eli5: Why do our ears pop when we change altitude? And if it’s pressure, why do they do it in pressurised plane cabins?
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>Why do our ears pop when we change altitude?
Our ear drums are extremely sensitive to air pressure they can detect a difference in pressure less than 1/10,000th of a pound per square inch and they have two sides.
One side is exposed to the outside air and the other is exposed to the air inside of our heads.
The air inside our heads is stuck in there unless we actively choose to open our eustachian tubes (yawning ect.).
This is useful because if sounds could get into our heads and change the pressure inside of them our ear drums wouldn’t flex when those pressure waves move around us.
>why do they do it in pressurised plane cabins?
Airplane cabins are pressurized to ~8,000ft so the pressure changes until you rise to ~8,000ft then it stops increasing until you descend below ~8,000ft.
Since we already discussed why pressure matters to the ear, I hope that you can see why airplane cabins changing pressure would cause problems with that system.
*I live 5,500ft above sea level and I only ever feel my ears pop when my outbound plane is landing near the coast so I’ve actually experienced this in practice, going 3,000 or so feet up doesn’t make my ears pop, it’s only the 8,000ft down that makes me want to pop my ears.
Airplane cabins are not fully pressurised, they are only partially pressurised. The pressure difference between the inside and outside of the cabin causes stress in the airframe and the bigger the pressure difference the more stress and therefore the shorter lifespan of the airframe. So airliners want to keep the pressure inside the cabin as low as possible to reduce the wear on their airframes and only pressurise them to the legal minimum pressure. So you will typically have a pressure inside the cabin equivalent to around 3000 m altitude. The airplane will go three times as high but the pressure inside the cabin will stay at this altitude.
This means that when ascending in an airplane your body will feel a pressure change as if you were climbing to 3000 m in just a few minutes. And when descending you will be descending the same 3000 m in a short time as well.
When at high elevation, like in an airplane or on a mountain, the air pressure decreases as you go higher. This can cause a pressure difference between the air inside your ear and the air outside. To equalize this pressure, your Eustachian tubes, which connect your middle ear to the back of your throat, open up briefly, allowing air to flow in or out, which is what you feel when your ears “pop.” This is why chewing gum, yawning, or swallowing helps.
EDIT: To answer the second part of your question, even though commercial airplane cabins are pressurized to a certain extent, they can’t maintain the same atmospheric pressure as you’d experience at sea level. The cabins are pressurized to a level equivalent to an altitude of around 6,000 to 8,000 feet, which is lower than sea level pressure.
So, as the plane ascends to cruising altitude, the cabin pressure gradually decreases, creating a difference in pressure between the inside of your ears (which are still adjusted to ground-level pressure) and the cabin. This pressure difference can cause your ears to pop.
Pressurized cabins do not maintain full sea-level pressure. Being in a pressurized cabin is about the same pressure that you would feel on top of an 8,000 foot mountain. There is enough pressure to be safe and for most people to feel comfortable, but still quite a pressure change from takeoff to cruising altitude (unless you took off from an airport that is high in the mountains).
It is pressure. The popping is the pressure inside your sinuses(?) equalizing with the exterior pressure.
The pressure inside a plane cannot be kept at ground level, it would be far too much for the fuselage to deal with, and would consume much more power. Planes are generally kept at a maximum of something like the equivalent of 8000 feet altitude at minimum. This is enough to keep people healthy and mostly comfortable.
So below 8000 feet, the pressure will be whatever it is outside, above 8000 feet it’s kept at that level artificially.
Next time you fly take a bag of chips and check it out when the plane reaches cruising altitude. The expanded, taught bag has the same pressure as the inside of your ear until it adjusts to the nee pressure via the eustachian tube.
I live on top a hill and without fail everytime I go down it on the way to work my ears pop lol, it was annoying for awhile but I’m now used to it.
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