Façades as a part of urban areas' components; play an important role in sound propagation which affect sound environment in a street canyon. A parametric study was performed in order to investigate the influence of façade's formation by segments ratio on sound fields in urban streets in terms of sound pressure level (SPL). A computer simulation technique based on a hybrid method combining ray tracing and image source modeling was adopted, and an omnidirectional sound source was used. Series of computer simulations of varied numbers of segments that form façades were investigated in order to evaluate the real effect of the diffusion reflections that happened by façades with formations; relative to the smooth façades on sound propagation in streets. Results, in terms of relative sound pressure levels, show that a positive effect can be observed in the reduction of sound levels.