Texture and timbre only reflect one half of the Audio UX® design process that we call the Audio Aesthetic. The other half is the gestural composition. What is the range of pitch? What direction is the sound moving? How many notes are there? These are three important questions a UX sound designer should ask when developing the gesture of a UX/UI sound. While there aren’t public standard practices or guidelines in place for Audio UX®, there is a growing library of common practice in the market. For example, downward gestures are most often used to articulate conclusion or negativity such as power off or battery low, respectively. Upward gestures typically communicate the beginning of an experience or positivity, such as power on, mic on, or success.For example, the listening sound (i.e. "Speak Now") found in the Google Assistant is a two-note gesture (upward octave) which gives the sound a sense of beginning or opening which encourages the user to respond. Harmony is also used to indicate the positivity or conclusiveness of an interaction. For example, a sound that is based on the first chord of a key (fondly called the “home” chord) usually gives the experience a feeling of completion.
The iconic Google Assistant VUI sounds.