# Slo - Sleep & Relax with Brown Noise

> Slo is a minimal sound machine for sleep, focus, and relaxation. The app carries 151 curated sounds; 144 of them play in the browser at slonoise.com with no download and no account. Available on iOS, Android, and Mac.

**Key features**

- 151 curated sounds in the app, 144 of them playable in the browser (brown noise, white noise, pink noise, nature sounds)
- Sound mixer with individual volume controls
- Saved mixes that keep playing with the screen off
- Intelligent sleep timer with gentle fade-out
- Brown, white, and pink noise varieties
- Nature sounds: rain, ocean waves, forest, thunderstorm
- Available on iOS, Android, and Mac

**Quick facts**

- Rating: 4.9 stars on the App Store
- Price: Free with optional premium
- Platforms: iOS, Android, Mac

**Sound types**

- Brown Noise: Deep, low-frequency sound ideal for sleep and focus
- White Noise: Equal energy across frequencies, masks distractions
- Pink Noise: Balanced frequency distribution, promotes deep sleep
- Nature Sounds: Rain, ocean waves, forest, thunderstorm, birds
- Mechanical: Fan, air conditioner, airplane cabin

**Use cases**

- Falling asleep faster
- Blocking distracting noises
- Deep focus and concentration
- Meditation and relaxation
- Studying and reading
- Baby sleep

## Links

- [Website](https://slonoise.com): Free browser-based sound mixer and the full guide library
- [iOS / Mac](https://apps.apple.com/us/app/slo-white-noise-sound-machine/id6739538343?pt=126878305&ct=llms-txt-en&mt=8): Slo on the App Store
- [Android](https://play.google.com/store/apps/details?id=com.sleep.sounds.noise.rain&referrer=utm_source%3Dslonoise_web%26utm_medium%3Dorganic_web%26utm_campaign%3Dllms-txt%26utm_content%3Dllms%26utm_term%3Den): Slo on Google Play
- [Resources](https://slonoise.com/resources/): Guides on sleep, focus, and sound
- [Privacy Policy](https://slonoise.com/privacy/)
- [Terms of Service](https://slonoise.com/terms/)

## Ready-to-play presets

Each URL opens the browser player with the layers and the sleep timer already set — no query string, no setup.

- [Rain sounds for sleeping](https://slonoise.com/play/rain-sounds-for-sleeping/): rain 55%, brown noise 25%, 45-minute timer
- [Ocean sounds for sleeping](https://slonoise.com/play/ocean-sounds-for-sleeping/): ocean 60%, pink noise 20%, all night
- [Pink noise for sleep](https://slonoise.com/play/pink-noise-for-sleep/): pink noise 50%, all night
- [Fan noise for sleeping](https://slonoise.com/play/fan-noise-for-sleeping/): ceiling fan 60%, brown noise 20%, all night
- [White noise for sleeping](https://slonoise.com/play/white-noise-for-sleeping/): white noise 45%, all night
- [Brown noise for sleep](https://slonoise.com/play/brown-noise-for-sleep/): brown noise 50%, all night
- [Thunderstorm sounds for sleeping](https://slonoise.com/play/thunderstorm-sounds-for-sleeping/): heavy rain 55%, thunder 45%, 60-minute timer
- [Green noise for sleep](https://slonoise.com/play/green-noise-for-sleep/): green noise 50%, all night
- [Brown noise for studying](https://slonoise.com/play/brown-noise-for-studying/): brown noise 45%, ambient rain 20%, 90-minute timer
- [Background noise for studying](https://slonoise.com/play/background-noise-for-studying/): cafe 45%, keyboard typing 20%, 90-minute timer
- [White noise for studying](https://slonoise.com/play/white-noise-for-studying/): white noise 45%, 90-minute timer
- [White noise for focus](https://slonoise.com/play/white-noise-for-focus/): white noise 45%, mellow wind 15%, 50-minute timer
- [Brown noise for focus](https://slonoise.com/play/brown-noise-for-focus/): brown noise 45%, mellow wind 15%, 50-minute timer
- [White noise for baby](https://slonoise.com/play/white-noise-for-baby/): white noise 40%, all night, with placement notes
- [Brown noise for ADHD](https://slonoise.com/play/brown-noise-for-adhd/): brown noise 50%, 50-minute timer, published with what the evidence shows
- [Rain and thunder](https://slonoise.com/mix/rain-and-thunder/): rain 55%, thunder 45%

Every preset page carries first-party acoustic measurements of the sounds it plays — loop length, integrated loudness, spectral centroid and band split — measured 2026-09-04.

## Comparisons

- [Slo vs Calm](https://slonoise.com/resources/slo-vs-calm/)
- [Slo vs Headspace](https://slonoise.com/resources/slo-vs-headspace/)
- [Slo vs BetterSleep](https://slonoise.com/resources/slo-vs-bettersleep/)
- [Slo vs Noisli](https://slonoise.com/resources/slo-vs-noisli/)
- [Slo vs White Noise](https://slonoise.com/resources/slo-vs-white-noise/)
- [Slo vs Dark Noise](https://slonoise.com/resources/slo-vs-dark-noise/)
- [Slo vs myNoise](https://slonoise.com/resources/slo-vs-mynoise/)
- [Slo vs Endel](https://slonoise.com/resources/slo-vs-endel/)
- [Slo vs Brain.fm](https://slonoise.com/resources/slo-vs-brainfm/)
- [Slo vs Noizio](https://slonoise.com/resources/slo-vs-noizio/)
- [Slo vs Portal](https://slonoise.com/resources/slo-vs-portal/)