A method for estimating the parmeters of the vocal-tract area function from the first finite formants frequencies of speech signal is propsoed. An improved vocal-tract area function model is suggested based on the perturbation approach to the solution of the Webster＇s wave equation of the acoustic resonance tube by Schroeter. By considering the cross-influence of the different resonance modes of the perturbation

a cross-sensitivity perturbation relation in matrix form is presented. A method to measure the cross-sensitivity matrix is proposed. An iterative perturbation algorithm for determining the area function parameters from formant targets is developed. By looking up a ＇formant-to-perturbation ＇mapping codebook

an optimal initial perturbation vector for given formant targets is selected.A step-by-step sub-target perturbation procedure and adaptive factor for perturbation increment are adopted.An effective realizaion of the estmation of the vocal-tract area function is illustrated with comparison to the published data.