This buzzing noise when in the UE4 editor is happening to me as well, but only with my home PC, which has much more powerful hardware than my work PC (and this issue has not arisen when using UE4 on that). I remember something similar when playing either Rust or DayZ; I’ll have to verify which one that was.
There are a number of posts that describe this same or a similar issue (links below), all dated 2014 and newer. Seeing as this is happening with my fairly new and powerful PC build, I’d be very curious to identify any hardware similarities in others’ PCs that are encountering this issue.
Perhaps someone at Epic could organize a survey on whether they’ve experienced this and requested data collection on hardware specifics of the users, so we may be able to identify a pattern. It seems Epic really cares about their users, and I’m sure all of us would really appreciate the effort.