AirPods Max active noise cancellation pared down by newest firmware
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."
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.
Read on AppleInsider

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!
Else there needs to be a class-action. https://t.co/am29MojmGc-- Quinn Nelson (@SnazzyQ)
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.
Read on AppleInsider
Comments
This could be controlled in the iPhone settings. If someone is drilling, banging, using a hedge trimmer, vacuuming and you don't want to be listening to music, strong ANC can block it. If the ANC isn't strong enough, it needs music playing on top to block out the noise.
B. RTings only makes a vague claim of reduced ANC performance..."blocks out a bit less noise between the mid-bass to high-bass range than the previous firmware."
C. Unlike the other headphones in the same category (like Sony XM4), RTings didn't bother to retest other categories for the AirPods Max with 4E71 firmware.
^^^ That last part is another reason RTings credibility on headphones takes a hit. You can't be cherry-picking which firmware updates to test extensively.
B. It has been widely noticed that ANC has got worse over time with the APPs. There was a professional study someone did a while ago comparing the pre and post update APPs, in which they found a marked difference in ANC performance.
C. Okay? So? A regression in one category isn't balanced out by a potential improvement elsewhere. If the ANC is worse, it's worse.
I don't want to hear tinny, whiny noise leaking in.
If anything, Apple is the company doing the customers a favor if they're lowering ANC is order to improve other characteristics for the actual audio reproduction.
anyways…
I love my Bose because they remove a lot of rumble noise in the plane and that makes the trip a lot less tiring. Too bad that Apple is letting in precisely those frequencies more.
Second, the video looks like it compared AirPods Pro in Transparency mode with and without ANC. This is the same as wearing and not wearing any hearing protection at all. Turning the them completely off would give more protection than wearing them with the Transparency mode on. In fact, the reports might be louder with Transparency on, depending on the volume setting, ie amplified louder than without AirPods Pro at all.
So they "benefit" with the ANC on because they also provide some very slight protection because of the fitted silicon tips that other AirPods lack. And still not adequate for the range. One day I'll have to try dedicated electronic hearing protection. I've tried bespoke molded earplugs and have not been happy with them.
Apple should tell us what the wanted to accomplish with the firmware upgrade, but they are historically vague to tight-lipped with a lot of their updates.