Diffractor for diffracting sound of traffic on a travel surface with at least one diffraction plate disposed laterally beside the travel surface. The diffraction plate is provided with a pattern of recesses in the upper surface thereof for the purpose of diffracting the traffic noise in a direction which differs from the lateral direction. Each of the recesses is divided into individual resonators by intermediate walls provided in the recesses. The recesses have acoustically substantially non-absorbing walls and are free of acoustically absorbing material. The intermediate walls between adjacent resonators have at least one throughflow opening along which the rainwater can flow from the one resonator to the other.