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Shape generated rain: three base styles, then intensity, drop presence and impact. Rain fine-tuning is free.
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Choose a masking sound for traffic, snoring or voices, then shape your own sound environment.
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Home and Current mix keep your sound environment easy to find and control.
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Premium adds mixing, eight frequency bands and saved environments. Supporter perks are planned for a future update.
Inspiration
Sound can be both a problem and a solution.
I have long been sensitive to voices, everyday noises, and snoring when trying to sleep. At the same time, I have also experienced being the person whose own snoring can disturb someone else. These experiences made me realize that problems caused by sound can affect both sides of the same environment.
My background is in seismic engineering, waveform analysis, and signal processing. I wanted to apply what I had learned about waves and signals to a different challenge: creating more comfortable everyday sound environments.
That idea became NemuTune.
What it does
NemuTune is a sound app that lets users create a sound environment that fits them, instead of simply choosing from a library of fixed tracks.
Users can play and adjust natural sounds such as rain, flowing water, wind, and waves, as well as masking sounds designed with common disturbances such as conversations, traffic noise, and snoring in mind.
Rain is generated on the phone. Start with Standard, Heavy or Quiet rain, then shape its intensity, raindrop presence and raindrop impact to create a texture that suits you.
The free version lets users play one sound at a time, including nature and masking sounds, Solfeggio tones, binaural sounds and ambient BGM. Rain fine-tuning and background playback are also available free. Free users can hear a 30-second preview of a Premium recommended mix.
Premium adds:
- Mixing multiple sounds into one sound environment
- Direct adjustment of 8 frequency bands
- Saving and reusing up to 5 customized sound environments
NemuTune can be used before sleep, while relaxing, or when creating a more comfortable environment for focused work.
The goal is not to provide medical treatment, but to give people more practical control over the sound environment around them.
How I built it
I built NemuTune with Flutter and Dart for iOS and Android.
The sound-design process began with MATLAB and digital signal-processing experiments. I tested frequency characteristics, temporal changes, masking behavior, and different combinations of generated and nature-inspired sounds, then brought those ideas into the mobile app.
During development, I also had to solve platform-specific challenges such as background audio playback, headphone and speaker behavior, media controls, in-app subscriptions, and premium entitlement management.
RevenueCat now powers NemuTune's monthly and annual subscriptions through purchases_flutter. The app loads the default offering, purchases the selected package, and unlocks Premium from the premium entitlement in CustomerInfo. Entitlement updates and Restore Purchases also go through RevenueCat.
The procedural Dart audio engine generates rain, masking sounds and ambient BGM and streams PCM to the platform audio output. Firebase anonymous authentication is in the current app; the permanent Supporter-grant pipeline is future work, not a live benefit today.
Challenges
One of the biggest challenges has been balancing technical control with comfort.
A sound can mask unwanted noise effectively but still feel unpleasant or tiring. Small changes in frequency balance, modulation, loudness, or transitions can significantly change how the sound feels.
Another challenge has been making a technically complex sound system understandable on a small mobile screen. I want NemuTune to provide meaningful customization without making users feel like they are operating professional audio software.
Cross-platform audio behavior has also required extensive real-device testing, particularly for background playback, Bluetooth and wired headphones, lock-screen controls, and subscription state changes.
Accomplishments I'm proud of
I released the first public version of NemuTune on iOS on August 6, 2026, and Android on August 18, 2026, during Shipaton. Android version 1.0.1 is published. The iOS 1.0.1 update was submitted for App Review on October 1 and is awaiting review.
Android validation covered purchase and Premium unlock, restoration after clearing app data, removal of Premium after cancellation and expiry, and a never-purchased account remaining Free after Restore Purchases. iPhone testing also covered the main Japanese and English flows, Premium access, background playback and lock-screen controls.
More importantly, I moved the project from MATLAB-based sound experiments into a working mobile product that people can actually use in everyday environments.
NemuTune now combines custom sound generation, masking concepts, nature sounds, detailed sound adjustment, background playback, and a freemium subscription model in one product.
Building all of this as a solo project has also taught me how closely sound design, mobile engineering, user experience, monetization, and real-device testing are connected.
What I learned
One of the biggest lessons from building NemuTune is that there is rarely one universally "best" sound.
Different people prefer different frequency balances, textures, levels of variation, and combinations of sounds. That reinforced my belief that the long-term value of NemuTune should come from personalization rather than simply adding more fixed audio tracks.
I also learned that real-device testing matters enormously for audio products. Technical behavior that looks correct in code can feel completely different through a phone speaker, headphones, Bluetooth devices, or while the screen is locked.
What's next for NemuTune
The next step is to make NemuTune increasingly personal.
I want to improve the way the app learns from users' preferences and helps them reach a comfortable sound environment with less trial and error.
My immediate focus is completing the iOS update and improving the app from real use. Supporter 2026 perks are planned for a future update for monthly or annual Premium members who join by October 31 (JST) and remain active on November 1. They include an original supporter-only sound, a badge and a vote on the next exclusive sound.
NemuTune starts with sleep, but the broader vision is to expand into relaxation, focus, childcare, and eventually a sound-environment optimization platform that helps people create spaces that better fit their preferences and situations.
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