TL;DR: Apple has confirmed that certain AirPods Pro units experience a sound issue in loud environments, resulting in static, crackling, or strange noise cancellation behaviors. In response, Apple has launched an AirPods Pro service program, where owners of the faulty earphones can get a replacement free of charge.
Apple's service program explains that the issue affects a small percentage of AirPods Pro units manufactured before October 2020. Owners of a faulty pair of earphones will experience either crackling or static sounds which increase while exercising, talking on the phone, or in loud environments. Other problems may be present with the earphones' Active Noise Cancellation, which could include an unexpected loss of bass, or the sudden increase of background noise.
AirPods manufactured after October 2020 aren't thought to be affected by the issue, according to Apple.
While frustrating, the good news is that affected AirPods Pro can be exchanged at an Apple Store or an Apple Authorized Service Provider free of charge. Apple explains that staff will test the earphones to determine whether one or both are affected, before arranging a free replacement. The AirPods case isn't affected by the issue and won't need replacing.
Apple's AirPods Pro were released in October 2019, meaning that anyone who bought the earphones during their first year of availability could be affected by the issue. AirPods Pro owners have been complaining for months about cracking, static, and odd noise cancellation behaviors, and just now Apple has acknowledged the issue and is doing the right thing.
If you own a pair of affected AirPods Pro, you have two years from the date of the original sale to access Apple's replacement program.