Your Pixel 2 will soon be free of both clicking and hissing.
Since its release, a number of users of the smaller Pixel 2 have reported a faint hissing sound that can be heard when the phone is placed near your ear during a phone call. My device doesn't appear to be affected, but those that are experiencing the issue should be relieved to know that a software update will soon be available that eliminates it for good.
This announcement came from a community manager of Google's Pixel User Community, and it's said that the update will be available "in the coming weeks." We certainly would have liked a more solid ETA, but having a light at the end of the tunnel is still great nonetheless.
Google recently fixed the clicking noise also found with the Pixel 2 in the November security patch, and that was discovered to be a bug with the phone's NFC chip. It's unclear exactly what's causing the hissing, but I suppose that won't matter in a few weeks.