Pole-zero multipulse speech representation using harmonic modelling in the frequency domain

When trying to increase the efficiency of the multipulse speech representation through a reduction in the number of pulses per frame, the use of a pole-zero filter instead of the classical LPC filter appears to be an appropriate choice, for voiced segments. In this paper, the possibility and advantages of using this kind of filter are investigated. The filter design criterion is the minimization of the mean squared error (m.s.e.) between its output and the original voiced signal, when the excitation is a suitable periodic impulse train. This is, however, approximately equivalent to finding the filter that minimizes the m.s.e. between its transfer function and the signal harmonics, at the harmonic frequencies, taking into account both magnitude and phase. Some preliminary results are shown, and the conclusion is drawn that pole-zero filters actually are good candidates for a more efficient multipulse representation of voiced speech. The design of an algorithm for filter computation, and the incorporation of these ideas into the general multipulse framework are also discussed.