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UW Researchers Prototype Sonar-Based Contactless Sleep Monitoring

Posted by timothy on from the while-you-were-sleeping dept.

n01 writes: Researchers of the University of Washington are testing the prototype of their ApneaApp to diagnose sleep apnea, a health problem that can become life-threatening. To monitor a person's sleep, the app transforms the user's smartphone into an active sonar system that tracks tiny changes in a person's movements. The phone's speaker sends out inaudible sound waves, which bounce off a sleeping person's body and are picked back up by the phone's microphone. "It's similar to the way bats navigate," said Rajalakshmi Nandakumar, lead author and a doctoral candidate in the UW's department of computer science and engineering. "They send out sound signals that hit a target, and when those signals bounce back they know something is there." In technical terms, the app continuously analyzes changes in the acoustic room-transfer-function (sampled at ultrasonic frequencies) to detect motion. This is very similar to what the iPhone app Sleep Cycle Sonalarm Clock does, except that the UW researchers have improved the sensitivity of the method so it can precisely track the person's breathing movements which allows it to not only detect different sleep phases but also sleep apnea events. The advantage in both use cases is that the sleep monitoring is contact-less (there's nothing in the user's bed that could disturb their sleep) and doesn't require any additional hardware besides the user's smart phone.

5 of 40 comments (clear)

  1. Uh oh...Batman becomes real? by Shoten · · Score: 4, Interesting

    Turning smartphones into sonar devices to monitor movements. I'm torn between "this is really cool!" and "these people are so full of shit and just trying to publish something to get tenure!"

    I wonder how they solve the problems of directional discrimination without multiple microphones? How can they tell what direction a response comes from, with only one mic? And how do they intend to make this work on multiple phones, for that matter...with their vast differences in both microphone and speaker setups? I'm really skeptical of this.

    They also talk about using ultrasonic frequencies...which I also doubt most phones can actually produce.

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    1. Re:Uh oh...Batman becomes real? by Shoten · · Score: 2

      How can they tell what direction a response comes from, with only one mic?

      It came from the person sleeping.

      The other problems, though, could be harder.

      Which person? How can they tell the difference between the person sleeping and...

      The other person sleeping next to them?
      The pet in the room?
      Curtains, gently blowing in the breeze?
      The person shifting in their bed?
      Sounds from heating/cooling coming online and the air shifting around in the room as a result?

      How can it tell the difference between a response...a change in the state of something in the room...and a change in the object composition of the room itself? Without directionality, I don't see how it's possible. And indeed, as someone else pointed out, they did say that it requires phones with two microphones...which I missed when I read the article. So the point seems valid...and most phones won't be able to do this. Come to think of it, I am trying to think of what phones I know for a fact have dual microphones, and I'm coming up short.

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    2. Re:Uh oh...Batman becomes real? by Livius · · Score: 3, Insightful

      Most people don't bring their pets to medical examinations.

      A home test might have some utility but it's not a proper sleep study.

    3. Re:Uh oh...Batman becomes real? by n01 · · Score: 2

      I've had users report back that the Sonalarm app worked well for them while sharing the bed with their partner. You have a bit of directionality because both the loudspeaker and the mic are located at the bottom edge of the iPhone, and also range is limited to around 1 to 2 meters, depending on the selected sensitivity. (Disclaimer: I'm the developer of the Sleep Cycle Sonalarm Clock app that I've referenced in the post.)

  2. Just listen for the snores by Anonymous Coward · · Score: 2, Interesting

    In all my nights doing polysomnographies, you rarely have silent obstructive sleep apnoeas, probably a better use for a microphone. If you have silent central types, you should worry about something else than dodgy sleep.