W3C CSS2 Cascading Style Sheets, level 2 - instructional media + ...

Contents
19 Aural style sheets
19.1 Introduction to aural style sheets . . . . . . . . 277 .
19.2 Volume properties: ’volume’ . . . . . . . . . . 278 .
19.3 Speaking properties: ’speak’ . . . . . . . . . 279 .
19.4 Pause properties: ’pause-before’, ’pause-after’, and ’pause’ . . 279 .
19.5 Cue properties: ’cue-before’, ’cue-after’, and ’cue’ . . . . 281 .
19.6 Mixing properties: ’play-during’ . . . . . . . . . 282 .
19.7 Spatial properties: ’azimuth’ and ’elevation’ . . . . . . 283 .
19.8 Voice characteristic properties: ’speech-rate’, ’voice-family’, ’pitch’,
’pitch-range’, ’stress’, and ’richness’ . . . . . . . . . 285 .
19.9 Speech properties: ’speak-punctuation’ and ’speak-numeral’ . . 288 .
19.1 Introduction to aural style sheets
The aural rendering of a document, already commonly used by the blind and
print-impaired communities, combines speech synthesis and "auditory icons."
Often such aural presentation occurs by converting the document to plain text
and feeding this to a screen reader -- software or hardware that simply reads all
the characters on the screen. This results in less effective presentation than
would be the case if the document structure were retained. Style sheet properties
for aural presentation may be used together with visual properties (mixed media)
or as an aural alternative to visual presentation.
Besides the obvious accessibility advantages, there are other large markets for
listening to information, including in-car use, industrial and medical documentation
systems (intranets), home entertainment, and 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 authors to
vary the quality of synthesized speech (voice type, frequency, inflection, etc.).
Example(s):
H1, H2, H3, H4, H5, H6 {
voice-family: paul;
stress: 20;
richness: 90;
cue-before: url("ping.au")
}
P.heidi { azimuth: center-left }
P.peter { azimuth: right }
P.goat { volume: x-soft }
This will direct the speech synthesizer to speak headers in a voice (a kind of
"audio font") called "paul", on a flat tone, but in a very rich voice. Before speaking
the headers, a sound sample will be played from the given URL. Paragraphs with
class "heidi" will appear to come from front left (if the sound system is capable of
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