Audio Intelligence is the software half of what Apple announced for the Series 12 and Ultra 4, and it runs on the S11 chip, the built-in microphones and on-device models, without creating or storing audio recordings. Live Rewind displays a transcript of what was said in the preceding 15 seconds, and a double press of the digital crown brings it up. Siri Recap works at the other end of the day, generating titles, summaries and key points from conversations to read back in the Siri app, and it leans on Private Cloud Compute rather than staying entirely on the watch. Sound Recognition runs locally and can pick out something like a doorbell going off.
Not all of it ships with the watches on September 18. Some of the audio features arrive in beta this fall. watchOS 27 lands earlier, on September 14, with a Siri Modular face that revives the old Siri face Apple removed in a later watchOS update, and it is expected on every Apple Watch model rather than only the new hardware. The hardware change underneath all of this is the rebuilt sensor on the back of both watches.