I found it best to not try and mask the T fully. Sure, some background noise is good since it gives you something to focus on. But if you try and fully mask it, it has 3 main negative effects in my experience:
1. It makes you dependent on the masking noise, making it so you never allow your brain to adapt to the T, and learn to fall asleep and stay asleep with it.
2. You may find yourself listening for your T (and perhaps mildly perceiving it behind the masking noise). In doing so, your brain is actively working and focusing on the T. Very hard to sleep once your brain starts that kind of active search and focus.
3. For some people who suffer from panic attacks and anxiety, they sometimes begin to have the same nervous reactions to masking sounds since the whole "I want things to just be quiet" thought process kicks in.
Here is the key thing to realize. Its very likely not the T itself that is keeping you awake. Rather, its your brain's reaction to the T that is keeping you awake. My T is loud enough that only a passing train can cover it, and I spent night after night awake and focused on it since I had also spent all day focused on it. Yet, when I wouldn't think about my T all that much during the day, I would end up not thinking about it much at night, and would end up sleeping fine. Its all part of the process of habituation to the T. And not trying to constantly mask the T is part of that process, as difficult as it may seem at first, when you "just want it to go away"