2012 PriusV sometimes weird sound when turning, sounds like a distant horn

In the past week, our 2012 PriusV started making a weird sound during some turns It sounds sort of like a honking horn a ways off, lasts only for a split second. It definitely gets your attention but isn't loud, sort of a brrr or honk is the best I can describe it. It's happened about half a dozen times so far, always when turning or merging at a decent speed. It's only a sound - there has been no change whatsoever in the performance or behavior of the car.

yesterday someone else heard it once too, so I am not imagining it or hearing other drivers honking. It's a weird sound, doesn't sound like anything mechanical or anything rubbing or cracking or anything like that.

what do you think it could be?

Doing a gggle search, the AI summary suggests that the PriusV could playing the 'reverse' or "vehicle approaching" safety sound. That's an interesting idea, but the AI doesn't share any sources. I'd like to hear what humans think?