This chapter asks how listening in the sciences became contested over time. Why did sonic skills, and notably diagnostic analytic listening, acquire such an ambiguous epistemological status? The chapter traces the rise of mechanical and visual technologies such as the spectrograph, and the shifting relationships of trust between makers and users of knowledge. It shows how each novel knowledge-making technology, either auditory or visual, requires processes of sensory calibration with existing technologies. And it discusses how sonification scientists have strategically presented visualization as both ally and enemy for trained ears, without yet finding a "killer application". Keywords Epistemological contestation • Sensory calibration • Trust between knowledge makers and knowledge users • Trained ears TwiTTering Timbrados On January 23, 2015, a Maastricht University lecture hall featured four Timbrado canaries, two Edison phonographs, a vintage gramophone, a serinette, a piccolo player, an artist-researcher, and an audience in eager anticipation. The artist-researcher, Aleks Kolkowski, intended to reenact and demonstrate how bird sound was recorded by bird researchers and the phonograph industry in the early years of the twentieth century. It was one CHAPTER 4