Google's latest Nest Hub smart display detects motion to track your sleep

It'll let you monitor your slumber without cameras or wearables.

It's been three years since Google launched its first smart display, with the Home Hub (later renamed the Nest Hub) claiming its space on our countertops and bedside tables. Since then, the company has made bigger, more useful versions of its connected screen. But they've mostly been little more than digital photo frames with speakers and Assistant built in.

With its latest Nest Hub though, Google has added a surprise feature that could make the smart display more helpful. The second-generation Nest Hub has a Soli radar sensor that detects motion, and it uses that data to determine if you're asleep.

Sleep-tracking via motion sensing

To recap, Soli was the product of Google's Advanced Technology and Projects (ATAP) division that used radar to detect motion "at various scales." It was implemented at a mainstream level in the Pixel 4 to wake the phone when you waved your hand over it. Soli has also shown up in the latest Nest Thermostat as a means to recognize if someone's in a room and to adjust the temperature accordingly.

Google Nest Hub 2nd gen showing a sleep report, and a phone showing the Google Fit app version of that report.

On the new Nest Hub, Soli will allow the device to "watch" while you sleep — without a camera. Google is calling this feature Sleep Sensing, and it's opt-in. You'll need to set the display up within a couple feet of your bedside and angle it toward your torso. After a calibration and setup process, the sensor can catch movements at "incredibly precise levels," according to senior product manager Ashton Udall. Things like the "micrometer movement of your chest moving in and out while you're breathing and laying in bed," for example. Then, Google's algorithm will analyze your motion and determine when you're asleep, restless or awake and give you a report each morning. You can also choose to share that info with the Fit app to see your slumber patterns over time.

This of course raises a few concerns, with the most obvious being the fact that there are plenty of movements in bed that have nothing to do with sleep. So what happens then? Google's algorithms will look at the motion data and analyze what patterns are sleep-related movement and ignore things that aren't. The Nest Hub is also designed to monitor one person at once, and during calibration you'll have to lay in the middle of where you usually sleep. It's not yet clear how well the device will be able to parse out movements of your partner — how well all this works is something we'll have to see for ourselves when we get to test one.

Those who usually sleep alone and have a partner stay over every now and then may also need to recalibrate their system or discount those nights (there will be an option to exclude a night on the display). Udall said you don't need to sweat the odd irregular evening since the goal here isn't to fixate on every day's results. "It's about your trends," he told Engadget. "We don't want to get people hung up on their nightly data." So if your dog jumps into your bed during a midnight thunderstorm, you shouldn't worry about it screwing up your results.

Animation showing what Google's Nest Hub Soli radar sees in its sleep sensing spectograph

Besides the system's effectiveness, there are also questions around privacy. Because it's only using radar and there's no camera onboard, the Nest Hub is at least not going to have images of your bedtime activity. The spectograph of what it sees is similar to a very busy ECG — lots of lines that rise and fall. The collection of that raw data is also processed on the device's onboard machine-learning chip, and what does get sent to Google is interpreted stuff like how long you were asleep and when you were restless. If Sleep Sensing is enabled, there will also be a visual indicator on the screen so you or your guests can be aware that the Nest Hub is monitoring your sleep.

The second-gen Nest Hub has a third mic (compared to the two before) and uses them to detect if you've coughed or snored overnight. It'll only turn on the mic when it senses you've fallen asleep and the audio info is processed locally and not sent anywhere. The display also has a new temperature sensor which it uses in addition to the ambient light sensor to identify changes in your environment. In the morning, you'll get a report on how you slept and if things like how cold or bright it was affected your slumber. You'll also see this in the Fit app and over time you can identify trends like whether you sleep better in the winter or if you wake up earlier when there's more light.

To develop its system, Google conducted over 110,000 nights of tests with about 10,000 individuals and benchmarked against established sleep studies. It found that compared to polysomnography studies, which Udall said are the "gold standard," its algorithms yielded no statistical difference. Also, when compared to popular devices in the market "and even clinically approved sleep trackers out there," Udall said the Nest Hub's performance was "on par or even better in many cases."

Google Nest Hub Sleep Sensing and Google Fit. The smart display showing sleep duration and a phone showing Google Fit telling the user how much sleep is recommended.

Again, it's hard to judge this without having tested it, but it's worth noting that many wrist-worn fitness trackers also detect your heart rate overnight. With that data, they can tell how deep you're sleeping and what restorative zones you enter, which might be more insightful. But Google's approach appears to be more about what's around you (noise, temperature, movement and disruptions) as opposed to your heart rate and body temperature. That could help with things that you have more control over, like turning the heat up or drawing the blinds, for example.

That's potentially the most helpful aspect of Nest Hub's Sleep Sensing feature, as Google integrates its findings with Assistant to suggest things like earlier bedtimes or routines for your bedroom lights. After 14 nights of tracking, Google will be able to recommend a schedule to "optimize sleep efficiency," based on guidance from the American Academy of Sleep Medicine (AASM), the American Heart Association and the World Health Organization.

Sleep Sensing will be free as a preview for anyone that buys the new Nest Hub until next year. Since Google just integrated with Fitbit, Udall said "we're just getting to know each other but we're actively exploring ways to bring these experiences together to create one awesome sleep solution from Google."

Google Nest Hub 2nd gen in four colors

Improved audio and connectivity

While sleep-tracking is the standout feature of the new Nest Hub, there are still a few improvements over its predecessor worth noting. It has an upgraded audio system similar to the Nest Audio speaker, promising 50 percent more bass than the original Hub. The new ML chip onboard should make it faster to respond to your Assistant requests (only available in the US), while its built-in Thread radio will enable support for the budding Project Connected Home over IP platform in future.

With its new third microphone, too, the Nest Hub should be able to hear you better from further away, and the Soli sensor enables gesture controls like tapping the air in front of the screen to pause playback or stop a timer. While not much else about the Nest Hub is different (its screen is still a cute 7 inches, for example), Google is offering a new color option: Mist. It's a light pastel blue in addition to the existing Charcoal (black), Chalk (gray) and Sand (pink) options.

The new Nest Hub costs $100 — $50 less than the original did at launch. It's available for pre-order today on the Google Store, Best Buy and Walmart and will arrive in stores on March 30th, when you can also find it at Target and The Home Depot. For those who want to track their sleep without a wearable, mattress sensor or camera, the Nest Hub could be potentially helpful. Google is clearly finding creative means to track your health without wearable sensors, just as it did with letting people measure their heart and breathing rates with their phone cameras. The company continuing to flex its software prowess for health-monitoring is an interesting sign of things that might come, especially as it starts to integrate more deeply with Fitbit.

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