Really interesting article, thanks for sharing, OP!
> If you push air into your middle ear cavity by pinching your nose closed while attempting to blow air out of it, air will be forced into this cavity. With more air in the inner ear, the pressure on both sides of the membrane will be equal and you will feel normal.
I know SCUBA divers don't have to do this constantly, only when descending. What's the physical reason behind this? Why doesn't the inner ear pressure go back to normal levels when the diver starts breathing normally again without pinching her nose?
It's because when you're under water ALL air is pressurized by the crush of the water around you.
When the scuba tank releases air into your lungs (and therefore your sinuses, which are connected to your inner ears), it's still partly pressurized, meaning it's at a higher density than it would be up at the surface. As long as you stay down, your inner ear matches the pressure level of the air at that depth. When you start to surface, the air in your lungs expands gradually. Same for the air in your inner ear, but your ears naturally bleed the over pressure back into your sinuses (unless you have a cold or something, in which case resurfacing can be really painful and must be done more slowly). It's just when you're going deeper that you need to force more air into the inner ear because what's already there gets compressed and your sinuses function like a check valve preventing more from getting in without intervention.
It depends on individual physiology, some people have eustachian tubes like railroad tunnels and have no trouble equalizing, while others have tight ones and struggle. You eventually learn your own personal best technique; I know that if all else fails, I can tilt my head back and look directly up while equalizing.
The sounds you hear during this process are pretty entertaining, too. Think of an elderly cat with a head cold, snoring.
It's like in the airplane, but reverse. In ascent, the air volume can naturally squeeze out. On descent however the air won't normally squeeze in easily.
I can open my eustachean tubes voluntarily with a yawning-like maneuver. Otherwise you have to pinch your nose and force the air either with your tongue and throat, or lungs.
> If you push air into your middle ear cavity by pinching your nose closed while attempting to blow air out of it, air will be forced into this cavity. With more air in the inner ear, the pressure on both sides of the membrane will be equal and you will feel normal.
I know SCUBA divers don't have to do this constantly, only when descending. What's the physical reason behind this? Why doesn't the inner ear pressure go back to normal levels when the diver starts breathing normally again without pinching her nose?