CJMY. Camille Gaubert’s column airs daily in the program “C Jamie”, presented by Jamie Gourmaud, Monday through Friday at 5pm on France 5.
Have you ever had such an unpleasant sensation, when TGV passes through a tunnel, the feeling that your ears are blocked? Sometimes there is pain too. Where does this impression come from? The problem is the wind. Normally, as the train moves forward, it displaces the air, chasing it towards the front or side of it. But in a tunnel the air is forced to accumulate in front of the train. This increases the pressure in front of the TGV and this air plug is under such pressure compared to the rest of the air in the tunnel that a wave is created. It’s the pressure wave that breaks our ears! It spreads from one end of the tunnel to the other at the speed of sound in both directions! It is 4 times faster than the TGV, which spins uniformly at 300 km/h.
pressure which also affects the train
Our ear is made up of the outer ear, which goes to the eardrum, then behind the middle ear and inner ear. When the wave reaches our ears, the pressure in the outer ear becomes stronger than in the inside. As a result, more pressure pushes our eardrums inwards, which is responsible for the unpleasant sensation. However, the pressure difference is not very large. This is equal to what is felt when the head is kept under 20 to 30 cm of water.
This pressure has an effect on the train as well: it wears out fast! Fortunately, the impact can be mitigated by ballasts, the large boulders that line the tracks and that absorb part of the pressure wave. Slowing down the train before entering the tunnel or making a TGV with a thinner nose could also limit damage. As for you, just think about yawning, swallowing or chewing gum to give your ears a rest!
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