Smoothing the evolution of the spectral parameters in linear prediction of speech using target matching

Linear prediction (LP) coefficients are used to describe the formant structure of a speech waveform. Many factors contribute to the frame-to-frame fluctuation of these parameters. These variations adversely affect the performance of the LP quantizer and the quality of the synthesized speech. For voiced speech, efficient coding of the pitch pulses at the output of the inverse formant filter relies on the similarity of successive pitch waveforms. The performance of this coding stage is also jeopardized by LP variations. In this paper, we propose a new method which smooths the evolution of the LP parameters. Our algorithm is based on matching the output of the formant predictor to a target signal constructed using smoothed pitch pulses. With this approach we have successfully reduced the frame-to-frame variation of LP coefficients, while increasing the similarity of pitch pulses.