A study was conducted on the prediction of transformer noise based on geometrical acoustic. For near field estimation, a revised radiation method called 2-dimensional noise analysis was applied. It is designed to calculate the noise around a transformer assembly including tanks, bushings and coolers. For far field noise estimation such as a substation boundary, a geometrical method called 3-dimensional analysis was applied. Considering the effect of sound reflection and diffraction, it is specially applicable for site with complicated landscape.