A procedure is suggested for improving LPC speech quality. The central theme is to introduce a parametric model of voiced excitation - a glottal source model. In the analysis this allows for a different method than the AR-estimation used in conventional LPC. Here, a method known as AR-X-estimation is used. A complete analysis and coding method is presented. It is found that the additional glottal parameters can be coded effectively such that the total bit rate is in the same range as for conventional LPC. The glottal LPC-vocoder does significantly improve synthesis quality as compared to standard LPC. It should be emphasized, however, that the glottal vocoder requires high quality speech as input, recorded in a phase linear system. Moreover, the computational complexity is high.
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