Various models describing outdoor sound propagation over wedge barriers and three-sided barriers are described. The starting point is the approximate solution for diffraction by a hard wedge given by Kouyoumjian and Pathak . This solution is extrapolated to cover the finite impedance case by employing arguments originating from Jonasson . The Kouyoumjian and Pathak solution is also used in connection with the calculation method originating from Pierce  for diffraction by a three-sided barrier. The theoretical results are compared with measured data for sound propagation over grass-covered earth berms, from a loudspeaker source. Calculated and measured results for a road traffic noise situation involving an earth berm are also presented.