A novel LPC synthesis model using a binary pulse source excitation

It is difficult to produce natural-sounding speech using LPC voice coding techniques (vocoder). The main problem is the simplistic model of the excitation source in terms of the pitch pulses and white noise used in the synthesis. The LPC vocoder requires robust and accurate pitch determination, which is a problem that still has not been completely solved. Recently, a multi-pulse approach for modeling the excitation source has been proposed by Atal. However, this approach requires a substantial increase in the bit rate over conventional LPC. We describe in this paper a novel pulse source model for improving the quality of LPC speech. The binary pulse source excitation is obtained from the speech signal using a nonlinear filtering procedure. Our approach is able to maintain good speech quality even at bit rates of 4.8 kbps or lower.