Nineteen Hertz and BelowAn Infrasonic History of the Twentieth Century

This is a history of a sound you cannot hear. Human hearing ranges, on average, between twenty and twenty thousand hertz, and infrasound vibrates at a frequency lower than twenty hertz, ever so slightly below the envelope of human audition.¹ Infrasound first rattled the scientific world in 1883, when the explosion of Krakatoa between the Indonesian islands of Java and Sumatra registered on barographs as subsonic vibrations powerful enough to circle the globe seven times.² Infrasound shuddered back into scientific attention immediately after World War II, when interest in infrasound oscillated between harnessing infrasonic vibrations as weapons and tuning into them as signatures or acoustic footprints of nuclear testing, unheard vibrations from a stealthy enemy. Because infrasonic vibrations are not easily dissipated by physical obstacles, they travel much farther than audible sound, a quality that makes them a useful means for measuring events occurring far away, from earthquakes and volcanoes to rocket launches. In 2011 the Comprehensive Nuclear Test Ban Treaty Organization presided over a controlled explosion in Israel's Negev desert to fine-tune their infrasonic-monitoring equipment; they found that the explosion was recorded by monitoring stations as far away as Mongolia.³ In February 2013, infra-sound sensors recorded the strongest infrasonic wave on record—a dense fireball blooming from the Chelyabinsk meteor as it exploded high above Russia's Ural Mountains. A report in Science described the "meteor's death throes" as emitting a piercing yet "silent scream," one that, while inaudible, nonetheless propagated powerful vibrations across great distances.⁴

As a liminal category alternately dubbed "unsound" or "sound-like,"⁵ infrasound affords scholars the opportunity to interrogate sensorial ambiguity. Sound studies scholar Jonathan Sterne differentiates between sound and other vibrations: "As part of a larger physical phenomenon of vibration, sound is a product of the human senses and not a thing in the world apart from humans."⁶ Such a definition authorizes sound studies to turn a deafear to those vibrations that are inaudible to humans yet are nonetheless key sensory capacities for nonhuman animals: ultrasonic vibrations among dolphins, bats, and dogs, for example, or infrasonic vibrations with which whales and elephants can communicate and anticipate danger in their immediate environments, such as earthquakes and tsunamis.⁷ How, then, might sound studies admit into its purview (its percussion?) those aspects of the vibratory world that are not, strictly speaking, sonic? To productively draw sensory studies into conversation with multispecies science studies requires that the nonhuman umwelt be examined as rigorously and on the same footing as the human sensorium (and, indeed, to query the very notion of a singular and homogenous "human sensorium" in the first place).⁸ A more capacious understanding of sound could consequently reorient its focus away from not only anthropocentric but also "earcentric" models of sonic perception in favor of an extracochlear modality that recognizes entire percussing bodies as vibratory sensory apparatuses.⁹

Once we retune hearing to incorporate the entire body, rather than ears alone, then the sensory hierarchy falls away. Sensory studies scholars consequently must admit the possibility that sound—or any other sense—cannot be studied (or experienced) in isolation but only on a spectrum with other sensory and affective states. Infrasound is on the fringe of the audible yet bleeds into the palpable. It occupies the threshold between hearing and the many other perceptual modalities that audition both complements and overlaps (most significantly, tactility and proprioception, but also nausea and dizziness, as well as affective, cognitive, and emotional states). The twentieth-century history of infrasound is one place to begin such a project, as it problematizes which vibrations do or do not count as "sound"; requires an extracochlear model of hearing; and attaches audition to somatic feelings and moods, including agitation, anxiety, irritability, and apprehensiveness.

In her history of vibration, Shelley Trower demonstrates how nineteenth-century physiologists, poets, and spiritualists used sound "to make audible the silent vibrations that were shaping the experience of modernity."¹⁰ Gillian Beer similarly notes late-nineteenth-century anxieties that attended the limits of perception: "Not only the distortion but...