# Sound assets and provenance

Verified 28 October 2026 against the original Freesound item pages and the linked CC0 1.0 deed. Both recordings are published under CC0 1.0 Universal. CC0 permits copying, adaptation and redistribution, including commercial use, without mandatory attribution. Courtesy credits are included in the prototype's teaching area. No endorsement is implied.

| Local file | Recording and creator | Original item | Downloaded file |
| --- | --- | --- | --- |
| assets/rain-on-roof.mp3 | Raining on roof, Duasun (2019) | https://freesound.org/people/Duasun/sounds/468024/ | https://cdn.freesound.org/previews/468/468024_5503971-hq.mp3 |
| assets/wooden-door-knocks.mp3 | Wooden Door Knock, FrostyFrost (2016) | https://freesound.org/people/FrostyFrost/sounds/348371/ | https://cdn.freesound.org/previews/348/348371_6138336-hq.mp3 |

Licence deed: https://creativecommons.org/publicdomain/zero/1.0/

Legal code: https://creativecommons.org/publicdomain/zero/1.0/legalcode.en

The included MP3s are the freely accessible high-quality previews of the CC0 recordings, not the original lossless WAV masters. They are stored locally and redistributed under the recording's CC0 dedication. No account, download credential or external playback URL is used by the app.

Runtime processing: rain is normalised, filtered below 85 Hz, and given a 1.2 second equal-power head/tail overlap to avoid the V0.1 silent loop join. The door recording is trimmed around its audible content, given short endpoint fades, normalised and filtered below 65 Hz. Source MP3 files are preserved byte-for-byte; processing is in browser memory.

The V0.2a atmospheric drone is original procedural Web Audio synthesis in audio-engine.js. Deep rumble and Unsettling atmosphere combine coloured noise, soft harmonic layers, slow noise-filter/level modulation and quiet early reflections. A 0.45 second crossfade switches character inside the same voice. No additional recording is used for either character. It has no third-party recorded content. No AI music service was used.

Licence-page metadata and SHA-256 hashes of the downloaded recordings are included in the review package under review-output/sound-studio-v02b/licence-evidence/. No noncommercial assets are included.



V0.2b retains the recordings and coloured-noise generator. Pitch now also shifts the noise playback spectrum, broad resonant bands and body/cutoff filters. Rumble pulse applies smooth surges to the full rumble; Atmosphere drift evolves separate noise bands at unrelated rates. Oscillator levels, recorded assets, licence terms and the 0.45 second character crossfade are unchanged.