Riddle me this:

How can, with no reference pitch of which I'm consciously aware, my ear-ringing sound flat?

Though I do have good pitch acuity, I do *not* have perfect pitch. So this is... confusing.

And annoying.

Near as I can figure, I must have *some* sort of internalised reference pitch; I'm just neither aware of it at a conscious level, nor know what pitch label it should bear.