Asked by: Antonio Hardy, London
The air pressure on your eardrum is normally balanced because your middle ear is connected to your sinuses via a narrow duct called the Eustachian tube. If the outside air pressure changes too quickly though (in an aeroplane coming in to land, for example), the Eustachian tube can’t equalise the pressure fast enough and the eardrum bows in or out. The popping sound occurs when the pressure rebalances and the eardrum suddenly flips back.
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