It sounds like a scream from the depths of the underworld. It’s a haunting, ear-piercing shriek that stirs something primal in the human mind. The Aztec death whistle, a small artifact shaped like a skull, produces one of the most terrifying sounds ever created by an ancient musical instrument (if you can call it musical that is).

Now, a study led by Sascha Frühholz, a cognitive neuroscientist at the University of Zurich, reveals just how unsettling this sound is — not only to our ears but also to our brains. Using replicas and original whistles, the researchers conducted a series of experiments to uncover how these sounds were perceived by modern listeners and processed by the brain. What they found was both chilling and fascinating.

The research suggests that the Aztecs may have used these shrieking whistles during sacrificial rituals, creating an otherworldly atmosphere steeped in fear and mythological symbolism.

But before I share with you the researchers’ findings, I’m sure you’re dying to hear how the Death Whistle sounds. Have a listen below — but be warned: turn down your speakers. You’ll thank me later.

The Sound of Fear

When an Aztec “death whistle” is blown, the sound can send shivers down your spine. This eerie instrument, dating back to postclassic Mesoamerica (1250–1521 CE), produces noises that resemble human screams or piercing winds. Ranging in size from 3 to 5 centimeters, they feature air ducts and chambers that create nonlinear, turbulent airflow when played. This creates high-pitched, scream-like sounds. This sound profile was further analyzed by comparing it with thousands of other noises, from animal calls to musical notes.

The study found that the whistles’ acoustic characteristics closely mimic sounds that humans instinctively associate with danger or alarm, such as screams or sirens.

“The whistles were uniquely crafted to elicit an emotional reaction,” the researchers noted. These reactions, the study showed, are deeply rooted in our evolutionary biology, as humans are hardwired to respond to certain distressing sounds.

The study used both original whistles, preserved in museums, and 3D-printed replicas. This allowed researchers to analyze the instruments’ physical and acoustic properties without risking damage to priceless artifacts. Modern listeners, unfamiliar with the whistles, overwhelmingly described the sounds as “screams” or “scary.”

According to Frühholz, this auditory resemblance is no coincidence. “This is consistent with the tradition of many ancient cultures to capture natural sounds in musical instruments, and could explain the ritual dimension of the death whistle sound for mimicking mythological entities,” he said.

The team took their investigation further by studying brain activity in listeners exposed to the sound. The results were striking. The brain’s affective neural system, which governs emotional responses like fear, lit up strongly. At the same time, regions linked to symbolic associations also activated, suggesting that the sound isn’t just frightening—it carries meaning.

Rituals and Mythology

But why did the Aztecs create such unsettling instruments? Researchers believe the answer lies in their cultural and religious practices. The whistles often depict skulls, possibly representing Mictlantecuhtli, the Aztec god of the underworld. Some theories suggest they were used during human sacrifices or funeral rites to symbolize the winds of the underworld, known as Mictlan. The terrifying sounds might have been intended to guide spirits or emulate the chaotic conditions of the afterlife.

“The whistles have a very unique construction, and we don’t know of any comparable musical instrument from other pre-Columbian cultures or from other historical and contemporary contexts,” Frühholz explained.

Others hypothesize a more practical use. The so-called “warfare hypothesis” suggests that these sounds were deployed on battlefields to intimidate enemies, creating an atmosphere of fear and confusion. This point is contested, however, as no such artifacts have ever been found close to a known battlefield.

A Universal Connection Through Sound

The study highlights a timeless truth: humans have always responded powerfully to sound. From the rhythmic drums of tribal ceremonies to the haunting tones of Gregorian chants, music and sound have long been tools for influencing emotions and conveying meaning.

For the Aztecs, the death whistle likely served a dual purpose. Its terrifying sound could evoke the presence of deities like Mictlantecuhtli, preparing sacrificial victims — and witnesses — for their mythological descent into the afterlife.

“Unfortunately, we could not perform our psychological and neuroscientific experiments with humans from ancient Aztec cultures. But the basic mechanisms of affective response to scary sounds are common to humans from all historical contexts,” says Frühholz.  

The findings appeared in the journal Communications Psychology.