CSS Aural Properties

Aural properties defines the aural rendering of a document.

Aural Style Sheets

Aural style sheets are the part of CSS that uses a combination of speech synthesis and sound effects to make a web document more accessible to visually impaired and screen readers.

Aural presentation can be used:

  • by blind people
  • in the automobiles
  • in devices like home entertainment
  • industrial and medical documentation systems
  • to help users learning to read or who have difficulty reading

When using aural properties, the canvas consists of a three-dimensional physical space (sound surrounds) and a temporal space (one may specify sounds before, during, and after other sounds). The CSS properties also allow you to vary the quality of synthesized speech (voice type, frequency, inflection, etc.).

An example of an aural style sheet:

  • h1, h2, h3, h4, h5, h6 {
  •     voice-family: male;
  •     stress: 20;
  •     richness: 90;
  •     cue-before: url("pop.au");
  • }
  • p {
  •     azimuth: center-left;
  • }
  • quotes {
  •     volume: x-soft;
  • }

This will direct the speech synthesizer to speak headers in a very rich male voice (a kind of "audio font").Before speaking the headers; a sound sample will be played from the given URL.

Paragraphs will appear to come from front left (if the sound system is capable of spatial audio). And quotes will be very soft.

Property
Values               
Description
azimuth angle
left-side
far-left
left
center-left
center
center-right
right
far-right
right-side
behind
leftwards
rightwards
inherit
Sets where the sound should come from horizontally.
cue cue-before
cue-after
inherit
Shorthand for setting the cue properties (i.e. cue-before and cue-after) in one declaration.
cue-after none
url
inherit
Specifies a sound to be played after speaking an element's content to delimit it from other.
cue-before none
url
inherit
Specifies a sound to be played before speaking an element's content to delimit it from other.
elevation angle
below
level
above
higher
lower
inherit
Sets where the sound should come from vertically.
pause pause-before
pause-after
inherit
Shorthand for setting the pause properties (i.e. pause-before and pause-after) in one declaration.
pause-after time
%
inherit
Specify a pause to be observed after speaking an element's content.
pause-before time
%
inherit
Specify a pause to be observed before speaking an element's content.
pitch frequency
x-low
low
medium
high
x-high
inherit
Specifies the average pitch (a frequency) of the speaking voice. The average pitch of a voice depends on the voice family.
pitch-range number
inherit
Specifies variation in average pitch.
play-during auto
none
url
mix
repeat
inherit
Specifies a sound to be played as a background while an element's content is spoken.
richness number
inherit
Specifies the richness of the speaking voice.
speak normal
none
spell-out
inherit
Specifies whether text will be rendered aurally and if so, in what manner.
speak-header always
once
inherit
Specifies whether table headers are spoken before every cell, or only before a cell when that cell is associated with a different header than the previous cell.
speak-numeral digits
continuous
inherit
Specifies how numerals are spoken.
speak-punctuation none
code
inherit
Specifies how punctuation characters are spoken.
speech-rate number
x-slow
slow
medium
fast
x-fast
faster
slower
inherit
Specifies the speaking rate i.e. number of words spoken per minute.
Stress number
inherit
Specifies the "stress" in the speaking voice.
voice-family specific-voice
generic-voice
inherit
Specifies a comma-separated, prioritized list of voice family names.
volume number
%
silent
x-soft
soft
medium
loud
x-loud
inherit
Specifies the volume of the speaking voice.
 
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