Estimation of speech spectra from whispers

The most obvious difference between normal and whispered speech is the excitation. However, there are other significant spectral differences between these two modes of speech. In particular, the formant locations are raised in whispers because of increased coupling between the vocal tract and the trachea. In addition, the noise excitation increases the variance of spectral estimates such as linear prediction. In order to reconstruct quality phonated speech from whispers, it is necessary to remove the bias in the formants and reduce the variance of spectrum. Methods for estimating the linear prediction spectrum from whispered speech are proposed. These include modification of the formants in the line spectrum domain and smoothing of the noisy linear prediction spectra.