Why does your ear pop in high speed trains at normal altitude?

Answer 1

IT is because of something called "The Bernoulli Principle".
This principle states that the more you increase the velocity of a liquid or a gas, the more you decrese the pressure exerted by it. The faster and faster you go in the train, the more the air pressure that it exerts upon you is decreased. This is the same principle that explains why an airplane's wing works.

Answer 2

There's changes in pressure do to the way the air moves around the train. Total pressure is the sum of static pressure and dynamic pressure. A moving train involves changes in the latter.

Answer 3

venturi effect