Aztec skull whistles sound like people screaming –

A new study by researchers at the University of Zurich published in the journal communication psychology Research has found that the scream-like sounds produced by Aztec skull whistles have horrific effects on today’s human listeners, which is reflected in their brain activity.

Aztec skull whistles are small (3-5 cm) clay skulls with tubular stems often found in burials and human sacrifice sites between 1250 and 1521. Archaeologists speculate that the skull image represents the Aztec wind god Ehecatl, who collected bones from previous ages of the underworld and worked with them to create humanity. They may also refer to Mictlantecuhtli, the Aztec god of the underworld, and the screams they emit may have prepared their victims for their descent into the underworld, perhaps the fifth level, filled with howling winds of agony. Another hypothesis is that the instrument simply imitated human screams as part of a sacrificial ritual.

Researchers are trying to understand the possible symbolic meaning of skull whistles by studying the effects of the sounds they make on human listeners. The study collected audio recordings of whistles from skulls unearthed in Mexico City’s temple district. They also performed high-resolution CT scans of samples from the collection of the Museum of Ethnology in Berlin, which they then used to create 3D digital reconstructions of the originals as well as accurate, playable replicas. Digital models reveal new details about how whistles produce sound.

Air is blown into a mouthpiece connected to the windpipe, which constricts at the distal end and connects to the inside of the skull. The rounded back of the skull is a counterpressure chamber in which air circulates and then flows from the collision chamber to a bell-and-whistle opening under the “chin” of the skull.

The models revealed the unique internal structure of the two opposing sound chambers, creating physical air turbulence as the source of the screams. “The whistle has a very unique structure and we are not aware of any similar instruments from other pre-Columbian cultures or other historical and contemporary contexts,” said [University of Zurich neuroscience professor Sascha] Early wood.

When test subjects heard recordings of death whistles, they recognized them as human screams.

While the brains of human listeners were being recorded, the Aztec death whistle was also played to them. Areas of the brain belonging to the affective nervous system responded strongly to the sound, reaffirming its daunting nature. But the team also looked at activity in areas of the brain that link sounds to symbolic meaning. This suggests the “hybrid” nature of these death whistles, combining the basic psycho-emotional impact on the listener with the more complex psychological processes of sound symbolism that mark the iconic nature of the sound.

In both contemporary and ancient cultures, music has always had a strong emotional impact on human listeners, hence its use in religious rituals and mythological contexts. Based on knowledge of how death whistles affect modern humans, it is possible that Aztec communities specifically used the fearful and symbolic properties of death whistles to influence spectators’ ritual procedures. “Unfortunately, we cannot conduct psychological and neuroscientific experiments on humans from the ancient Aztec culture. But the basic mechanisms of emotional responses to scary sounds are common to humans from all historical backgrounds,” Frühholz said.

Original skull whistle sound clip:

High-pressure replica of a skull whistle:

Replica of a skull whistle played at high pressure