Soundscape studies typically distinguish between three sources of sound: biophony, sounds produced by animals, plants, and other biological entities; geophony, sounds produced by non-living features such as water or wind; and anthrophony, sounds produced by humans and human technology. Recent developments in the study of hybrid ecosystems and ecological robotics challenge these categorizations. A series of four soundscape interventions are considered, which lead to the proposal of a new category: robophony. These interventions — robots and autonomous digital agents — operate in feedback loops with the existing bio-, geo-, and anthrophony in the ecosystem. The properties that emerge from these cases: site specificity, hybrid sourcing, and layered temporality form the basis of this new category of sound in the soundscape.