Sleep as Android measures your sleep using various sensors. You can use sensors that are in your phone, or purchase additional devices and use their sensors, or use a combination.
1. Motion sensors
Basic sleep tracking is done using a motion sensor.
Can be either in the phone or in a connected wearable. If you want to track motion using a wearable, see Smartwatch and Wearables.
Our invention — the sonar — brings contact-less motion tracking. No more need for a device attached to your wrist or in the bed. It uses your phone’s speaker and microphone to sense movement in the near surroundings. Can be used only on the phone. Can detect breath rate in ideal conditions.
You don’t need any new hardware for that – everything is already in your smartphone: microphone, speaker, and required computing power.
Sonar can use different frequencies, you can change the frequency in Test sensor section - see sonar testing section bellow.
During tracking with sonar the phone produces ultrasonic signal (which cannot be heard by most). Even tiny movements distort the reflected signal which allows us to track them when we record them with the microphone.
On many devices Sonar tracking is so precise we are even able to track your abdominal movements and display your Breath-rate in the sleep graph.
|Sonar won’t work with connected headphones.|
The sonar sensor might not work on Android 11, when the tracking is started automatically due to changes in the permissions - apps running in the background cannot ask for the mic.
To workaround this we would need to have the "Draw over other apps permission" and start a transparent short lived screen before we start the sleep tracking service.
Please see the history of the issue here:
The slider changes the strength - the higher the sensitivity, the higher the strength
Choice of different frequency of the sonar signal
Passive infrared sensor is mounted on the Sleep Phaser and can detect breath rate in addition to coarse movement.
See How to track sleep for details on optimal setup of your sensor in the bedroom for best results.
2. Body sensors
2.1. Heart rate sensors
Heart rate is used to better distinguish awake state.
See Heart rate docs.
3. Breath rate / SpO2 sensors
Breath rate detection is used to monitor healthy levels of breathing and tries to catch early signs of breathing disturbances.
See Breath rate docs.
4. Light level sensors
Ambient light sensors that are present in nearly every smartphone measure the level of ambient light in your bedroom.
See Light level detection docs.
5. Testing sensor
Settings → Sleep tracking → Test sensor
You can test sensor function - we recommend testing it especially when using sonar, to make sure sonar is supported on your device.
You should see a green graph, reacting to your movement. The label of the graph tells you, which sensor is used for this test - this sensor will be used during the sleep tracking.
5.1. Accelerometer testing
Accelerometer sensor is a system sensor, so there are rarely issues with this sensors.
5.2. Sonar testing
Sonar testing screen allows you to test the capability of your phone to produce the signal, the strength of the sonar signal, and also changing the sonar properties - the frequency and the sensitivity.
Sonar testing screen is always labelled as "Testing sensor: Sonar".
The slider changes the strength - the higher the sensitivity, the higher the strength
Choice of different frequency of the sonar signal
The number you see in the middle of the screen is strength of the signal - the higher th better.
The Sleep Duration is total sum of all your sleep phases (Light, REM, and Deep), not counting the awake phases - because when awake, you are actually not sleeping.
So on default settings, the Sleep duration is always a bit shorter than the duration of tracking.
If you wish your Sleep duration is the same as tracking duration:
Disable the awake detection in Settings → Sleep tracking → Awake detection.
You can also try to adjust the sensitivity of each type of settings to get optimal results. In most cases, too much awake periods are caused by significant HR peaks.
If you are not sure, where those awake periods come from, please use Left ☰ menu → Support → Report a bug, and send us the application log.
Enable the tracking in Settings → Sleep tracking → Wearables →Bluetooth Smart (might be hidden under Advanced section).
Try to pair with your device (this may not be required for all devices and OS versions).
Make sure no other app is using your device while sleep tracking.
If nothing helps please send us a debug report using Left ☰ menu → Support → Report a bug..
|BT Smart heart rate tracking only works from Android 4.3 onward|
We use a different input than polysomnographists, and define our own sleep phases, reflecting an objective aspect of sleep, easy to measure with common devices. One naturally needs to ask whether there is any relationship between the EEG-phases and our ACT-phases.
Fortunately, several research teams raised similar questions before (See this one, or this one, or this one, or this one). They measured a bunch of people on a traditional polysomnograph and recorded their physical activity at the same time (By filming them and then counting the movements manually, or by using accelerometer readings). The published analyses show that there indeed is a significant statistical relationship between EEG-phases and body movements.
You can also read about comparison of Sleep as Android algorithms and Sleep lab results on our blog here.
Battery saving mode currently resumes full tracking before the smart wake up period in order to find the best moment for your wake up, so the tracking uses up just a fraction of the battery consumption for the whole night. If the battery would drop under your defined stand-by threshold (default: 10%) the battery saving mode will re-occur.
Accelerometric sensors are really sensitive, which is great for sleep tracking. Normally, what you see when you leave the phone on the table gets immediately dwarfed when you do some more significant move. Just leave phone on the table for a while and you will see a dramatic development, but then move the phone and you will see all the development is really tiny in comparison to the new peak.
So what you see is random noise, given by very small vibrations of the table or in very calm areas by seismic movement. We mark the data relatively, so you always get it distinguished into light and deep sleep. But the algorithm works well only in conditions that are assumed by it, i.e. in the bed with relatively large movement peaks.
To be more specific, if you leave the phone on a table, you can get values perhaps on the scale of 0.000001 to 0.000009 m/s2 (The value is made up here, but it is physically very small). In the bed, you may get values from 1 to 9 m/s2 (which is physically large). The algorithm sees though just that the high value is 9 times higher than the low value, in both cases.
We had to do this because every accelerometer (in different cell phones) measures differently, so we couldn’t assume any standard conversion formula that would respond to absolute values.
So if you use the phone in the bed, it is in fact drastically different from measuring on a calm spot, just like the table.
Please do not hesitate to ask for any clarification at firstname.lastname@example.org. You can also read more about comparison of our data with the sleep lab results in this post.
This depends on several factors. The general rule is to not allow the pet to move your phone, ideally only your movements should move the device. So in this case it’s best to place Your device either under the pillow or to have an armband or smartwatch/smartband. If your pet is a calm one, it may just work. However, if your pet is used to jump in and out of bed several times a night, the sleep tracking will most probably register these events as light sleep occurrences.
Ultrasound is generally considered safe if it is at normal volume. Regarding health effects, it works in a similar way to normal audible sound, i.e. very loud ultrasound can damage your hearing, whereas at low volume it is safe to hear. When using speakers, smartphones are nowhere close to be able to produce such loud sounds as to damage your hearing.
We also use ultrasound that is very close to the hearing range (around 20 kHz), so the effects of the ultrasound are almost identical to hearing a high pitched sound at the same volume (expect you can’t hear it at all).
The ultrasound volume we use is around 40 dB – which is lower than normal speech volume. You can measure the sound level yourself using e.g. this app.
For pets that are able to hear it, the ultrasound emitted from Sleep as Android is a constant low noise. The situation is similar to e.g. refrigerator noise. It is there, you can hear it, but it’s not so much disturbing. The ultrasound definitely cannot damage your pets hearing at the volume used in Sleep as Android.
Bats can be confused and fly into walls.
The only difference between normal audible sound and our sonar is that the frequency is a little higher (normal frequencies 2 Hz-20 kHz, our sonar frequencies 18 kHz-22 kHz). This is so small difference for the mic and speaker membranes that there is definitely no chance of damage, even with prolonged usage.
Usually this is not caused by the sleep tracking directly as this is usually not consuming too much resources (usually around 1-3% battery per hour of tracking).
The issue appears because we hold a wake lock (keeping the phone awake) – any badly written apps may access the CPU extensively during the sleep tracking time. We suggest checking which services are running before you get to sleep.
For us it is hard to debug this. Also battery statistics are not a hint here as all battery consumption is accounted to the app which holds the lock even it did not consume the battery – this is by design in Android.
To conclude, this issue may happen, although we did not get any similar reports for a very long time now. But the most probable cause is some wrong 3rd party service or app on your device.
To see more on the issue we would need a debug report (menu > report a bug).
A good test would be to reboot your phone before sleep tracking (or kill any unnecessary services running) and see if that helps.
At first Sleep as Android may look complex with all its options, but in fact it is fairly easy to get started improving your sleep and wake up.
You can delve deep into all the amazing options Sleep as Android provides later on. But to get started just rely on our carefully selected defaults.
Use the top right plus icon to set up your Alarm time (e.g. 8:00). Tap the desired time directly on the clock - hours first, minutes second.Figure 1. Tap on the (+) iconFigure 2. Tap on the desired time - hours firstFigure 3. Tap on the desired time - minutes second
Confirm the selected time with SET button, it will show you the new alarm settings. Confirm the alarm with DONE.Figure 4. Confirm the time with SET button.Figure 5. Now you see the new alarm’s settings.Figure 6. Confirm with DONE
Smart wake up makes sure to find the best time for your wake up between 7:30 – 8:00 based on your sleep cycle.
You can now see the alarm scheduled on the main screen.
Tap the moon and Sleep tracking starts, we use your phone’s sensor to find out what sleep phase you are in (see How it works).
We recommend turning on airplane mode during sleep tracking
Now just place the phone on the mattress near your body (see Setup sleep tracking) so it is able to sense your movement and wake you in the right sleep phase to bring your wake up experience to a new level
After dismissing the alarm in the morning you will see your sleep phases, deep sleep % and more..
This can be a result of multiple things, so please make sure to do the following troubleshooting:
Make sure you have Sleep as Android Gear Addon installed on your phone
It can happen that the addon cannot be started by us if it was force stopped previously. In that case please go to Play Store app on your phone, open addon page tap on “OPEN”.
Opt out of any battery savers that you might have on your phone, for all involved apps (Sleep as Android, Sleep as Android Gear Addon, Samsung Accessory Services) – to find out how to do that, please consult dontkillmyapp.com
Samsung Accessory services sometimes misbehaves and prevents connection to the watch for 3rd party apps. Please uninstall and reinstall it.
We have reports that this can happen on some devices, this depends on how the device mixes audio channels.
Try different frequency in Settings → Sleep tracking → Test sensor, frequencies are listed in drop down menu list.
We have reports that on some device you can hear audible artifacts during sonar tracking. It sounds like this:
Some of the signal gets into audible spectrum probably due to either insufficient quality of the speaker or some post processing which is applied to the output on your device firmware.
We have also some reports that Sonar can get audible suddenly during tracking in the night. Unfortunately we are not sure why this could happen, we only have very few such reports and we are not able to reproduce this on our phones.
To make any audible artifacts less likely:
Go to Settings → Sleep tracking → Test sensor.
Try different frequency from the drop down menu list.
When you find the least affected frequency, you could try lowering the volume a bit (the sliding bar). But keep it as high as possible to maintain reliable results.
|If the volume needs to be adjusted, always confirm that sonar is still working - ideally after you change settings, try to sit calm in font of the test for few seconds and than move slightly - do you see a spike?|
Probably some filter to enhance audio experience is applied to speaker or mic.
Try different frequency in Settings → Sleep tracking → Test sensor, choose a frequency from the drop down menu list.
When you find the least affected frequency, you could try increasing the recording threshold a bit in Settings → Sleep noise recording → Recording volume threshold.
You can also try a different combination of Input / Output in Settings → Sleep noise recording → Input / Output (may be hidden under Advanced). The most effective solution so far seems to be changing Input to UNPROCESSED.
|We have also discovered, that this exact issue can be solved by different positioning of the phone - if the bottom of the phone (where mic and speaker are) is not touching any surface, the artifacts are gone. So try to put the phone on a book or something similar with the bottom of the phone over the edge. If you are not hearing the sonar itself during tracking, but it only gets recorded, this usually helps.|
If you get completely flat graphs with automatic tracking with sonar sensor after upgrading to Android 11, make sure the app has permission Draw over other apps, Display over other apps or Appear on top (Samsung).
This permission is necessary for accessing the microphone from the background.
System settings → Apps → Sleep → Appear on top / Display over other apps
System settings → Apps → More options (⁝) > Special access > Appear
on top / Display over other apps
If the tracking stops completely after few minutes, the background processes are restricted by your system.
Make sure no system restrictions are applied to Sleep as Android, or any companion app for a tracking with wearable: Check our guide here.
If the guide won’t help, send us your log using Left ☰ menu → Support → Report a bug.
Please make sure that you are not accidentally starting the Sleep as Android app from your watch. This would start sleep tracking immediately.
Make sure you are not using automatic start of sleep tracking in Settings → Sleep tracking → Automatic sleep tracking → Start sleep tracking.
You can find more information about automatic sleep tracking start here.
If your volume gradually lowers after a while, when the tracking is running, the option Turn off when sleeping is enabled. This feature lowers the system-wide volume, so it affects even music played outside Sleep.
Go to Settings → Sleep tracking → Lullabies → Turn off when sleeping.
Extend the minimal playback time (5-90 min).
Or disable the feature completely by setting it to Use current device volume.
|The volume needs to be kept at maximum when tracking with sonar for maintaining the reliable results.|
Unfortunately, this also affects media volume in 3rd party apps, and we cannot control those separately from sonar media volume. This means that while using sonar, you can only use media apps on full volume.
You can set a time delay on start of tracking in Settings → Sleep tracking → Awake detection → Delayed sleep tracking.
- External players
When using sonar, you cannot control media volume by volume buttons as it always jumps back to maximum.
You can control volume of lullabies from the Sleep app (Settings → Lullabies), and from the Lullaby add-on pack.
When you lower the volume with volume buttons, the lullaby volume is estimated and adjusted accordingly, sonar volume is still kept at maximum.
Usually battery consumption issue or related issues causing phone over-heating during sleep tracking are not caused by the sleep tracking directly.
In most cases sleep tracking itself is not consuming too much battery (usually around 1-2% per hour of tracking). But because we hold a wake lock (keeping the phone awake) any other usually badly written apps may access the CPU extensively during the sleep tracking time. We would suggest checking which services are running before you get to sleep. For us it is hard to debug this. Also battery statistics are not a hint here as all battery consumption is accounted to the app which holds the wake lock even it did not consume the battery (this is by design in Android).
A good test would be to reboot your phone before sleep tracking (or kill any unnecessary services running) and see if sleep tracking will still consume too much battery afterward. Features within Sleep as Android which may cause higher CPU load during tracking include noise recording. You may try tracking without it for a reference. Also I would strongly recommend to track with airplane mode on.
The red block indicates that something went wrong with tracking at that time and the device stopped providing sensor data for some reason. Usually those are some non-standard battery optimizations or battery savers, the battery gets too low so we preserve it for the alarm or connectivity issue if you use a wearable.
1. Battery restrictions
Make sure no system restrictions are applied to Sleep, or any involved apps like wearable companion app).
See our guide here, and follow the instructions.
2. Too low battery
When the battery is too low (usually below 10%), data collecting is terminated to preserve enough battery for alarm.
When the battery was too low, there is a battery icon is displayed on the graph:
3. Connectivity issues with a wearable
When the connection with the wearable is lost, you can see red sections on the graph. The app always tries to reach the wearable again.
The graph can look like this:
Opt-out from any battery restrictions is applied by your system (https://dontkillmyapp.com/)
Pair the wearable with your phone in System settings.
Make sure the BT is not lost, and try lowering the distance between the phone and the wearable.
Try settings the device as Trusted device.
Unfortunately due to dummy security restrictions the Android team introduced in 4.2 there is no option to enable airplane mode from an app automatically. You always have to use the settings or long touch power button. If you have a rooted phone you may consider using https://play.google.com/store/apps/details?id=lv.id.dm.airplanemh we have support for that in Sleep. There is a similar hack for 4.3.
If you don’t agree with the Android team design decision you can upvote issue 40497 here http://code.google.com/p/android/issues/detail?id=40497.
There is no clearcut answer to which day the sleep between them belongs.
We have decided to attach the sleep to the day after, because how you slept will largely determine how your day will be.
If you have separate mattresses there is minimum interference from your partner. If you have one big shared mattress (which isn’t recommended as you partner may need different mattress for his healthy sleep), it could still work assuming you keep your phone close to your body and ideally on your side of the bed.
You can also consider using a armbands or smartwatches. This certainly solves the problem for a little convenience trade-off.
If both of you are tracking, you can enable pair tracking, which filters out the partner’s activity.