I didn't get tinnitus from a vaccine, luckily. I've had it for many years, and I think it was due to going to too many rock concerts (and playing in too many bands). I just saw this and wondered if anyone had noticed this. I did get a temporary increase in tinnitus from a medication last year, but it went away. Your friend's tinnitus may have come from COVID, or maybe a medication. NSAIDS can do it too.

Thanks for the link. I am plagued by this as well, but so far, still have normal hearing. It can be influenced by substances. I once took a glaucoma eye drop which made my tinnitus 100 X worse. Unbearable! I couldn't sleep; it was awful. Discontinuing the drop made it go back to its original level, which I hardly notice. I'll try lemon juice. I wonder if lime juice works; I add that to my water a lot.

@Organist1 I have heard there can be several causes and too much ear wax is one. It must be horrible for a musician.

@JackPedigo I barely notice it normally, and think it came from listening to loud music for too long.

@Organist1 It is said as we age frequencies in the high range start to drop out. I had a hearing test and that was the case. In our brains are receptors that respond to the different frequencies and when the sound is not there the receptors try to create one, sort of like the missing limb pain. I tried looking for some cure and there is an experimental one that tries to find the specific frequency affected and then use a transducer to recreate that frequency. Like you, sometimes it's very low but most of the time louder.
[mayoclinic.org]
[ata.org]