At what level can human body withstand a sudden pressure drop?

Question

i.e a sudden pressure drop inside the submarine which may harm the eardrums of human

Answer 1

I saw on tv that in the 50ties, they did experiments with humans on rocket chairs. The chair was accelarated with a rocket engine to 1200 miles / hour and then stopped within 2 seconds to speed 0.
The people on the chair survived although they had internal bleedings.

Answer 2

Not sure what you really want to know. The interior of a submarine is pressurized at atmospheric pressure. If it wasn't, the occupants would have to breathe compressed air which means that the sub couldn't rise and lower at sufficient speed to make it useful. The construction of the hull of the sub is what keeps it from collapsing inward. If the sub goes to deep, then the external pressure of the surrounding water will crush the sub. The human body can take a lot of pressure change providing that the air that they breathe is at the same pressure of the surrounding air. If this wasn't so, then men could not climb mountains or scuba dive. Hope this provides some help.