Rounding Rush audio engine-bed.wav is adapted from loop_0.wav, "racing car engine sound loops" by domasx2, published July 24, 2011 on OpenGameArt. Source: https://opengameart.org/content/racing-car-engine-sound-loops Original download: https://opengameart.org/sites/default/files/loop_0.wav License: CC0 1.0 Universal, Public Domain Dedication https://creativecommons.org/publicdomain/zero/1.0/ The source author describes this recording as a loop cut from a public-domain car recording and confirms the replacement with that public-domain source in the July 24, 2011 comment. The current asset and license were checked Oct 13, 2026. Changes: removed DC offset, crossfaded a 24ms loop boundary and normalized to 0.24 RMS. Mono 44.1kHz 16-bit PCM. Preparation is reproducible with scripts/prepare-rounding-audio.mjs and the original download. Original SHA-256: 69d74b106509037ce547429e4c3f9ae906b0fffe88d0bb8b3b5a8b0cfc239048 Adapted SHA-256: dfde73a39393f65324660ff7dcdf21a6f79df25895e13763403768a73c26ef8a Additional engine recordings by FreeCarSoundsGaming, published September 14, 2020 on Freesound. The author identifies all three as car recordings made with a lavalier microphone and optimized for looping in FL Studio. engine-rev-low.mp3: "Revving.ogg" Source: https://freesound.org/people/FreeCarSoundsGaming/sounds/535041/ Public high-quality preview used: https://cdn.freesound.org/previews/535/535041_11894201-hq.mp3 SHA-256: 74a5e1f8907318ebe53a33f00cdf4a76b0b3f3d853ead099a5e6d56bf501c9c1 engine-rev-high.mp3: "Revving_2.ogg" Source: https://freesound.org/people/FreeCarSoundsGaming/sounds/535040/ Public high-quality preview used: https://cdn.freesound.org/previews/535/535040_11894201-hq.mp3 SHA-256: 78539526307953587d8d233afe2f83688a40c0122385cc9c5128db10b427dd8b engine-muscle-idle.mp3: "Muscle_Idle.ogg" Source: https://freesound.org/people/FreeCarSoundsGaming/sounds/535038/ Public high-quality preview used: https://cdn.freesound.org/previews/535/535038_11894201-hq.mp3 SHA-256: a1c447e6d1c872c1b408b68a4e2fcbffde7d181ce8f51e8e514a9769d65b4ecb nitro-pressure.mp3: "Compressed Air-Short-13" by wavecal22 Source: https://freesound.org/people/wavecal22/sounds/753130/ Pack: https://freesound.org/people/wavecal22/packs/41685/ Public high-quality preview used: https://cdn.freesound.org/previews/753/753130_1068206-hq.mp3 SHA-256: 1e50a05882fb915b93160402cb6c4ff60ba43b29681371923176fb0116cd3f24 The source is from the author's "Compressed Air FX (Canned Air)" pack. It is a compressed-air recording used as a game boost/pressure-release effect, not a claim to be a recording of a nitrous-injected engine or a commercial game. All four Freesound assets: CC0 1.0 Universal, Public Domain Dedication. License on each individual sound page verified October 13, 2026: https://creativecommons.org/publicdomain/zero/1.0/ The shipped MP3s are unchanged Freesound high-quality preview transcodes, not the original Ogg/WAV uploads. Their hashes can be checked with: node scripts/prepare-rounding-audio.mjs --verify Playback adaptations: decode locally once, fold to mono, remove DC offset, normalize with peak headroom, and crossfade engine/sustain loop boundaries. Four actual engine recordings crossfade with RPM/load and car-specific tone. The air recording supplies nitro attack, a looping middle section, and release. The conditioner is prepareRecordingData() in rounding-rush-audio.js. Procedural combustion is an offline/unavailable-sample fallback only and stops when engine recordings load. Road, tire, wind, a quiet turbo tone, a short low boost accent and dashboard cues remain original synthesized effects. Nothing in this sound package is taken from a commercial racing game. Recorded gear transitions ------------------------ engine-shift-up.wav and engine-rev-blip.wav are excerpts of "Car Engine Contact Recording-Mini Cooper S 2019_Gear Shift.wav" by TheLittleCrow, published January 14, 2023 on Freesound. Source: https://freesound.org/people/TheLittleCrow/sounds/669623/ Public high-quality preview used: https://cdn.freesound.org/previews/669/669623_5672786-hq.mp3 Source preview SHA-256: 565a783fee236deafb4a480cc41ad3799517ba7688f8fec580120f26056626a4 License: CC0 1.0 Universal, Public Domain Dedication. https://creativecommons.org/publicdomain/zero/1.0/ The individual source page and license were verified October 13, 2026. The author records a Mini Cooper S in sport mode with two contact microphones: left channel on the chassis and right channel on the engine block, and identifies audible gear shifting. The upshift excerpt captures the recorded rev drop at 9.18-9.75 seconds; the rev-blip excerpt captures the rise at 43.75-44.40 seconds. The latter is used to accompany downshifts; it is credited as a recorded rev rise. Changes: decoded the public MP3 preview with mpg123-decoder 0.4.12, extracted the specified intervals, balanced channel RMS, mixed 58% chassis / 42% engine block, removed DC offset, normalized with a 0.72 peak ceiling, and applied 6ms/35ms boundary fades. Saved mono 48kHz 16-bit PCM WAVs. Playback follows each selected car's pitch and actual gear direction. The decoder is an offline preparation tool only and is not a game dependency. To reproduce, install mpg123-decoder 0.4.12 in a separate tools folder, then run: node scripts/prepare-rounding-audio.mjs --shift-mp3 source-preview.mp3 path/to/mpg123-decoder/index.js engine-shift-up.wav SHA-256: cd28021d165d5f8406775d1c5abe45d0ed54c127ee48f543126847c5080c4fd5 engine-rev-blip.wav SHA-256: c1e45af44260a163b55bc7d46c689eb6bbb031e2324d5e0fbe464def1d688db7 Gear changes use these actual engine excerpts, with clutch-load cuts and rev recovery in the continuous engine mix. If the excerpts fail to load, a short pitch transition reuses another available real engine recording. No generated noise click is used for a gear shift. CRASH FOLEY RECORDINGS crash-impact.mp3: "Car Crash (with Glass)" by magnuswaker Source: https://freesound.org/people/magnuswaker/sounds/592388/ Public high-quality preview used: https://cdn.freesound.org/previews/592/592388_11537497-hq.mp3 SHA-256: 0169d0fe29c4aba3cf1b0dd94c186a5fb917e9eef975c9a1485568d4a325d822 The author recorded metal computer-case panels impacting one another and combined those recordings with glass that they had smashed. This is recorded foley designed as a crash, not a recording of an actual vehicle accident. crash-scrape.mp3: "Metal Scrape" by dslrguide Source: https://freesound.org/people/dslrguide/sounds/321480/ Public high-quality preview used: https://cdn.freesound.org/previews/321/321480_5485024-hq.mp3 SHA-256: e36dd4f89f5eb4ce45f5c95f584f4c16f3f3df0c27b1969ff6a22c3fb1681c97 The author recorded a metal axe dragging across rusty metal with a Rode VideoMic Pro and Zoom H5 recorder. Used for road-rail and body scrape layers. crash-glass.mp3: "Glass Break" by avrahamy Source: https://freesound.org/people/avrahamy/sounds/141563/ Public high-quality preview used: https://cdn.freesound.org/previews/141/141563_1422573-hq.mp3 SHA-256: 3cf725050dd2a3685f0c80b165c22c63615059f3bb10695ae20ba3dd398bc7b4 The source author describes breaking a glass window. Playback uses 0.20-1.72s to remove the silent lead-in, for severe impact shatter and a quieter delayed shard/debris tail; this separate glass layer is absent on minor contacts. All three crash recordings: CC0 1.0 Universal, Public Domain Dedication. License verified on each primary sound page October 13, 2026: https://creativecommons.org/publicdomain/zero/1.0/ The shipped MP3s are unchanged public high-quality preview transcodes. Playback adaptations: decode once, fold to mono, remove DC, condition levels with a .72 peak ceiling, pitch/filter/envelope by impact severity and surface, combine at most five short layers, and briefly lower driving audio for clarity. No crash recording is taken from commercial gameplay. If downloads fail, original decaying-impact, scrape and shard buffers are computed once as a fallback and then reused. All crash effects share the existing 12-voice cap.