Aircraft audio depends mostly on distance. The same jet is a shriek on the tarmac, a roar at five hundred metres, and a soft rumble overhead at altitude. A volume change does not turn one into another: air absorption removes high frequencies as distance grows, and doppler shift only happens when the aircraft is passing. These prompts treat distance as the main parameter.
Every clip shows the exact prompt that produced it. The render script reads its prompts from the same file as this page. Copy one, change a word and generate your own.
commercial jet taking off from close beside the runway, enormous rising turbine roar with a ground rumble, outdoor
jet airliner passing high overhead at cruise altitude, soft distant rumble with no transient detail, open sky
small propeller aircraft flying low past the listener, buzzing engine with a clear doppler drop, open countryside
helicopter hovering overhead, heavy rhythmic rotor thump with a turbine whine underneath, outdoor, seamless loop
helicopter approaching from a distance, passing overhead loudly and receding, full doppler arc, open field
inside a passenger aircraft cabin at cruise, steady broadband air rush with a low engine drone, seamless loop
aircraft landing gear touching down on a runway, tyre chirp and rumble with reverse thrust roaring, exterior
military fighter jet passing low and fast, tearing afterburner roar arriving late with a violent doppler, open sky
small quadcopter drone hovering close then moving away, high buzzing rotors, outdoor, quiet park
airport tarmac ambience, distant jets, ground vehicles and radio chatter, wide open outdoor, seamless loop
These models respond to physical description. Name the material, the action and the space.
commercial jet taking off from close beside the runway, enormous rising turbine roar with a ground rumble, outdoor
"Ground rumble" is the low-frequency component you only hear near the aircraft, and it is what makes close sound close.
jet airliner passing high overhead at cruise altitude, soft distant rumble with no transient detail, open sky
"No transient detail" is a negative instruction that models air absorption. Distance removes the top end, and saying so works better than filtering afterwards.
helicopter approaching from a distance, passing overhead loudly and receding, full doppler arc, open field
Naming all three stages gets a complete pass in one render, so you do not have to automate a hover into a flyby.
helicopter hovering overhead, heavy rhythmic rotor thump with a turbine whine underneath, outdoor, seamless loop
A helicopter is two sounds stacked: a slow blade thump and a fast turbine whine. Naming both stops it sounding like a fan.
Air absorbs high frequencies far more than low ones, so a distant aircraft has a different spectrum from a close one, with the attack smeared by travel time. Prompting the distance gets you that physics. Rolling off the top of a close recording sounds muffled instead of far away, which is the usual reason a stock flyby will not sit behind a wide shot.
A hovering helicopter has no pitch shift; a passing one has a pronounced one. Confusing the two is the most common aviation error in edits: a hover loop panned across the stereo field still sounds stationary because the pitch never moves. If the aircraft crosses frame, ask for the doppler and render the whole arc in one clip so the shift is continuous.
Inside a cruising airliner, the dominant sound is boundary-layer air rushing over the fuselage: broad, smooth, close to pink noise, with the engine drone well below it. "Steady broadband air rush with a low engine drone" reads as a cabin immediately. Prompting the engines gives you something that sounds like standing outside one.
The models run on your machine, which changes the cost, the privacy and what you can automate.
Weights are fetched once. After that, generation, the library and the API all work with the network off. Everything lives in one SQLite file and one folder of WAVs under ~/.soundbox, and nothing is uploaded.
Soundbox runs an MCP server in the same process, with tools for generating and listing sounds. Generated files come back as absolute paths, so an agent can copy them into a project.
Every model's terms are shown before you download it, and non-commercial weights need an explicit confirmation. Soundbox is MIT. The licence of the model that made a sound governs what you may do with it.
claude mcp add --transport http soundbox http://127.0.0.1:17494/mcpcurl -X POST http://127.0.0.1:17494/api/generate \
-H 'Content-Type: application/json' \
-d '{"model":"audiocpp-stable-audio-3-sfx","prompt":"8-bit coin pickup blip","duration_s":1}'