T. V. Ananthapadmanabha
Voice and Speech Syst., 53, ``Girinivas,'' Temple St., Malleswaram, Bangalore 560 003, India
Vocal tract shape made up of cylindrical sections of equal length can be determined given the formant data of vowel sounds; the number of sections equals twice the number of formants. For an adult male speaker, use of four formants, results in a large section length of 2.125 cm. If section length of 0.5 cm is desired, 17 formants have to be specified which appears impractical. A method for obtaining vocal tract shape with small section lengths, given only a few lower formants (up to fourth or fifth) is presented. For vocal tract of M sections, only the lower M/2 formants are independent and upper formants are constrained by the lower formants. This constraint gives unrealistic locations for the upper formants. One method for predicting the upper formants would be to use those of a uniform tube of same length as that of the vocal tract. For a desired section length (say 0.5 cm), the required formants (say, 17) can be specified by using the given lower formants (say, four) and predicted upper formants (say, from 5 to 17). Validation of the method using x-ray data and simulated vocal tract shapes is presented.