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Popping Ears

Popping Ears

Have your ears ever popped on an airplane trip? This Science Update explains why it happens.


Transcript

Ears that pop under pressure. I'm Bob Hirshon and this is Science Update.

Perhaps a recent plane trip prompted David Lewis of Arlington, Washington, to call with this Why Is It question:

Lewis:

Why do your ears pop during altitude changes? What causes that?

We consulted David Eisenman, an ear specialist in Washington, D.C. He says it has to do with the middle ear, an air-filled space behind the eardrum. Whenever the air pressure outside changes, the air pressure inside the ear has to adjust.

Eisenman:

And the way it does that is through a transfer of air through a tube called the eustachian tube that goes to the back of the nose. That tube allows air to get in and out of the middle ear as needed to adjust for pressure changes. When you're on an airplane and you undergo a rapid pressure change, that tube needs to work a little harder and a little more rapidly than it normally would.

Thus causing the popping sensation when air suddenly rushes in or out of the tube. Dr. Eisenman says it's ok to try and equalize the pressure if your ears get uncomfortable.

Eisenman:

And the way you do it is by trying to get the eustachian tube to open and close, such as by swallowing or chewing on something. Or you can pinch your nose and try to push air actively back into the middle ears to do that.

If you would like to pop a science question on us, call us at 1-800-WHY-ISIT. I'm Bob Hirshon for AAAS, the Science Society.


Making Sense of the Research

The ear is a delicate instrument. The essential parts of the middle ear are a thin, stretched piece of skin called the tympanic membrane, or eardrum (which is, in fact, a lot like a drum), and three tiny bones (the smallest in your body) commonly called the hammer, anvil, and stirrup. When sound waves flow into your ear through the ear canal, they push on the eardrum and cause it to vibrate. The small bones pick up the vibrations of the eardrum, amplify them, and pass them on to the inner ear for processing.

In order for this to work, your body needs to keep the air pressure inside the middle ear in a pretty tight range. Too much air pressure could burst the eardrum. Too little could cause the eardrum to collapse, which would mean it couldn’t vibrate.

But within that range, the ear also tries to stay in balance with the air pressure surrounding you. Normally this isn't a problem; air pressure changes on the ground are small and very gradual. But when you go up or down in an airplane, the air pressure changes rapidly. And the middle ear has to adjust in order to keep the eardrum vibrating normally.

When you're taking off, it's a little easier for your ears to adjust. That's because the pressure outside is dropping, and air will naturally pop out of the ear, like air rushing out of a balloon.

When you're landing, the air pressure outside your ear is rising, and you need to cram more air back into your inner ear to keep up with it. But it's a lot easier to let air out of a smaller space and into a bigger space than vice versa. Think of the balloon again: inflating a balloon takes more work than letting the air out. So balancing the air pressure in your ears while you're landing usually takes more effort on your part. Swallowing or chewing gum often helps force the air bubbles back up the Eustachian tubes into your middle ear.

As Eisenman explains, this usually isn't dangerous. But more dramatic changes in pressure can cause ear damage. That's why scuba divers have to be careful to go down and come up slowly; water pressure is much more powerful than air pressure. (Think of how your ears feel when you just dive to the bottom of a pool.) And airplane trips might be hazardous too, if it weren't for the fact that cabins use artificial air pressure to make the changes as mild as possible.

Now try and answer these questions:

  1. Why do your ears pop on an airplane?
  2. What are the eustachian tubes and the eardrum? How do they figure into this explanation?
  3. Suppose you were cruising at 30,000 feet in an airplane, and the cabin's pressurizing equipment suddenly failed. What would happen to the air pressure, and to your ears?
  4. Suppose you cruised in an open airplane at 10,000 feet for half an hour, and then parachuted out. What would happen to your ears?

For Educators

How Hearing Works, by How Stuff Works, includes a detailed tour of the ear.

The Human Ear, by the Physics Classroom, focuses on how ears pick up sound waves.


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