Here we consider the periodic array of the unit cell in Fig.1, in which the geometric configurations and the constituent materials for the cell are fixed. We vary the filling fraction (size) of the cylinder to discuss its effect on the eigenfrequency and its corresponding eigenmode of acoustic waves in phononic crystals. Two different configurations (one without coating and the other with coating) with two different sizes of cylindrical leads, one 1cm and the other 2cm, are examined. The first case, we consider a periodic array containing non-coated lead cylinders. The second one is that the cylinder is coated by a fluid-like material with 1cm coating thickness. Also, to understand the effect of coating thickness, we also consider the case of 2 cm coating thickness.