Ask the ExpertCategory: EqualisationWhy do some people have to equalise mor often than othrs?
Ali asked 2 years ago

I just saw a freediving video of a guy diving with a gopro on his head to 57meters and he eqalises only about 9 times altogether …. I already need significantly more equalisations between surface and the first 30 meters. Why is this so?

1 Answers
Freedive International Staff answered 2 years ago

hello, you are asking 2 different questions:

– why some people need to equalize more often than others?
people are different and may have different bigger or smaller middle ear, sinuses, but more likely it’s the diameter of the eustachian tube and how “clean” and “uncongested” this area is, which makes the difference between how often people need to equalize. people with small or obstructed E-tubes will need to equalize more often, because every time they equalize, the air passing through and entering the middle ear is less than in a person with big and open E-tubes.

– why do we (all and not only someone) need to equalize more often at shallower depth and less at depth: this has to do with a physics law called Boyle’s law. Without going into too much detail, the difference in pressure from 0 to 10 meters is double (1 bar to 2 bar), which means that if an airspace on the surface is 100ml, by the time you reach 10 meters you will need to add 100ml of air to that airspace to have it completely equalized. But from 10 to 20 you will not need to add another 100ml, because the pressure at 20 is not double than at 10, but only half (2 bar to 3 bar), so you will only need to add 50ml of air to equalize. From 20 to 30 meters it will be even less, and so on.

Freedive International