Mine is sensorineural. Exposure to loud noise is the cause. I've been going to loud ass death metal concerts in tiny bars in Chicago for years and it finally started catching up to me mid-2019 or so. When I wasn't seeing music live, I was blasting it through my in-ear earbuds, too. So I did it to myself. Except one instance where a coworker dropped a wooden pallet flat on a finished concrete floor inside the warehouse a couple feet from my head. It hit the ground with a loud crack and my tinnitus has been worse ever since, with my hearing capabilities following suit.
Tinnitus in most cases is a result of hearing loss, and in many of those cases the frequency which you "hear" inside your own head most closely resembles the frequencies at which your hearing sensitivity is impaired. It can have other causes, though. I know earwax buildup and a history of ear infections are a couple of them, but it's late and I can't be assed to look it all up right now. Depending on the cause, some tinnitus is actually reversible, but in most cases, including mine, it's permanent.