Modeling formant dynamics in speech spectral envelopes

The spectral envelope of a speech signal encodes information about the characteristics of the speech source. As a result, spectral envelope modeling is a central task in speech applications, where tracking temporal transitions in diphones and triphones is essential for efficient speech synthesis and recognition algorithms. Temporal changes in the envelope structure are often derived from estimated formant tracks, an approach which is sensitive to estimation errors. In this paper we propose a speech source model which estimates frequency and amplitude movements in the spectral envelopes of speech signals and does not rely on formant tracking. The proposed model estimates the amplitude and frequency shifts for each sub-band and time frame of a speech signal using the information from the previous time frame. Our experiments demonstrate that the model captures temporal structures of spectral envelopes with high precision. The proposed model can thus be applied as an accurate low-order representation of temporal dynamics in speech spectral envelopes.