A further test of a two-formant model

The concept of F2′ as an upward weighting of F2 to allow for the perceptual contribution of upper formants [F2′ being calculated according to the formula proposed by R. A. W. Bladon and G. Fant (Quarterly Progress and Status Report, R. I. T. Stockholm, 1978–1, 1–8)] is reviewed critically in the light of the demonstration that vowels exist which sound different although they have the same F1 and F2′. A procedure for generating vocal tract shapes from such formant frequencies yielded shapes which correspond to humanly realizable vowels and yet which are markedly different shapes. Three pairs of vowels synthesized with these formant frequencies were judged by listeners to be auditorily as different as the pair [i-e] which is phonemically contrastive in many languages. It is concluded that this two-dimensional model of vowel perception is inadequate, at least as currently formulated.