Typically the Eustachian tube within the middle ear opens to regulate pressure in the ears. Swallowing and yawning contracts muscles in the back of the throat that help control the function of the ear and this sometimes relieves the feeling of fullness that comes when the air pressure within the Eustachian tube is not being regulated properly, as with flying. But the fullness or the feeling that you can't hear properly can be a sign of a more serious blockage within the middle ear.

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