The Pixel 2 is having high pitch and clicking sound problems, according to a number of users on the Google product forums. At the moment there are over 100 responses to the thread from a user complaining of high pitch frequency sounds coming from their Pixel 2, in addition to sounds of the device clicking, to which others have commented and confirmed that they're devices are doing the same thing. At the moment it's not clear what is causing the issues with the phone and whether it will cause any functional issues down the road, but with it not be normal for devices to make such noises it's probably not something that users will want to simply try and deal with.
For now users having this problem with the Pixel 2 are recommended by Google to begin the process of an RMA, so they can get their devices swapped out under the warranty and get a fresh replacement. Specifically, the post from an Expert on the support thread is stating that if users are having these issues on their device, they should contact one on one support to discuss RMA options, which would be the replacement of the phone after users have sent in the damaged device.
There are two options for RMA replacements according to one user in the thread. The first is where users would send in the old device, and once it's received a new one would be mailed back out. This has a turnaround of about 5-10 days but it's completely free and requires no authorization hold. The second option Google will give users will be free as well, but there is an authorization hold placed on a payment method while the new phone is being sent out. During this time users get to keep the old phone in their possession so they're not without something to use, and this type of replacement usually takes less time. There's no mention yet of what the root of the problem is, but this would seem to be the first issue that has popped up for the smaller Pixel 2 made by HTC, whereas the Pixel 2 XL made by LG has had a couple of issues so far.