Use of the transmission line matrix method for the sound propagation modelling in open-space

Ground characteristics and atmosphéric conditions stand for determining factors when considering long range sound propagation. Hitherto more or less excluded from many areas of research because of their computational cost, temporal methods have been knowing a revival of interest for a few years, mainly due to the increase in computational power. Indeed these methods constitute an alternative to more common approaches because they can provide many informations on the physical phenomenon. The Transmission-Line Matrix (TLM) method is an alternative approach of time-domain modelling because it rests on a physical interpretation of the sound diffusion process at each point of a spatial grid representing a discretized domain of propagation. It allows to take into account most of the influent phenomena occurring in reaslistc propagation conditions. This paper focusses on the complex impedance ground effect modelling and presents also the implementation of anisotropic vertical sound speed grandients and of atmosphéric attenuation in such a method