In the previous subsection, we mentioned that the speech space has several dimensions, which might depend on the particular voice synthesizer being used. In order to make our presentation more concrete, we now describe the dimensions that can be used with the MultiVoice synthesizer.
The MultiVoice provides nine predefined voices, which are modeled as distinguished points (constants) in the speech space. We list below the MultiVoice names for the voices, together with the name used within AFL for them.
A user can save a particular speech state in a variable and refer to it later. For example, execution of the statement[+]
saves the value of *current-speech-state* in program variable name. Statement
retrieves the value saved in variable name. Male and female voices are to be thought of as lying in distinct disconnected components of the speech space, since it is not possible to move from a male voice to a female voice simply by changing parameters that affect voice quality[+]. Switching from a male to a female voice is thus analogous to changing fonts, while modifying voice quality parameters is like scaling different features of a specific font.
The MultiVoice parameters (and their default values) that are implemented as dimensions in AFL are shown in ta:par. They are: the speech rate, the volumes of the speaker and the earphone port, five voice-quality parameters, and seven parameters that deal with pitch and intonation. The column labeled ``step size'' will be discussed later on.
Table: Implemented MultiVoice parameters
We assume that these dimensions are available and can be changed by the statements that are defined in the next subsection.