With taking part of an interdisciplinary CNRS research program, we intend to constitute a simulation tool for complex urban soundscapes. For this purpose, we aim to quantify the urban diffusion factor, related to the surface roughness distribution of the urban frontages, taking into account its volume location and its specular surface distribution. Characterization of this distribution leads us to use a fractal technique for modeling the complexity of urban surfaces, through developing a unique method 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. In order to perform an experimental validation of this angle dependent scattering characterization model, we attempt to define an MLS multisensor method of measurement, applied to the 19 th frontage morphology of the « rue d'Orléans » in Nantes. Scattering experimental results will then be compared to the described scattering pressure function at each incidence angle. Another comparison to a 1/5 th scale model measurement will provide the acoustical scattering effect of the frontage components, in order to define their qualitative contribution for diffusion. Developed in the aim of architectural design tools for urban acoustics, this frontal angular diffusivity factor allows a good evaluation of the acoustical local reaction of an urban surface. With discerning the morphological attributes of main types of architectures, we will then be able to compute their specific acoustical behavior at every frequency, from the numerical 3-D data of their geometry.