Multiple scattering and possible localization of sound propagation in hard-sphere gases

Effects of the disorder (or free-orientation) on the multiple scattering situation by using discrete velocity models for the possible (dynamical) localization and/or delocalization of (plane) sound waves propagating. in dilute monatomic hard-sphere gases are presented. After comparing with previous free-orientation (n = 2) results, we show that there also exists a certain gap of the spectra for the relevant Periodic (wave-propagating) operator when the disorder or free-orientation exists and when a periodic medium with a gap (in spectra) is (slightly) randomized (like our orientation-free 6- and 8-velocity case's) then possible localization and/or delocalization occur in vicinity of the edges of the gap, even when multiple scattering is being considered.