Night sound chart explained
What the night sound chart actually shows
Restful’s optional night sound curve shows relative sound level changes in your room. It is off by default; it does not detect sleep or measure sleep stages, and it is not a medical measurement.
Turn on “Optional relative sound curve” on the night screen and Restful asks for microphone access when the night starts. The microphone then records short pieces; on the phone, each minute becomes one uncalibrated sound value. The App compares values within that same night, and quieter and louder stretches appear on the curve.
Checked 26 September 2026 · Released App version 1.0.8 · US price is a dated observation
How it works
Read the chart honestly
Start and end are button times
The session begins when you start it and ends when you stop it or the App ends it. These are not detected sleep-onset and wake times.
Relative sound, not sleep stages
Version 1.0.8 marks the curve Quieter, Moderate and Louder and no longer shows a score or Asleep and Deep sleep figures. Earlier versions put deep, light and awake labels on the same relative values; none of these was validated against measured sleep stages. A quiet person who is awake looks the same as a quiet person asleep.
Compare only within one night
The values are not calibrated decibels and are scaled against the same session. A fan, partner, or the App’s own sleep sounds can change the curve.
The details
What happens to recording pieces
Audio processing occurs on the phone; Restful does not upload audio or journals. Since version 1.0.7, new recording pieces are deleted after analysis and at session end, and earlier local leftovers are cleared when the App opens.
Versions through 1.0.6 could leave raw pieces on the phone. Copies already contained in older iCloud or computer backups cannot be deleted by the App.
Crash reports and App-session records do go to Sentry. They do not contain the microphone audio or journal database. Read the privacy policy for the broader data explanation.
Limits
Session conditions and gaps
- With the curve on, keep the iPhone near the bed and charging. If the screen stays locked on battery power for about an hour, the recording stops and no curve or Journal entry is saved for that night; the alarm timer keeps running.
- Nights without the curve, under an hour, or with too little usable recording are not saved to the Journal.
- An interruption such as a call can leave missing minutes; since version 1.0.7, a longer interruption may appear as a gap in the curve rather than as a quiet stretch.
- Insights need seven recorded nights before they fill in, and then compare session length and timing. That threshold does not make the sound curve a validated sleep measurement.
A direct answer
Can this chart tell me how long I slept?
No. It knows when the App session started and ended, and how sound varied during that session. It cannot tell whether you were asleep, awake but still, in REM, or in a deep stage.
For storage, diagnostic and backup details, read the privacy policy. The press kit also covers what changed in versions 1.0.7 and 1.0.8.