Formant frequency estimations of whispered speech in Chinese

Formant frequencies are important cues for characterizing
whispered speech. However, it is difficult to exactly estimate its formant by
the conventional linear prediction coding algorithm. The main reason is that the
formant bandwidth of a whisper is wider than that of voiced speech. This brings
up the pole interaction problem that then leads to the result that one or more
real roots are regarded as spurious and deleted from the original LP polynomial.
To reduce the degradation of pole interactions, an improved root-finding formant
estimation algorithm has been proposed. In this algorithm, the whisper formant
bandwidth is modified to make the spectral energy of the remained formant
polynomial equal to that of the original LP polynomial. Experimental results
with six Chinese whispered monophthong phonemes show that the formant
frequencies obtained by the proposed algorithm produce a more reliable formant
spectrum than the one that does not consider the pole interaction effect.