The Google Pixel has issues. It's still the best phone out there, but it's not perfect, and one such issue consistently been reported is the phone's single downward-facing speaker tending to distort at high volumes. What was initially thought of as a hardware malfunction appears to have been resolved (or is resolvable) using software.
According to a number of people who downloaded the February 2017 security update onto their Google Pixel this week, the sound issues appear to have been fixed — at least for some. Two commits to AOSP in January — one from Google and the other from HTC — tell the story of a company looking to both its internal software team and its manufacturing partner to figure out exactly what has been happening.
What does this mean? Well, as Russell Holly pointed out, it's very difficult to make speakers act identically inside a phone, since there are always going to be variances in temperature, humidity and slight alterations to the size and shape of the cavity itself. What Google can do is resolve the issue for the largest number of people through a software calibration, which it appears to be doing here.
If you're using a Google Pixel with the latest security update, has it resolved your audio problems? Or did you not have one in the first place? Or have you still been unable to buy one?