It might be the specific Unity version and maybe it also only happens on particular USB audio interfaces and not others. I just ran into a download-only Unity game in this jam and in the USB interface, it always crackles, but in the stock audio, it doesn't. Almost always, neither WebGL nor download crackles for me on any Unity game on the USB interface.
The only way to be sure now is I should finally try Petville on download (which I never did yet) and see if the same thing happens. If it does, there might be some strange audio bug similar to the one Godot 4.x has (but I think that Godoit one only affects web, this Unity one would seem to affect Desktop too so it might be worse in a way), on some particular Unity versions and particular USB interfaces. Right now, I did not confirm that it does this on the download version of Petville, but if it does, there may be some combination of specific audio interface and specific Unity version used that causes persistent audio crackling.