I've noticed a faint ticking sound when I hold my Pixel 2's earpiece up to my ear while the screen is unlocked, and it seems that I'm not alone. It's very quiet - on par with a ticking wristwatch - and seems to occur every half-second or so. I've also found that it only happens while NFC is enabled; disable NFC, and the clicking stops. My coworker's Pixel 2 doesn't exhibit this behavior, so I've contacted Google Support and received an RMA. I'll probably order that replacement in the next day or two but was wondering if anyone else was experiencing this with their new phone.