The aural style sheets are predicted to serve aural media. Saying that, the aural media type, although predicted in the CSS 2.1, it has been deprecated furthermore. The media type speech is replacing the aural type in the newer versions of style sheets.
This media type is used to convert the on screen content to a screen reader for the user agents designed for non-visual media, such as speech synthesizers. The main purpose for it is to increase the accessibility of internet and it is widely used by visually impaired users. Beside these advantages, the aural media type is often used in, i.e., medical or entertainment industries.
The CSS for the aural media consists of a three-dimensional physical space (sound surround), temporal space (sound before, during and after other sounds) and the quality variations of synthesized speech (frequency, inflection?).
Beside style sheet standard units, the aural media type introduces three more:
The angle units may be given as deg, grad and rad referring to degrees, grads and radians respectively. The values may be negative. If the value is "0", the unit may be omitted.
Examples: the right angle is "90deg" or "100grad" or "1.570796326794897rad".
The time units may be given as ms or s referring to milliseconds and seconds, respectively. The values may not be negative. If the value is "0", the unit may be omitted.
The frequency units may be given as hz or kHz, referring to Hertz and kilohertz, respectively. The values may not be negative. If the value is "0", the unit may be omitted.
Examples: the value "200hz" is a base sound and the value "6khz" is a treble sound.