Sonar: Revolutionary contactless sleep tracking

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Revolutionary contactless sleep tracking

Introducing a new way of sleep tracking using ultrasonic waves.sonar2

Have you been interested in monitoring your sleep, only to be repelled by the fact that you need a phone in your bed? Or an expensive hardware?
Sleep tracking has been known as a notoriously uncomfortable process, where you worry about hot phones under your pillow and cables twisted around your legs.
Over the last year, we have developed a way to put that all behind. A way to track movement at a distance — with ultrasound.

A sonar on your phone.

You don’t need any new hardware for that – everything is already in your smartphone. Microphone, speaker and a hell of a computing power. The only thing missing was the code. Not anymore.

Sleep as Android now uses your phone as sonar to contactlessly track your sleep.

With other sleep trackers, you need to have some device in your bed – a wearable or a smartphone. With Sleep as Android, you just put your phone on a nightstand and go to sleep. It will monitor your movement with the sonar.

And not only the movement!

Breathing detection

At half a meter range, sonar is so accurate it can measure your breathing rate.

Sleep as Android can also measure your breathing at range with sonar.

In the morning, you’ll see a line showing the development of your breathing throughout the night.

What is this good for? People usually don’t have a clue whether they suffer from any nightly breathing disorder.
Sleep as Android will keep an eye (umm…ear actually) on your lungs and will show you in the morning how many times you have stopped breathing.

Health concerns

  • Sonar emits sound that is on the edge of audible and inaudible sound (around 20 kHz). The frequency itself is perfectly safe for human hearing.
  • The volume of the sound is maximally around 50 dB, which is less than the volume of a normal conversation. A refrigerator sound level is comparable.
  • 1 meter away from the phone, the sound level can be compared to a pin falling to the ground

Ultrasound does not pose any threat to your health.

  • Since the sound is so low, animals usually do not care about our sonar.


  • On some devices you can hear audible artifacts during sonar tracking. Some of the signal gets into audible spectrum. This can be due to insufficient quality of the speaker, or some post processing which is applied to the audio output.
  • Sonar won’t work with headphones, so it is not possible to listen to lullabies privately before sleeping.

How to try it?

  1. Download Sleep as Android app from Play Store.
  2. Start the app, go to Settings > Sleep tracking > Sensor and select Sonar.
  3. Let the app test your phone if sonar works for it.
  4. Start sleep tracking by tapping on the moon button in the main screen of Sleep as Android.


Please see the docs.


18 thoughts on “Sonar: Revolutionary contactless sleep tracking

    1. Hello Alison, the blue numbers are maximum and minimum of your breathing rate throughout the night.
      When you stop breathing for a considerable period of time, we add a marker to your graph. You can also set up an Apnea alarm to wake you up when you stop breathing.

    1. Hi Dinh, could you please try it? The heater will probably not emit ultrasound signals, so it shouldn’t interfere with the sonar measurement. But please try it (you can do that with the free version) and then please send me a debug log (menu-report a bug) and a screenshot to

      1. Hi Jiri, just being curious as I never asked this before. Does the sonar work if I use a Pebble watch with heart rate sensor? I observe that on nights when I sleep with HR on, there is no sonar recorded and vice versa. Not sure if this is how the app is set up(?)

  1. Hi Jodi, I have been using my smartphone for a long time tracking my sleep with your app. I have a tablet so I used the tablet with the sonar in addition to the smartphone. The results seem quite different. The smartphone shows consistently about half (plus) the deep sleep as the tablet shows. For example, last night the smartphone shows 2:48 4x and the tablet shows 4:59 8x. Have I done something wrong with the setup?

  2. Hi! I am just giving sonar a try. Before sonar, I used to listen to audio while going to sleep. I sleep alone so don’t use headphones (which the FAQ says you can’t do) and just play it quietly into my space. The problem is the volume now turns up involuntarily every few minutes. I can turn it down manually, but it just keeps continuing to rise again every few min. Obviously, this doesn’t work since increased volume can startle you awake! Is there anything I can do about this issue? A setting I can change, etc?

    1. Hi Danae, yes, we need to keep media volume up for the sonar, so you can’t change it by volume buttons. But you can change the lullaby volume separately in Settings-Lullaby.

    1. Hello Charrat, yes, there should be no problem with using both at the same time. The only issue would be if there are some exposed continuously moving parts in the machine that would get detected by the sonar.

  3. Hi there, was trying sonar with galaxy s7 edge, on 10% and on 50% setting but the sound recording also recorded the sonar beebs. I read a article about this problem but it didnt come up with a solution. I was wondering if you know about a “fix” for this or is it still a mystery?
    Ps: im not a sound expert and was wondering if i should just switch to motion detection or try a smart watch or other device?

  4. Hello, is it normal to hear sonar beeps/noise during playback in the morning?
    My device is S7 Edge and I can definitely hear those weird sounds from sonar while playing.

    Is this an issue to be solved, or not?


    1. Hi Valo, sorry for the late response. Yes, on some devices this is normal. You should definitely experiment with the Settings>Sleep tracking>Test sensor. You should be able to get a balance of the sonar volume where you would not hear the artifacts, but sonar would be still working.

      We are working on solving this issue on our side with the second round of sonar redesign.

  5. Hello,
    I have a refrigerator in the kitchen which produces some noise when it’s working. In my bedroom which is next to the kitchen I can hear such sounds. And I wonder if such sounds will be perceived and consequently recorded by the Sonar as snoring?

    1. Hello Nina, they should not. We check for frequencies not only of the sound itself, but also for some rhythmicity in the sound. So unless the refrigerator makes sound with the breathing frequency (around once per four seconds or less often), then it’s okay 🙂

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