Apple often rolls out background software updates to its truly wireless earbuds like AirPods and AirPods Pro. Usually, these updates focus on minor bug fixes, but a recent AirPods Pro update appears to have made some notable changes to sound quality and noise cancellation.

Following user reports on Reddit and other outlets, RTINGS decided to retest AirPods Pro after updating to firm 2C54. The testing revealed a few notable changes, for better and for worse.

One of the biggest improvements, according to RTINGS testing, came to frequency response consistency. This describes the “variations in a headphones’ frequency response due to their fit on your head.” Prior to firmware 2C54, RTINGS described the frequency response consistency of AirPods Pro as “just okay.” The update, however, made things ”significantly better.”

Another significant improvement came to bass accuracy. While RTINGS had already described AirPods Pro bass accuracy as “excellent,” the 2C54 update makes another “fairly significant improvement.” Elsewhere, RTINGS says the update included a “very slight reduction in mid accuracy” as well as a slightly reduction in treble accuracy.

The most notable change, at least according to users, affects noise isolation. RTINGS says that the update to 2C54 bought a “fairly significantly drop in isolation performance,” particularly affecting the bass-range.

While Apple has not formally acknowledged these complaints from users, it has pulled the the 2C54 for AirPods Pro. This prevents additional users from installing the update, but it doesn’t do much for those users who had already installed it. The update was initially released on December 16 and was pulled shortly after that.

Updates for AirPods and AirPods Pro are often released very quietly, and installed in the background — so most users might not even realize when their AirPods are updated. You can check your AirPods Pro details by going to Settings > General > About on your iPhone, and looking for the “AirPods Pro” tab when your AirPods Pro are connected.

Have you noticed any change in your AirPods Pro sound performance? Let us know down in the comments. You can read the full RTINGS review here.