[username190]

Rtings did find something similar with the AirPods Pro, seeing a "fairly significant drop" in December 2019 and another "slight decline" in October 2021:

> We've tested 'Noise Isolation' with a couple of other firmware updates. We didn't get noticeable differences with firmware update 2B588, released in November 2019. Apple may have tweaked the ANC in this update, but not enough to noticeably impact the overall performance. There have also been user reports that the ANC became worse after firmware update 2C54, released in December 2019. After updating this firmware, our results showed a fairly significant drop in isolation performance, primarily in the bass range. This means that with ANC turned on, they won't do nearly as good a job blocking out the low engine rumbles of planes or buses as they did before this update. Our latest retest uses firmware update 4A400, released in October 2021, which shows that their overall noise isolation performance has been further weakened. [0]

[0] https://www.rtings.com/headphones/reviews/apple/airpods-pro-...