Most of the discussion of the firmware update focuses on the effectiveness of the ANC. But there has also been a very real issue with crackling while using ANC that sounds like a blown speaker. This too is no doubt a software issue. I experienced it during phone conversations when I would speak. Couldn’t hear it when someone else talked and couldn’t hear it during music (that I could tell). Switching apps is not a helpful suggestion!
This is a hardware issue.
My APP's worked perfectly for 4 months but one day my right Pod suddenly started to rattle like crazy in NC and Transparency modes. Apple will replace these, not much questions asked as they seem to already know how widespread this issue is.
I keep my ears clean and wiped the Airpods clean with a moist cloth almost always before putting them back to the case so I'm not sure is it caused by moisture getting into the microphones or is there just some part that fails after time..