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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




Preliminary archaeoacoustic analysis at Tarxien Neolithic Temples, Malta

Tags: archaeoacoustics , archaeo-acoustics, low-frequency, infrasound, transducers, Malta, Tarxien, Neolithic, SBRG, SB Research Group

A few days before and in conjunction with the Archaeoacoustic Conference  "The Archaeology of Sound" in Malta on 19th -22nd February 2014, a small group of SBRG members performed several archaeoacoustic measurements on some ancient temples in Malta.

In particular measurements were taken at the temples of Tarxien on the island of Malta, and the temple of Ggantija and Xaghra circle on the island of Gozo.

Thanks to Heritage Malta we obtained the authorization for admittance to places normally closed to the public to take acoustic measurements.

The Neolithic temples of Tarxien are in the town of Tarxien on the north side of the island. This is totally surrounded by houses and as a result, it was not very easy to take high-level recordings inside. The analysis of the recordings took a few weeks, but it looks like there is a very low frequency coming from underground in the range between 21Hz and 23Hz, encroaching sometimes infrasound frequencies with a peak of around 18Hz.


 Fig. 1 - Three examples of recordings taken in two different locations within the archaeological complex: the audio track is constant for each recording. There is a  large peak with a maximum of around 21 - 23Hz in almost all surveys, sometimes extending to 18Hz. The hump at the end of the plot in the range of the ultrasounds is an artifact determined by the characteristics of ultra-sensitive microphones, but no ultrasounds were detected inside the temples of Tarxien



Fig. 2 - The trace recorded in the nearby hypogeum of Hal Saflieni, located a short from the temples of Taxien. The very low volume at the start of the line of sound should not deceive: the recording was made at a lower volume. But whatever the volume of the recording, this does not change the result because the peak at 21 - 23Hz, detected in the Temples of Tarxiem, is missing. It is clear that these inaudible seismic noises are probably originating from a nearby geological fault (Malta is in an area with a lot of tectonic plate movements)

As we know and we have verified in previous research on ancient sites in Europe (Bosnia-Herzegovina, Serbia, South England, and also Alatri in Italy), this type of frequency, if at an appropriate volume and not too high, can have a positive effect on brain activity. This effect is particularly evident in people who practice meditation. During the measurements we also attempted to verify the presence of a resonance phenomenon within the comples’s two temples, those in the best condition for this purpose. Various musical instruments were used, from primitive shamanic drum to percussion bells, but without success. Unfortunately, the structure is too destroyed in its higher portions that are deemed to have been covered by a dome roof.


Fig. 3 - The operations of recording inside the temples


These temples were brought to light by the Maltese archaeologist T.Zammit in 1915 after some local farmers had complained in 1913 that when plowing the field above the temples, the plough was ruined by large stone blocks. These temples were further excavated in 1954 by English archaeologist J.D. Evans and four years later by D.Trump who discovered the re-use of them in the times of the Roman Empire as a cellar.

This Neolithic complex was initially built between 3,600 and 3,000 BC as a sacred place, but at the beginning of the Bronze Age (2400-1500 BC) the original temples were reused as storage of funeral urns. This indicates that the original population was replaced by newcomers with different social customs.


Fig. 4 - A look taken from the gates of the temple. At the center of the curator of the archaeological site that has helped us for a better understanding this structure



Fig. 5 - A few more striking image of the prehistoric complex that, as we see, is surrounded by a densely populated town


In addition in the 1950s, where a piece of the megalith was missing, the structure was reconstructed in several places using Portland cement. This ran the risk of restoring something not true to the original, but according to the tastes of the restorer. The type of material used, compared to the original coral limestone megaliths in their uncorrected position, may have been detrimental to the proper sound functioning of the old structure. Also the concrete reconstructions may have damaged the original stone. Unfortunately at the time of the restoration this problem was unknown.

The reconstructed parts of the megaliths appear very light compared to the original under infrared photography, whereas in normal photography, the remanufactured parts appear more visible because they are brighter. The infrared photography also cancels the dark color due to molds and lichens present on the surface of the megaliths and prevent you from grasping the structural element in its entirety.



Fig. 6 - Some infrared photographs which highlight the original stone (in gray) from the reconstructed concrete (in white). In infrared photography the difference between the two different materials is exaggerated by the reflection of sunlight



Fig. 7 - The same architectural element taken using two different techniques. Above: photograph taken with an Olympus E- 5 digital camera with proprietary software which enhances contrast. Below: the same subject taken with a modified Canon infrared camera. There is a clear lack of ability to reflect the sun's rays on cement that looks almost white in color, while the sky is almost completely black


The temple complex consists of four sacred temples. The first of which is located on the eastern side and built between 3,600 to 3,200 BC. Unfortunately despite the five apses being clearly visible, only the foundations remain. The South Temple is the most highly decorated with megalithic constructions that also contain the lower part of a colossal statue of a female figure and the East Temple with its walls of stone slabs and well shaped 'oracle' holes were both built between 3,150 and 2,500 BC. The Central Temple has six apses arranged on one floor and contains evidence of a cover arcs.

Our research group performed measurements on two of the four temples.


 Fig. 8 - What remains of the colossal statue of a woman (Mother Goddess) in the South Temple. This is a copy, the original is in the museum of Archeology, Valetta


With the vibrations from the subsoil, it was observed that some megaliths appear to act as vibration transducers and some concavities or holes in their inner seem to project and focus these vibrations. The mechanism appears to be very interesting and detectable by instruments: an ancient lost technology that can now be rediscovered through the use of today's sophisticated equipment, but once found only by the sensitivity of a person.

The holes found in the megaliths are very deep and are considered to have been used to support the foundations of some sort of barrier or door. But the direction of the holes seems rather directed to a greater sound diffusion of mechanical vibrations as a kind of forerunner to speakers. The mechanism discovered by our associate anthropologist researcher dr. Alesandro Severi, seems to provide an intriguing interpretation of  this archaeological site but requires further in-depth analysis. Certainly we to exercise caution before saying as reported above, so we are already preparing a new inspection on the site to recheck the measurements.


Fig. 9 - A sensitive hand can discern the low-frequency vibration of the air


 Fig. 10 - Graphical extrapolation of the sound from the megaliths


A sincere thank you to the curator of the archaeological site, Joanne Mallia, Prehistoric Sites Department of Heritage Malta, for her kindness and courtesy. Her help enabled us to have access to more parts of the ancient temple.

It will be necessary in the coming months to further survey the archaeological site to study what we found on this occasion.

Paolo Debertolis, Nina Earl - March 26, 2014




Our colleague professor Lucia Krasovec Lucas leaves our research group


It is with regret our colleague from Politechnic of Milano and founder member of SBRG, Prof. Arch. Lucia Krasovec Lucas, is reluctantly forced to withdraw her commitment from our research group. 

Of recent months, Lucia‘s academic obligations at the Politechnic of Milan have increased. So ends three last years of working together, during which Lucia always provided us with determination and professionalism. An example of this is the mapping of the Ravne hypogeum during our research in Bosnia-Herzegovina in 2011. As a consequence, the status and purpose of SBRG will undergo some changes.

She deserves our appreciation and gratitude as well as our good wishes for the new challenges that lie in front of her.

SBRG – February 11, 2014




Archaeoacoustical analysis of Cividale del Friuli Hypogeum using a shamanic drum

TAG: archaeo-acoustics, archaeoacoustics , hypogeum , Cividale del Friuli, resonance, ultrasound, infrasound, shamanic drum, SBRG, SB Research Group

On 21th of February 2014 we revisited Cividale del Friuli Hypogeum (Italy) to stimulate the resonance phenomenon in those chambers whose structure has been unaltered.

In particular, we wanted to test the resonance of one of the Hypogeum deeper chambers in which the effect appears to be more intense (chamber D on the map), this chamber is oriented within a few degrees of south.

Fig. 1 – Above: the map of the Hypogeum of Cividale del Friuli. Below: the entrance to the deeper chamber (marked D on the map)


This room is tuned to a frequency of around 101- 103Hz (102Hz on average), it is sensitive to songs and prayers (mantras) sung at this frequency by a male voice. The female voice, which does not have this range, is unable to stress the structure.

SB research group began to study this underground structure not based on the commonly held hypothesis that the Celts used it as a burial place, or it was used as a prison by the ancient Romans and Longobards. Our study was based on the hypothesis suggested by the independent researcher V. Maestra who suggested it is much older. He considered this structure to be a temple dedicated to the Mother Goddess. In fact this temple has sound resonance characteristics that would suggest it was geared for sacred rituals and not as a burial place.

During our study we found only two chambers (C and D of the map) to be sensitive to the resonance phenomenon. These are most likely the only rooms which have retained the original features and have not been modified in later times for a different use.

Our earlier research has been published in the international literature in the United States (here).

If we consider the Hypogeum of  Cividale to be a temple of Mother Earth whose date has been lost in time, we must consider that this cult was usually conducted by priestesses. For this reason we have compared it to the more well-known underground Hypogeum of Hal Saflieni in Malta notoriously dedicated to Mother Goddess.

But if priestesses conducted the religious rites in this structure, it seems counterintuitive that the only way to stimulate the resonance effect, which creates a strong emotion in those present in the rituals, was only through a male voice. Surely if our hypothesis is correct, there must be other ways to activate this process.

After taking this into consideration, we decided to use an easy to play acoustic instrument which would have been available in the historical period corresponding to the construction of a temple dedicated to the Mother Goddess.

We discarded wind instruments as the tone was too high or other methods such as glass goblets. Instead we looked at the kind of percussion instrument that is known as a "shamanic drum" still commonly used today in Celtic music performed in Northern Europe and also shamanic rituals.

This ancient instrument is found in virtually all cultures of the world and are still made today. It is a drum with one head, built on a circle in solid wood on which is stretched an animal skin, typically goat or deer, but skins can also be derived from different animals, depending on the area and culture.

These skins are stretched on the wooden circle still wet with ropes to reach the right amount of tension when drying.

Typically they range in diameter from 30 to 50 cm, and usually on the back side the shamanic drum is a handle. This can be made from ropes or parts of skins cut into strips and then tied, or with a wooden cross that allows it to be grabbed firmly with one hand while the other hand remains free to strike him with a wooden beater that can be made
of leather or other materials.

There are still a large number of craftsmen who can make such drums in many versions, and different patterns present on the skin can make a drum have a unique sound.

The sound is deep, but if the skin is damp from moisture, the tone changes as it vibrates less. The skin needs to be dry to produce the correct sound.

So the sound can change very quickly and is conditioned by the environment, if this is humid then the skin needs to be heated over a fire in order to obtain a more pure sound.

For our research we used a shamanic drum with a diameter of 50 cm made from goat skin. On the skin is a symbol of the Thunder Bird with two heads from Native American mythology, created by the craftsman who produced it. This design does not change the sound characteristics of the instrument, but it is purely for decoration.


Fig. 2 – The shamanic drum used during the experiment seen from the front


This drum has an average resonance frequency of around 55Hz when beaten at the center. As previously mentioned, the sound characteristics of this instrument can be undermined after a prolonged stay in the moist environment such as that found in Cividale Hypogeum.   This meant that at the start of the experiment the drums were working more efficiently than after prolonged exposure to the moist environment. The tone of the sound can also change depending upon where the beater strikes the skin, for example at the periphery the tone rises, but there is also a decrease in sound pressure that can be exerted.

The drum used in our experiment was placed at the end of the chamber D. As expected, the greatest effect was achieved by placing the drum in the sound node previously found. The term "node" refers to the point in the interior space of the chamber where the greatest effect acoustic resonance effect is felt. In this case about half meter from the bottom of the chamber and one meter in height. The resonance effect decreased dramatically the further away we moved from this point.


Fig. 3 – The drum has been used in different parts of chamber D, but the best configuration occurred in node sound (image below)



The frequency response of the structure was amazing, even though the drum had a frequency extension of i around 55Hz, the room responded at 103Hz, the frequency for which it is tuned. It is conceivable that the high sound pressure exerted by the drum or one of its harmonic vibrations put the chamber into this resonant vibration.

This effect amazed us, however graphical analysis of the recorded files has shown there are two very distinct peaks, the first from the shamanic drum, the second from the chamber.

If we look at the logarithmic plot of the recordings made during our  sound tests, we notice the presence of two peaks of greater intensity. If we put the cursor on the second peak in the graphic program, we can verify that the response of the chamber is tuned on 103Hz. This graphic
behaviour is the same one that is obtained by the male voice tuned to the same frequency of the chamber. If you point the cursor to the first peak it reads 55Hz, which is the average frequency of emission of the shamanic drum. As you can see, the sound response of the chamber in volume is equal to the sound pressure exerted by the drum. There are also higher harmonics of a smaller volume.


 Fig. 4 – The logarithmic graph that come out from the analysis of the recordings : two peaks of the same volume are evident, one determined by the sound of the drum (first from left ) and one from the chamber


By drumming at a certain rate, the chamber almost continuously vibrates. These vibrations, that are composed of frequencies in which we are investigating in another area of research using EEG, are capable of interfering with brain activity, and can create a state of ecstasy.

What seems clear at this point is that if this was originally an underground temple of Mother Earth, it was not necessary that a man was present to use his voice to generate the resonance response, rather it was sufficient that the Mother Earth priestess used a drum during a ceremony, beating at the right pace and in the right position (acoustic node). While it is conceivable that the onlookers were sitting on the seats carved into the rock in several places close to the celebrant.  We have verified that sound easily travels within the Hypogeum.


Fig. 5 – The digital recording equipment (Tascam DR -680) and Sennheiser mics (MHK3020), as from our standard SBSA protocol


On one of the recorded files after the beat of the drum it is possible to hear distinctly the response of the chamber that creates saturation within the microphones (here). To listen to this file you need to use a good pair of stereo headphones with a large bass component. If you use standard computer speakers you may run the risk of not hearing anything.


We had heard about the risk of remaining too long in the hypogeum due to Radon gas emissions from below, we wanted to measure the radioactivity using a Geiger counter (GAMMA - SCOUT model w/ALERT).

The environment was free from any radioactivity, we measured a maximum of 0.08 to 0.09 mSv/h. There is therefore no danger in this environment. It should be remembered that in the underground Ravne tunels in Bosnia, we measured a maximum radioactivity of 0.20 mSv/h. We have to recall too that the alarm threshold is set at 0.4 mSv/h, while values
greater than 0.60 mSv/h reveal the presence of a radioactive source.



Fig. 6 – The Geiger counter demonstrates a very low radioactivity levels because the underground structure is protected from the action of cosmic rays  and there is no presence of Radon gas


All recordings were performed according to the Standard SBSA protocol.

Paolo Debertolis - January 24, 2014


A sincere thank you from the SBRG research group to the owner of Cividale del Friuli Hypogeum, Mr. Gaetano Bront for his helpfulness and kindness in allowing us to enter even at night his ancient monument for our experiments. Heartfelt thanks also to Mr. Federico Morandini, who patiently gave us the keys of the hypogeum to conduct our research at all hours of the day and night. Thanks also to our new collaborator, Mrs. Dolores Dreosti, for her support in Cividale del Friuli researches.



Translated by Nina Earl


Preliminary results of the archaeoacoustic study of Alatri Acropolis

Tags: archaeoacoustics, archaeo-acoustics, Alatri , polygonal walls , low frequency sound, infrasound, SBRG, SB Research Group

Interesting data was collected in August 2013, so it was decided to return to this beautiful ancient town to confirm the data.


Fig. 1 – A winter image of Alatri among the olive trees of Montelungo hill (in the foreground)


Indeed, at the highest point of the acropolis there is an explanation of why there was a megalithic temple stood on top of the hill, on which was subsequently built the present Cathedral of Alatri. The vibrations discovered are loud with a low frequency and are significant based on what we found previously in facilitating prayer and meditation.

The photo below shows the dimensions of the temple blocks on top of the Acropolis,  the remains of which were used as a foundation for the construction of the cathedral. The joints are numerous free of cement and still perfect, with a similar construction to those found in Cuzco in Peru.


Fig. 2 – One of the many blocks of the ancient temple which now form the foundation of the wall on the north side of the Cathedral of Alatri. In the picture the author of this article appears as a to give an idea of scale (author is 1.74m tall)


On this occasion the recordings were taken inside and outside the present church which is dedicated to Saint Paul and built on top of the pagan temple. Inside, free from external environmental sounds, the recordings were splendid. Outside far less so as result of the continuous noise from vehicles passing along a road situated at the base of the hill on which Alatri sits and also from human activities in the city itself.

The recordings were carried on at dawn and, in addition to studying the archaeoacoustics, we received were able to contemplate the beautiful landscapes visible from the Acropolis during winter.

We were there on December 21, 2013, to observe if the ancient engraving found on a stone in the South-East corner of the giant walls, had a significant alignment during the Winter Solstice sunrise, but this was not the case. This incision, which functioned as an astrolabeis oriented to the equinoxes only, as for the other references on it, there are many theories, however a definitive interpretation seems to be far away.


Fig. 3 – The landscape visible from the corner of the South-East acropolis during the sunrise of December 21, 2013 (above). In the foreground of the image below to the right and below the ancient astrolabe oriented to the equinoxes is visible, it probably dates back to the construction of the Acropolis or shortly thereafter


The equinoxes were evidently important in the rhythm of the seasons for the people who built this acropolis. It should be remembered that the Porta Minore (Minor Door) placed in the North wall of this sacred citadel is astronomically oriented totally to light only during the equinoxes, whilst the Porta Maggiore (Major Door) located in the South wall, is perfectly oriented to Astronomical North.

It is unfortunate that the authorities continue to ignore the astrolabe, an extraordinary sign of the engraved on a huge stone liberated some decades from soil coverage. It is evident that there is an unacceptable deterioration by the water as evident in the photo taken in August 2013, and in December of the same year. Its possible the frosts present after heavy autumn rains have played a role in degrading the incision due to the relative hardness of the stone itself . It would takes so little to protect it!


Fig. 4 – The ancient astrolabe as seen in August of 2013 (above) and in December of the same year (below). The difference is not attributable to a different time in which the photos were taken, because both were photographed at dawn, but by a real deterioration


Many other stones of these cyclopean walls are suffering from similar degradation, but the disrespect of man for his historical treasures is clear.

Upon analyzing the various files recorded at Alatri, the motivation for the construction of the temple on the hill now occupied by the town of Alatri seems clear.

As in other sacred sites studied by SBRG there is something special. In particular, at the level of what historians refer to as the "navel" of the acropolis located on the north side of the church built over the ancient temple.


Fig. 5 – The main façade of the cathedral-basilica of St. Paul Apostole (side East) built over the ancient temple


Fig. 6 – Most of the recordings were taken on the top of the Acropolis, known as the "navel " of the acropolis


There is a significant prevalence of low frequencies here as shown in the graph of data recorded at midnight on the North side of the ancient temple, (which is now a Catholic church). This anomaly is even more evident when it is compared with files recorded on the same night at the East side of the Acropolis.


Fig. 7 – Most of the sound files in the "navel" of the fortress were recorded at night


Fig. 8 – Graph collected in the "navel" of the hill which has a frequency of around 30 -31Hz (above) for comparison with that found along the East side (below)


As you can see from figure 7 and 8 above, the second graph is without the peak of low frequencies found at the center of the acropolis of around 30 - 31Hz.

The sound seems to be concentrated solely in the navel of the acropolis and fades into nothing when moving away from the navel. It is likely the vibrations are coming from the geological fault that runs very close to Alatri, with its vibrations channeled via some strange phenomenon to the top of the hill. 


Fig. 9 - The map of the acropolis (above) and its aerial view (below). The upper side corresponds to the North (images from the archive of O.Tofani)  


Fig. 10 – The geological map of the area of Alatri shows a significant movement of the fault which may explain the vibrations that are picked up on the Acropolis of Alatri (map made by geologist Dr. Rocco Torre)


The continued exposure to these vibrations in the absence of noise could have a significant effect on the psyche of those who came for prayer and meditation, facilitating access into a mystical state. Even though they did not have the same equipment we have today, these ancient people were aware of the conditions required to achieve such a mystical state, perhaps by simply sensing that in that place they were closer to God. Maybe this was an ancient wisdom where more attention was given to the care of the spirit than in present times.

The Minor Door which is perfectly oriented along the equinoxes (it lights up fully on the equinox for only a short period, just as the eight faces of the Great Pyramid of Giza), is a great place to record the vibrations without being disturbed by noise from the open field. It offers protection that has enabled some recordings to be almost noise free.



Fig. 11 - The author of the article is a useful comparison to understand the size of the stone blocks that make up the city walls, near the Minor Door, each of which weighs a dozen tons


The files recorded very early in the morning inside the Minor Door have similar characteristics to those files recorded at the top of the hill. In them, there is a little noise from the outside environment, muffled by its fairly protected position.  Here there is a sample file to listen to, however to be sure of hearing all of the low frequencies, it is suggested you listen using high-fidelity stereo headphones where possible, because normal computer speakers do not have a sufficient frequency response to play low frequency sounds.

The graph common to all collected files inside the Minor Door shows similar trends to those gathered on the top of Alatri. This is because this door is not far from the top.

Changes in the volume in the various graphs are determined by the change in recording volume. What matters in this research is mainly concerns the shape of the graph. 


Fig. 12 – The shape of the graph of the collected files taken close to the Minor Door is very similar to those found on top of the hill


We also examined the surrounding areas of Alatri to detect if the same type of vibration is present elsewhere. In fact there is something in the nearby hills, however it is only perceptible using instruments rather than physically. We have to remember that low frequencies are non-directional and are not absorbed much by the soil, they can therefore travel long distances. But the low volume sounds found for example on the rise facing of Alatri’s, Montelungo hill, are not felt like those on the top of Alatri Acropolis. This may explain why the ancients chose the hill of Alatri to build their temple even when they had a large number of hills with similar characteristics to choose from.


Fig. 13 – Image of the recordings made on the hill of Montelungo – La Crocetta


In a nutshell, although we have to be careful, we can assume that the decision to build the acropolis right on top of the hill at Alatri was motivated by more mystical - spiritual reasons than by consequences of a choice of military defense. This would also explain the perfect orientation of the ports in the walls of the acropolis, more typical of a “sacred” instead of a fortress.

At this stage, it becomes difficult to explain another mystery. In this acropolis the doors, despite the difficulty of the accurate placement of huge stone blocks are perfectly oriented. It is not clear why on the flat space of the temple, where the construction problems were minor, it was constructed without a perfect North-South or East-West orientation. Of course, the topography of the area may explain the polygonal aspect of the acropolis that perhaps follows the natural shape of the hill, however this does not explain why the main temple was not equally oriented according to astronomical criteria, when situated on top of a relatively flat hill.

In fact the wall of the North side of the temple it is still oriented along an azimuth of around 259° (261° on some maps) instead of 270°. This deviation of about 11° (or 9°) to the East-West axis appears mysterious and inexplicable, given the perfect orientation of the gates in the walls which would be much more difficult to correctly place from an architectural point of view. Surely there must have been another reason, perhaps a political reason to align the temple in this way.


Fig. 14 – It is fairly easy to measure the azimuth of the ancient temple following the North -East corner of the basilica built on the temple and following the same orientation



The recordings made in the perfect silence of the Basilica Cathedral of Saint Paul, captured the same vibrations although at a lower volume than outside. This is attributable to the fact that below the church there is an underground structure the remains of the ancient temple that, by the presence of air inside it, brakes the transmission of low frequency sounds, more rapidly and intensely through the rock.

It is conceivable that the ancient pagan temple, that still lies below the church, did not suffer from this defect and the effect on the human organism was more intense to better transmit the mechanical frequency. For this reason those who place themselves close to the "navel" feel this phenomenon much better, even if outside noise from modern life distracts them.



Fig. 15 – The recordings inside the Basilica Cathedral of St. Paul the Apostle were carried out mainly in the left aisle because this was most free from the noise coming through the windows


All recordings were performed according to the new SBSA Protocol (see here for details) to avoid the presence of any spurious electromagnetic waves that would affect the recordings. Using used broad-spectrum electromagnetic wave sensors under the SBSA Protocol, nothing was found that could affect the recordings was detected in this location.


Fig. 16 – The electromagnetic wave sensors were used according to the SBSA Protocol


This March we hope to carry to conclude our archaeoacoustic research in this beautiful city.

Paolo Debertolis - January 16, 2014


We would like to thank Don Antonio Castagnacci for his availability to grant us the opportunity to make recordings, including inside the Basilica - Cathedral of St. Paul (Cathedral of Alatri) and for his help, also to his collaborator Mr. Sisto Macciocca.

We would like to also thank the independent researcher Ornello " Paolo" Tofani and his son Claudio for the documentation and the extraordinary support provided in this research.



Translated by Nina Earl


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