Why is there a sense of pressure change inside the ear when someone goes down a mountain?
The pressure inside the middle ear is keeps equal to the external ear (so to the exterior too) because of a communicating duct between the middle ear and the pharynx known as the auditory tube, or Eustachian tube. When someone goes down a mountain the air pressure upon the middle ear enhance and it is essential to do some exercises like fake swallowing to force the opening of the pharyngeal orifice of the auditory tube to equalize the pressure again.