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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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