Sleep is a state that is characterized by changes in brain wave activity, breathing, heart rate, body temperature, and other physiological functions.  Sleep is usually divided into REM (rapid eye movement)  and NREM (Non-Rapid Eye Movement)  stages.  During REM sleep, all muscles seize to move except eyes.  During this stage eyes moves rapidly while all muscles are paralyzed.  REM stage accounts for about 25% of each night’s sleep. REM sleep is the period during which psychological repair of the cells takes place.   Dreams that takes place during REM sleep are remembered.  Non-REM sleep has three stages, namely  Non-REM1, Non-REM2 amd Non-REM3(SWS) stages.  Non-REM1 stage is the first stage where sleep onset occurs and the sleep is the lightest. This stage accounts for 5% of the sleep duration.  Non-REM2 stage is the deeper sleep stage which accounts to 45% of the sleep duration. Finally Non-REM3 stage is also known as Slow Wave Sleep (SWS) is the deepest stage of the sleep. This stage  amounts to 25% of the  total sleep duration.  The rest of the sleep period is classified as the REM sleep during which time all movement stops.

Tracking sleep  and understanding the how you sleep is important since getting enough sleep is essential for developing and maintaining a health mind and body.  Tracking sleep allow you to determine if you are sleeping enough  and whether your sleep disturbances are a result of a sleep disorder. Sleep apnea is one of the most commonly pronounced sleep disorder which disrupt the sleep continuously resulting in feeling of tiredness through the day and  may lead to more serious conditions such as Alzheimer.  Among other causes of sleep disorders stress, obesity , insomnia , sleepwalking, difficulty falling asleep  can be listed as examples.  It has been reported than sleep disorders could be an early sign of Alzheimer’s disease.  Understanding the sleep architecture and measuring the sleep quality is  the first step in  diagnosis and cure of sleep disorders or underlying causes.

soundSleep is an ambient sensor  for monitoring sleep quality and reporting sleep quality index.