“If Human Ears Were Tuned to Bat Frequencies": Inaudible Sound and the Sciences of Bat Echolocation

This report provides draft excerpts from my PhD dissertation titled "The Inaudible Sounds of Science and Medicine: Animals and Media from the Galton Whistle to Bat Echolocation," a chapter of which explores the laboratory work of Donald R. Griffin – and especially the emergence of the concept of bat echolocation – as it contributed to a sonic history of "ultrasound" and other typologies of liminal sound vibrations. Such "inaudible sounds" repeatedly defied amplification (efforts to make them louder); their frequencies were too high or too low to vibrate the human eardrum. But humans have long suspected that insects, bats, dogs, and other animals could hear them and communicate through them. The following research on bat echolocation in the Griffin laboratory is one aspect of a much more comprehensive historical project, which platforms nonhuman listeners in 19th- and 20th-century experimental contexts as they repeatedly pushed the limitations of human hearing. Broadly speaking, the dissertation suggests that animal figures are useful vectors for exploring an expanded history of sounds, including high-pitched frequencies, in science and medicine. My objective is to better understand how scientists designed media and choreographed animal listeners in order to make meaning from the sounds they could not hear on their own. I am most invested in understanding how humans exploited, collaborated with, and coexisted with animals to make sense of the insensible – or, to understand the unheard bestial worlds of communication. 

In this report, I draw on material from the Donald R. Griffin Papers, held at the Rockefeller Archive Center, which includes a vast array of Griffin's laboratory notebooks, correspondences, sound films, newspaper clippings, and publications. The analysis spans the years between Donald Griffin's first experiment on bat navigation in the dark (1938) – conducted during his early graduate training years – and his postwar research on the physical principles of bat pulses into the 1960s.  More specifically, I characterize the ways in which various forms of media were deployed in experimental settings to study bats and the inaudible sounds emitted by them for orienting their bodies in flight. Scientists and collaborators of the Griffin lab relied on an array of mixed media, from the sound transposing devices of Harvard physicist George W. Pierce, to mechanical-visual apparatuses such as cathode-ray oscillograms and sound spectrographs, through to hand-written laboratory notes and printed correspondences and – ultimately – the bats themselves, to answer their questions. Furthermore, I explore the epistemic techniques of listening for sound and silence in the Griffin laboratory, in which the ears and eyes of scientists interfaced with special acoustic media to produce certain knowledges about bats and their patterns of flight. This project also engages with the highly militarized scientific contexts that constituted Griffin's work on bat echolocation.