Aural Style Sheets

Sound in Space

Spacial characteristics of sound make it easier to tell various voices apart, by placing them in different locations in space. There are two CSS properties that define where the voice is spatially: azimuth and elevation. Azimuth has the following values:

• angle
  This is the exact degree number for where the voice should be coming from, for example 30deg or 359deg
• behind
  This keyword places the sound as coming from behind rather than the front
• leftwards
  This keyword subtracts 20 degrees from the current angle, making the sound come from the left
• rightwards
  This keyword adds 20 degrees to the current angle, making the sound come from the right

More about azimuth

Voice Characteristics

The properties of voice characteristics specify what the voices will sound like. This includes details such as their speed of speech, pitch, and range. The properties are:

• speech-rate
  This indicates the speed of speech, generally in words per minute. The options are:
  • number
    A specific number of words per minute.
  • x-slow
    80 words per minute (WPM)
  • slow
    120 WPM
  • medium
    180-200 WPM
  • fast
    300 WPM
  • x-fast
    500 WPM
  • faster
    Adds 40 words per minute to the current speech
  • slower
    Subtracts 40 words per minute from the current speech
• voice-fmaily
  Similar to the "font-family" property, this is a comma separated list of generic and specific voices. Generic voices are like “male,” “female,” and “child.”
• pitch
  This property defines the specific pitch or frequency of the voice. Possible values are:
  • frequency
    A specific value in hertz (Hz)
  • x-low
  • low
  • medium
  • high
  • x-high
    These don't have specific values as they depend upon what voice-family is used. For example, an x-high male voice might have a lower pitch than a medium or low female voice.
• pitch-range
  This indicates the variation in average pitch for the voice. The default value is 50, but you can change it to any number between 1 and 100.
• stress
  This indicates the amount of stress or "local peaks" should be applied to the voice. The default value is 50, but you can change it to any number between 1 and 100.
• richness
  This determines the richness or brightness of the voice. A rich voice will "carry" through a large room while a smooth voice will not. The default value is 50, but you can change it to any number between 1 and 100.

Speech Properties

These properties define how more complex parts of speech like punctuation and numerals are spoken within the element. There are two properties:

• speak-punctuation
  This defines how punctuation is spoken
  • code
    Punctuation is to be spoken literally within the text.
  • none
    Punctuation is not to be spoken, but to be rendered as natural speech with pauses.
• speak-numeral
  This defines how numbers are spoken
  • digits
    Each separate number is spoken individually. ie. 163 is said "one" "six" "three"
  • continuous
    Numbers are spoken as full numbers. ie. 163 is said "one hundred sixty-three"

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