i did some research, not much, before buying a noise generator for my kid. Basically long term exposure to any level of "noise" may be "harmful". I don't recall the mechanics of how, though. I think something like <4 hours per day was considered "acceptable". So if you're already near a laptop fan all day and then you run noise machine at night to sleep...

Believe me, sometimes tinnitus means i don't care if i damage it more, i just need outside to be slightly louder than inside my head.