How Do Aztec Death Whistles Make That Chilling Sound?
As far as cultural artifacts are concerned, few sound quite as intimidating as the Aztec death whistle. Not only is the word “death” right there in the name, but the Aztec culture has a reputation for religious ceremonies involving sacrificial rituals. Add to that the fact that the whistles are shaped like human skulls, and the imagination can run wild with macabre possibilities for the meaning and purpose of the death whistle. But the instrument was not necessarily deployed for morbid uses. Let’s take a closer look at the function of these ominous-sounding objects.
The name “Aztec death whistle” is actually a colloquialism. The whistles are also known as ehecachichtli, and in scholarly circles, they’re referred to as skull whistles due to their shape. Their exact origin is unclear, but researchers estimate they date to between 1300 CE and 1521 CE. The whistles were made of clay or bone and were small enough to be held in the palm of the hand. The holes for blowing into them were located at the top of the skull.
Some scholars have theorized that the skull design represents the winds of the mythological underworld Mictlan, while others suggest the whistles symbolize the Aztec wind god, Ehecatl. And due to the fact that many whistles were discovered during burial site excavations, it’s commonly believed that they served a purpose in burial ceremonies, and possibly human sacrifice rituals. There is also speculation that they were used as a warfare instrument, played on the battlefield in order to intimidate enemies.
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The skull whistles are capable of producing sounds that are unsettling and even frightening to the listener. They make a chilling sound often compared to a high-pitch human scream or shriek. In 2024, a team of researchers at the University of Zurich led by neuroscience professor Sascha Frühholz conducted a study to analyze the whistles, including their psychological impact, and published the findings in the journal Communications Psychology.
Participants were asked to listen to recordings of original and replica skull whistles (without being told what the sound was), identify what they were hearing, and rate their feelings about the sound. Researchers also recorded the brain activity of the participants while they were listening to the recordings.
The study resulted in listeners identifying the skull whistle recordings as the sound of a human scream and rating it, according to a press release issued by the researchers, as “extremely chilling and frightening.” Brain activity indicated that regions belonging to the affective neural system were activated during listening, confirming the unsettling nature of the sound.
Consider that fair warning, then, before listening to the sound of the skull whistle, though for anyone who’s curious, a selection of sound samples from the University of Zurich study can be found here. The variety of samples includes recordings of the whistles being blown with different air pressures; lower pressures result in a more windlike tone, while higher air pressures are more screamlike. A longer clip, played in a more varied style, is available here. And a popular video (below) features a demonstration by Indigenous instrument maker Xavier Yxayotl.
To learn what causes the skull whistle’s distinctive sound, Frühholz’s team used CT scans and 3D imaging to visualize the inner mechanisms of the instrument. The scans revealed a cylindrical duct leading from the top opening, tapering to a point of constriction along three opposing chambers, known as the counter pressure chamber, collision chamber, and bell cavity.
The design results in an unusual, turbulent airflow that creates a Venturi effect — a drop in pressure that occurs when air (or liquid) flows through a constricted point, and results in increased velocity. (An everyday example of the Venturi effect is how placing your thumb over the opening of a garden hose results in a faster stream.) In the case of the skull whistle, the increased air velocity results in acoustic distortions, which become all the more pronounced the harder the whistle is played. To quantify the sound, the researchers ran a spectrum analysis, which showed elements of pink noise and, not surprisingly, a great deal of high frequencies. The whistles also corresponded to a distinctive pitch associated with primate screams.
The result was something truly unique. The skull whistle, as Ars Technica pointed out, “doesn’t fit into any existing Western classification for wind instruments.” In the study, Frühholz similarly expressed the prevailing, almost supernatural mysteriousness of the skull whistle, noting, “We don’t know of any comparable musical instrument… from [any] other historical [or] contemporary contexts.”
