A robot sounds like its size and its era. Small modern machines are quiet, precise and electric; large ones are hydraulic, heavy and slow; retro ones clank and whir with visible mechanism. Any of them sounds alive when its movement has a shape: a start, a travel and a stop. A servo that only hums sounds like a fan.
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.
small robotic servo motor moving an arm and stopping precisely, clean electric whir with a settling click, close mic, dry
giant mech taking a single heavy step, hydraulic servo whine with an enormous metal foot slamming onto concrete
robot transforming, cascade of servos, hydraulic hisses and metal panels locking into place, close and mechanical
small robot vocalising in expressive electronic beeps and warbles, curious and questioning, dry
robot powering up, rising electrical whine with systems clicking online and servos calibrating, close mic
robot powering down and collapsing, servos losing tension with a descending whine and metal settling
heavy hydraulic piston extending under load then venting pressure, industrial and close, dry
retro tin robot walking, clanking metal feet with a whirring clockwork motor, close mic, dry
robot targeting scanner sweeping, thin oscillating electronic tone with tiny servo adjustments, dry
robot malfunctioning, servos grinding and stalling with electrical sparks and distorted vocal glitches
These models respond to physical description. Name the material, the action and the space.
small robotic servo motor moving an arm and stopping precisely, clean electric whir with a settling click, close mic, dry
"Stopping precisely" with "a settling click" gives the movement an endpoint, so the servo sounds controlled instead of idling.
giant mech taking a single heavy step, hydraulic servo whine with an enormous metal foot slamming onto concrete
Scale comes from the two layers together: the whine says it is powered, the slam says how big it is.
small robot vocalising in expressive electronic beeps and warbles, curious and questioning, dry
Emotional direction works here, unlike in most categories, because expressive beeping is a performed convention the model has heard often.
retro tin robot walking, clanking metal feet with a whirring clockwork motor, close mic, dry
"Clockwork" and "tin" place it decades before hydraulics, a period cue as strong as a visual one.
The most common robot-sound mistake is rendering only the travel: a whir with no beginning and no end. Real actuators engage, move and arrive, and the arrival is a small mechanical event that tells the audience the motion was finished and deliberate. Ask for it: "stopping precisely", "locking into place", "with a settling click". Those few words separate a machine from a fan.
Small robots are electric: high-pitched, quiet, fast, clean. Large ones are hydraulic: low, slow and loud, with pressure release in every movement. This maps so directly onto perceived size that you can change a robot's scale by swapping those words and leaving the rest of the prompt alone, which helps when a design brief changes and you need the same motion at twice the weight.
A mech step is three sounds: the servo that lifted the leg, the mass that landed, and the frame rattling afterwards. Generating them separately and stacking them gives a heavier result than a single render, and lets you retime the impact to the animation frame without moving the servo. Transformations work the same way: they are a sequence of small events you can control individually.
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}'