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Simple question:

If a commercial airline cabin is pressurized, why do my ears pop as we ascend and descend? I was always told this was due to a change in pressure, but if the cabin and my body are at the same pressure, there should be no force causing my ears to pop.

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    $\begingroup$ Cabins are pressurized between 6000 and 8000 feet of altitude, until you reach these altitudes the pressure inside the aircraft is increasing or decreasing depending on if you are ascending or descending. The pressure must match the ambient pressure at your destination so they can open the door. $\endgroup$ – Ron Beyer Jun 18 '16 at 3:33
  • $\begingroup$ "if the cabin and my body are at the same pressure" - this is incorrect which leads to your confusion. When the pressure outside your body changes, there are all kinds of cavities inside you which are at different pressures. Almost nothing is "at the same pressure". That's why the cabin pressure is changed slowly, to allow for equalisation. It's also why a sudden decompression can be very painful. People have suffered from all kinds of barotraumas. $\endgroup$ – Simon Jun 18 '16 at 6:05
  • $\begingroup$ The middle ear is like a VSI, it equalizes pressure... only after a lag time. $\endgroup$ – mins Jun 19 '16 at 13:59
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Here is an illustration of how cabin pressure changes during a typical commercial flight: source: http://aerosavvy.com/aircraft-pressurization/image source: http://aerosavvy.com/aircraft-pressurization/

Note how when the pressure outside the aircraft is changing, the pressure inside the aircraft is also changing, but not as much.

During the flight shown here, you would experience about the same pressure changes that you would in an unpressurized Piper Cub that only went to 7000 feet.

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    $\begingroup$ Not exactly the same as an unpressurized flight to 7000ft. The rate of change is much lower inside a pressurized cabin. An airliners typical vertical speed is around 1000-2500 feet per minute and the cabin pressure changes at approx 300fpm. $\endgroup$ – Sami Jun 18 '16 at 4:18
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    $\begingroup$ Good answer, but you should cite the source of the image. $\endgroup$ – OSUZorba Jun 18 '16 at 4:50
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    $\begingroup$ @Sami: Absolutely correct for, say, an unpressurized 7000ft ASL test flight of a commercial passenger jet. Cabin pressure would follow the red line to 7000 and remain there until it met the red line at the right side of the diagram. -- But I was actually thinking of a typical flight in, say, a Piper J-3 cub, which climbs at about 350 to 400 fpm with 2 aboard. $\endgroup$ – A. I. Breveleri Jun 18 '16 at 4:50
  • $\begingroup$ @OSUZorba: I put the image source in the description but I forgot you need edit privilege to see it: aerosavvy.com/aircraft-pressurization $\endgroup$ – A. I. Breveleri Jun 18 '16 at 5:00
  • $\begingroup$ Lower pressure means also less weight. $\endgroup$ – dani Jun 28 '16 at 11:16

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