Just under 8kHz. The tinnitus frequency seems like its about about a major fifth higher, so ~12kHz.

I also notice in general that it's much more pronounced after I've been wearing earbuds, even if the volume is turned way down.

Jeez you're range of hearing is capital F Fucked. Did you go to school next to an airport and live backstage at a heavy metal concert? No disrespect.

No, but I'm 58 years old. Hearing loss is just a Thing That Happens sometimes.

An example graph that highlights the degradation over the decades.

https://www.cochlea.eu/en/pathology/presbycusis

Remind me to avoid getting old.

Damn, why didn't I write myself a note?