A method is presented for the automatic extraction of voice source parameters from speech. An automatic inverse filtering algorithm is used to obtain an estimate of the glottal flow signal. Subsequently, an LF-model [1] is fitted to the glottal flow signal. In the current article we will focus on the improvement of the automatic fit procedure. To keep track of the performance of the fit procedure, a quantitative evaluation criterion is preferred. It is difficult to obtain such a criterion for natural speech. Therefore, we propose an evaluation method in which synthetic speech is used. We also conducted qualitative tests for disturbances that are often found in natural speech, i.e. source-filter interaction.