Through collaboration in an interdisciplinary CNRS research program with the LCPC, the LAUM and the CRESSON Laboratories, we are intended to constitute a simulation tool for complex urban soundscapes. For this purpose, we aim at quantifying the diffusivity of the urban morphology. The built urban structure is considered as a non-entire dimensional network, taking the volume structure and the multiscale distribution of specular surfaces within the urban space into account. For this distribution, acoustical diffusion is considered. Its multiscale characterization leads us to use a fractal technique for modeling the complexity of urban surfaces. To do so, we develop a method to quantify scaling morphology of the town with a capture procedure based on Minkowski's operators. The generalization of this measurement technique through the three dimensions of the urban shape provides an angle-dependent diffusive polar response for urban frontages, through computation of the diffusion volume of the structure. This new multiscale analysis tool of urban structure has been applied to a 19th urban morphology. Considering these results pertinent for implementing a raw diffusion model, fractal computing of diffusive geometry will be able to provide angular acoustical diffusion parameters, in order to generalize this method to any complex diffusion system.