Makes sense, and I've also read it's very hard to study as well. Different causes with the same perceived sound sounds like a diagnostic nightmare

It seems like it could be some kind of feedback loop where the false signalling is actually inducing a physical response that can be recorded under ideal conditions. At the end of the day, the eardrum is an audio transducer, and every other such device we know of can make "fake noise" by being pushed into an unstable state.

Yeah, I always thought it was just the brain filling in the blanks by lack of data as in no data meaning "constant sound" or something.

If you can actually hear the tinnitus it's very promising for curing it, if it's a spasm in a micromuscle of the ear trying to free the hair from mucus there could potentially be a way to have something slow release a muscle relaxant in the ear to remove it as an example.

That's still a physical sound even if the source is internal or at the sensor.

"Non-physical sound" would necessarily be errant nerve signaling or hallucination, something on the brain side of the sensor.