Formant Synthesis

The vocal tract (the throat from the vocal cords to the lips) has certain major resonant frequencies. These frequencies change as the configuration of the vocal tract changes, like when we produce different vowel sounds. These resonant peaks in the vocal tract transfer function (or frequency response) are known as "formants".

It is by the formant positions that the ear is able to differentiate one speech sound from another. Here are a few examples of English vowels with their corresponding lowest three formants for an average male speaker. Vowel sounds are in bold type and all values are in Hertz.

beet

270, 2300, 3000

bit

400, 2000, 2550

bet

530, 1850, 2500

bat

660, 1700, 2400

but

640, 1200, 2400

boot

300, 870, 2250

The SoftVoice synthesizer simulates the human speech production mechanism using digital oscillators, noise sources, and filters (formant resonators) just like an electronic music synthesizer. Because of this, we have the same flexibility as a music synthesizer to create different voice "patches", or presets. SoftVoice TTS comes with 20 preset voices which can be modified by the programmer or user.