and penetrate a water body at whim to catch its prey entirely by surprise with little or no splashing.

An Olympic diver's dream, if you will. By studying the bird in detail, one Japanese bird-watching engineer, Eiji Nakatsu, modified the trains to give them their characteristically shaped noses. And, incredibly, it worked. After the changes were made, the Shinkansen’s “tunnel boom” problem evaporated, enabling locals and tourists alike to enjoy the majestic beauty of Japan in peace. It also had other benefits, such as reduced drag, improved fuel efficiency, and increased speed. 

And all thanks to a little bird. Nature, it turns out, might be the greatest engineer of all time!