Overview of voice signal processing Normally, voice is transmitted to the human ear by means of an acoustic wave travelling through the air at the speed of sound. A conventional analog telephone transmits sound through a wire as an electrical signal which travels at close to the speed of light. To do this, the acoustic signal generated by the human vocal chords must first be converted to an electrical signal, and then converted back to an acoustic form before it can be heard by the human ear. These two conversions are done by a telephone mouthpiece and earpiece respectively.
Planning your voice segments Step-by-step instructions on how to create voice segments are given later in this section, but there are different approaches to this, so it is worthwhile taking some time to plan what you are going to do:
The voice segment database There is a voice segment database for each language. By creating an application profile for each language, you can make the same application work with different languages.
Creating prompts The set of prompts that are used by a particular state table are grouped in a prompt directory. All prompts used by a state table must be in the same prompt directory. Different state tables can use the same prompt directory.
Creating multilingual applications You can create a voice database for each language, dialect, or regional accent you want to use for voice output. You can even use different voice databases for different voices speaking the same voice segments in the same language. You also create a voice database for each TDD language to be used for telephony devices for the deaf.