This paper, proposes a method of voice signal analysis based on predictability measures. The objective is the differentiation of three groups of signals: healthy, nodules on the vocal folds, and Reinke's edema. This method is a slight reformulation of a measure called predictive power (PP) that uses the relative entropy between the signal and its prediction error to capture information about the predictability of the patient's voice production system. A wavelet decomposition model provides the predictions. The results obtained for the healthy group were substantially higher than those of the pathologic groups. This decrease of predictability may be interpreted as an indication of the increase of intricacy and irregularity associated with the studied larynx pathologies.