In the latest iOS 12.2 beta Apple has improved audio message quality by switching to a different codec for files.
Details on the improvement in audio quality were shared on Twitter this morning, and we confirmed the change on our own devices. Apple previously used the .AMR file format for its audio messages, but in the beta, has swapped over to .CAF.
The Opus codec, coming in a 24000 Hz, is a big increase from the old AMR codec at 8000 Hz. Opus is used by other messaging services like WhatsApp, Telegram, and WebRTC.