Do not think this one's easy! I have ALL AirPods sounds off, Find My has nothing to do with this, and I'd like to know what I'm hearing/why I'm hearing...
This has been happening to me a ton, and I even managed to find someone on MacRumors noting the same issue. (https://forums.macrumors.com/threads/why-do-airpods-pro-2-make-a-quiet-chime-recording-now-in-thread-a-little-while-after-being-put-away.2429789/)
My AirPods Pro 2nd Gen make this very musical chime that's completely different than any other built-in noticable chime. It doesn't sound intentional to the user, since it is SUPER quiet. It only happens about 5-10 seconds after I put both Pods back in their case.
This is the sound, captured from the MacRumors post:
I'm curious what everyone will come up with here...
I haven't been able to Google up an answer to this, but that may be because the description is very similar to normal behavior that a lot of people seem to ask about.
[Edit: tl;dr: It's a microphone calibration of some kind, and happens about once per week per AirPod when the case is not...