Pixel 2 XL users are complaining about a rattling sound coming from the speakers
This happens to be a widespread issue. Between reddit and the Google Product Forum, there are over 100 threads from upset Pixel 2 XL users including one gentleman who is on his third unit. His comment? "I am on my third Pixel 2 XL. All of them have the same issue where the speaker distortion and rattling affect the conversation quality of the phone call.
It's ridiculous that Google launched such a poor quality product and after most of us paid full price they are now offering major discounts to capture new users."
The issue with the speakers seems to occur at all volume levels, so this has nothing to do the typical distortion that some might hear with the sound output cranked up to the maximum setting. Hopefully, this will be fixed by an upcoming software update. Still, it is another issue that will be added to the Class Action lawsuit reportedly being prepped against LG, HTC and Google.
source: reddit, GoogleProductForumAndroidPolice