Some early iPhone 7 and 7 Plus adopters are complaining of an audible "hissing" sound when the devices' A10 processors run into heavy demands.
The issue was first brought to public attention by 512 Pixels' Stephen Hackett, and has since been pointed out by a number of people online, such as TechCrunch's Darrell Etherington. Hackett commented that after calling AppleCare, support staff decided to offer a replacement unit.
Some previous iPhone models have allegedly experienced similar trouble. It's unclear how widespread the current situation is, or which exact components may be responsible, since there's nothing on the A10 — or anything else in the iPhone 7/7 Plus, short of the audio system — that should be capable of directly generating noise.
The issue could involve the RF transmitter, or some other form of interference with the speaker system.
Whether or not the hissing is common, it might imply a defect with the first batch of phones, for which Apple would have to offer a number of free replacements. The iPhone 7 and 7 Plus were only launched on Friday.