Mine sounds exactly the same! I usually describe it as the sound of "brightness" and it does feel like something coming from inside my head, instead of from the outside word.
As many people, I cope with mine by just ignoring it, most of the time. Sleeping has been hard though, since I can remember. Today I resort to some kind of color noise, such as a fan, air conditioner, or white noise apps (brown noise works best) or I just fall asleep (often with aid) watching TV or listening to a podcast.
In the end, it's not really a practical problem, but a more philosophical one: it makes me sad to think I'll never be able to experience silence.