Utilizing noise mapping for environmental impact assessment in a downtown redevelopment area of Seoul, Korea

In environmental impact assessment, noise impact assessment usually consists of three stages: surveying the existing noise levels, predicting noise levels induced by future construction works and predicting noise levels after the completion of a project. The distance-attenuation relation of a point source, which has been used in Korea to predict the noise level due to its simplicity, does not consider complex acoustic phenomena like multi-reflections, diffractions and absorptions that arise due to the complex topographic configurations of surrounding buildings and terrains. To consider such physical and acoustical complexities, a noise mapping tool is adopted to produce a series of three noise maps: for the present environment, for the planned construction works and for the future. For meaningful noise mapping, both acoustically- and topographically-good information is essential. Standard sound power levels and directivities of various construction equipments are required. Exact scheduling of construction processes and equipment locations must be provided. When the legal limit is exceeded, mitigation measures are applied to satisfy these limits and a subsequent noise map is constructed to verify the effect of these measures. Foreign prediction models are adopted for the situations in Korea if a certain validation condition is satisfied.