tunnel and ear ???
Why feel pain in the ear when we entering a tunnel by car?
Some people experience a bit upon driving up a high hill or going in an aeroplane, because of the pressure differential between the inside and outside of the head. That's why ears 'pop'. The pressure shouldn't change from ambient inside a tunnel.
Could it just be that the echoes produce a painful level of sound?
I am not understanding why tunnel is circular
this isn't the case so much with a car and tunnel, where you better the hell expect the tunnel cross-section to be quite a bit bigger than the car cross-section in both width and height. but i remember when i lived in New Jersey and i would take the PATH train into NYC that there was a sorta compression wave that we experienced when the train just entered a long tunnel (went from being an elevated train in open air to being a subway in a tunnel not much bigger in cross-section than the train). especially if you were in the front car of the train.
because the air in the tunnel was mostly stationary before entering and the train is much slower than sound, the train acted like a plunger in a syringe and had to suddenly start pushing a column of air in front of it forward. that increased the pressure in the bubble just in front of the front car of the train and some of that increased pressure leaked into the front car.
but it doesn't explain it for the OP who is driving or riding in a car and going into a tunnel that one reasonably expects is a lot bigger than the car in cross-section.
That's interesting about the train. I was unaware of that effect.
The human ear can register extremely small pressure differences. There are a lot of people who can be very sensitive to this, especially if they have issues equalizing the pressure on from the inner portion.
I have been in places where the tunnels were relatively small and if you are going fast enough, cause a slight discomfort. Much like driving fast and suddenly rolling down a window in your car (except this situation is the exact opposite scenario).
In europe trains have to be airtight because of this - when you enter a tunnel only 1m or so wider than the train at 150mph you better beleive there is a pressure build-up.
I can certainly understand it from the high-speed train perspective, and from a car one ala Fred's experience. I guess that I've never thought of something that tight being used for autos. My only experience with highway tunnels is going through the Rockies from Alberta to BC, and I've never noticed anything there. Of course, those are big tunnels.
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