Tracking spectral resonances
An adaptive filter approach that tracks the time-varying parameters of the vocal tract and updates the parameters during the glottal closed phase interval can reduce the formant estimation error. The authors describe three adaptive algorithms for estimating time-varying vocal track parameters: weighted recursive least squared (WRLS), WRLS with variable forgetting factor (WRLS-VFF), and weighted least squared lattice (WLSL). A recursive equation to update the forgetting factor in the WRLS-VFF algorithm is derived, and experimental results for both synthetic and real speech for the above algorithms are given. Results show that the WRLS-VFF algorithm offers a more accurate formant estimation and a faster formant tracking ability than either the WLSL or the WRLS algorithm.<<ETX>>