Since that mp3 file just keeps restoring itself when you delete it, that could be just some app is stuck in some kind of one-off glitch. All apps have their own folders that are essentially not visible unless you're intentionally trying to directly view them, and given that file is only a few bytes in size it's likely to be something like sound effect some app makes as an indicator of some function (i.e. tap on an app button and there's a chirp).
In this instance finding the source app is going to be a challenge but if it is just a glitch, have you just restarted your Pixel? A restart often fixes a lot of occasional glitches that pop up. If you have and that file continues to keep restoring itself, then it's a matter of trying to determine the source of the problem.
How quickly does that file restore itself after you delete it? A few minutes? A couple of days?
-- If the former, try what
@ocnbrze suggested, restart your Pixel into its Safe Mode, delete that mp3 file, and see if it returns. If not that's an indicator some app you've installed is the culprit. It helps narrow down the list apps to look into but if you have a lot of installed apps you're still stuck with what could be a tedious project to determine just which app. Start going through your apps in batches using Force stop and Clear cache until you find the app in question, then do the same individually, that batch, to find just which one.
-- If the latter, Safe Mode isn't a practical option, using a smartphone in Safe Mode for an extended time is more than just annoying, it will involve issues with basic functionality (i.e. apps syncing with their online services).
https://www.hardreset.info/devices/google/google-pixel-6/safe-mode/