The Acoustics of War, by Daria Vaisman

By the early 1990s, the United States was reassessing its self-image. The major conflicts of the last century—the two World Wars and Vietnam—had, for the most part, already been consigned to history (for a younger generation, they were only more media kitsch). But a protracted Cold War had kept the United States in a defensive posture for decades; now that the USSR had dissolved, the US no longer worried about the threat of a nucle­ar attack. The military wanted weapons that reflected the US’s new international role. What to do? In 1991, the Pentagon issued a directive to test an emerging class of arms: Called "non-lethals," these weapons were meant to disable their targets "in such a way that death or severe permanent disability was unlikely."

Most international policy was, at that point, riot control. The US had become a peripatetic interventionist, dabbling in United Nations sanctions and adjudicating regional skirmishes as if they were protests at a college rally. For an optimistic military administration, non-lethals were the humanitarian antidote to atom bombs. By 1996, the US had invested nearly $37 million in research for non-lethal weapons.

The ideology behind "non-lethal" weapons was not new. Police had used chemical sprays and rubber bullets, to name just two, to quell domestic riots in the US throughout the 1960s. A second-wave of non-lethals were introduced in the Gulf War and then, later, in Somalia in 1994: sticky foams to adhere a person to an object or another person; caustics to dissolve tires and roadways; lasers to disorient and temporarily blind; acoustic weapons that used high-decibel noise to cause pain, or infrasound to cause unbearable nausea. The US had already discovered, while dropping bombs over Vietnam, that sudden, high-decibel noise would deafen people, though this was not what non-lethal researchers had intended. (The 1907 Hague Convention clearly prohibits the use of "arms, projectiles, or materials calculated to cause unnecessary suffering.") But it presented an interesting question: Was it possible to project sound at a precise decibel level that caused pain without permanent ear damage? Furthermore, there was anecdotal evidence suggesting that at the right frequency, infrasound would "liquefy [people's] bowels and reduce them to quivering diarrheic masses."

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