Noise propagation in residential areas and similar environments is characterized by multiple scattering of sound between buildings. Approximate solutions to this problem are obtained by modelling this type of propagation as diffusion of incoherent sound particles. These solutions describe the gross dependence of sound energy density on the distance from the noise source(s); the relevant parameters of the environment are the (average) height, scattering cross section and absorption of the buildings. Particular consideration is given to the propagation of noise from freely flowing traffic, for which not only average values of the energy density but also expressions describing the range and frequency of fluctuations are presented.