There have been a lot of complaints about loud Xbox One units last month and we've received letters about it here on Gamereactor as well. Now Microsoft officials has acted and says they will replace all of those units:
"We have heard that a small number of Xbox One owners in some situations may hear a noise from the console that is too loud. While this does not affect the safety or functionality of the system, we're asking customers who believe they are experiencing this issue to contact Xbox Support: https://support.xbox.com. At the request of our customers, we are exchanging those consoles for new systems."
Thanks, Kotaku.