Using a computer program for the evaluating of free eligible rotation-symmetrical cylinder shells the number of magnitude of the natural-frequencies were estimated. Assuming the skull of being annulary fixed the calculated values doe in the same range as those got from deat bodies or macerated skulls respectively. Modeling the vibration conditions for the non-fixed border of the skull, the mode shifts into a singulaer point on the rotations axis. In fact the mode in exactly known basis fractures tends to go to the vertex.