Stuart Hayward of Fernbank School, asks :-

Why do our ears pop when we drive up or down hills?

Ian Stewart, an ear, nose and throat surgeon at Dunedin Hospital, responded.

When you go up or down hill, the air pressure changes so that the air behind your ear drum in the middle either expands (going up hill) or shrinks (going down hill). The eustachian tube, which passes from the back of your nose up to the ears opens to either let air out of the middle ear or to let ear into the middle ear. The popping is the sound of a rush of air entering or leaving the middle ear.

The small eustachian tube often does not function well in young children or for anyone with a cold or with sinus problems. When an aircraft ascends or descends similar but more extreme pressure changes occur as when travelling up or down hills. Air leaks fairly easily out through the eustachian tube when it expands during the ascent of the aircraft so that seldom causes problems. On descent the higher outside airpressure can compress the eustachian tube, thus effectively closing it. You will quite often see babies crying because of ear pain when an aircraft is descending. One way to open the eustachian tube and thus to equalise the air pressure is to swallow. That is why New Zealand airlines give passengers lollies just before descent. I think they are the only airlines to do this.

So when descending in an aircraft swallow regularly. (This is worth practicing before your first flight.) If this doesn't work try pinching your nose and blowing gently while swallowing. Dont blow too hard and dont blow without swallowing. It is the difference between entering a room by opening a door and entering a room by kicking the door down.