One of the things tested in the test for deciding whether someone is allowed 2 or 3 kids should be testing how small an electrical spark they can hear while blindfolded where they show a sign of hearing it by reacting to hearing it. The hearing ability, at least for high hearing, can be further improved by creating evolutionary pressure for clear Eustachian tubes because a difference in pressure between both sides of the ear drums reduces the amount of high frequency vibration of them in response to sound. Temperature changes of the air are creating a pressure differnce at the eardrum all the time. There's also a disadvantage in having clear Eustachian tubes which is that the clearer somebody's Eustachian tubes are, the more easily water can go into the inner ear when swimming underwater, especially when very deep with high pressure. That problem can be solved by creating evolutionary pressure for people to be able consciously control their nose muscles to hole their breath by closing their nostrils instead of by closing the valve people close to make more air come out of their mouth when playing a wind instrument. The test should test how much of the way people can close their own nostrils without touching them with their hands.
We should also track down those men who are the very best at how much of the way they can close their nose without touching it and allow them to donate sperm to millions of women who want to raise children on their own because once evolution has made some people able to completely close their nostrils, the next evolutionary change of clear Eustachian tubes will follow naturally for people from deep freediving tribes. Somebody should invent a spear gun that people can wear around their neck instead of holding in their hand while freediving for fish because that way, they will be able to swim more efficiently. Also, somebody should invent a type of googles that will turn each set of parallel light rays in the water into parallel light rays going in the same direction in air but spaced further apart just before they enter the eyes so that the evolutionary pressure for underwater vision with those googles won't resist the evolutionary pressure for vision working in the way described in the previous post. Fortunately, the fish to be caught are much bigger than pupil size preventing evolutionary pressure of super sharp underwater vision which would sacrifice super sharp air vision.
That evolutionary change doesn't just improve hearing. It also prevents feeling a pressure change in the ears with height as well as removing the runny nose caused by the common so that people no longer care if they have the common cold and the only symptom of it being having slightly weaker muscles. Another thing that would create evolutionary pressure for clear Eustachian tubes once evolution of the ability to close nostrils has already occurred is that the clearer their Eustachian tubes are, the less their ears will hurt if they dive to the ocean floor which is sometimes 20 m deep where they are, so the more likely they are to dive that deep so the less likely they are to starve to death from not catching enough fish.
It would be even better if we could select for people who any time after reproduction age can freedive through ice cold water to what ever depth will have them evolve to take 4 minutes to dive to and return from that depth and then do it again and again and then come out appearing very dark on an infrared camera for quite a while. That's because people would even evolve the ability to hold their breath for 4 minutes while moving because a certain swimming speed minimizes the amount of oxygen consumed for distance, to thrive in a wide range of temperatures, to not feel pressure changes in their ears or the bends with height at all, and to grow until reproduction age so that people below reproduction age will be shorter than those at and above reproduction age because a certain tall height will be evolutionary stable for people past reproduction age because being bigger consumes less oxygen per body mass per distance but being smaller is better for not having too much weight to support when you're walking. If only there was a way to make that evolutionary change without some people dying in the process.