The magnitudes of the laser pulse induced perturbations in the cavity gas are quantified as a function of system parameters. The conditions for which linear acoustic theory, non-linear acoustic theory, and shock gasdynamic theory represent accurate descriptions of these thermally driven acoustic phenomena are delineated. For gas flowing through a laser cavity, expressions are presented which relate instantaneous perturbations of local velocity to those of density. These cover both acoustical disturbances and hydrodynamic events such as turbulence. The non-flow limit is also examined.