Automatic parametrization of voice source signals: a novel evaluation procedure is used to compare methods and test the effect of low-pass filtering

There is a need for automatic methods for parametrization of the voice source signals. Representatives of the two types of methods that have been used most often for parametrization were tested and compared. For this purpose a novel evaluation procedure is proposed which makes it possible to perform the numerous tests needed for a detailed comparison of the methods. This evaluation procedure revealed that in order to reduce the average error in the estimated voice source parameters the estimation methods should be able to estimate noninteger values of these parameters. The proposed evaluation method was also used to study the influence of low-pass filtering on the estimated voice source parameters. The factor low-pass filtering was chosen because low-pass filtering is probably used in all methods in which voice source parameters are estimated. It turned out that low-pass filtering causes an error in all estimated voice source parameters. On average, the smallest errors were found for a parametrization method in which a voice source model is fitted to the voice source signals, and in which the voice source model is low-pass filtered with the same filter as the voice source signals.