There have been only anecdotal reports about AirPods Max having less effective Active Noise Cancellation since May's firmware update — until now.
In May, Apple released firmware for the AirPods, AirPods Pro, and AirPods Max, which didn't add new features but tweaked the firmware of the personal audio devices. It appears that the firmware update has made the AirPods Pro's ANC system slightly worse.
Testing performed by RTings.com on how the AirPods Max handles noise isolation was updated on Friday, warning that the introduction of firmware 4E71 has changed ANC. After the update, the report found the system "blocks out a bit less noise between the mid-bass to high-bass range than the previous firmware."
RTings confirms that Apple has nerfed the effectiveness of noise cancellation on AirPods Max with firmware 4E71. This is the iPhone throttling saga all over again. There may be a good reason; if so, SAY SOMETHING!— Quinn Nelson (@SnazzyQ) October 22, 2022
Else there needs to be a class-action. https://t.co/am29MojmGc
The range found by the report spans low rumbling sounds, such as vehicle motors, train travel, and plane engines. Following the update users could expect to hear those more post-update than before — but this will vary per individual user based on hearing.
Even so, the report adds that while the update did slightly change the level of isolation it delivers, it's still a "relatively minor difference." ANC still reduced sounds such as ambient chatter and AC units "extremely well."
While there has been some low-level chatter about the ANC difference since the firmware's introduction, there hasn't yet been any official confirmation from Apple about the change. Research by AppleInsider also indicates there hasn't been an increase in service requests since the update, connected to the firmware or otherwise.