POROUS MATERIALS FOR SCALE-MODEL EXPERIMENTS IN OUTDOOR SOUND-PROPAGATION

The accuracy of acoustic scale modelling strongly depends on the choic e of porous absorbing materials with properties at the scale frequenci es which resemble those of full size absorbers. In this paper the Atte nborough impedance models are used to identify a combination of micros copic parameters, which ensures that the surface impedance is scaled c orrectly at the model frequencies. The theory and methodology for the selection are given. Measurements of microscopic and acoustic properti es of several uniform common porous materials suggest that the theoret ical assumptions are reliable. (C) 1996 Academic Press Limited