If you think of tinnitus being a frequency (let's assume it's one for this example, but this all holds for multiple frequencies and losses) that is persistent, whatever you listen to will have that frequency masked or removed: you won't hear it because it is drowned out by your tinnitus. An audiogram hearing test (done via Health app, or third party app like Mimi) your hearing test will show that missing frequency (and more). After you activate "Headphone accomodations" what you hear will be boosted in all the right places by an amount that will counteract your hearing loss. So, you'll be able to hear the frequencies again! Music like you heard it in your teens. I think you can do the same on macOS, too. Headphone accommodations, Hearing aid and Personalised audio are separate but related features.