Why are some iPhone 7s making hissing noises?

Over the past couple of days, multiple reports of the iPhone 7 making “hissing” noises have cropped up. Gizmodo has a nice roundup here, but the gist that 512 Pixels’ Stephen Hackett noticed it and several others have followed up to say they’re hearing the same thing. It’s one of those issues that could rise to the level of a [insert word here]-gate. It also could not be a big deal at all, which is iMore’s analysis. But in a quiet room, with the phone under he