Third one has it as well. Starting to think this is quite widespread.
Not sure what to do. Part of me thinks to wait to see what officially happens or wait 2 weeks for a newer batch and replace again...
Mine has it as well, but only audible if you put your phone right next to your ear in a quiet room.
It's possible previous versions had similar as well but nobody noticed? I don't think it's worth going through the hassle of getting a new phone as I have to try really hard to hear anything at all.