Model for the memory of a bell sound, after Jean-Martin Charcot, in: Gilbert Ballet, Le langue intérieur et les diverses formes de l’aphasie. Paris: Félix Alcan, 1888, 25.

Today, supersonic speed is defined as the speed of an object in relation to the speed of sound in the same medium. This definition goes back to physicist Ernst Mach’s experiments on the supersonic motion of a projectile—and its photographic visualization by the physicist-photographer Peter Salcher, published in 1887. It is common knowledge in the history of science that this and other experiments by Mach influenced (though to a debatable extent) Albert Einstein’s theory of special relativity. However, little attention has been paid to the role of sound in these experiments. My book project traces how, between 1860 and 1930, sound became a new relational feature and thereby an epistemic tool—paving the way for new notions of the relativity of space and time.

I follow Ernst Mach, a border-crosser between the natural sciences and the humanities, to trace the emergence of new techniques of “thinking with sound” in a range of disciplines. As a philosopher, Mach also contributed to the contemporary debates about human perception, and about thinking and feeling with and in sound, that were initiated by 1860s neuanatomists’ identification of the auditory cortex in the human brain and by subsequent experiments on auditory cognition in the field of experimental psychophysiology. I show how these new insights were taken up by various disciplines such as psychoanalysis, philosophy, linguistics, pedagogy, and experimental aesthetics (with relational concepts such as “absolute pitch,” “the reader’s inner voice,” and the singer’s “laryngean memory”) and how they left the academic realm to become influential in the arts, industry, and warfare. In turn, knowledge in auditory cognition around 1900 was facilitated by new audio technologies that provided alternate modes of sound simulation and sound reproduction, and by the foundation of a series of sound archives to collect, preserve, disseminate, and—most importantly for my argument—study and compare sound data.

Focusing on these historical conjunctions, the study is primarily microhistorical (with case studies taken from Germany and France), but at key intersections, it points back to the use and value attributed to sound in the early modern period. It also offers a historically grounded encounter with current trends in auditory neuroscience, sound studies, or more generally the “sonic turn” in research.