The behavior of density disturbances in an air-water flow was measured by local resistivity probes. The disturbances were introduced into an established air-water flow by periodic secondary air injections. The experimental wave velocities are in fair agreement with the one-dimensional kinematic wave theory, based upon the work of Lighthill and Whitham, but this theory does not adequately predict the perturbation growth and decay rates. A modification, taking into account turbulent diffusion, is developed.