Vowel Synthesis Using Resonant Circuits to Represent Formants
Erich S. Weibel · The Journal of the Acoustical Society of America · 1954
The amplitude spectrum of a vowel is a product of two factors, the spectrum of the wave generated by the vocal cords and the transfer impedance. The characteristics of a vowel, namely, position, width, and magnitude of the formants are given primarily by the transfer impedance. This transfer impedance may be expanded in a partial fraction series. The first three terms of this series, representing the first three formants of the vowel, are realized as parallel resonant impedances. A current proportional to the vocal cord wave is passed through these impedances. A voltage having the desired vowel spectrum is now obtained as the sum of the voltages developed across the resonant circuits. The position, width, and magnitude of the three formants are independently controllable. Three formants suffice for production of realistic vowels.