App that records sounds at night: how it works

What the app does while you sleep

The microphone stays on all night, but the app (also called a sleep recorder) doesn’t record everything. It keeps measuring the background noise of your bedroom: the usual quiet, with the fridge in the distance or the street. As soon as a sound rises above it by a set margin, the app starts a clip.

What happens next:

1. The clip starts just before the sound. The app always keeps the last few seconds in memory, so you hear the start of the sentence, not just the end. Sleepeek keeps 2 seconds before and 2 seconds after each sound.
2. It stops when the room is quiet again, or after a maximum length. In Sleepeek, a clip lasts 60 seconds at most; a long stretch of snoring is split into several clips, grouped together in the morning.
3. The background noise adjusts by itself. If it rises during the night (the heating coming on, rain), the app adapts and stops keeping that steady noise.

The result: instead of an eight-hour file, you get a list of short sounds, each with its time. That’s the difference from a voice recorder, explained in the guide to recording yourself sleeping.

How it tells snoring from talking

Each clip goes through a sound classifier: a model trained to recognize sounds from thousands of examples. On iPhone, Apple provides a built-in classifier, Sound Analysis, which can identify over 300 sounds (Apple Developer). An app can use it or its own model.

The classifier doesn’t decide on a single instant. It analyzes the clip in slices of a few seconds, and the clip gets the type that comes up most: snoring, talking, coughing, or “other” when nothing clearly stands out. Sleepeek works on 3-second slices, on the phone, without a connection.

This sorting is sometimes wrong. The most common mistakes:

• heavy breathing, mouth open, filed as snoring;
• a very short mumble, which can end up as “other” rather than talking (when people talk in their sleep, it’s often mumbling);
• the sounds of the person sleeping next to you, counted as yours.

So listen to the clips before you trust the totals, especially if you’re trying to find out whether you snore.

Where to put your phone

Distance matters more than the phone model. Too far, and a whispered sentence doesn’t rise above the background noise; too close, and every rustle of the sheets starts a clip.

• On the nightstand, about 50 cm (20 inches) from your head, screen up.
• Never under the pillow or the duvet: fabric muffles sounds.
• On the side of the person you want to record, if there are two of you.
• Away from a fan or an air purifier, which covers quiet sounds.

Sounds that fool the app

Setting the sensitivity

Sensitivity is how far above the background noise a sound has to be to start a clip. The more sensitive the app, the more quiet sounds it keeps, and the more useless noises it keeps too.

• You get too many pointless clips (sheets, breathing): lower the sensitivity by one step.
• You can’t find a sentence someone heard you say: raise it by one step.
• Change only one setting per night, or you won’t know which one made the difference.

In Sleepeek, you set the sensitivity in Settings: a sound is kept when it rises 4 to 24 dB above the background noise, depending on the slider, and 10 dB by default (“Normal”). Start with the default and adjust after a night or two.

Battery and storage

The microphone runs for hours: keep the phone plugged in. With Optimized Battery Charging on, iPhone can pause charging at 80% overnight and finish just before the time you usually unplug it (Apple Support): staying plugged in all night is expected.

As for storage, an app that starts when it hears a sound only keeps short, compressed clips. That’s much lighter than a continuous recording. Delete the nights you no longer need and mark as favorites the clips you want to keep.

What stays on your phone

With Sleepeek, sound sorting happens on your iPhone and the clips are saved there. They only leave your phone if you share them yourself: a clip, a video or a report to show your doctor.

Before installing another app, check its privacy section on the App Store: it says what data the app collects and whether it leaves the phone.

When to see a doctor

French national health insurance (Assurance Maladie) lists these signs, among others, as symptoms suggestive of sleep apnea (ameli.fr, in French). If you recognize any of them, talk to your doctor:

• intense snoring, every night, for a long time;
• pauses in breathing, noticed by the person sleeping next to you;
• waking up with a start and a feeling of choking;
• excessive sleepiness during the day.