This article investigates the role of listening in the knowledge making practices of Western scientists, engineers, and physicians from the 1920s onwards. It does so by offering a two-dimensional typology of the modes of listening that they employ. Distinguishing between two dimensions allows us to make sense both of the purpose and of the ways in which scientists, engineers, and physicians have listened to their objects of study; and it also allows us to appreciate the importance of shifting between modes of listening. At the same time, we argue, understanding the role of sound in knowledge making cannot be limited to the study of listening alone; rather, we have to pay attention to how listening is embedded in broader sonic skills-including the handling of tools for the making, recording, storing, and retrieving of sounds. keywords sound studies, listening, skills, history of science, engineering and medicine Well and sorrowfully do we know the listener who is no listener at all, who passively sits through a concert, intellectually contributing nothing; waiting, like a cabbage or a stone, for something to happen to him. He hears without listening.