Question: where are octahedral voids located?
Answer: The body centre of the cube is not occupied but it is surrounded by 6 atoms (4 in same plane, 1 above and 1 below). On joining these face centers, an octahedral void is formed. Thus, number of OV at body centre of the cube is 1. Besides the body center, there is one OV at the center of each of the 12 edges.