Hi!
Mine was a hissing sound, long before it became tonal. In fact, I was never really bothered by nor did I know that what I was hearing was tinnitus, not until it became tonal. Before it became tonal and constant, I was able to hear it only temporarily when yawning or clenching my teeth. Whatever hearing loss I had previously, my latest acoustic trauma made it worse. So I am pretty sure that my tinnitus was noise induced.
So there you have it, that's how it has progressed in my case. Hearing loss due to headphone overuse and loud music, followed by static noise, followed by somatic tonal tinnitus and fleeting tinnitus, followed by acoustic trauma, followed by constant tonal tinnitus.
My luck in this unlucky series of events is that my tinnitus is only mild. I hope it stays so and I try to preserve the hearing I have left. But it's not always easy when you are constantly exposed to noisy machinery as soon as you step out the house door.
What's worse is that you can damage your hearing inside your own home. Too much listening to music, game streams, gaming, television, radio, pods, vlogs, movies, streaming movies, talk shows, video calls, voice calls. Then you step out the door to get some sunlight and get to the school or a job, and of course you bring your phone and your "earins" and "airpods" with you, because it's much better to listen to music while you commute than to talk to strangers. It's a lifestyle that consumes us, and most of us don't stop for a second to think about it until it's too late. I know, because I have been there.
Do you have any measurable hearing loss? I see you listed smoke detector alarm as a possible cause. That could very much be what has caused your tinnitus. Assuming you have excluded other possibilities. Noise related tinnitus is most commonly caused by loud and sudden sounds. I know smoke alarms are very loud, and the sound they produce is like ear piercing. At least the ones I have had were like that. I would normally just listen to them for no more than a second, when testing them each year. Listening to them any longer than that would make my head explode. That's what it felt like, before I even had tinnitus. I no longer test them, and just pray and hope that I never have a fire at home, or at work.
When you get down to it, I think the character of the tinnitus will depend on things like what part of the hearing range is impaired and how severe it is. But it is more caused by nerve damage than hair cell damage, and by neural network changes at the brain level.