This contribution is based upon the environmental specificities of the urban built form and it is part of the Research Programme CNRS‐Interdisciplinary Programmes for Towns ‘‘Towards an Urban Sonic Ambience Simulator.’’ Its purpose is to develop an acoustic model based upon fractal measurements of urban interfaces, to be applied for sound simulations. The fractal technique exposed here for modeling the complexity of urban forms quantifies discrete morphologies of the town with an automatic capture procedure based on Minkowski’s operators. In order to model the complexity of urban streets, the dilution measurement is given for a collection of urban surfaces with fractal indicators to evaluate the spectral diffuseness for every element. The implementation of the diffusive acoustic model will then be performed using finite‐element software, composing the diffusive surfaces collection as a complex equivalent urban configuration. The final comparison with the results of on‐site experimentations will give a spectral approach of the diffusion coefficient for the urban configuration. In the near future, the technique described in this paper aims at allowing the spectral control of the acoustical parameters by connecting a fractal morphological evaluation and a qualification of the acoustical phenomenon, modeled as a diffusive process.