@siosal Yes, losing hearing is only one cause of tinnitus. I experience it just about every night when I take my hearing aids out so you're right about the brain filling in for what it is expecting.
I could not find anything about the Eustachian tube shrinking by doing a Google search. It would not surprise me if something like that happens though. It would seem that a shrinkage would not necessarily cause a blockage problem, which typically opens when we yawn or swallow.
Regarding you perception of losing speech sounds, you may not want to wait too long to address the problem. Hearing only gets worse as we age. It never gets better on its own. Hearing aids only help a bigger problem.
Thanks for sharing your input. It kept me thinking
Tony in Michigan