Sorry to hear of you audio problems
You certainly must recognize that the modern dive classes are very abbreviated in length and content
I agree more time should be spent on many aspects of diving , but the restrictive time restraints in the modern basic diving class does no allow to adequate time to cover all aspects of diving.
Some day proper equalization techniques will be discussed and maybe practiced in class
Many years ago there was a board titled "Free Dive List."
Eighteen years ago the Free Dive List organized and sponsored the huge 2000 Free Dive Party which was the last gathering of the worlds "Fathers of Free diving and Spear fishing." It was a very monumental event in the history of spear fishing . The 50 or so fathers came from all points of the globe for this last hurrah; Central and South America, Europe, Australia, the Pacific Islands and North America -three were honored from Orange County California the late Ron Merker, (@ dr bills instructor) Allan (Omar) Wood and my self.
We all had several thing in common; we all began diving in the 1930s and 1940s prior to Cousteau and his bubble machine graced our shores and all those who were active participants from that era all suffered from reduced hearing.
Hearing aids were a common accessory to most attendees, If not a lot of "Hu ? what did you say was hears during the day"
Some will state it was longevity others improper equalizing techniques -- But one thing was evident we all were suffering from partial or almost complete hearing loss.
FYI
Only a hand full of the Fathers have survived the passage of the last eighteen years ~~ One by one they have passed on and are now diving on that big reef in the sky.-- the end of an era
SDM. III