Chinese researchers have made a significant breakthrough in addressing the issue of “tunnel boom” in preparation for the launch of the latest prototype maglev train in China. The maglev, capable of reaching speeds of 600km/h, has faced challenges due to the shock waves that occur when the train exits tunnels. These shock waves, known colloquially as “tunnel boom,” can cause disturbances for both humans and animals, in addition to structural damage, and have posed a serious concern for operational safety. However, a solution has been found with the installation of innovative soundproofing buffers at tunnel mouths, which can reduce the shock waves by up to 96%. This breakthrough promises to improve operational safety, reduce noise pollution, and enhance passenger comfort. The tunnel boom problem is more prominent in high-speed trains, as the shock waves increase significantly with speed. For conventional high-speed trains traveling at speeds up to 350km/h, the boom occurs in tunnels longer than 6km, while for maglev trains traveling at 600km/h, the boom can occur in tunnels as short as 2km. The porous structure of the new buffers allows trapped air to escape before the train reaches the tunnel mouth, effectively suppressing the boom in a similar manner to a silencer on a firearm.
Magnetic levitation is the technology behind maglev trains, where magnetic forces suspend the train above the guideway or rail, reducing friction. Electromagnetic suspension (EMS) is one type of maglev, where the train is levitated by an attractive force between electromagnets and the track. Electrodynamic suspension (EDS) is another type, where superconducting coils embedded in the guideway and train create repulsive and attractive forces to levitate the train. China has been at the forefront of high-speed maglev development, with the first maglev line making its debut in 2004 between Pudong airport and the outskirts of Shanghai. Although initially eclipsed by the development of conventional high-speed rail, maglev trains are now making a comeback with the state-owned manufacturer CRRC. The new maglev model was launched in 2021, offering a quiet and smooth ride.
While no specific maglev lines have been planned yet in China, there is speculation that a future line may connect Beijing and Shanghai, reducing journey times to 2.5 hours. In China, high-speed rail travel is cheaper than air travel, leading to potential carbon savings as flights emit more CO2 per distance traveled. Japan is also exploring the possibility of long-distance high-speed maglevs with the Chuo Shinkansen, a line that will link Tokyo, Nagoya, and Osaka. originally scheduled to begin service in 2027, the project has faced delays and the opening date is now uncertain.
Source: https://www.theguardian.com/environment/2025/aug/07/maglev-train-researchers-may-have-solved-tunnel-boom-shock-waves
