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Archaeoacoustic analysis of Ggantija, Gozo

Tag: archaeoacoustics, archaeo-acoustics, low-frequency, infrasound, Malta, Gozo, Bronze Age, Neolithic stone circle, Xaghra, Ġgantija, brain activity, SBRG, SB Research Group

As part of the research carried out on some of Malta’s Neolithic temples, we performed some interesting research on the island of Gozo with very good results especially in Xaghra stone circle.

The Temple of Ggantija was devoid of underground vibrations, however like Tarxien temples on Malta, nearby Xaghra Stone Circle appears to be a real nerve center of vibrational energy from underground.

This energy is a mechanical vibratory stress that appears to have a broad peak, reaching between 25Hz and 34Hz. It is extremely powerful, more or less comparable to what was found in the temples of Tarxien, but with a slightly longer high frequency range and oscillating just a little bit. Its origin is to be found in the movement of friction between the African and Eurasian tectonic plates close to the archipelago of Malta.


Fig. 1 - The line of contact between Nubia and Eurasia plates


Fig. 2 - Velocities of GPS stations along the Nubia-Eurasia plate boundary (Serpelloni E et al. Geophys. J. Int. 2007;169:1180-1200)


In addition to Tarxien, we found something equally powerful in our research within the temple of Cybele at the archaeological site of Felix Romuliana, Serbia.

The broad peak at Xaghra Stone Circle seems to intrude in the field of infrasound and in the audible band comfortably up to 40Hz. At this frequency, this vibration is clearly perceptible to an attentive ear and for those who are more sensitive, via the vibrator sensors of body (Meissner mechano-receptors).

This explains why to this day some meditation groups visit this place to carry out techniques of mental concentration for religious, philosophical or spiritual purposes. Access to the site requires the permission from the Maltese authorities, Heritage Malta.

In previous research in other sacred archaeological sites by SBRG, these vibrations are perceived by many sensitive people as unspecified energy from the ground, with a clear effect on the human body and in particular brain activity.



Fig. 3 - The extraordinary peak of low frequencies constantly present in all the recordings made at Xaghra Stone Circle



The stone circle is located a short distance from the most famous Ggantija Temple. It was discovered for the first time at the beginning of 19th century, then rediscovered in the 1960’s and subsequently investigated in a joint collaboration between the University of Malta and the University of Cambridge between 1987 and 1994. Following this excavation, it was then covered again to preserve its characteristics.

It is believed that the first settlement dates back between 4,100 and 3,800 BC. Subsequently, as with the Tarxien temples in Malta, it was adapted to become a burial place from the same community who practiced its rites near temple of Ġgantija around the period 3,000-2,400 BC.

Even though the Maltese/English archaeologists found many parts of skeletons, this now partially collapsed underground structure, was probably at one time a sacred temple. The fact that the remains were incomplete and separate lends to the theory that they were not originally buried here, but moved to this place, probably adapted as a mausoleum for the ancestors.

Originally this archaeological structure had a huge stone entrance that led to the steps to reach the caves below where some altars were placed. The whole surface area was surrounded by megalithic stones arranged in a circle, as to demarcate the sacred area located below. In the underground area there was a central hall enclosed by the altar and divided internally by large stone slabs all around the now partially collapsed caves.


Fig. 4 - Graphical reconstruction of the stone circle of Xaghra. Circled in red the two positions in which the microphones were placed


Our archaeoacoustic measurements were carried out in two main locations: a deep well on the side of the walkway leading to a stone staircase that leads to the central hall of the hypogeum; in a collapsed cave that overlooks the main hall of the Hypogeum (A and B respectively on the above image). The ultra-sensitive microphones (Sennheiser MKH 3020) were dropped from the surface without going into the deep wells because this is expressly forbidden by the authorities. In this way the shielded and sufficiently long coupled cables were left suspended so that the microphones did not touch the ground. This was done in this way in order to avoid friction with the ground by the microphones which would have led to the generation of spurious noises affecting the recordings. The position of the microphones appeared sufficiently deep and sheltered from the wind. Also, during recording we carefully assessed if the sounds coming from the microphones were genuine and not from the result of human activity or the movement of the wind. We repeated several recordings over this time period with a long pause between the different files.



Fig. 5 - The handlings to place the microphones present into the well at the side of the walkway which leads to hypogeum (position A in Figure 4)


In both locations A and B where the microphones were placed (at about twenty meters from each other), the same low vibrational frequency as an engine in motion was detected. The sound is more likely to be attributable to the underlying tectonic movements as opposed to underground streams, given the scarcity of this natural element in the Archipelago of Malta. In the vicinity of the megalithic circle there was no factory or human activity capable of generating a noise of this frequency, that we were aware of.


Fig. 6 - One of the caves that overlooked the main room of the hypogeum


 Fig. 7 - The archaeological site is protected by a fence and closed by a gate. Access is only possible on request to the government institution Heritage Malta. It is not possible the access the zone in the Hypogeum


As with other research carried out by SB Research Group at other archaeological sites in Europe, we can theorize that inside the stone circle was a “covered” hypogeum. Such a structure could certainly have acted to intensify the vibrations, in a similar way to how a sound box of a musical instrument works.

Such vibrations have a definite effect on the emotional sphere of those who stood in prayer or meditation in this hypogeum creating the real “sacred space” of the area of the most famous temple of Ggantija.


 Fig. 8 - During the initial listening before recording, it is important to assess by clap if the microphones may be affected by noise from the environment. In this case, it was verified that the microphones had been pushed so deeply as to be scarcely affected by the noise environment


 Fig. 9 - Even in position B (Figure 4) the sounds detected were similar to those detected in the well at the side of the walkway (A position)


We conducted thorough research of the sounds coming from underground in in the temple of Ggantija, but apart from the noise pollution from the sites nearby access road (at higher frequencies than those found in Xaghra megalithic circle) we did not find anything which compared to the sound spectrum found inside the stone circle.


Fig. 10 - Ggantija as seen in its entirety. Above: view from the hill in front of the temple. Below: the appearance of the temple seen from the back


The research also aimed to establish if there was any resonance phenomena inside the apses by playing musical instruments, however the presence of metal cages designed to shore up the huge stones of the site meant this was not possiblbe. They acted as interference obstacle in reflection of the sound waves, so we cannot pronounce definitively on this aspect of the temple.



 Fig. 11 - The presence of numerous tubes containing the stones frustrated any attempt to verify the presence of a resonance phenomena that could be stimulated by musical instruments (eg drums or percussion bells)


Equally the areas without props have undergone such alterations over the millennia, such as to alter their original form with domed roof  to make virtually impossible an adequate assessment in the field of sound resonance maybe desired by their builders.


 Fig. 12 - Even in the most sacred part of the temple the alterations or deterioration of the structures have meant that nothing has been detected


Fig. 13 - Plot of recordings made in Ggantija Temple, unlike in Xaghra stone circle, nothing unusual was detected. The peaks in the middle of the curve are simple ambient noise


It should be noted that some megaliths have similar holes to those at the Tarxien Temples. This could indicate that at the time they may have acted as transducer of vibrations coming from underground. Functioning in a similar way to bagpipe reeds, used to expand the vibrations coming from underground. However these vibrations are present in Xaghra Stone Circle, but not in Ggantija Temple.


Fig. 14 - The holes in the Ggantija megaliths, quite similar to those found in the Temples of Terxien


We wanted to find a base line noise in this area that could serve as a reference for the recordings in the above mentioned temples. For this purpose we chose the hill in front of Ggantija, where there are still prehistoric settlements. In particular, we dropped microphones through the entrance of a prehistoric tank (that is dry now), on top of the hill and dug into the rock.

The track recorded in the prehistoric tank is devoid of any peak from noises coming from underground confirming the uniqueness the Xaghra Stone Circle recordings.


 Fig. 15 - The hill facing the temple of Ggantija. The site of a prehistoric settlement which has not yet been deeply research


Fig. 16 - The dry tank excavated in the rock where our microphones were placed


Fig. 17 - Above: the look and feel of the recordings made in the tank. There is absolutely nothing significant. Below: the sound curve measured inside Xaghra Stone Circle for comparison. It is evident in this recording (as inside the stone circle) that there is a powerful vibration with a top peak of 28Hz


How did the ancient megalithic civilization become aware of the vibrations present in this area and the caves at Xaghra stone circle? We propose a simple answer, given the high noise level of those frequencies present in the human hearing spectrum they would have been heard by placing an ear to the ground for the transmission of vibration via bone conduction.

It is likely that these vibrations, close to the rhythm of brain wave frequency, created a sense of exaltation and mysticism in those present. When it was intact, it must have acted as a sound box for someone engaged in prayer or meditation. Probably he felt himself enveloped in the sounds of the womb of the Mother Goddess, and in touch with the depths of the planet.


Fig. 18 - Graphical reconstruction of the Xaghra stone circle inside Ggantija museum (Heritage Malta - Ggantija Museum)


Fig. 19 - Some of the votive objects found during the excavations of Xaghra stone circle (Heritage Malta – Ggantija Museum)


Our warmest thanks go to the Maltese institution Heritage Malta for giving us access to Ġgantija Temple for our research, and in particular, our gratitude goes to Dr. Daphne Caruna, curator of the archaeological site, who controlled, assisted and helped us during our surveys.

Paolo Debertolis, Nina Earl - April 5th, 2014




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