According to one MacRumors forum member Jgpsolo, “It is a high-pitched crackle like an audio pop that happens in the earpiece top speaker intermittently during calls. Some calls are fine and others crackle. It is not audible on earphones or on speakerphone, only through the earpiece. The caller on the other end doesn’t hear it.”
So why do we say that it isn’t a defective unit? It is because it is speculated that it could be a software issue with the phone, rather than a hardware one. Jgpsolo adds, “I don’t know whether this is hardware or software related, but one thing that made me think it’s software related is that if you switch on to speakerphone for a few seconds then back to earpiece, the crackles resolve for the duration of the rest of the call. If this was a hardware issue with the earpiece, doing this shouldn’t make a difference.”
Some users have found success in factory resetting their iPhones, and some are claiming that even after getting a replacement unit the problem persists, so hopefully if it is a software issue, Apple will issue an update that will address it soon.
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