The Incredible Sound Effects of Malta’s Hypogeum Hal Saflieni

The Hypogeum of Hal Saflieni in Malta is a UNESCO World Heritage Site which is believed to be the oldest prehistoric underground temple in the world.  The subterranean structure is shrouded in mystery, from the discovery of elongated skulls to stories of paranormal phenomena. But the characteristic that has been attracting experts from around the globe is the unique acoustic properties found within the underground chambers of the Hypogeum. 

Hal Saflieni Hypogeum is a cultural property of exceptional prehistoric value, dating back approximately 5,000 years and the only known example of a subterranean structure of the Bronze Age. The 'labyrinth', as it is often called, consists of a series of elliptical chambers and alveoli of varying importance across three levels, to which access is gained by different corridors. The principal rooms distinguish themselves by their domed vaulting and by the elaborate structure of false bays inspired by the doorways and windows of contemporary terrestrial constructions.  

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Malta’s Hypogeum: A Sanctuary of Mystery

Although not known for certain, it is believed that the hypogeum was originally used as a sanctuary, possibly for an oracle. It is for this reason that a unique chamber carved out of solid limestone and demonstrating incredible acoustic properties has been called ‘the Oracle Chamber’. According to William Arthur Griffiths, who wrote ‘Malta and its Recently Discovered Prehistoric Temples’, a word spoken in the Oracle room is “magnified a hundredfold and is audible throughout the entire structure. The effect upon the credulous can be imagined when the oracle spoke, and the words came thundering forth through the dark and mysterious place with terrifying impressiveness."

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Limestone doorways of the Hal Saflieni Hypogeum. (Hamelin de Guettelet/CC BY-SA 3.0)

It is said that standing in the Hypogeum is like being inside a giant bell. At certain pitches, one feels the sound vibrating in bone and tissue as much as hearing it in the ear.  Sarasota arts and architecture critic Richard Storm explained the sensation: "Because you sense something coming from somewhere else you can't identify, you are transfixed."

Photograph of the Hypogeum of Ħal-Saflieni made before 1910. (Public Domain)

The acoustic properties within the Hypogeum have already been studied extensively. It was found by Maltese composer Ruben Zahra and a research team from Italy that sound resonates at 110 Hz within the Oracle chamber, and this matches the same or similar frequency that has been found in many other ancient chambers around the world, including Newgrange in Ireland.  According to Dr Robert Jahn from Princeton University, it may be the dimensions of the room or the quality of the stone that determines the exact pitch of this echo behavior.

But the question remains – was it intentional? Was the Hypogeum actually designed to enhance amplification? If so, why? Is it possible that the designers of these spaces knew something that modern scientists are rediscovering? 

Ritual Chanting and Brain Activation

One theory put forward by Paolo Debertolis and Niccolo Bisconti of the Universities of Triests and Siena respectively, is that the chamber was constructed in such a way as to create acoustics that would affect the psyche of people, perhaps to enhance mystical experiences during rituals, and this perspective has received scientific backing.  Dr. Ian Cook of UCLA and colleagues published findings in 2008 of an experiment in which regional brain activity in a number of healthy volunteers was monitored by EEG through exposure to different resonance frequencies. Their findings indicated that at 110 Hz the patterns of activity over the prefrontal cortex abruptly shifted, resulting in a relative deactivation of the language center and a temporary shifting from left to right-sided dominance related to emotional processing. This shifting did not occur at other frequencies.   

The sanctuary chamber. (-jkb-/CC BY-SA 3.0)

Whether it was deliberate or not, the people who spent time in the Hypogeum under conditions that may have included ritual chanting -- were exposing themselves to vibrations that may have impacted their thinking. In addition to stimulating their more creative sides, it appears that an atmosphere of resonant sound in the frequency of 110 would have been “switching on” an area of the brain that bio-behavioral scientists believe relates to mood, empathy, and social behavior.

Despite the plethora of research on the acoustic properties of the Oracle Room, there remain just as many questions as answers. It is for this reason that the Hypogeum was the key location for the Archaeoacoustics Conference held between 19  ^th and 22  ^nd February. During the event, a multi-disciplinary undertook a challenging and unprecedented experiment.  Ultrasensitive microphones were placed in the Oracle Chamber of the Hypogeum and digital recorders were used to test the response of the chamber by different voices and by simple musical instruments which could have been present in the time the Hypogeum was in use (4000 - 2,500 BC).

The results revealed that a male human voice can stimulate the resonance of the structure at two frequencies (114 Hz and 68-70 Hz).  The use of a horn and conch shell did not create any resonance at all, while a friction drum produced low resonance. Interestingly, a shamanic natural skin hoop drum created a strong stimulation of resonance by harmonics of the drum at 114 Hz. The response was the same as that produced by a male voice singing 'oooh'. A female voice did not produce the same effect. 

The Minister for Culture inaugurated the renovated museum on April 28, 2017. It now features a new climate control system for the Hypogeum and an expanded visitor center. The site welcomed visitors again on May 15, 2017.

The facade of the museum after restoration in 2017. (Continentaleurope/CC BY-SA 4.0)

The Hypogeum of Hal Saflieni in Malta stands as a testament to ancient ingenuity, its significance amplified by its UNESCO World Heritage status. Its enigmatic allure, from the discovery of elongated skulls to tales of paranormal encounters, continues to captivate explorers and scholars alike.

While we may never know for certain what transpired within the Hal Saflieni Hypogeum 5,000 years ago, scientists are moving ever closer to unravelling some of the mysteries of this ancient and incredible site.

Top image: Malta’s hypogeum Hal saflieni. Source: damian Entwistle/CC BY-NC 2.0 DEED

By April Holloway