Soln

Sleep Engine

Free · In-App Purchases · Designed for iPad. Not verified for macOS.

Not a white noise player. Soln measures sleep resistance nightly, plays five audio layers at your heart rate, and stops when you sleep. 7 days free, then buy once. Soln is a sleep engine built on cognitive load theory. Different from other sleep apps Most sleep apps are just players — they start audio and leave you to it. Soln calculates how hard it will be to fall asleep tonight, decides which layer to start at and how long to stay there, then stops when you're out. You don't have to manage anything. Five audio layers · Silent preparation — nothing playing, just space for your mind to settle · Minimal white noise — a steady background to mask outside noise · Heart rate-synced white noise — audio tempo follows your heart rate; as it slows, so does the sound · Tonal fade — frequency gradually drops, sliding your brain from alert to relaxed · Semantic drift — soft, loosely connected speech that gives your mind something to dissolve into instead of looping the same thought (paid) How long you spend on each layer isn't fixed — it depends on how you're doing tonight. Apple Watch auto-stop When you fall asleep, Apple Watch detects it. Soln fades the audio out over two seconds, then stops. No timer to set. No sudden silence to wake you (paid). Nightly assessment Before bed, based on today's mood and last night's sleep, Soln estimates how hard it'll be to fall asleep and gives you an optimal bedtime window and expected sleep onset time. In the morning, three scores: reaction, memory, and mood. Sleep well, score well. Sleep poorly, score reflects that. Straightforward. Full sleep history A three-color ring for each night. Long-press any day for that night's detail and sleep-onset timeline. One-time purchase Free for 7 days, full features included. After that, a one-time purchase permanently unlocks everything. Tied to your Apple ID — restore on any new device. No ongoing charges.

Ratings & Reviews

  • This app has not received enough ratings or reviews to display an overview.

The developer, Nan Yu, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary based, for example, on the features you use or your age. Learn More

    Accessibility

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Information

    Provider
    • Nan Yu
    Size
    • 3.4 MB
    Category
    • Health & Fitness
    Compatibility
    Requires iOS 17.0 or later.
    • iPhone
      Requires iOS 17.0 or later.
    • iPad
      Requires iPadOS 17.0 or later.
    • Mac
      Requires macOS 14.0 or later and a Mac with Apple M1 chip or later.
    • Apple Vision
      Requires visionOS 1.0 or later.
    • Apple Watch
      Requires watchOS 10.0 or later.
    Languages
    English and 11 more
    • English, Dutch, French, German, Italian, Japanese, Korean, Portuguese, Russian, Simplified Chinese, Spanish, Swedish
    Age Rating
    9+
    In-App Purchases
    Yes
    Copyright
    • © 2026 Yu. All rights reserved.
  • Developer Website
  • Privacy Policy

    • More by Nan Yu