I used to hear the 16KHz whistle of CRT monitors. Of course, there is no whistle with LED monitors, but I stopped hearing the CRT whistle before they went obsolete. It was my first sign my hearing was declining.

I thought I was protecting my ears from loud noises like rock concerts and gunshots. But I didn't know that driving with the window down damages the hearing. I crossed the country many times with the window down. I'm pretty sure that was the cause as my left ear is much worse off than my right.

I don't need a hearing aid yet, but I'm pretty careful in wearing ear plugs whenever there are loud noises.