Trying to make a contribution...
Assuming nobody has played a joke on you and placed a hidden glass vial undercover somewhere 😄, I‘d say one hears a smaller, loose or loose enough, piece of unpainted metal hitting a much heavier, fixed piece of unpainted metal; both have to be unpainted (unless there’s glass other than the windows and windshield in our cars?), otherwise you wouldn’t have such a clear bell-like sound; one of them has to be small and loose enough to resonate (hence the noise), and the other large enough and not moving, so as not to resonate (as it doesn’t give any noise of itself). The clarity of the sound does indeed lend to believe at least one of the pieces hitting each other is chrome (very hard, unyielding surface, that transmits vibrations really well and allows the piece to resonate clearly).
The smaller piece has to be free to move quite a bit, hitting the other piece very cleanly, as the noise is very clear, not muted or dull. It is not close to the other piece (in a relative sense), otherwise you’d hear it rattling, not hitting.
It also seems like maybe the small piece is hanging, at least partly loose, as in the third and fourth instance of the noise on your recording, is is almost as if the loose piece is hitting the larger piece quite frankly at first (third instance), and then kind of more lightly and right after on the fourth instance, like on the rebound or as if it were swinging, hitting a bit hard the first time (very clean and clear sound), having been jostled from its hanging position by some movement of the car, and then hitting again from its own momentum on a backswing or something like that.
A lot of reading into the ashes or the clouds, but to recap, try to think of a smaller piece of metal (although not that small, since the noise is not small) hanging loose and hitting an unpainted, very solid other part. It is hanging freely enough to hit another piece, but still attached somewhere, because it keeps doing the exact same noise repeatedly (it’s not moving around). It’s got to be something which is normally attached by two (or more) screws, one of which came off (hence the hanging), the other still there, but also coming loose (otherwise no swinging and no clear bell-like ringing). It has to have clear space around it to be able to swing back and forth.
Finally, it may be decorative, as you don’t seem to report that any mechanism is inoperable?
If the phone was in the car, I’d say the object is also in the car, not underside.
In addition to the window mechanisms as candidates, is there any void (empty space) and a candidate part inside the seat (head rest armature)?
