Lab. for Advanced Comput., Univ. of Massachusetts, Lowell, MA 01854
The influence of spatial geometry and material composition on acoustic radiation is considered. Numerical methods are presented that compute the scattered wave field for wavelengths between the Rayleigh scattering and geometrical optics regimes. The transition from extended to localized modes and their dependence on the wave number, average sound-speed fluctuations, and volume fraction of the scatterers is demonstrated. It is shown that the sound-speed contrast must exceed a minimum value for the localized modes to exist. A spatially varying eigenfunction decomposition of the intensity field is carried out to demonstrate this localization effect.