This study deals with the ill-posed problem of inversion of the articulatory-to-acoustic relationship, i.e., the recovery of vocal tract geometry from formant frequencies. A small database of articulatoryacoustic data has been established for one subject. A midsagittal-toarea function conversion model, which works both for vowels and fricative consonants, has been developed from these data. This model has finally been used as a major constraint for an optimization algorithm based on a gradient

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... escent technique, in order to regularize the ill-posed inversion problem. Other spatial and temporal smoothing constraints have also been used. Single vocal tract configurations, as well as entire [VC] sequences, could be recovered using adequate initial conditions.