坐火车进隧道，耳朵为什么难受？

Going into a tunnel, your ears feel funny. 火车进隧道时，耳朵怪怪的。 The air outside your ear pushes harder. 隧道里的气压，比外面更大。 But the air inside your ear stays the same. 可耳朵里面的空气，还按老规矩。 The two sides push against each other. 两边气压一较劲，耳膜就被顶了。 That is why your ears feel blocked. 耳朵闷闷的，就是这么来的。 Swallowing or chewing opens a small tube. 吞口水、嚼嚼东西，能打开小管子。 Then the pressure balances, and ears feel fine. 气压一对平，耳朵立马就舒服了。