Representing sound
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).
Timbre
The timbre of a sound describes its quality and character (without regard for its pitch or volume).
Tonality
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.
Dynamics
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.
Envelope
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.
Attack
The attack refers to the initial speed of a sound, before it reaches maximum amplitude.
Decay
The decay refers to the amount and speed at which a sound’s amplitude decreases after its attack (until its amplitude is zero). The larger the decay, the longer and slower a sound will feel.
Effects
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.