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
Behind places the sound as coming from behind rather than the front. - leftwards
subtracts 20 degrees from the current angle - rightwards
adds 20 degrees to the current angle
Voice Characteristics
The properties of voice characteristics specify what the voices will sound like. Including
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
- number
- 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.
- frequency
- 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.
- code
- 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"


