For installers with an ELEVENLABS_API_KEY, text-to-sound-effects turns a written sound-palette into files in one pass, and lets you iterate on words ("more felt, less glass") instead of on a synth patch. The model is good at materials and bad at abstractions; prompt accordingly.

The endpoint

POST https://api.elevenlabs.io/v1/sound-generation with header xi-api-key.

Field	Range / default	Use for UI sounds
`text`	required	The material-first prompt below
`duration_seconds`	0.5–30, default auto	0.5 for ticks and taps; 0.6–1.0 for tones; never auto for UI
`prompt_influence`	0–1, default 0.3	0.8+ — functional sounds need literal, low-variance output
`loop`	false	Only for ambiences and processing loops
`model_id`	`eleven_text_to_sound_v2`	—
`output_format`	`mp3_44100_128` default	`pcm_44100` if you will post-process; MP3 otherwise

Each generation costs 200 credits; the free tier's 10,000 credits a month is roughly fifty sounds — enough to generate a six-sound family three or four times over while you tune the prompts. SDKs: @elevenlabs/elevenlabs-js (never the deprecated elevenlabs npm package) and elevenlabs on PyPI.

The prompt formula

Material + action + envelope + mood + frequency hint + purpose. The model responds to physical descriptions and audio vocabulary (transient, one-shot, dry, muted, no tail), not to UI nouns ("a success sound" produces a stock jingle).

tick     → "single very short tick, fingernail on thin plastic, dry, no tail, bright, one-shot UI feedback"
tap      → "soft muted tap, felt mallet on a small wooden block, dry, clean transient, short body, no reverb"
send     → "two quick rising notes on a muted kalimba, warm, dry, short decay, confirmation"
receive  → "two soft descending notes on a glockenspiel, gentle, dry, short, incoming message"
error    → "short low dull thud with a slight downward pitch, rubber on wood, dry, no tail"
success  → "three ascending mellow marimba notes, major, warm, dry, short decay, completion"

Rules that came out of use:

Say the material and the stick. "Felt mallet on wood" and "fingernail on plastic" are different sounds; "a click" is a lottery.
Say "dry" and "no tail" every time. The default has room reverb, and reverb is the first thing that breaks sound-spec.
Give the contour, not the emotion. "Two rising notes" beats "happy." "Downward pitch" beats "sad."
One session, one material. Generate the whole family in one sitting with the same material phrase prefixed to every prompt; it is the cheapest way to get sounds that belong together.
Ask for 0.5 s and cut. The model pads short prompts with air; a 0.5 s request trimmed to 80 ms is cleaner than a 0.1 s request.

After generation

Every file still needs sound-spec: trim leading silence to zero, high-pass at 150 Hz, peak to −3 dBFS, mono. scripts/sound-family.mjs does the trim and peak with ffmpeg when it is installed; the high-pass and the LUFS check are a five-second ffmpeg or DAW step.

The shipped script

node scripts/sound-family.mjs family.json --out public/sfx reads a manifest of { material, sounds: { name: { prompt, seconds, synth } } }, calls ElevenLabs when the key is present (or --provider synth to force the offline path from sound-generation-open-source), writes normalized files and a manifest.json. Add --dry-run to print the prompts without spending credits.

When to apply

An installer has the key and the sound-decision-framework has said yes to at least one sound. For a launch video, launch-video-sound picks the register first: under a beat track the track carries the pops, and in the dry, bed and foley registers (A, B, E) sound-from-motion synthesizes the cues from the motion. Generate only a one-off that the cue sheet's kinds do not cover, such as a riser or a cinematic impact. Use the same prompt formula and trim its lead-in; an impact's transient lands on the contact frame per sound-motion-sync, and a riser ends where the gap before the reveal opens.

Gotcha

Generated files are not deterministic. Regenerating tick next sprint produces a different tick, and a family with one re-rolled member sounds patched. Commit the WAVs, record the prompts and settings in the manifest, and regenerate the whole family when the material changes.

Sources

ElevenLabs API reference, Create sound effect — fields, ranges, defaults, output formats.
ElevenLabs product guide, Sound effects — prompt vocabulary (impact, whoosh, one-shot, loop, drone, braam).
ElevenLabs pricing — 200 credits per generation; 10,000 free credits a month.
Envato, UI sound design with AI — the Action + Material + Mood + Frequency + Purpose formula; prompt-influence bands.
Related: sound-palette, sound-spec, sound-designer.