Here’s the crux of the article in video form:
Some Google Pixel 7 series users have taken to the official support forum, Reddit, and the Issue Tracker to report a strange high-pitched noise that can be heard in video recordings. Most reports suggest that the issue popped up after users installed the December update. According to the reports, even when users record videos in silent environments, there’s a high-pitched noise that can be heard when they play back the video.
The noise is easily ascertainable and ruins the audio experience. Here’s one such example from a user who recorded the clip on their Pixel 7 Pro. If you’re sensitive to high-pitched sounds, I’d suggest skipping the video, unless you want to watch some cute cats on mute.
While it’s hard to say for certain whether or not this is a hardware or software problem, granted that it popped up only after users installed the latest update, it’s most likely a software bug. However, while I found a couple of reports suggesting the issue was on the Pixel 7a too, in my testing on the 7a, I couldn’t replicate the problem. Although, it’s worth pointing out that my Pixel 7a is running the latest QPR2 beta update. Speaking of which, one Pixel 7 user took to the Issue Tracker to claim that they are facing the issue even on the latest QPR2 beta update with the build number AP11.231117.006.
From what I’ve gathered, it appears that the high-pitched noise from the mic in video recordings on the Pixel 7 series doesn’t even get fixed after a reboot. In fact, booting up the device in Safe Mode bears no fruit too. The current status of a report on Google’s Issue Tracker about the problem is ‘Assigned’. So it’s likely that the issue is being looked into by a Google engineer. However, there’s no official acknowledgment yet, so the wait for a fix is on.