Formant-Amplitude Measurements
Gunnar Fant, K. Fintoft, Johan Liljencrants, Björn E. F. Lindblom, J. Mártony · The Journal of the Acoustical Society of America · 1963
Five alternative measures of formant amplitude are defined from circuit-theory analysis of speech production. Each of these is studied analytically as a function of increasing voice fundamental frequency, assuming constant shape and size of voice-source pulses. Some of the formant-amplitude measures display periodic fluctuations with maxima each time a harmonic of the voice fundamental passes through the formant center. This effect, as well as the over-all relations between the various measures, have been verified in human speech within an ensemble of sustained vowels uttered at a large variety of voice fundamental-frequency levels at constant articulation and constant voice effort. The first-formant amplitude is found to increase at a higher over-all rate than predicted from a vocal source of uniform pulses. A systematic departure from the theory of the model found in the second-formant amplitude of one of the subjects suggests a coupling between the vocal-cavity resonances and the vibrations of the vocal cords. Special requirements for formant-amplitude measurements of unvoiced sounds are discussed.