Last fall, immediately after the release of the 3rd generation AirPods, Apple subtly improved the sound quality of the AirPods Pro.
Developer Marco Pfeiffer found mention of support for the new AAC-ELD codec in the announcement of AirPods 3. This codec provides voice transmission during calls in HD quality. According to the developer, AirPods Pro received the same codec along with one of the software updates.
AAC-ELD, or Advanced Audio Codec-Enhanced Low Delay, is a variant of the AAC standard used by most streaming services, which also includes improved audio quality and reduced voice delay.
It’s possible that Apple also added the AAC-ELD codec to older AirPods models, but Pfeiffer couldn’t confirm that because he doesn’t own such headphones.
