Apple released a firmware update for their AirPods Pro back in December, according to a recent report this update may have reduced the effectiveness of the Noise Cancellation feature on the headphones.
The news comes in a report from RTINGS who have said that the 2C54 firmware update that landed on the 16th of December has made the noise cancellation feature worse.
Update 01/10/2020: After updating to Firmware 2C45, we retested the headphones and our results showed a fairly significant drop in isolation performance, primarily in the bass-range. This means that with ANC turned on, these headphones won’t do nearly as good a job blocking out the low engine rumbles of planes or buses as they did before this update. This review reflects these changes.
Whilst the update did improve a things like base accuracy it would appear that it may have reduced the effectiveness of the Noise Cancellation, we presume this will be fixed in a further update.