Apologies if this is the wrong place to post this.  I suspect I might
be a candidate for Tinnitus, although I don't think I have symptoms.
But I was a headphone-wearing D.J. for a few years.  Here's an
experience I've had occasionally:

I'm driving on a backroad or a highway, and suddenly am aware of a very
high-pitched sound (like what you hear coming from the back of a TV
set, for instance).  After perhaps 5 seconds or so, sometimes more,
sometimes less, it drops off to silence.  The drop off is more like a
Doppler gradual drop-off rather than a sudden stop.  I've noticed a
number of times that the sound also seems to gradually appear.  This
happens perhaps once a month, but so far never in the same location on
any given roadway.

So my question is, does this fit as a possible symptom for the early
stages of Tinnitus, or might I actually be hearing something that is
physically present in the environment (passing through a microwave
tower beam or other transmission tower)?

Thanks for any thoughts or insights.  8-)

Tom