ABSTRACT
Acoustic propagation in dispersions has interested scientists and mathematicians for very many years and sound has always fascinated human beings. As an incidental consequence of this work on acoustics, Rayleigh derived the famous long wavelength limit result, which explains the blue colour of the sky. P. Lloyd and M. V. Berry were really interested in the density of electron states in disordered materials and their result for acoustic scattering appears almost incidentally. The chapter shows that R. E. Kleinman’s iterative solution to the Helmholtz equation can easily be generalised to the case of two coupled fields and two Helmholtz equations in the more complex problem of thermo-acoustic scattering. Very many solid systems, especially soft solids, can be viewed as systems of particles interacting through forces of the same order as those present in acoustic fields. Thus acoustic, electromagnetic, neutron and electron scattering all have a common mathematical basis.
