Originally published at: Apple Watch Series 12 and Ultra 4 Add Health Sensing and Audio Intelligence - TidBITS
Apple has introduced the Apple Watch Series 12 and Apple Watch Ultra 4, focusing on the new Health Sensing System and Audio Intelligence, both powered by the new S11 chip.
Health Sensing System
To improve the Apple Watch’s ability to track heart rate and heart rate variability, Apple redesigned its optical and electrical heart sensors, with larger, more power-efficient green LEDs in the optical sensor. Combined with the S11 chip, the new Health Sensing System measures heart rate every 5 seconds—60 times more frequently than before—and heart rate variability up to every 5 minutes, or 24 times more frequently. The more frequent sampling should produce smoother, more representative data by reducing the influence of outlying individual readings. A new heart rate complication displays your heart rate at a glance throughout the day.
Apple is also using the increased sampling rate to power a new Readiness feature that combines recent activity, training load, sleep score, and vitals into a 0–10 score accompanied by a recommendation such as Recover, Pace Yourself, Ready, or Go For It. Other health trackers from Garmin, Whoop, Oura, and others have offered similar features, but I’ve never seen much utility in them. Speaking as a certified running coach, I think it’s important for people to listen to their bodies when training seriously, and some metrics can be useful for athletes. However, most people don’t have the flexibility to change their behavior much based on a readiness score, and they aren’t stressing their bodies enough to bother anyway. What are you going to do, call in sick to work or pass on grocery shopping because you got a 3 on your readiness score?
Apple says it also rebuilt the pedometer model to provide more accurate distance measurements during indoor walk or run workouts, and the S11 chip allows more accurate step counts throughout the day. More accuracy is always welcome, but remember that the 10,000-steps goal originated with a 1960s Japanese marketing campaign, rather than scientific research. I can’t see a more accurate step count making a difference to most people’s health.
Audio Intelligence
More interesting is the new Audio Intelligence feature, which uses the microphones in the Series 12 and Ultra 4 to listen to ambient sound and provide four features, two familiar and two new ones that require additional unpacking:
- Sound Recognition: This long-standing feature of the iPhone, iPad, and Vision Pro listens for and reports on ambient sounds like doorbells, crying babies, and sirens. It’s important for those who are deaf or hard of hearing, and having it on an Apple Watch, even when the iPhone isn’t present, could provide a welcome awareness of nearby events.
- Music recognition: The music recognition feature Shazam isn’t new to Apple Watch, but the Series 12 and Ultra 4 can now automatically recognize nearby music and display the result in the Music Recognition widget in the Smart Stack.
- Live Rewind: If you have trouble hearing or remembering what was just said in a conversation, you can double-press the Digital Crown to show the previous 15 seconds of conversation as a text snippet. You can also ask Siri about the snippet or save it to the Siri app for later reference.
- Siri Recap: Live Rewind works only on the last 15 seconds, but Siri Recap creates high-level summaries of conversations that you can review later. When it’s turned on, Apple Intelligence automatically generates a title and key points in the Siri app.
You’re probably thinking, “Wait, so if you enable these features, your Series 12 or Ultra 4 Apple Watch can be listening to everything around it all the time?” You would be excused for feeling that’s a bit creepy, but Apple took pains to emphasize the privacy features surrounding Audio Intelligence, including:
- No recordings: These features don’t create or store audio recordings, and the raw audio data is inaccessible to watchOS, apps, the user, and Apple. A new Secure Exclave compartment on the S11 chip processes that raw audio in isolation from the rest of the system, then immediately deletes it.
- User control: Apple says that users must enable each Audio Intelligence feature, decide when and where Siri Recap takes notes, and toggle it on and off from Control Center. But really, will most people who want to use it ever turn it off?
- No speaker identification: Audio Intelligence doesn’t identify speakers or attribute speech to different people—Apple says that’s to protect privacy, but I suspect it’s also a technological limitation.
- Curated summaries: Siri Recap produces only a brief, high-level summary of conversations, not a full transcript, and Apple says it will try to exclude sensitive information like financial information and government-assigned identifiers.
- Activation alerts: Much like the recording light on Meta’s AI “perv” glasses, Live Rewind attempts to make it clear that it has been activated with an audible chime, plus a full-display animation and microphone indicator. I very much doubt most people will understand what these alerts mean.
- End-to-end encryption: Live Rewind text snippets that you save and Siri Recap summaries are end-to-end encrypted when synced between your devices through iCloud. Because Apple doesn’t hold the encryption keys, it can’t read the synced data.
- Auto-deletion: If you take no action, Live Rewind snippets disappear about 30 seconds after the Apple Watch display dims, and Siri Recaps auto-delete after 7 days if you don’t explicitly save or export them.
Sound Recognition and automatic Shazam recognition will be available immediately with the Series 12 and Ultra 4. Live Rewind and Siri Recap will arrive in beta in late 2026, initially in English, and won’t be available in the EU at first. They also require Siri AI and an iPhone 16 or later, excluding the iPhone 16e, and Apple says daily usage limits will apply because they rely in part on server-side models.
Apple seems to have said nothing about how Audio Intelligence interacts with laws governing the interception or electronic overhearing of conversations. The lack of a saved audio recording isn’t necessarily a Get Out of Jail Free card: some federal and state laws regulate acquiring the contents of a conversation electronically, and consent requirements vary by state. We’ll see if Live Rewind and Siri Recap attract legal scrutiny in areas with stricter consent laws.
Other Details
Beyond the Health Sensing System and Audio Intelligence features that come with the improved heart rate sensors and S11 chip, the Ultra 4 remains largely unchanged. The main improvement comes in battery life, with the Ultra 4 offering up to 50 hours of everyday use. The new Extended Workout mode delivers up to 25 hours of battery life with full GPS and heart rate readings; the Max Extended Workout mode can track outdoor runs, walks, and hikes for up to 45 hours while still taking GPS readings every second.
Everyday battery life for the Series 12 is unchanged at up to 24 hours, but it will now offer up to 10 hours of battery life during an outdoor workout—25% more than the Series 11. Both the Ultra 4 and Series 12 charge faster than ever, with just 15 minutes of charging adding 18 hours of battery life to the Ultra 4 and 12 hours to the Series 12.
The Series 12 brings back ceramic cases alongside the usual aluminum and titanium—ceramic last appeared with the Series 5. Aluminum models replace Ion-X front glass with Ceramic Shield 2, which Apple says is 60% tougher than the Series 11’s Ion-X glass, while titanium and ceramic models use sapphire front crystals. The Ultra 4 case continues to rely on 3D-printed recycled titanium and is essentially unchanged.
The Series 12 aluminum models come in black, space gray, light gold, and a new dark bronze finish. The titanium models come in natural titanium and radiant gold, and the ceramic cases are available in pearl white and night blue. The Ultra 4 still comes in natural titanium and black, just like the Ultra 3. Apple also updated band colors and patterns, most of which are quite muted. The metal Milanese Loop now comes in radiant gold and dark bronze to match those case finishes. The Ultra 4’s silicone Ocean Band now comes in translucent black, translucent kelp, and translucent gray.
Starting prices for the aluminum and titanium Series 12 and the Ultra 4 remain unchanged from the previous generation: $399 for aluminum Series 12 models, $699 for titanium, and $799 for the Ultra 4. The new ceramic Series 12 starts at $899. For budget-conscious buyers, the Apple Watch SE 3 remains available starting at $249.
Apple is accepting pre-orders now, with availability starting on 18 September 2026.