Aural CSS

Aural style sheets

To provide visually impaired users access to your pages CSS has provided some formatting declarations that will control how your pages are converted to synthesized speech. To date there are no browsers or addon products that
will take advantage of these features. One similar application would be the Hawaii Education Literacy Project’s
Freeware application Read To Me.

Although their program uses proprietary scripting to define how web pages are converted to speech it seems to be a good partial simulation of what will be provided by Aural style sheet declarations in future versions of web browsers.

There are three main groups of Aural declarations that will be available to Authors.


Volume properties

The first group will allow the author to control the volume and flow of the content through pauses. It will also provide a way to combine audio files that will be played in the background at defines times as the text is generated.

The possible declarations include:
volume, speak, pause-before, pause-after, pause, cue-before, cue-after, cue, play-during


Spatial Values

The second set of declarations will control the 3D spatial value of the direction of the speech. This is similar to the properties that are found in VRML and Multimedia Games.

Spatial Property Declarations include:
Azimuth which positions the sound in a 360 degree plane can be
used to position the direction of the speaker and if more than
one speaker is active then relative positions will be used to
offset their position to reduce confusion.

Values include: angle, left-side, far-left, left, center-left, center, center-right, right, far-right, right-side, behind, leftwards, rightwards

Elevation: is used to position the Y value or height of the direction the sound is coming from.

Values include: angle, below, level, above, higher, lower

By using these two declarations if you wanted the sound to come from the lower right you would set Azimuth to right and Elevation to lower.


Voice characteristic properties

The final group of declarations will control the quality of the voice used to generate the synthesized speech. Choice of characters the rate of speech and the ability to control how words are emphasized to provide sentences structure will allow authors to tweak their presentation.

The possible declarations include:
speech-rate, voice-family, pitch, pitch-range, stress, richness, speak-punctuation, speak-date, speak-numeral, speak-time