A Comparative Study of Formant Frequencies Estimation Techniques

This paper presents two techniques of formants estimation based on LPC and cepstral analysis. These methods are implemented with Matlab and applied to the problem of accurate measurement of formant frequencies. The first algorithm estimate formant frequencies from the all pole model of the vocal tract transfer function. The approach relies on the source – filter model supposing that the speech signal can be considered to be the output of a linear system. The spectral peaks in the spectrum are the resonances of the vocal tract and are commonly referred to as formants. The cepstral algorithm picks formant frequencies from the smoothed spectrum. The approach relies on decomposing the speech signal by homomorphic deconvolution into two components: the first component presents the excitation, while the second component is intended to present vocal tract resonances. The result, called cepstrum, is then used to estimate the smoothed spectrum. Formant picking is achieved by localizing the spectral maxima from the envelope. Results show the efficiency of LP based technique and the limitation of the cepstral technique in the estimation of formants of high frequencies.