A paste of mine from another related thread:
I have very bad tinnitus, due to numerous head injuries. Commonly called "ringing in the ears" it's actually a constant hum, not unlike what some pieces of electronic equipment produce.
I've learned to mostly ignore it, and it's one of the reasons the VA gives me hearing aids, to mask it with louder ambient sounds. I have a 10% VA disability for it. But in the quiet of the night it becomes very intrusive, so I do one of 2 things:
I keep the TV on in the bedroom, which my partner generously allows me. The auto-off timer is set, so it doesn't stay on all night, turning off just a little after I normally fall asleep.
Alternately I use a sound generator. They're quite sophisticated now, with a whole range of sounds to select, not merely the "white noise" the first versions had. My favorite is Summer Night, with insect sounds and other animals, and the wind in the trees, very much like when I'm actually camping.