# Recorded audio: credits and licences

Two groups of files, both played on the SFX bus by `scripts/ui/space_audio.gd`
(catalogue and rules in `scripts/sim/space_recordings.gd`, design notes in
`docs/AUDIO.md` → "Recorded audio").

**Space carries no sound.** Only the Mars clip is sound travelling through air.
The rest are radio or plasma waves picked up by antennas and turned into audio,
or sonifications (images mapped to sound). The game's captions say which.

## 1. Space recordings and sonifications — `assets/audio/space/`

NASA material is used under the NASA Images and Media Usage Guidelines
(<https://www.nasa.gov/nasa-brand-center/images-and-media/>): NASA content,
including audio, is generally not subject to copyright in the United States.
Chandra material: "Chandra materials on this site have been produced for NASA
at the Smithsonian Astrophysical Observatory (SAO) under contract NAS8-03060.
For Chandra content, no claim to copyright is being asserted and the material
may be used in accordance with NASA guidelines"
(<https://chandra.harvard.edu/photo/image_use.html>). No NASA / Chandra logo is
used and no endorsement is implied. Credits below are as given on each source
page.

| File | What it is | Kind | Instrument · date | Credit | Source page (downloaded file) |
|------|-----------|------|-------------------|--------|-------------------------------|
| `mars_perseverance_wind.ogg` | Martian wind at Jezero crater, rover self-noise filtered out (NASA's filtered version). | Sound in air, recorded by a microphone | Perseverance EDL microphone · 20 Feb 2021 | NASA/JPL-Caltech | <https://science.nasa.gov/resource/nasas-perseverance-rover-microphone-captures-sounds-from-mars/> (`45704_1st_Sounds_from_Mars_filters_out_rover_self-noise.wav`) |
| `saturn_cassini_skr.ogg` | Saturn kilometric radiation (radio emission from the auroral regions). NASA shifted the frequencies down by a factor of 44 and compressed 27 min into 73 s. | Radio data → audio (frequency-shifted) | Cassini RPWS · from Apr 2002 (released 25 Jul 2005) | NASA/JPL/University of Iowa | <https://science.nasa.gov/photojournal/eerie-sounds-of-saturns-radio-emissions> — PIA07966 (`PIA07966.wav`) |
| `jupiter_juno_aurora.ogg` | Radio emissions (7–140 kHz) from Jupiter's auroras after Juno's 27 Aug 2016 perijove, "shifted into a lower register"; 13 h of data. | Radio data → audio (frequency-shifted) | Juno Waves · 27 Aug 2016 (released 2 Sep 2016) | NASA/JPL-Caltech/SwRI/Univ. of Iowa | <https://science.nasa.gov/photojournal/juno-listens-to-jupiters-auroras-sing/> — PIA21037 (audio track of `PIA21037_JPL-20160901-JUNOf-0004-180.mp4`) |
| `ganymede_juno_flyby.ogg` | Radio waves (10–50 kHz) during the Ganymede flyby, shifted into the audio range; the jump in pitch is a change of magnetospheric region. | Radio data → audio (frequency-shifted) | Juno Waves · 7 Jun 2021 (released 17 Dec 2021) | NASA/JPL-Caltech/SwRI/Univ of Iowa | <https://science.nasa.gov/photojournal/audio-of-junos-ganymede-flyby> — PIA25030 (audio track of `PIA25030.mov`) |
| `earth_chorus_vanallen.ogg` | "Chorus": very-low-frequency radio waves in Earth's radiation belts, naturally at audio frequencies. | Plasma / radio waves → audio (played as received) | Van Allen Probes EMFISIS · 5 Sep 2012 (released 27 Nov 2012) | Science@NASA and NASA's Goddard Space Flight Center | <https://svs.gsfc.nasa.gov/11073> "Earth's Song" (audio track of `Earthsong-540-MASTER_high.mp4`) |
| `voyager1_interstellar_plasma.ogg` | Electron plasma oscillations in interstellar space beyond the heliopause; "the waves detected by the instrument antennas can be simply amplified and played through a speaker". Rising tone = rising density. | Plasma waves → audio (played as received) | Voyager 1 Plasma Wave instrument · Oct–Nov 2012 and Apr–May 2013 (released 12 Sep 2013) | NASA/JPL-Caltech/University of Iowa | <https://science.nasa.gov/photojournal/voyager-captures-sounds-of-interstellar-space> — PIA17045 (audio track of `PIA17045_20130906-320.mp4`, one pass) |
| `m87_chandra_sonification.ogg` | Chandra X-ray image of M87 swept like a radar; radius → pitch, brightness → volume. The X-ray-only layer. | **Sonification** (not a recording) | Chandra ACIS image → sound · released 16 Sep 2021 | X-ray: NASA/CXC/KIPAC/N. Werner, E. Million et al.; Sonification: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida) | <https://chandra.harvard.edu/sound/m87.html>, <https://chandra.harvard.edu/photo/2021/sonify4/> (`sounds/m87_xray.mp4`) |
| `galactic_centre_chandra_sonification.ogg` | Chandra, Hubble and Spitzer images of the central ~400 ly read left to right (xylophone / violin / piano); the last 30 s, ending at the bright region round Sgr A*. | **Sonification** (not a recording) | Chandra + Hubble + Spitzer images → sound · released 22 Sep 2020 | X-ray: NASA/CXC/SAO; Optical: NASA/STScI; IR: NASA/JPL-Caltech; Sonification: NASA/CXC/SAO/K. Arcand, SYSTEM Sounds (M. Russo, A. Santaguida) | <https://chandra.harvard.edu/sound/gcenter.html>, <https://chandra.harvard.edu/photo/2020/sonify/> (`sounds/galactic_all.mp4`) |

Not included, on purpose: ESA's Huygens descent audio of Titan (ESA material
is not automatically free to reuse), Perseverance SuperCam clips (co-credited
to LANL/CNES/CNRS/ISAE-Supaero), InSight SEIS clips (instrument provided by
CNES/IPGP), and the Chandra M87 composite (it includes NRAO/VLA radio data).

## 2. Sound effects — `assets/audio/sfx/`

Made from Kenney's **Sci-Fi Sounds** pack (version 1.0, 2020-10-11),
<https://kenney.nl/assets/sci-fi-sounds>, whose `License.txt` reads:
"License: (Creative Commons Zero, CC0) http://creativecommons.org/publicdomain/zero/1.0/
— This content is free to use in personal, educational and commercial
projects. Support us by crediting Kenney or www.kenney.nl (this is not
mandatory)". Credit: **Kenney (www.kenney.nl), CC0**.

| File | Made from (Kenney Sci-Fi Sounds) | Used for |
|------|----------------------------------|----------|
| `launch_rumble.ogg` | `spaceEngineLow_000` (low-passed, swell) + `lowFrequency_explosion_000` | probe / uncrewed mission launch |

## 3. The project's own sound effects — `assets/audio/sfx/` and `assets/audio/ui/`

Supplied by the project owner (September 2026, via the sound board) and kept
as originals in `tools/audio_src/custom/` (a `.gdignore`d folder: never
imported or shipped). Files named `…-Elevenlabs.wav` were generated with
ElevenLabs Sound Effects on the owner's account and are used under that
account's ElevenLabs terms: a paid plan, which grants commercial use with no
attribution (confirmed by the owner, 2026-10-26; `docs/LICENSES_AUDIT.md` B5).
The others were made by the owner for the game (confirmed 2026-10-26;
`docs/LICENSES_AUDIT.md` B6).

| File | Made from (`tools/audio_src/custom/`) | Used for |
|------|---------------------------------------|----------|
| `sfx/ship_depart.ogg` | `ShipLaunch.mp3`, first 5 s, 1.8 s fade-out | crewed, colony and gate ship departure; Far Future cruise |
| `sfx/gate_open.ogg` | `MAGSpel-A_dark_viscous_magi-Elevenlabs.wav` | a gate opens; Far Future gate transit |
| `sfx/data_home.ogg` | `transmit.wav`, its first sound (the data burst) | probe data / crew or colony news reaches Earth |
| `sfx/ff_warp.ogg` | `SCIShip-Spaceship_diving_int-Elevenlabs.wav` | Far Future warp leg |
| `ui/transmit.ogg` | `transmit.wav`: the burst, 0.25 s, then its chime | a radio message is broadcast |
| `ui/hud_tick.ogg` | `ROCKImpt-Very_soft_tile_hover-Elevenlabs.wav`, first 0.2 s | hovering a button |
| `ui/hud_blip.ogg` | `UIClick-A_very_soft_premium-Elevenlabs.wav` | pressing a button / a time step |
| `ui/hud_chirp.ogg` | `UIClick-light_card_flip_tap-Elevenlabs.wav` | selecting a target |
| `ui/hud_chime.ogg` | `chime.wav` (uploaded as `1ca0545c-c848-4f18-9eb6-702734687905.wav`) | a transmission card in the log |
| `sfx/ff_jump.ogg` | `MAGSpel-A_dark_viscous_magi-Elevenlabs.wav` (as `gate_open`) | Far Future jump |
| `sfx/fly_whoosh.ogg` | `WHSH-A_short_soft_and_sa-Elevenlabs.mp3`, first 1.5 s | long camera flights in the Solar System view |
| `ui/research_start.ogg` | `ResearchStart.mp3` (lead-in room tone trimmed) | "Research begins…" |
| `ui/breakthrough.ogg`, `ui/omni_go.ogg` | `BreakThrough.mp3` | a technology unlocked; a search result taken |
| `ui/reply.ogg` | `reply.mp3` | a reply from another civilisation |
| `ui/year.ogg`, `ui/year_jump.ogg` | `year.mp3`, `YearJump.mp3` | +1 yr; +10 / +50 yr / Next |
| `ui/toggle_on.ogg`, `ui/bookmark.ogg` | `UIClick-A_very_soft_premium-Elevenlabs.wav` | a toggle switched on; a bookmark added |
| `ui/toggle_off.ogg`, `ui/tab.ogg`, `ui/bookmark_off.ogg` | `UIClick-light_card_flip_tap-Elevenlabs.wav` | a toggle switched off; a module opens; a bookmark removed |
| `ui/omni_open.ogg` | `UIMvmt-A_mouse_hover_sound-Elevenlabs.mp3`, first 0.15 s | the search box opens |
| `ui/error.ogg`, `ui/warning.ogg` | `error.mp3`, `warning.mp3` | "Can't…" status lines; research idle |
| `ui/zoom_in.ogg`, `ui/zoom_out.ogg`, `ui/system_open.ogg` | `SolarSystemZoom.mp3` | into / out of the Solar System; another star's system |
| `ui/boot.ogg` | `ShipComputer.mp3`, 2–12.5 s of 33 s, 3 s fade-out (−22 dBFS RMS) | the boot screen as the game starts |

Processing: mono, 44.1 kHz, silence trimmed, short fades; the `sfx/` files are
loudness-matched like the Kenney ones (−19 dBFS RMS), the `ui/` files to the
loudest-46 ms level of the synthesised sound each replaces (so the game's
volume settings still fit; the Sfx palette ones to its −18 dBFS, with the
palette's per-sound gains on top); Ogg Vorbis. Rebuild with
`python3 tools/build_space_audio.py --custom-only`.

## Processing

`tools/build_space_audio.py` (numpy / scipy + an ffmpeg binary, e.g. from the
`imageio-ffmpeg` wheel) downloads the source files listed above (cached in
`.cache/space_audio/`, or `--cache DIR`) and: mixes to mono; trims (Mars 0–16.6 s, Saturn
8–38 s of 73 s, Jupiter 27.6–52.4 s of the video, Ganymede 10–40 s of 49 s,
Earth 0–28.9 s, Voyager 12.05–24.1 s (one pass), M87 0–32.9 s, Galactic
Centre 34–63.8 s of 64 s); matches loudness to about −21 dBFS RMS (effects
−19 dBFS) with a −1.5 dBFS peak ceiling; fades in / out; resamples (22.05 kHz
for the recordings, 32 kHz for the sonifications, 44.1 kHz for the effects);
and encodes Ogg Vorbis. No other change was made to the content (no pitch or
speed change beyond what NASA / CXC published).