In this work, a finite element approach is presented for modelling sound propagation in perforated dissipative mufflers with non-homogeneous properties. The spatial variations of the acoustic properties can arise, for example, from uneven filling processes during manufacture and degradation associated with the flow of soot particles within the absorbent material. First, the finite element metho...

In a second experiment, a microstrip patch antenna was attached directly to a thermalite block (440 x 215 x 100 mm) and the dipole-like radiation panems measured in an anechoic chamber. The results given in Figs. 20 and h show the effect of placing radar absorbent material (RAM) on the block ends to absorb the surface wave contribution. With no absorbent material the surface waves result in som...