New S. Korean Technology Limits Tunnel Sonic Booms from Express Trains | Be Korea-savvy

New S. Korean Technology Limits Tunnel Sonic Booms from Express Trains

SEOUL, Dec. 23 (Korea Bizwire)The Korea Railroad Research Institute (KRRI) said Tuesday it had developed new technology that can drastically reduce the noise that is generated when an express train enters a tunnel.

Field testing of the new technology has also been completed.

The noise is generated due to the compression of the air inside the tunnel that occurs when an express train enters at high speed.

When a high-speed train enters the tunnel, it results in a change in air pressure inside the tunnel, generating an impulsive-like wave.

This wave generates a noise similar to an explosion at the end of the tunnel. The phenomenon is referred to as a micro-pressure wave or tunnel sonic boom.

Since sonic booms are a significant disturbance to those living near a tunnel, it is an important issue in the design of high-speed railroads.

The KRRI-developed noise reduction hood was inspired by a shark that opens its gills wide both ways to reduce the pressure of seawater coming into its mouth when it swims rapidly.

Kim Dong-hyun, a senior researcher at the KRRI, noted that the newly-developed hood could reduce the noise by about 84 percent, far higher than technology used in Japan, Germany and China, which offers a sound reduction of about 50 percent.

In addition, the length of the newly-developed hood is shorter than that of existing hoods, thereby contributing to reducing construction cost by about 40 percent.

Kevin Lee (

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