Room acoustic simulations usually assume the acoustic impedance of surfaces to be independent from wave incidence angle – in other words locally reacting. For most materials this is a valid assumption. Some porous absorber structures are, however, non-locally reacting: Their surface impedance expresses a dependence on the direction of an incident wave – more exactly on the elevation angle. Still, it can be useful to allocate an angle-independent representative impedance value to the material surface in order to simplify the simulation significantly at the cost of a manageable error. It is common practice to take the impedance at normal incidence or the impedance experienced in a uniform distribution of directions (diffuse field) as this representative value – all yielding non-negligble errors. This thesis tries to improve on previous methods by finding a representative impedance that takes into consideration the true incidence angle distribution experienced by a porous absorber in a real environment. With a theoretical construction of the incidence angle distribution and the definition of an effective impedance, small improvements are achieved in numerical simulations of an oversimplified room geometry.<\/p>\n
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