The Technical Principles Behind SleepCore
by Karry · Emmo Corp.
Foreword
As a programmer, I spend most of my time solving problems.
Over the past few years, our products have served tens of millions of users. As the user base has grown, the work I need to handle each day has also increased: product development, system stability, user feedback, and various technical decisions.
Extended periods of high-intensity work led me to encounter a very common problem — sleep issues.
At first, I tried many common methods to improve my sleep:
- Adjusting my sleep schedule
- Establishing good sleep hygiene
- Using white noise
- Meditation and relaxation
When it comes to sound in particular, I found that on many nights, I would drift off to sleep while listening to Wang Liqun's "Records of the Grand Historian" on Ximalaya, or to the sound of rain as white noise.
These methods did help at times, but I also gradually began thinking about a deeper question:
Why do certain sounds make it easier for people to fall asleep?
Driven by curiosity, I started reading a large amount of sleep-related research, including papers on neuroscience, brainwave studies, and sound rhythm. I was trying to understand several key questions:
- How does sound affect brain activity
- How different frequencies affect relaxation levels
- How the brain gradually transitions into sleep
As my research deepened, I gradually realized that sound is not just part of the environment — it could also serve as a tool to guide the brain into a sleep state.
The design philosophy behind SleepCore was shaped gradually through this research and practice.
Sound and the Brain
Even at night, the brain remains sensitive to sound.
The human auditory system does not fully shut down during sleep. Even after we have fallen asleep, the brain still responds to sounds in the environment.
For example: the sound of rain, a campfire, the wind outside the window. I wonder if others share the same experience as me — opening a sleep channel on TikTok before bed and slowly drifting off while listening to these sounds.
These sounds all share a common characteristic: they are stable, repetitive, and have a clear rhythm.
When the sounds in the environment remain stable, the brain gradually lowers its alertness, making it easier to enter a relaxed state.
This is also why many people find it easier to fall asleep when listening to the sound of rain or ocean waves.
Understanding Brainwaves
To understand why sound affects sleep, we first need to understand a concept: Brainwaves.
When neurons in the brain are active, they produce weak electrical signals. These electrical signals form brainwaves of different frequencies.
Different brainwave frequencies correspond to different mental and physiological states.
| Brainwave | Frequency | State |
|---|---|---|
| Gamma | 30–100Hz | High focus |
| Beta | 12–30Hz | Alert thinking |
| Alpha | 8–12Hz | Relaxed |
| Theta | 4–8Hz | Drowsy |
| Delta | 0.5–4Hz | Deep sleep |
During the natural process of falling asleep, the brain typically goes through this sequence of changes:
Beta → Alpha → Theta → Delta
Simply put:
- When awake during the day, the brain is primarily in Beta waves
- When relaxing, the brain gradually enters Alpha waves
- When drowsy, Theta waves appear
- During deep sleep, Delta waves dominate
Therefore, if we can create an environment that makes it easier for the brain to enter the Alpha or Theta state, it may help people fall asleep faster.
Sound Rhythm and Brainwaves
Research has found that the brain possesses a very interesting property:
The brain gradually synchronizes with external rhythms.
This phenomenon is known as Brainwave Entrainment.
When the brain continuously receives a certain stable rhythmic stimulus, neural activity may gradually shift toward that rhythm.
For example, when we hear a stable, slow rhythmic sound, the brain may gradually enter a more relaxed state.
This is also the core principle behind many sleep-aid sound technologies.
Monaural Beats
Currently, common rhythmic sound technologies mainly include three types:
- Binaural Beats
- Isochronic Tones
- Monaural Beats
SleepCore primarily uses Monaural Beats.
This method works by superimposing two sounds of close frequencies, producing a slow rhythmic variation.
For example:
When a 130Hz sound and a 133Hz sound are combined, they create a rhythmic fluctuation of approximately 3Hz.
This rhythm happens to fall within the brainwave frequency range associated with relaxation or sleep stages.
Compared to other techniques, monaural beats have several advantages:
- No headphones required
- More natural sounding
- Better suited for extended playback
Therefore, it is well-suited as an all-night sleep environment sound.
Fixed Rhythm and Dynamic Rhythm
In SleepCore's design, we did not use just a single fixed sound pattern.
Our sound system includes two rhythmic structures:
Fixed Frequency Rhythm
Used to create a stable, continuous sound environment that allows the brain to remain in a relaxed state.
Dynamic Rhythm Variation
In certain scenarios, the sound frequency gradually changes over time, for example:
Alpha → Theta → Delta
This change simulates the natural process of falling asleep.
By gradually lowering the rhythm frequency, the brain can transition more smoothly from an awake state to a sleep state, without any abrupt changes.
In terms of sound design, SleepCore does not rely on a single sound type.
We combine white noise, pink noise, and brainwave rhythm sounds to build a more stable and comfortable sleep sound environment.
White noise can help mask sudden environmental noises and reduce external disturbances; Pink noise is softer, with a spectral distribution closer to natural environmental sounds, making it easier to help people relax.
On this foundation, we add rhythmic sounds so that the overall sound environment remains stable while also having subtle rhythmic variations, making it easier for the brain to enter a relaxed state.
Conclusion
Beyond the core brainwave sound system, SleepCore has also designed a series of features centered around "understanding sleep."
For example:
- Sleep Star Chart, presenting sleep structure in a more intuitive way
- Sleep Debt, helping users understand the cumulative effects of chronic sleep insufficiency
- Emotional Sleep Score, expressing sleep status with simple emoticons
- AI Sleep Q&A, helping users understand sleep-related questions
- Brainwave Awakening, making the waking process more natural
The goal of these designs is not to add more features, but to help users more clearly understand their own sleep and gradually establish a stable sleep rhythm.
What we have done is design a more stable, natural sound environment based on research in sleep science and neuroscience.
In such an environment, the brain can gradually relax, making it easier to enter a sleep state.
SleepCore hopes to accompany you through every day and night.
SleepCore's sound design references publicly published research in neuroscience and brainwaves, including Brainwave Entrainment and the effects of rhythmic sounds on EEG activity.
References
Da Silva Junior, M., Freitas, R. C. d., dos Santos, W. P., Da Silva, W. W. A., Rodrigues, M. C. A., & Conde, E. F. Q. (2019). Exploratory study of the effect of binaural beat stimulation on EEG activity pattern in resting state using artificial neural networks. Cognitive Systems Research, 54, 1–20.
Schwarz, D. W. F., & Taylor, P. (2005). Human auditory steady-state responses to binaural and monaural beats. Clinical Neurophysiology.
Ioannou, C. I., Pereda, E., Linden, D. E. J., & Bhattacharya, J. (2015). EEG effects of short binaural beat presentation on EEG responses of musicians and non-musicians. PLOS ONE, 10(7), e0134284.
Jirakittayakorn, N., & Wongsawat, Y. (2017). Brain responses to a 6-Hz binaural beat: Effects on EEG theta activity. Frontiers in Neuroscience.
https://pubmed.ncbi.nlm.nih.gov/28701912/Jirakittayakorn, N., & Wongsawat, Y. (2018). Effects of a 3-Hz binaural beat on sleep stages. Frontiers in Neuroscience.
https://pmc.ncbi.nlm.nih.gov/articles/PMC6165862/Ingendoh, R. M., Posny, E. S., & Heine, A. (2023). Binaural beats to entrain the brain? A systematic review of the effects of binaural beat stimulation on brain oscillatory activity. PLOS ONE.
https://pubmed.ncbi.nlm.nih.gov/37205669/Perez, H. D. O., Dumas, G., & Lehmann, D. (2020). Binaural beats through the auditory pathway: EEG connectivity patterns.
https://pubmed.ncbi.nlm.nih.gov/32066611/