This study examines the traffic noise reduction effects of the diverse efficiency features of a sunken square, and investigates the reduction effects and characteristics of noise alterations according to the construction conditions in order to verify its possibility as a new noise reduction facility. The measured data were analyzed. As a result, (1) the traffic noise from the roads around the sunken squares exceeded the regulatory standards; (2) the sunken squares were protected from noise; (3) the sunken spaces yielded a greater reduction by 6∼7dB than the flat ground thanks to the diffraction effect; and (4) there were fine changes to noise according to the conditions of space construction. In short, a sunken square has the potential to afford new applications as a noise reduction facility in a highly concentrated downtown with the existing defects solved. In addition, its use for effective noise control is evident based on the noise characteristics of a space. Future studies need to include efforts to provide clearer quantitative data, as well as research on shape, layout, and materials.