iPhone 7 terrible hissing sound

I have changed 4 iPhone 7 - 128 gb, silver grey and i had the same terrible hissing sound issue, even with the idle processor.

I contacted with AppleCare support but still no solution to my issue, they told me to return my phone and take another one or just wait.

How is possible that Apple still haven't got a public reply to the customer that have got these issues?

Of course, when making a video or a phone call, everything it's amplified.