https://www.theverge.com/circuitbreaker/2017/9/26/16369818/iphone-8-crackling-apple-confirms-fix-coming

Some iPhone 8 owners are running into an issue with the phone’s earpiece: when they make a call, the earpiece makes a disruptive “crackling” or “static” sound that disrupts the audio. Dozens of people on the MacRumors forums, Apple’s support forum, and Reddit have reported experiencing the issue. It was also present on one phone owned by a Verge editor.

Apple said in a statement that the issue only comes up in a “small number” of cases and that the company is working on a software update to fix the problem. “We are aware of the issue which is affecting customers in a small number of cases,” an Apple spokesperson said. “Our team is at work on a fix, which will be included in an upcoming software release.”