The human brain is wired to fear the sound of people screaming. So the U.S. Air Force tried to weaponize that effect in the...

The human brain is wired to fear the sound of people screaming. So the U.S. Air Force tried to weaponize that effect in the form of horrific, unsettling noise bombs that would scare the wits out of enemy troops.

Beginning in 1964, the Air Force began work on “Pyrotechnic Harassment Devices,” or PHDs. The project derived from the philosophy that it’s better to break an enemy’s morale than to simply kill them. This goes even more so for insurgent wars, when it’s extremely important to avoid harming civilians.

“This device is an air deliverable unit that generates noise over a six hour period to harass, by generally upsetting enemy troops and thus lowering their efficiency for fighting,” technicians at the Air Force Armament Laboratory explained in their final report. “By dropping a number of units around an enemy group under attack, the PHD may cause general confusion.”

The Pentagon had decades of experience and foreign examples of “noise” as a psychological weapon. During World War II, specialized U.S. Army units used huge loudspeakers to confuse German soldiers in France. Aircraft blared out propaganda messages a few years later over Korea. During the Malayan Emergency, British pilots adapted those same techniques against ethnic Chinese guerrillas.

But to be effective, planes with speaker systems had to fly low and slow. This made the aircraft – commonly referred to as “bullshit bombers” – easy targets for guerrillas on the ground.



The PHD addressed this basic problem. The Air Force wanted noise-emitting devices that would be small enough to fit inside a pod-shaped SUU-13 dispenser. Instead of orbiting low and close to the enemy, the planes could drop the screaming pods before speeding away.

The Air Force hired a company called Special Devices, Inc. to build the prototypes. At first, the flying branch hoped that the pods would boom, bellow and shriek out gunshots, human and animal screeching sounds and the clanging of industrial machinery. Engineers recorded a host of specific samples to analyze, such as people firing .30- and .45-caliber guns and male and female screams.

The recordings also included a “neutral scream” consisting of a mix of the male and female versions and the cries of elephants and panthers, according to the official report. But after experimenting with a variety of mechanisms, Special Devices could only build pods that spewed out shots, whistles, whines and other white noise.

Most importantly, the pod’s size imposed limits on how the devices actually generated sounds. Unable to fit in an audio storage device and speaker in such a tiny space, the technicians had to rely on simpler gas-driven noise makers.

“Human voices and animal noises … are not possible to reproduce because the extreme amplitude or frequency modulation requires some type of programmer to control the pyrotechnic output,” the company’s report explained. “The development of such a controller was beyond the scope of this program, and would have rendered the PHD unit prohibitively expensive.”

The final design had clusters of blank cartridges to simulate gun sounds. Each canister would fire eight bursts of eight shots total over a period of six hours. The bomblet fired each burst at random intervals. Each time, a special bellow would let out a screaming whine.

After the device had finished the full cycle, a one pound explosive charge would blow up the whole unit. If enemy troops tried to tamper with the PHDs on the ground, a special circuit would activate this self-destruct mechanism early.

With the help of inflatable bladders at each end, the canisters could float on the water or stay stable on solid ground. The rubber doughnuts also helped slow down the devices as they fell to earth.



Tests at Eglin Air Force Base in Florida exposed a number of potential problem. For one, the PHDs were easy to spot from the ground. The screaming sound was terrible … and not in a useful way. “There appears to be no way to make a pyrotechnic scream simulator with satisfactory characteristics for the PHD unit,” the engineers lamented in their findings.

Still, based on the experiments, the technicians recommended further work and the Air Force Armament Laboratory suggested using the data to set some minimum requirements for the size and shape of future devices. New types of harassing bombs should only try and make one type of noise … and do it well.

The Air Force was satisfied enough to order more research.

But unable to come up with a mechanical or pyrotechnic scream generator, the flying branch built speaker boxes that could spit out any recorded sound. Cargo planes would drop these “screeming meemies” into enemy territory.

In the end, despite the expanding war in Vietnam, none of these systems saw combat there or anywhere else. However, the Pentagon never gave up on the idea of using annoying and disturbing sounds to dislodge the enemy.

In 1993, Army psychological operations troops blasted animal screams and industrial noise at the Branch Davidian compound in Waco, Texas. The acoustic barrage failed to break the will of cult leader David Koresh and his followers – and federal authorities eventually stormed the site, leading to a fire that killed 76 people.

In Iraq and Afghanistan, American troops deployed the so-called “Long Range Acoustic Device” – a.k.a. the LRAD – and similar equipment.

While designed primarily to broadcast voice messages to approaching individuals, the LRAD can also blare out “warning tones” more than 1,500 feet away. Law enforcement and shipping companies have bought LRADs to deter rioters, prison inmates and pirates.

Those are scary, but at least they don’t scream like people.