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We recorded the “voice” of the Bosnian Pyramid of the Sun (Visoćica hill)


TAG: bosnian pyramids, pyramid Bosnia, Visoko civilzation, archaeology, archaeo-acoustic, voice pyramid, Bosnian Pyramid of the Sun Foundation, ultrasounds, SBRG, SB Research Group


Abstract The objective of our research included the audio gamma recording of the ultrasound vibrations coming out of the Bosnian Pyramid of the Sun (Visoćica hill) and pointing towards outer sky as already detected by other researchers coming before us. For this experiment we used a compounder in order to turn ultrasound vibrations into audible sounds. Results were astounding, but we will carry out the experiment again during our next expedition at the end of February, in order to verify if results are scientifically reliable and can be repeated by means of a very rigid protocol for each recording. Therefore, so far present results have to be considered preliminary. Paolo Debertolis, Giorgio A. Battistoni, Valeria M. Hocza  - 28 January 2011.


The objective of our research included the audio gamma recording of the ultrasound vibration coming out of the Sun Pyramid and pointing towards outer sky as already detected by other researchers coming before us. The scientific expedition left Trieste on 23 January and included only three researchers: Lucia Krasovec Lucas, architect, expert of ancient structures, Valeria Hocza, scientific assistant and Paolo Debertolis, medical anthropologist.

The research was carried out in two days from 24 to 25 January 2011.

Unfortunately on the first day a snowstorm deposited on our path more than a metre of snow

We immediately realized we could not get to the plateau west of the Sun Pyramid by car, despite the four-wheel drive which could have saved us a good distance to reach the top.

Therefore we had to walk with our boots and gaiters from the foot of the Sun Pyramid, up to the top with the snow still falling.


Despite the difficult climb and the snow storm, the scenery between one snowfall and another was amazing


In order to reach the top we had to walk along the path starting at the bottom of the Sun Pyramid on the most eastern portion of the northern facade; more or less below the first excavating surveys. Afterwards the path rounds the eastern facade with two hairpin bends and then reaches the southern facade, the most ruined part, owing to trenches dug by different armies to approach the Western part at the crossroads with the plateau.

From there, even with the best weather conditions, one must walk to the top, dominated by the medieval fortress destroyed by the Ottomans after conquering Bosnia at the end of the Middle Ages.


Different sceneries from winter to summer in the path leading to the Sun Pyramid. This is the plateau west of the Pyramid.



Also during the last Balkan war the top of the Pyramid was a strategic place guarded by the Bosnian Army for the whole war until Dayton’s agreements stopped the last war in Bosnia (21 November 1995), after three years of the bloodiest war in Europe since 1945.

The idea of recording ultrasound frequency with  a compander was put forward by our instrument expert, eng. Giorgio Battistoni, who built one on purpose for our team, by developing a consolidated project published by a well known Italian Journal on Electronics.

Companders are processors of sound dynamics belonging to a group of electronic devices operating essentially on the level or width of the audio signal variations depending on the range of levels and the spectrum distribution of the compandor itself.

The compander used by our team could turn ultrasound vibration into audible sounds.


The compandor used on the Sun Pyramid



Materials and methods

It has often been cleared that an apparently innatural 28KHz ultrasound frequency originates from the Sun Pyramid and Vratnica mound.

Ultrasounds can be briefly described as mechanical waves that we cannot hear even if they reach our ear because their frequency is higher than the maximum frequency detected by human beings. Actually because of its nature, the human ear can convey to the brain – which will then turn them into sounds – only acoustic waves having frequencies between 20 Hz and 20,000 Hz, even though not all individuals can detect these degrees. Therefore frequencies lower than 20 Hz and higher than 20.000 Hz cannot be detected by human beings as sounds, whereas many animals can hear frequencies lower than 20 Hz and others higher than 20,000 Hz (or 20 Kilo Hz).

However there are instruments suitable to detect frequencies overcoming our hearing abilities; on the Sun Pyramid actually such instruments recorded sounds with 28,000 Hz frequency.

Yet one thing is reading 28 KHz on a scale or on a display, another thing is listening or analysing that emission confirmed by the instrument.

To achieve this we benefitted from a project published by an Italian Journal, which is well known for the manufacturing of electronic kits not available on the market. The Journal’s name is Nuova Elettronica.

Issue 245 of 2010 published a project that could prove useful for our research, i.e an instrument able to “convert ultrasounds into audible sounds”.


Instrument’s features

This project takes advantage of the ability of a particular microphone, which can be defined more correctly a supersonic sensor. Such sensor detects sounds whose frequency ranges between 10 and approximately 65 KHz.

The circuit diagram is displayed in the following figure.


Briefly one part of the instruments generates a variable frequency thanks to a knob and from that frequency the instruments withdraws the frequency received by the microphone. The result of such withdrawal can be heard into the headphones. For example, let us suppose that the microphone is detecting a 40 kHz-frequency (not audible); if, by rotating the tuning, we produce a 50-kHz frequency we will hear a difference between 50 and 40 kHz, i.e. a 10-KHz sound and  it will be  an audible frequency.

The signal coming from the sensor is then applied to an amplifier and the tension gain at this stage is approximately 100 times. In order to hear ultrasounds detected by a microphone, they need to be “conveyed” to a lower frequency, in order for them to be heard by a human being. The system we used is similar to that used in several radio receivers, in which the high frequency signal of dozens or hundreds MHz is lowered deeply compared to the incoming signal.

The instrument uses a variable beat-frequency oscillator and a two-entry mixer, used to produce an outgoing signal equal to the difference between the frequencies of the incoming signals, one generated by the instrument and the other coming from the microphone. The first frequency can be tuned with a tuner, as if looking for a radio station.

The “different” signal is then cleared from possibile tension peaks and is conveyed to the second part of the intrument which amplifies it and conveys it to the headphones and/or to a recorder. The volume can be tuned.

The instrument’s wire diagram is the following:



The equipment is included in a plastic container and powered by a 9 Volt battery.

The supersonic sensor we used (technical sheet here) has been manufactured by the American company Knowles Acoustics and, despite its very small size, it implies very advanced technology: the equipment contains highly miniaturized mechanic and electronic components integrated in the same silicon substratum.

A further, but important technical detail is the assembly of the small microphone on the focal point of a metal parabola, so as to collect the very straight ultrasound waves at best.



To use the instrument, the parabola with the microphone must aim towards the direction to be examined, and by rotating the tuning potentiometer, ultrasound waves can be detected (if present), heard in the headphones or recorded if a tape or digital recorder is connected.

This is just the beginning of the use of these instruments to ultrasound detected on the top of the Sun Pyramid. One can listen to the released sound, but at a lower tone, since the real sound is so high-pitched we could not imagine; the interesting feature to be searched is a possibile sound modulation. This is what we will try to do during the analyses of the different recordings.


Further equipment

For our measurements of possibile raioactivity we used a GAMMA-SCOUT w/ALERT portable Geiger counter manufactured in Germany with a steel-coated GM tube filled with halogen gas, dosing of alpha, beta and gamma rays, rotating discriminator.

It is a very compact and portable equipment with internal memory which records radiation trends in the different periods and USB port to download measurements on the PC.

To look for magnetic fields, we used a EMF Tester PCE-G28  equipped with 3D external probe and a wide LCD display.

By placing the probe in the interested area this instrument enables the measurement of the magnetic field on the three axis without moving the probe in the space.


The experiment

A preliminary remark must be made. Two scientific teams already used instruments to detect the presence of an ultrasound beam coming from the top of the Sun Pyramid and pointing to the sky.

The first team to notice this ultrasound frequency released at the top of the Sun Pyramid was a group of Croatian researchers, who came in the Bosnian Pyramids’ Valley on 10 and 11 April 2010, led by the physicist Slobodan Mizdrak, from Zagreb. The instruments used in their research were an 823 EMF gaussmeter with internal probe and an 828 EMF gaussmeter with a 3D external probe, gauged in the factory.

Two devices have been used to analyse the frequency: an oscilloscope and a spectrometer

For second, again in 2010, dr. Harry Oldfield, a British independent researcher detected the electromagnetic fields above the Sun Pyramid with a special camera using the Polycontrast Interference Photography technique (PIP camera, an evolution of Kirlian’s camera). He was able to reveal the ultrasound radiation accumulated in the pyramid as well as its release through the top.

The main features of the ultrasound frequency were a continuous emission of 28,000 Hz. During the Croatian team’s walk to the top of the Sun Pyramid, instruments did not show ultrasound frequencies on the whole western side. Such frequency appeared surprisingly only at the top of the pyramid and only within a metre’s radium. Outside a 5-meter diameter no sound could be detected by the instruments.

The Zagreb (Croatia) team detected the same emission frequency (28kHz),  and even the same sinusoidal shape, also at the centre of the plain placed at the top of Vratnica’s barrow, but also in a few passages on the sides of Ravne’s underground complex.

Therefore we decided to carry out a different survey. We wanted to record the “voice” of the pyramid with the compandor. We also brought a gaussmetre equipped with 3D external probe and a Geiger counter.


We have looked all over the top for the right position of the ultrasound beam emission


Once we reached the top, unfortunately the wind and the snow created many interferences and we had to keep the microphone’s protection cap on at the centre of the compander’s parabola, in order to avoid spurious influences.

We had to explore many places on the flat top of the pyramid before detecting the ultrasound radiation outside the walls of the Medieval citadel at the highest spot of the top, slightly westwards.


Despite the snowstorm and the cold weather we managed to find the origin of the strong ultrasound beam


By using our hearing as a reference, we discovered that the ultrasound beam is much wider compared to what the Croatian team reported after catching it only on their instruments’ displays.

The sound can be heard as a continuous whistle, and tends to fade away by withdrawing from the top progressively and not abruptly.

Unfortunately the recording is disturbed by the wind which can be clearly heard, our voices and the voices of two boys who followed us to the top maybe intrigued by our instruments, and even the continuous barking of the boys’ dog.

Unfortunately, after half an hour of analyses and approximately fifteen minutes of recording we had to interrupt the experiment and go downhill because of the worsening of the very cold weather and dusk coming in rapidly.

First we checked if in the same place there was an anomalous gamma radiation with the Geiger counter or if there were magnetic fields.

The radiation we detected was the natural one, contained into normal ranges recorded all over Bosnia (0,06.-0,22 µSv/h).


Radioactivity levels were perfectly normal where ultrasounds could be detected. During the photo shooting we detected only 0,10 µSv/h on the Geiger counter.


Similarly we looked for magnetic fields with the gaussmeter equipped with a 3D probe. In this case too the analysis was negative: there is no magnetic field on top of the Sun Pyramid.


No magnetic field can be detected by the gaussmeter with 3D external probe on top of the Sun Pyramid


This last data is very important because the whistle cannot be referred to radio waves originated by radio stations or repeaters placed nearby.

The whistle, turning the 20,000 Hz vibration into an audible sound can be clearly heard even though it is disturbed by other sounds (two small parts of the non-processed original recording, can be downloaded here and here; in the first recording our voices and the dog’s barking overlap the sounds, the second recording has been carried out on a different ultrasound frequency, besides a different emission frequency and the children’s voices overlap; in both recordings the wind blowing can be heard sometimes).

However, having learned from experience, on the next day we wanted to go in other areas around the Sun Pyramid to verify if this vibration could be felt in other places too. For this reason we reached several excavation survey sites on the northern facade and started measurements.

The walk was shorter than the previous day, but not less impracticable, with more than a half –metre snowfall and a short uphill path.

At the Deset Probe (survey number ten), placed in the lower two thirds of the northern facade, almost setting the microphone’s parabola on the ground, we detected a similar ultrasound frequency, i.e. a continuous whistle, yet also coupled to a series of bursts, as if the wind were blowing into the microphone.


Measurements on the Deset Probe have been carried out more rigorously and with the instrument’s maximum sensitivity


However that day, despite the heavy snowfall, the sun shone again and there was no wind. The microphone was well secured to the main instrument, without anomalous contacts.

Such sounds cannot be heard by human ears and therefore can be ascribed to the womb of the Sun Pyramid. We make this recording available, even though our voices overlap them. At a certain point the change in the whisle is due to a small tuning shift. Background noises are not caused by wind nor by clothes or cables.

(Original recording lasting 1,39 minutes: here).


Graphic spectral analysis of 5 seconds of the ultrasound recorded on the Deset Probe (analysis by Giorgio Battistoni)


The idea we came up with is that at Deset Probe level there is some sort of energy leakage present inside the pyramid. But this is only theory, so far not supported by evidence.


The Deset Probe in today’s version (winter) and in the Fall (November 2010)


Obviously our next mission at the end of February will include the repetition of the experiment in order to verify if results are scientifically reliable and replicable. Moreover we will implement a very strict protocol for all recordings. Therefore, so far present results have to be considered preliminary.


Inside Ravne’s tunnels complex we did not detect the ultrasound frequency coming from the Sun Pyramid


Possibile ultrasound catching inside Ravne’s underground complex was disappointing. No unusual vibration was detected except below the monolyths where there are underground water flows which could generate such vibrations, softened by the megalyths. However this part is still being studied.

Paolo Debertolis, Giorgio A. Battistoni, Valeria M. Hocza –   January 28, 2011


SB Research Group thanks Nuova Elettronica and in particular mr. Leonardo  Righini (managing editor) for authorizing the publication of an excerpt of the project “Converting ultrasounds into audible sounds” and also for the images (taken from journal n. 245/2010 to be referred to for more technical information) and most of all for manufacturing the instrument.



1) P. Debertolis, V.M. Hocza: "November 2010 Report on the Bosnian Pyramids – Ravne’s tunnels (Preliminary study approach)", SBRG, 4 November 2010

 2) P. Debertolis, V.M. Hocza: "November 2010 Report on the Bosnian Pyramids – Ravne’s tunnels (Theories about artefacts and structure)", SBRG, 16 November 2010

3) P. Debertolis, V.M. Hocza: "November 2010 Report on the Bosnian Pyramids – Ravne’s tunnels (The initial measurements)", SBRG, 20 November 2010

4) P. Debertolis: "Ricognizione aerea sulle piramidi di Bosnia – La Piramide del Sole bosniaca",SBRG, 4 September 2010

5) P. Debertolis, S. Acconci, L. Krasovec Lucas, V. M. Hocza:”Definitive report on our first scouting into the new section of Ravne Labyrinth in December 2010", SBRG, 12 December 2010


(translated by dr. Raffaella Agosti)


Verification in February 2011 by P. Debertolis, V.M. Hocza: "Still checking on the voice of the Bosnian Pyramid of the Sun"

Video of the experiment of January 2011 and the verification of February 2011, here



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