Slo: Sleep Sounds, Brown Noise

Melted Butter

Contains adsIn-app purchases

About this app

Slo is a brown noise and sleep sounds app with 70+ curated sounds for sleep, focus, and relaxation. Play deep brown noise on its own, or mix it with rain, waves, and fan sounds — each layer with its own volume — and set a sleep timer that stops playback automatically.

Key features

• Brown noise – deep, low-frequency rumble many people choose for focus and sleep
• White, pink & green noise – broadband noise colors for masking background sound
• Binaural beats & frequencies – binaural beats, solfeggio tones (396–963 Hz, including 432 Hz and 528 Hz) and Schumann resonance tones
• Rain sounds – steady rainfall and distant thunderstorms
• Waves & water – ocean waves, river, waterfall
• Fan sounds – ceiling fan, table fan, airplane cabin
• Nature & ambience – forest, birds, wind, fireplace, campfire, train
• Sound mixing – layer sounds, each with its own volume control
• Sleep timer – playback stops on its own after you drift off

Made for

• Light sleepers who use steady sound to mask traffic, neighbors, or a snoring partner
• Students and deep workers who keep brown noise or fan noise running for hours
• People who wind down to binaural beats, solfeggio tones, or steady frequencies
• People who use sound masking at night to make tinnitus ringing less noticeable
• Anyone building a consistent wind-down routine — same mix, same timer, every night

Why Slo?

A focused sound machine, not a content platform: 70+ curated sounds, a mixer with per-layer volume, and a sleep timer. No voices, no playlists — steady sound that sits in the background while you sleep, study, or work.

Slo is free to download and try; the full sound library is a premium purchase inside the app.

FREQUENTLY ASKED QUESTIONS

What is the best app for brown noise?
Slo is built around brown noise: play it on its own, or layer it under rain or a fan sound with a separate volume for each layer, and set a timer so it stops on its own.

Does brown noise help you sleep?
Brown noise doesn't treat anything — what it does is mask. A steady low-frequency sound covers unpredictable noise like traffic, doors, and snoring, which is why many light sleepers keep it running at night.

Can I use Slo for tinnitus?
Steady broadband sounds like brown and pink noise can help mask tinnitus ringing — many people set a low volume that makes the ringing less noticeable at night. Slo is a sound player, not a treatment; persistent or one-sided tinnitus needs a medical assessment.

What are solfeggio frequencies and binaural beats?
Slo includes solfeggio tones (396–963 Hz, with 432 Hz and 528 Hz), Schumann resonance tones, and binaural beats — steady tones many people play for meditation and winding down. Try one with headphones and keep it if you like it.

What's the difference between brown, white, pink and green noise?
White noise spreads energy evenly across all frequencies (like static). Pink noise shifts energy toward lower frequencies (like steady rain). Green noise centers on the middle of the spectrum. Brown noise goes deepest — a low rumble like a waterfall or strong wind. Slo includes all of them, so try each and keep what suits you.

Can I use it for studying and focus?
Yes. Many users prefer brown noise or fan noise as a steady background for studying and deep work, because a constant sound gives the ear nothing new to chase.

Can I mix multiple sounds together?
Yes. Layer brown noise with rain, add thunder over a fan, and set each sound's volume separately to build your own soundscape.

Does Slo have a sleep timer?
Yes. Set the timer when you press play and playback stops automatically.

Is Slo free?
Slo is free to download and try; the full 70+ sound library is a premium purchase inside the app.

Ratings and reviews

Edit: Im changing my review to 4 stars instead of 1 only bc I did finally get help. Yes the app, showed the card it would charge after the free trial, and yes, I did use the app free one time during the trial period. It was difficult to get help, as the first person told me there was nothing that could be done, but someone followed up and helped Delete my subscription!! I only wanted the 3 day free trial and the app is not allowing me to cancel. Now.youre charging me for something I dont want!!

absolutely love this app! i depend on white noise as background noise due to sound sensitivities and this app runs it perfectly! i love that running the sound in the background is a free option, where as most apps make you pay for that, or it doesnt work. i switched to this one for that reason and i dont plan on going back! also not to mention the variety of sounds that are free and even more if you pay the subscription. keep doing what you're doing the way you're doing it!

This app is great except for the fact that it shuts off randomly during the night and wakes you up. If it were consistent and played throughout the night it would be 5 stars easily. I've done all the optimization they recommend and it still shuts off every night. Reply: Yes my phone is always on the charger every night when using the app. Edit: What I'm hearing from the developer is that the app isn't compatible we with Samsung and instead of fixing the issue they blame the phone manufacturer.

What’s new

Bug fixes and improvements