Apple has said a small percentage of AirPods Pro units may have some issue related to crackling sounds and some issues related to Active Noise Cancellation. Apple does occasionally feel the need to launch a repair program if the problem is significant enough and it seems with some models produced this year, that is the case.
Apple has specified that, “a small percentage of AirPods Pro may experience sound issues.” – Any that were manuafactured before October 2020.
“An affected AirPods Pro may exhibit one or more of the following behaviors:
Crackling or static sounds that increase in loud environments, with exercise or while talking on the phone
Active Noise Cancellation not working as expected, such as a loss of bass sound, or an increase in background sounds, such as street or airplane noise”
You can find more information about the repair program, as well as what to do if your AirPods have issues here.