Question 1

How does Nostril track breathing during sleep?

Accepted Answer

Nostril uses three independent machine learning classifiers running simultaneously: YAMNet (a deep learning model trained on 521 audio classes via CoreML), Apple's SoundAnalysis framework for cross-validation, and custom FFT spectral analysis. All three must agree before classifying each 5-second audio window as nasal breathing, mouth breathing, snoring, or ambient noise.

Question 2

Is my audio recorded or uploaded?

Accepted Answer

No. All audio processing happens entirely on your device using the Neural Engine. Zero audio is recorded, stored, or uploaded. Only statistical results (percentages, episode counts, intensity scores) are saved locally.

Question 3

What is the Control Pause test?

Accepted Answer

The Control Pause is a clinically recognized breathing fitness metric from the Buteyko method. It measures your body's tolerance to CO2 by timing how long you can comfortably hold your breath after a normal exhale. Most beginners score 10-20 seconds; 40+ seconds indicates healthy nasal breathing.

Question 4

What languages does Nostril support?

Accepted Answer

Nostril is fully localized in 9 languages: English, German, French, Spanish (Spain), Spanish (Mexico), Portuguese (Brazil), Portuguese (Portugal), Italian, and Chinese (Simplified).

Question 5

Is Nostril free?

Accepted Answer

Nostril is free to download with core features available. A premium subscription unlocks unlimited sleep tracking history, detailed analytics, and all reminders.

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