Another user has shared their own experience today. Fortunately, this time it was a lot more mundane: what sounded like just some person talking to their coworkers in a warehouse. The second user also checked for any background apps or other rational explanations but found nothing.
Eavesdrop on strangers in high definition! | Video credit — Apple
Possible explanations
But there are definitely other possible explanations for this weird phenomenon. The first post had people commenting about possible carbon monoxide poisoning which can lead to exposed individuals experiencing hallucinations. Though unlikely — as the poster said they had working detectors and their husband heard the same thing — it is still a possibility.
Another explanation, and something that seems far more likely, is an iOS 18 bug. This year Apple had one bad software update after another and iOS 18 was no exception. As some commenters pointed out, it is very likely that iOS 18 is playing random background audio even without showing YouTube or other offending apps open.
So if you suddenly start hearing voices coming from your iPhone 16 you should force close the YouTube app before calling an exorcist.
