Mine started when I was 12 for no apparent reason. A visit to the pediatrician, a hearing test that found my hearing was normal, and that was that. 65 years later (I'm 77) it's EXACTLY the same in pitch and volume, a loud high-pitched whine that doesn't bother me in the least. Once I got used to it and realized it was a permanent thing, it ceased to be annoying or a problem, probably when I was in high school. In my case ANC was most definitely NOT the cause (in 1960). Unless the Russians were already testing their Havana Syndrome weapon in Milwaukee.... One more thing: aspirin and/or caffeine make mine significantly louder for a few hours, though it's still not bothersome.