I'd love your thoughts on why it might be hardware. I reason that my hearing is generally fine - there's no issue picking apart loud complex music (I love breakcore!).

But play two songs at the same time, or try talking to me with significant background noise, and I seem to be distinctly impaired vs. most others.

If I concentrate, I can sometimes work through it.

My uninformed model is a pipeline of sorts, and some sort of pre-processing isn't turned on. So the stuff after it has a much harder job.

I don't have much beyond what I said. It happened to me after repeated exposure to dangerously loud sounds in a small room. I can hear faint sounds, but I have trouble with strong accents and I can't understand words if there's a lot of background noise. I noticed it shortly after I left that band, and I left because the last practice was so loud it felt like a drill boring into my ears.

I don't think I have any harder time appreciating complex music than I did before, but I'm more of a 60s-70s rock kinda guy and a former bass player, so I tend to focus more on the low end. Bass tends to be less complex because you can't fit as much signal into the waveform without getting unpleasant muddling.

And of course, just because we have similar symptoms doesn't mean the underlying causes are the same. My grandfather was hard of hearing so for all I know it's genetic and the timing was a coincidence. Who knows?