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# Estua
Sleep noise that never loops
48 kHz · real-time synth · zero loops
iOS Android Watch Live
Sleep apps loop a recording. Estua has no recording: it composes the sound live on your phone and can prove the result never repeats. No account, nothing streams.
[App Store](https://apps.apple.com/app/estua/id6784632438)Google Play · soon
Swift Kotlin AVAudioEngine DSP watchOS 8K+ dl Updated 2026-05
## See it running
Official App Store screenshots. Scroll sideways for more.
**Music that never repeats**Generative, endless. Resume the last session or start a new one.
**Sound born on your device**Synthesised live. Offline, no cloud, no account.
**A palette of real instruments**Celeste, piano, Rhodes, bells, music box, handpan, marimba, two guitars, organ, strings, choir, harpsichord, warm pad. Spatial audio on headphones.
**Provably non-repeating**The session screen shows the math: recurrence about 1.1 × 10¹² years, 3.36 bits per note, divergence within 40 seconds, builds checked by SHA-256 in CI.
**Open, not a black box**Each engine part was switched off and measured alone. One test found no audible effect; it is published anyway, labelled exactly that.
**Breathes at your resonance**Experimental: a sweep finds your breathing rate and the music breathes at it. Heart rate can come from a wearable via HealthKit.
**Tuned to your ears**Eight tones, raise each until you just hear it. The mix gets a per-band boost mapped to your hearing.
**Warm, never dark or sad**Relax, Recover, Focus, Sleep. All four written to stay calm.
**Focus that breathes**Work/break cycles. On breaks the sound just softens. 25:00 on the clock.
## Four modes
### Relax
A warm, close space for the end of the day.
### Recover
Open, temple-like. For resetting.
### Sleep
Deep and enveloping. Keeps its character for hours because it is synthesised, not looped.
### Focus
Built around work/break cycles, kept deliberately plain.
## What makes it different
- **A certificate you can check**Each second is a trajectory of a deterministic dynamical system, and the engine can emit a machine-checkable certificate that it never repeats. The ∞ in the icon is that.
- **The numbers are on screen**Recurrence time, bits per note, divergence. Shown for the session you are hearing.
- **100 styles**Living mode drifts between them so hour three still moves.
- **Seeds**Save a seed and get the same session back, note for note. Years later too.
- **Real instruments**Fifteen voices. HRTF spatial on headphones.
- **Nothing leaves the phone**The App Store privacy label reads Data Not Collected.
## Day to day
- **Opens where you need it**Pick a goal once during onboarding.
- **Bedtime**Gentle reminders. A long sleep timer that fades out instead of cutting.
- **Health and streaks**Mindful minutes go to Apple Health. Streaks and stats in the app.
- **Hands-free**Siri Shortcuts and widgets.
## Under the hood
The audio thread has a hard deadline: fill the buffer before the hardware asks, every time, or the listener hears a click at three in the morning. That rules out memory allocation, locks, and anything with unbounded latency inside the render callback. Hours of continuous 48 kHz synthesis come from that discipline. The full story is in the DSP post below.
## Free and premium
Free: about 90 minutes a day, all four modes, a starter set of styles, no account. Premium: unlimited time, all 100 styles, Living, the long sleep timer, full offline. Monthly, yearly, or lifetime.
Estua is a general-wellness audio app, not a medical device. The resonance and hearing-check features are labelled experimental in the app.
### Want a month on us?
Beat Signal Lock — match the waveform — and we hand you a promo code.
[Play Signal Lock →](https://uranashel.com/unlock.html)
## The engineering behind it
[2026-04-10 · 20 min
### Sound that never repeats
](https://uranashel.com/blog/estua-non-repeating-audio.html)[2025-11-10 · 18 min
### Sleep, waves, and why your brain likes surf
](https://uranashel.com/blog/estua-sleep-and-waves.html)[2025-08-02 · 21 min
### Life on the audio thread
](https://uranashel.com/blog/dsp-audio-thread.html)
---
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