Lighting devices are disclosed. One lighting device includes a housing, a light source, and a panel. The light source is mounted within the housing and configured to emit light sufficient for general illumination of an area. The panel is supported by the housing at a location to receive light from the light source at one or more light input surfaces of the panel and output the received light from the light source via a light output surface of the panel facing the area. The light propagates within material of the panel from the one or more light input surfaces to the light output surface. The light output surface of the panel comprises a noise reduction structure.