Mine is also in both my ears and my head. Left ear is a mid-range tone, pretty constant, but will vary slightly in pitch and volume. Right ear is much fainter, and only really there if I plug the ear to listen to it. In my head it is all electrical, like the power station that
@Vicki14 described. That's the one that is most variable - on good days it has no specific location in the head and just sounds like background tinsel. On bad days it locates to a specific part of my head - worst when in the front - and can zip around various high frequencies. That's pretty hard to take when it happens, but luckily is pretty rare.
As I write all that, I wonder how I'm coping. And yet, things are usually not so bad. Thankfully, with some care, and appropriate use of plugs, I'm able to keep the volume of all three sources at something manageable. But it's always touch/go, because any one of the sounds can decide to have mind of its own.
I'm really curious about the original head/habituation question as well. My understanding is that the ears habituate relatively well over time. But the head... is less clear to me. Anyone who can provide insight, that'd be amazing.