This study presents a revised 3D ray tracing method by combining it with indoor space partitioning. This method divides an entire indoor space into limited convex polyhedron subspaces, and thus reduces the number of surfaces intersected with rays, and omits the validity test of the collision point on the reflecting surfaces. Combining it with a microscopic traffic simulation tool and a vehicle noise emission model, and taking the influence of diffraction into account, the method can be utilized in simulating dynamically the process of traffic noise diffusing inside the building through windows. Meanwhile, this study selects two different types of indoor architectural layouts in order to demonstrate the efficiency of this method, the influence of diffraction and of the state of windows, and the differences in indoor noise on different floors. A comparison study on before-and-after indoor space partitioning shows that the method is efficient.