I had this issue and have already had both pods replaced. The right one started first, was replaced by Apple after a chat session with Support. A few weeks later, the left one started having the problem. It only took a few minutes in Chat to get them to initiate a replacement of the left one. They sent me new buds by mail and then I returned the old ones in the same box.
In both cases, the issue was a rapid popping sound that sounded like a crackle that occurred when I spoke on the phone or even moved my head around. It immediately went away if I switched noise cancellation to OFF. If I put it on Transparency or Noise Cancellation, it came back.
I bought my AirPods Pro in late 2019.
BTW, when you receive one new bud, it's a pain to get the other bud and the replacement one to work together with the same case. One issue is if the replacement bud was shipped with older firmware. You need to put that one bud in your case, take the other one out, pair the case and new bud with your phone, plug the case into power, then wait about 30 min with your phone nearby for the firmware to update. Then try re-pairing with both buds in. I had to repeat several different times to get it to work. It might have gone easier if the old bud to be sent back wasn't still in range of the case.
