Somnia: Teeth Grinding Tracker

Somnia is a teeth grinding (bruxism) and snoring tracker. Leave the phone face down on the nightstand and it detects grinding, snoring, sleep talking and coughing, and estimates four sleep stages. It never saves audio, so nothing can be played back, and sound is analysed on the device only.

23:40 — Face down on the nightstand. Pick one of 14 sounds to fall asleep to: rain, waves, wind, a fan, an air conditioner, a moving train, a stream, a waterfall, white, pink and brown noise, a low drone, a singing bowl. None of them are audio files. They are synthesised as they play, which keeps the app small and means there is no seam where a loop repeats. Two seconds to fade up, then 45 seconds to fade out at the 30-minute mark.

00:12 — Asleep. The microphone stays open. Recording runs as a foreground service, so the screen going dark does not stop it.

02:30 — Snoring starts. Audio captured at 16 kHz is cut into 64-millisecond frames and split across 32 mel bands. Loudness alone does not decide anything. The cues are band ratio, spectral flatness, how fast the sound rises, and how long it lasts — and after an event ends, whether its spacing matches a breathing cycle, checked by autocorrelation. Grinding, sleep talking and coughing are separated the same way.

03:05 — Turning over. Body movement from the accelerometer, and sound pressure at that moment. Those two signals are the entire basis for estimating sleep depth. No heart rate, no SpO₂, because this is built for people who do not wear a watch to bed. Every 60 seconds it places one of four stages — awake, light, deep, REM — smoothed with an actigraphy weighting across the surrounding two minutes.

06:45 — Alarm. Registered as an OS alarm clock, which is why the app does not ask for the extra exact-alarm permission.

07:00 — Up. The night is one band across the screen. The score runs 0 to 100 and breaks down as duration 35, efficiency 25, continuity 20, depth 12, quiet 8, computed against a 7.5-hour target.

— No audio is kept
Worth stating as a feature. This app never writes sound to disk. What remains is numbers — the sound-pressure trace, the spectrogram image, the time and type of each event — and those stay on the device. There is not one line of code in the app that sends any of it anywhere.
The trade is that you cannot play your snoring back. If listening to the recording is the point, this is the wrong app.

— Free of charge
A full night's recording, all four event types, four-stage sleep, the score and its breakdown, the alarm, eight of the fourteen sounds, and the detection sensitivity control. History covers the last 3 days, and events are listed 3 per type.

— Pro adds
The full history, up to 40 events per type, the spectrogram — the whole night's sound as one image — and all 14 sounds. Monthly, yearly, and a one-time purchase.

— Please note
This is not a medical device. Sleep stages are estimated from movement and sound; they are not measured. It does not detect sleep apnea, so if you suspect your breathing stops at night, see a doctor.
Records cannot be exported or deleted. Interface in English and Japanese.