About the science of sleep
The sounds and visuals in Nerukoneko are designed to follow published research on sleep. This page explains which parts of the design draw on which findings.
Please note that everything here is simply a summary of what researchers have reported. It is not a promise that this app will improve your sleep. Nerukoneko is not a medical device and is not intended to diagnose or treat any sleep disorder. If sleep troubles continue for a long time, please talk with a doctor or another qualified professional.
Musical tempo (60–80)
Some studies report that listening to calm instrumental music at a tempo of 60–80 (the number of beats per minute, close to a resting heartbeat) before bed was associated with falling asleep sooner and with better sleep quality (several meta-analyses; for example, Frontiers in Neurology 2024, covering 13 trials and 1,007 people). Every piece of music in this app is composed within that tempo range, and we confirm it by machine measurement when the tracks are added.
The character of the sound (leaning on lower tones)
Research has reported that a steady sound made mostly of low tones, with the higher tones kept gentle — often called "pink noise" — supported deep sleep, while other reports note that high, sharp sounds can be more arousing. For that reason, the night ambiences in this app (rain, waves, the sound of a distant train, and so on) are only included after machine measurement confirms that their high-frequency content is kept low.
Volume, and lights out once you drift off
In its environmental noise guidelines, the World Health Organization (WHO) recommends that a bedroom stay quiet during sleep. In keeping with that, this app lays the ambient sounds far softer than the music, lowers the volume as play goes on, and — once your finger has come to rest and you are judged to have fallen asleep — turns off the sound, the vibration, and the screen. It never keeps playing sound until morning.
Deep Night mode (with earphones only)
There is a sound technique that plays slightly different pitches into the left and right ear, so that the brain perceives the difference as a soft "beat." Some studies have reported a positive influence from this technique on falling asleep and on sleep quality (for example, a randomized controlled trial in Scientific Reports 2024, and a systematic review in 2025). This app's "Deep Night" mode gently lowers that beat as play goes on. Because it needs stereo playback, it only works when earphones are connected.
The light of the screen
Research has reported that strong blue light at night suppresses melatonin (a hormone that supports sleep). The screen in this app is built around dark night tones and warm colors, dims automatically as play goes on, and turns the display itself off once sleep is detected.
How the play is built (moving attention gently along)
Research has reported that picturing one unrelated image after another makes it harder for the chain of worrying thoughts that keeps you awake to continue, so it becomes easier to fall asleep (a method known as "cognitive shuffle"). The way small games with different rules keep switching in this app is that idea, retold as a story set in the world of the night.
Slow rocking, slow breathing
Some studies report that slow, continuous rocking helped people fall asleep (Current Biology 2019), and that breathing slowly, about six times a minute, helps calm the body and mind. Carrying a kitten softly along, and the slow rise and fall of a sleeping cat's belly, are gentle touches inspired by those reports.
From the in-app note ("About the science of sleep," in Settings):
The sounds in this app are made in line with research reporting that calm music at a tempo of 60–80 helps you relax before bed (several meta-analyses). Deep Night mode is a gentle effect based on research into a sound technique that slowly lowers a soft beat. It does not promise any medical benefit.
- Support contact: https://nerukoneko.panmarie.com/support
Last updated: July 14, 2026