What is sleep tracking?
Sleep tracking enables you to measure quality of Your sleep.
During the night, your body cycles through several sleep phases. Sleep as Android uses your device’s sensors (accelerometer or sonar) to create a graph of these phases.
Measuring your sleep cycles enables the app to:
- Visualize the sleep process in a sleep graph and hypnograms
- Calculating your deep sleep % and cycle count, which can be an indicator of healthy / unhealthy sleep.
- Smart wake up, finding the best moment for the alarm to wake You up.
- Gathering statistics to analyze your sleep in the long term.
- Setup goals and improve your sleep parameters
How does sleep tracking work?
Sleep tracking uses your device’s sensors to measure how much you move during the night. This is called actigraphy. Actigraphy is based on the finding that body movements are directly related to the current sleep phase. Generally, more movement means lighter sleep. More about the method in the theory section or on Wikipedia.
You can use either accelerometer or sonar as sensors. Select your sensor in Settings > Sleep tracking > Sensor.
Sensor
Sleep as Android supports two ways of sleep tracking out of the box. Accelerometer and Sonar.
- Accelerometer measures the magnitude of your sleep movement by a tiny electromechanic device that is present in every smartphone. The phone has to be in bed with you in order to transfer your motion to the accelerometer.
- Sonar measures your movement by low-ultrasonic waves (we use 18-22 kHz) that traverse through air. Sonar is able to detect your breathing motion, so in addition to mapping sleep motion, it can also point to possible breathing issues. For sonar to work, the phone has to lie still on a bedside table.
Tracking with accelerometer
Accelerometer can be either in the phone or in a wearable device. The measuring device has to have direct contact with you to be precise. This means that the phone has to be in bed with you. Accelerometer is the default sensor and works on every phone.
The movement is measured relatively. This means that it doesn’t matter whether you are a tiny girl or a McDonald’s regular – the app is always able to distinguish between ‘moving a little’ and ‘moving a lot’. Heck – it should be able to measure a fly sleeping on the phone! You always see the maximum of your movement as a maximum of the sleep graph – and the same with minimums.
If you leave the phone lying on the table, you will get some readings. Some people have written us that Sleep as Android does not work because of this notion – but the device is so sensitive that if you leave Your device lying flat somewhere on the floor or a table, you are effectively using the app as a seismograph (i.e. tracking ground movement).
Phone placement
Mattress types
Another decisive factor for data accuracy is the the mattress type. In general sleep tracking works better on mattresses which do better transmit your movements to the phone’s accelerometer sensor. In general, sleep tracking works well on most mattresses out there excluding some 100% slow foam mattresses (such as Tempur) where it may be necessary to use an arm band or other similar solution.
Data accuracy
Tracking with sonar
Sleep as Android enables you to use the phone’s microphone and speaker as a sonar (for range and movement detection using ultrasound). It works on a lot of phones, but not all (some are unable to produce or capture frequencies above human hearing range). See the growing list of compatible devices.
The phone has to be on a bedside table, lying still. Sonar has effective range of about 1 meter. The closer you are, the more precise are the results.
Breathing detection
If you are close enough (reliable distance is about 0.5 meter), sonar is able to detect your breathing motion. In the morning, you will see a plot of your breathing level as a blue line with pinpointed periods of low or no breathing activity.
The numbers in circles signify your maximum and minimum breathing rate (breaths per minute) for a given night.
Is tracking with sonar bad for your health or for the device? Find out here. (Spoiler alert: It’s not bad!)
Phone placement
To obtain best results while tracking with sonar, keep the phone on your bedside table. The range of the sonar is 1 meter.
To detect respiration, make sure to be closer to the phone – the respiration detection range is around 0.5 meter.
Start sleep tracking!
To start sleep tracking, tap the 
button on the 
Alarms tab.
NOTE: The moon button can have one of 3 colors:
- cyan – default
- green with progress – 2 hours countdown to bedtime
- red – it’s past bedtime
The phone will use the accelerometer sensor by default, sense your movements during sleep and estimate your sleep phases. The result of sleep tracking is an actigraphic record of your sleep (sleep graph). Sleep graphs are explained in more details in How it works and Statistics.
The sleep tracking screen shows current time, time to alarm, smart wake up window and much more. But for starters, let’s just focus on:
pause button – will pause sleep tracking for 5 minutes (to tell the app that you’re awake, e.g. to go on the toilet)
lullaby button – will start playing a lullaby, which will fade out after a preset time
On the background, a graph of your movements starts to show up moments after you start sleep tracking.
Settings explanation
When you first install Sleep as Android, you do not have to set anything in order for sleep tracking to work. Later, you might discover that there are some things you might want to tweak.
Go to Settings > Sleep tracking.
Silent profile when tracking
On: Starting sleep tracking puts the phone in the silent mode so no notifications or phone calls are heard. Alarms will be heard.
Delayed sleep tracking
When enabled, sleep tracking will not start immediately when you click the moon button, but after a set delay.
Airplane mode
For Android version less than 4.2 (or for any rooted devices), Sleep as Android can turn on airplane mode automatically. For higher version Android, this setting only turns off WiFi and the user has to do any airplane mode settings manually: long press power button > Airplane mode.
IMPORTANT: We do strongly recommend using airplane mode during the whole period of sleep tracking in order to lower “electromagnetic smog” in your bedroom.
Flip to pause
Simply flip the phone over to add +5 minutes to your current pausing time.
Hidden morning stats to avoid rating bias
Seeing the hypnogram and actigraph in the morning may already influence how you rate you sleep. This options allows to hide the measured results until you do you rate your sleep with stars.
Stand-by and charging
Screen dimming
- Disabled: Leave screen on during sleep and show sleep graph
- Dim: Let the system control screen during sleep
- Dim with clock: Show clock for 20s, then let the system control screen during sleep
- Clock screen on: Leave screen on during sleep and show clock
