Porous materials for scale model experiments in outdoor sound propagation

The accuracy of acoustic scale modelling strongly depends on the choice of porous absorbing materials with properties at the scale frequencies which resemble those of full size absorbers. In this paper the Attenborough impedance models are used to identify a combination of microscopic parameters, which ensures that the surface impedance is scaled correctly at the model frequencies. The theory and methodology for the selection are given. Measurements of microscopic and acoustic properties of several uniform common porous materials suggest that the theoretical assumptions are reliable. (C) 1996 Academic Press Limited