Sleep as we know it, goes through cycles during the night.  In each cycle are stages.  We will briefly discuss them here.  For more complete definitions, check out Wikipedia here.


Cycle lengths are about 90 minutes long, with each subsequent cycle getting a little longer thru the night.  So, for a standard 8 hour sleep, you go through about 5+ cycles.  Not counting awake, there are are 2 classes of stages per cycle.  1) Non-REM and 2) REM


The first cycle stages are the 3 non-REM stages, N1, N2, N3.

Stage N1

Very light sleep, easily wakened, getting drowsy.  Brain produces ‘Theta’ waves.

Stage N2

Light sleep, heart rate slowing, body temperature drops.  This stage comprises about 40% to 60% of adult sleep time.

Stage N3

Known as the deep or Slow-Wave sleep, harder to awaken. Body does a lot of repairing and energy regeneration.  This stage basically disappears during the latter cycles, as REM increases.

Stage REM

REM = Rapid Eye Movement.  Brain becomes more active. Stage becomes longer thru the night. Dreams occur.


Each stage has a purpose, and each stage has characteristic brain wave patterns as noted on an EEG. 
The frequencies are listed here (HZ):

N1: 8 – 12
N2: 4 – 8
N3: 1 – 4
REM: 15 – 30

Our app tries to mimic these frequencies during the above stages with pink noise.


The body has its own natural drives for the various stages and how much it ‘wants’.  However, there are outside factors that can affect the quality and quantity of the sleep stages.

Deep Sleep (N3)

The body gets most of the deep sleep up front in the first cycles, then after that goes into REM and light sleep (N2).
The two main factors that can lead to less deep sleep are:

1. Age:  Deep sleep time reduces as people get older
2. Interference:  Pain, medical problems, sleep apnea, sleep disorders


It has been noted that too much or little of this stage can affect how you feel during the day. The so called ‘night owl’ person can tend to get more REM than the ‘early to bed’ person.

Too Little:  Feel groggy, difficult to focus, memory issues.  Medications can cause this, especially anti-depressants.

Too Much: More than 25% total for the night can cause increased brain activation and being angry and irritable, possible leading to symptoms of depression and anxiety.


Sleep is also affected by exercise, stress, temperature, light, chemicals, alcohol, irregular schedules.


Alcohol before sleep tends to suppress the early cycle REM stages with a rebound later in the night as the alcohol is metabolized. More frequent awakening also occurs.

Stress and Anxiety

These 2 bad boys make it more difficult to fall asleep and the sleep tends to be lighter with less deep and more REM sleep.


The most common culprits here are caffeine, alcohol, nicotine, antihistamines, anti-depressants, beta and alpha blockers.

Beta Blockers

Linked to decreased REM and deep sleep, leading to daytime sleepiness.

Alpha Blockers

Linked to decreased REM and daytime sleepiness.


Decreased duration of REM and some (SSRI) can lead to insomnia.

Cold Temperatures

Decreased or total absence of REM (very cold).


Unfortunately, as we get older, our time in deep sleep seems to lessen and we spend more time in N2.  In this stage, it is easy to awaken, and may account for the frequency of nighttime awakenings.


The theory of our app is to continually promote the ‘normal’ pattern of sleep, via pink noise prodding, and hopefully counteract outside interference with your good sleep cycles.


Install from the Google Play Store or the Apple App Store.
Open the app and you will see the start screen shown below.

Select either:

Pink – Sleep Cycle

This choice will give you the full night pink noise prodding, synced to a normal night of sleep cycles and stages.  This selection will lead you to a Terms of Use screen, then to the main play noise screen.

Pink Noise Only

This option will play steady pink noise for as long as you want.

Play Noise Cycles

This is your start screen to play pink noise all thru the night in sync with normal sleep cycles and stages.

Set minutes to fall asleep

Select the minutes it takes you to fall asleep, in general, at this point in time.  It can change and adjust this value if needed.  During these minutes, pink noise is played without any frequency variation, just a nice, steady stream. This can really help you to quiet your mind down and, we find, that it help stop your thinking, which can sometimes make falling asleep more difficult.

At the conclusion of these start minutes, the cycles and stages begin and continue until you wake up.

Note:  If you are still awake for some reason at the end of these start minutes, just tap the Stop button and Play again to restart.

Audio Buttons

Play:  Press to begin the night of cycles and stages
Pause:  Press to temporarily stop the audio.  Your place in the cycles and stages is saved and will continue on Resume
Stop:  Press to completely stop the cycles and stages

Cycle – Stage Status

After you press Play, the screen and the buttons turn dark, and a cycle-stage status will show at the bottom.  This will change thru the night and inform you of what cycle and stage you are in.  Hopefully, you won’t be waking up to see this, but if you do it is there and is interesting.

Good Wake Times

This is found at the top of this screen.  Tap to open a list of suggested wake up times.  These times are based on completion of a cycle, so that you don’t interrupt a cycle in the middle of a needed stage, such as REM.

The idea here is to change your going to bed time, if needed, so that your wake up (alarm going off) is in one of these good zones.


Tap the 3 dots, upper right to open the stage totals options screen.

Here you can make small adjustments to the totals of the 3 main stages:  Light, Deep, REM

Adjusting the totals is something you may wish to try if you find your daytime symptoms coincide with either an excess or deficiency in a certain stage type, as discussed above.

Another reason to change the percentages, would be to bring them into age related alignment.  The percentages in each stage change from childhood to adulthood and can be found on many websites.

Babies usually spend about 50% in REM and in a few years, the REM is down to about 25% and is replaced with N3 (deep) sleep. In adolescent years, the deep sleep decreases and is replaced with N2 (light) sleep.

By age 70, most of the night is in N2 with, unfortunate, frequent awakenings.

If you have a Fitbit with sleep evaluation and find that you would like to further ‘prod along’ a certain stage type, then perhaps this adjustment is something you may want to try.

Device Display Setting

Your phone may automatically turn off after a short period of time depending on your display setting. Of course you do not want this as our app needs to work for many hours.

Android Devices

This requires turning on Developer Options

Settings > Device Information or About Phone > Build Number
Tap on Build Number 7 times to unlock Developer Options
In Developer Options, turn Stay awake ON (phone stays on with cable connected)

iOS Devices

Settings > Display & Brightness > Auto-Lock: Never
In the morning you can change the setting back to your normal Auto-Lock time


We think it is very cool to interact with available technology for the evaluation of sleep.  Some of the Fitbit products have sleep evaluation capability.  We use the new Fitbit Charge 4 and show below a screenshot from our Galaxy S8 device.

Note:  We are not affiliated with Fitbit in any way.

Fitbit Interact

Since Fitbit does evaluate sleep, summarizes data and provides you with an overall ‘Sleep Score’, we found it very interesting to compare nights using The Good Sleep pink noise app to nights without it. 

Note: There are several devices and apps out there to do this sleep evaluation for you.