# One family of sounds

> Design four to six sounds that share one material, and give each one the right pitch, length, loudness and file format.

Module: Sound · Level: intermediate · 7 min · https://school.agents.org.in/media/sound/one-family-of-sounds

Tap each card below with sound on. Five different jobs, and yet they clearly come from the same product. That is not luck. They are all the same small struck bar, played higher, lower, shorter or longer.

*[Interactive demo: One material, five sounds. Higher dot, higher pitch. Longer bar, longer sound.]*

A product's sounds work like a typeface. One family, several weights. **Five sounds from one material feel like a product; five sounds from five packs feel like clip art.**

## Pick one material

Start with a physical thing, not a style. "A felt mallet on a wooden bar." "A fingernail on thin plastic." "A muted glockenspiel." Every sound in the family is that thing, struck differently.

Apple's sound team works this way: they record real instruments like marimba and kalimba, and once tapped a hollow watch case with mallets to find its ring. Real materials make new technology feel familiar. The default AI failure is the opposite: a glossy sci-fi "digital blip" that belongs to no product.

> **In plain words.** An earcon (A short interface sound whose meaning you learn from its shape, like a rising tone for joining a call. It does not imitate a real-world noise) is a short sound whose meaning you learn, like the rising tone when someone joins a call. It does not imitate anything real; its shape tells you what happened. A sound palette (The small, matched set of four to six sounds a product uses, all made from one material, like one typeface in several weights) is the small, matched set of them a product uses.

## The grammar of a family

Meaning comes from the shape of the sound. People learn it in a handful of hearings.

| What changes | Rule | Why it works |
|---|---|---|
| Size → pitch and length | Small things tick high and short (40 to 120 ms). Big things land low and long (300 to 800 ms). | Physics. A chip is lighter than a page. |
| Direction → meaning | Rising = success, open, join. Falling = dismiss, leave, error. | Every operating system you have used. |
| Interval → feeling | A major third or a fifth confirms. A tight, clashing step warns. | Consonance sounds safe; dissonance sounds tense. |
| Complexity → priority | One hit for frequent things. Several notes only for rare ones. | A busy sound heard often tires people out in a day. |

Notice the cards above: `send` rises, `error` falls and clashes, `success` is the only one with three notes.

## A family is small

Most products need four to six sounds, not forty:

- **tick** for a toggle, a selection, a snap. One hit, 80 ms or less, high.
- **tap** for a press, only in products built to feel physical. Up to 120 ms.
- **send** for sent, saved, done. One or two rising notes, up to 250 ms.
- **receive** for an incoming message. Two notes, lower than send, up to 400 ms.
- **error** for a rejected submit. Low, falling, up to 200 ms, beside a shake.
- **success** for a rare milestone. Three notes, up to 800 ms.

Write the family down as a list before generating anything. It is your sound design system.

**Design the family first (paste into your agent):**

```text
Design a sound family for this product before making any audio.
Pick ONE physical material (for example "soft felt mallet on a small wooden bar") and derive every sound from it.
List 4-6 sounds max as a table: name, role, contour (rising/falling), notes or pitch, duration in ms.
Rules: small/frequent = high, short, single hit; rising = success; falling and dissonant = error; only rare milestones get 3 notes.
No stock UI packs, no sci-fi blips.
```

## The numbers

Most "this sound feels wrong" complaints are a spec miss, not a taste miss: too long for its animation, too loud next to speech, or a sliver of silence before the hit.

| Kind | Length |
|---|---|
| Tick, toggle, snap | 40 to 80 ms |
| Tap, press | 80 to 150 ms |
| Hover | 0 ms. Hover is silent. |
| Send, save | 150 to 250 ms |
| Notification | 200 to 600 ms |
| Error | 100 to 200 ms |

A handy rule from Toptal: a sound should not outlast the animation it goes with by more than about 300 ms. A 120 ms press with an 800 ms tail is a bell, not feedback.

**Loudness.** Taps and ticks sit around −18 to −14 LUFS (Loudness Units relative to Full Scale: how loud a whole piece of audio sounds to a person. Closer to zero is louder; −14 is loud, −30 is quiet), below speech and above silence. Notifications may go to about −12. Peak every file at −3 dBFS (Decibels below the loudest a digital file can go. 0 dBFS is the ceiling where sound distorts, so UI sounds peak at about −3 dBFS) so it never clips. Put the design level in the file and the person's level in the volume control; never bake "a bit quieter" into the asset.

**Format.** Mono (Sound on one channel instead of separate left and right. UI sounds are mono because phone and laptop speakers fold stereo into one anyway), 44.1 kHz. Phones and laptop speakers fold stereo into mono anyway. Keep a WAV as the master and ship MP3 or Opus. Trim the start to the first audible sample: five milliseconds of silence up front is a visible sync error. Fade the last 10 ms so it ends without a click.

**Shape.** Cut everything under 150 to 200 Hz; laptop speakers cannot play it and it only eats headroom. Keep the body between 500 Hz and 4 kHz, where every device is honest.

*(Check on the worst laptop speaker you own, not studio headphones at midnight.)*

## What a designed effect is made of

For films and marketing pieces, Leon Lin's earshot project measured dozens of professional sound effects and found the same habits again and again:

1. **One gesture each.** A pitch that sweeps, notes that step up, a gate that speeds up into the cut.
2. **Its own frequency band.** Typing has nothing low; impacts live low with a thin tick on top. The middle is left for voice and music.
3. **A hard end.** Short sounds hold, then stop. No long reverb ride-out.
4. **Mono for objects, wide for textures.** A click is mono; a shimmer can be wide.
5. **Placed by kind.** Clicks land their attack on the moment; a whoosh peaks on the fastest frame; a riser ends on the hit.

Repeated sounds vary in *take* (four recordings cycled, a tiny level change) rather than random pitch. The UI click is the exception: one voice, one level, every time.

**Check yourself:** A product's error sound is a bright, rising two-note chime, 700 ms long. What is wrong?

- [ ] Nothing, it is pleasant
- [x] It rises and is consonant, which reads as success, and it is far too long for an error
- [ ] It should be stereo
- [ ] It should be louder so people notice

*Why:* Direction and interval carry meaning: rising and consonant says success. An error should be low, short (100 to 200 ms) and falling, with a shake as its visual twin.

## In the skill

- https://school.agents.org.in/skill/sound/sound-palette.md
- https://school.agents.org.in/skill/sound/sound-spec.md
- https://school.agents.org.in/skill/sound/designed-sfx-anatomy.md