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Handhelds Hardware Hacking Medicine Technology

UW Researchers Prototype Sonar-Based Contactless Sleep Monitoring 40

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.
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UW Researchers Prototype Sonar-Based Contactless Sleep Monitoring

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  • by Shoten ( 260439 ) on Sunday June 14, 2015 @10:40AM (#49908563)

    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.

    • by Livius ( 318358 )

      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.

      • by Shoten ( 260439 )

        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

        • by Livius ( 318358 ) on Sunday June 14, 2015 @11:13AM (#49908665)

          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.

        • by n01 ( 693310 )
          Starting with the iPhone 5, the iPhone actually has 3 built-in microphones. They are used to improve intelligibility during phone calls, but unfortunately an app can't record from multiple microphones directly (i.e. by getting 2- or 3-channel PCM sample data). I'm not sure how this is for Android phones.
        • It won't work well for people who can't sleep without their spouse or pet next to them, sure. But a controlled study won't do that person any good.

          Given my insurance, which is good, it would be cheaper to check in to a hotel and use this app to decide if I need formal diagnosis. By the time it comes out, speech recognition will require the hardware issues be solved, so no hardware expense.

          If I feel I have sleep issues and this says no apnea, I can look into other options before incurring medical tests.

          And t

          • by n01 ( 693310 )
            I've heard back from the users of my app that Sonalarm actually worked pretty well when they shared their bed with their partner. The idea is that you place your iPhone on your bedside table (which has to be at your side of the bed, so the other person sleeping will be out of range).
        • 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.

          You create a baseline for the null or empty room, either by capturing the room empty or by creating an average of a few nights' observations.

          Transfer functions don't relate to spatial localization, they're different ways of figuring out directionality and both are independently reliable. Our head

        • by tlhIngan ( 30335 )

          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?

          First off, sonar can be made discriminatory by simple correllation of the signal. That eliminates noises in the room by default. It's usually a brief chirp, and you only have to sample for a few millisecond

    • by n01 ( 693310 )
      I've read on a German website about the UW prototype that it requires a smartphone that can record from two microphones at the same time, so this probably solves the directional discrimination. The UW prototype uses 18-20 kHz which most adults can't hear. I know the iPhone's frequency range and it goes right up to 20 kHz for both playback and recording (disclaimer: I'm the developer of the Sonalarm app [apple.com] that I've referenced in the post and my app uses the 18.5 - 20 kHz range, IIRC).
    • Unless you're sleeping in a dormitory they don't need directionality; the phone can assume any fluctuation (doppler/impluse response/etc) comes from your movement.

      The phone's tiny speaker and mic can probably reach 20-24khz, which is *barely* ultrasonic but outside most human hearing. Your pets may no longer want to sleep with you, however.

      • by n01 ( 693310 )
        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 [sonalarm.net] that I've referenced in the post.)
    • by arielCo ( 995647 )

      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?

      They don't, and they don't need to. Think of the ultrasound motion sensors in car / room alarms: if you emit chirps inside a closed volume they'll bounce off everything solid, and the pattern received at any point depends on everything inside, so you'll know if something moves. If you can keep track of the changes, you know if it's moving rhythmically and at what rate. Using multiple frequencies makes it more sensitive to changes, roughly speaking.

      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.

      Again, no need. Put on some earplugs, or stick your head in

    • Don't most modern phones have multiple microphones on them being used for noise reduction purposes?

      • by n01 ( 693310 )
        Starting with the iPhone 5, the iPhone actually has 3 built-in microphones. They are used to improve intelligibility during phone calls, but unfortunately on iOS an app can't record from multiple microphones directly (i.e. by getting 2- or 3-channel PCM sample data). I'm not sure how this is for Android phones. (Disclaimer: I'm the developer of the Sleep Cycle Sonalarm Clock app [apple.com] that I've referenced in the post.)
    • Batman becomes real alright. Didn't you notice the acronym?

      UW - Universal Wayne.

    • Many phones have 2 mics, to do noise cancellation. Maybe it only works on those

  • The alarm clock that I need has to go the bathroom, fetch a glass of water and pour it on my face. Anything less is useless for me.
    • by n01 ( 693310 )
      Good idea! Why don't you start a Kickstarter campaign for an alarm clock that pours water on your face to wake you up? No need for a robot to go to your bathroom - it can have a water tank.
  • That should mean I can go to the bathroom without turning the lights on, just by having my phone emit ultrasound.

  • by Anonymous Coward

    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.

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