As part of research into another subject, I need a crash course
in hearing related issues for background reference.

Specifically, I am looking for known conditions/causes for a
person to hear a tone in one ear that lasts for only a few
seconds, perhaps 10 or 12 at most. Sometimes this may be
accompanied by a brief "stuffiness" to the ear, like water
is in it. Typically, the tone starts out at a given volume
where nothing else is heard and gradually fades to nothing.
The frequency heard may change from incident to incident.
It is a pure tone, often described as similar to the trick
of running a wet finger around a wine glass rim.

I know of tinnitus, but as far as I know this is typically
a relatively constant volume at unchanging frequencies.

What I'm looking for lasts only seconds. Otherwise hearing
is normal, even passing routine exams.

Interestingly, I've experienced this a few times myself.

Feel free to get technical.

Brian