A method to determine the position and length of the heart sound S1 is presented. First, the envelope of PCG is determined by calculating the mean Shannon energy of PCG signal. Then, the envelope is compared with a Gaussian template. When they match, the position of the heart sound is taken as the position of maximal of the template and the length of the sound is determined from the parameter σ of the template. The accuracy and noise robustness of the method was evaluated using quasi-artificial PCG signals and real PCG records form a group of healthy volunteers. The results were good in comparison with other methods reported in literature.