Sounds have measurable characteristics that can indicate how effective a sound will be at creating a desired effect. A technique that portrays these characteristics is called sound visualization. On a graph, the x-axis portrays one characteristic (such as time) and the y-axis portrays another characteristic (such as amplitude). In some cases, a characteristic is graphed using only a single axis.

These guidelines describe how sound can be visualized as a function of time, frequency (how high-pitched or low-pitched a sound is), or timbre (the character of a sound).

* Time
* Frequency
* Timbre

Representing Sound

The timbre of a sound describes its quality and character (without regard for its pitch or volume).

* Timbre types

Timbre

Tonality refers to two types of sounds:

* *Tonal sounds*, which are more musical in nature, including melody, motif, and harmony
* *Atonal sounds* (also called non-harmonic sound), which resemble everyday sounds or noise – they don’t conform to traditional musical compositions

Sounds can be designed using tonal or atonal elements, and sometimes a sound will be comprised of both. Tonal sounds work best to communicate personality, emotion, and state changes, whereas atonal sounds better support motion transitions and express a sense of haptic feedback.

Tonality

In sound design, *dynamics* refer to changes in volume or loudness on either a micro scale (volume changes to a single sound) or a macro scale (volume changes to a set of sounds). 

Dynamic variation allows sounds to feel natural and realistic. Dynamic changes can highlight sonic moments of interest, create a sense of progress through a musical narrative, and give sound a natural quality.

* Examples

Dynamics

The envelope of a sound refers to changes in a sound’s amplitude over time. An envelope is comprised of many technical components, but the two most basic are the rise (*attack*) and fall (*decay*) of a sound.


Envelope

**Reverb** and **delay** are effects that can add a sense of space and depth. To keep sound effects from becoming too prominent a part of an earcon’s sound, they should be used sparingly.

The more reverb and delay a sound has, the more **wet** the sound is as opposed to dry.

Effects of sound attributes

Sound attributes can be adjusted in a variety of ways to create a specific effect.
* Representing sound 
* Timbre
* Tonality
* Dynamics
* Envelope
* Effects

University of Michigan - Ann Arbor

Sound communicates information in ways that improve the user experience

Sound

Material Design Documentation

About sound 

"Sound can give expression to interactions and reinforce specific functionality."

- Sound use cases
- Hero sounds
- Notifications
- System sounds
- Ambient sounds


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