The highest quality speech output can be achieved through digitalization at a sampling rate of 10,000 to 25,000 samples per second. Speech synthesis is generally provided by hardware, either through one or more microchips installed in the computer or by a separate peripheral with its own power supply and speaker that can by plugged into a port on the computer. Software is less expensive than the hardware. Speech Rec ognition Speech recognition provides support for people who cannot use a keyboard, roll a screen up or down, exit a file, produce a spreadsheet, or perform other tasks. After a day or two of training, speech-impaired children and adults are able to use speech recognition systems in special schools and in rehabilitation training.
Isolated words are single words or short phrases, such as computer commands.
In an isolated utterance system such as Dragon Dictate, when a word is spoken, the microphone translates the word into an audio signal. The speech-processing board then converts the audio signal into digital data that will be processed by the computer. As the speech data characterizing the word enters the computer, a recognition program compares it to the acoustic word models resident in the active vocabulary. The statistical language model helps select the most likely words, which are sent to the display. For years, people have dreamed of having natural, continuous voice input for their computers' applications.