Excessive traffic noise is a major environmental complaint in residential areas. This paper investigates a SOA based hierarchical services structure for urban traffic strategic noise mapping. Service Oriented Computing Environment (SORCER) is employed to build a highly flexible distributed platform. As the key service in our structure, Noise Propagation Calculation Service and its technical detail will be introduced. The service implements functions of sound objects generation, attenuation terms calculation and line source segmentation. The Noise Propagation Calculation Service aims to generate good-quality calculation solutions in a reasonable time. At last, this paper introduces a real traffic noise mapping project to demonstrate the service and the architecture.