Almost everyone's familiar with the ear pop that accompanies take-offs and landings in planes. For the most part, they're pretty harmless and are usually preceded by some savoury candies, so I'm not complaining. If you have a cold while this is happening however, then say a prayer and stuff a hundred Alpenliebes in your mouth, because you're in for a world of pain! As to the reason why this pop happens in the first place, audiologist and clinical associate professor from NYU Langone, William H. Shapiro puts it pretty succinctly.
It has everything to do with the Eustachian tube, a pressure releasing valve that connects your middle ear to the back of your throat.
As you ascend in an airplane and the air pressure decreases, the air trapped in your inner ear causes your eardrums to push outward, which can also cause some discomfort.