In this work, we numerically investigate the existence of phononic band gaps in the layer-by-layer rods structure. For the numerical calculations the finite difference time domain method was used and the transmission, as well as the band structure (using periodic boundary conditions and the Bloch theorem), was calculated. Several different materials (considered as the rods materials) were examined and the effects of all the geometric parameters of the structure were also numerically investigated. The results show that this structure seems to have very promising features as a phononic crystal giving, under certain conditions, a full 3D band gap. Taking into account that it is already known for its use as a photonic crystal, a certain belief for its use simultaneously as a photonic and phononic crystal rises.