It seems that Apple has quietly upgraded the audio speech code in AirPods Pro to AAC-ELD, which offers full HD voice quality. This is the same codec that is supported by the latest AirPods 3, however, Apple made no official announcement that it will include this code with AirPods Pro too.
AAC-ELD (Enhanced Low Delay) is a new profile for communication that transfers data at a rate of 24,000 Hz ( + SBR) in mono in both directions. It was mentioned by Apple in the announcement of AirPods 3 last year. The benefit of using AAC-ELD is that it provides HD voice quality which sounds more natural during communication.
AirPods Pro now support AAC-ELD for communication
Developer Marco Pfeiffer discovered the change and wrote about it in a blog post on Medium. He noted how Bluetooth communication uses HFP (Hands Free Profile) which is based on two codecs:
- CVSD – transfers at 8,000 Hz in mono in both directions
- mSBC – transfers at 16,000 Hz in mono in both directions
These low transfer rates mean that companies that use Bluetooth for communication are somewhat limited in the quality that they can offer. mSBC is the preferred codec and is supported by Mac, iOS, and Android, as it provides improved quality, but it is also optional and not supported by all OEMs.
To investigate and confirm his findings as to whether AirPods Pro got the upgrade or not, Pfeiffer used Console.app on his Mac, which shows a detailed log of services, including the Bluetooth daemon. He was able to confirm that his AirPods Pro were using AAC-ELD for communication.
As Pfeiffer only had access to AirPods Pro, he has been unable to confirm whether older AirPods models (first and second generation) also use the new profile.
Although the audio quality is clearly better than the previous profile used by AirPods Pro, it is still not great. As per Pfeiffer, you would need at least 44,000 Hz sample rate in stereo for the best result, but that is not supported by Bluetooth for communication. Still, Pfeiffer considers this the biggest improvement to Bluetooth audio quality since 2009.