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Warning to the readers

SBRG’s research for an archaeoacoustic standard

TAG: archaeoacustics, archaeo-acoustics, archeology, electromagnetic waves, ultrasound, infrasound, voice pyramid, SBRG, SB Research Group

In mid-September 2013, the SBRG research team members interested in archaeoacoustics (not everyone in the team works on this topic) gathered in Zagreb (Croatia) at the Demiurg D.O.O laboratories to draw up an archaeoacoustic protocol and to develop a standard applicable to any archaeological site. Indeed it is important to define a standard at international level in order for other researchers to apply the same methodology that allows repeating any previous detection.

Most of the constructive criticism that was received in the last year questioned some of the final results by suggesting that there was a possibility that radio waves could have contaminated and tainted our records by infiltrating into the ultra-sensitive microphones used for the research. This is a possibility because condenser microphones are sensitive to radio waves, but only if these radio waves are very powerful and very close.

Besides mobile phones, which are always strictly switched off (also the battery has to be removed, because even when turned off mobiles phones regularly give the user's location through occasional pulses) the real concern was for radio waves coming from unusual terrestrial electromagnetic fields originating either from the abnormal diffusion of the magnetic field or from the tectonic movements of the Earth's crust.

In order to avoid any of the above, the physics researcher, Slobodan Mizdrak, devised specific electromagnetic sensors that can be used at the same time as microphones on the digital recorders that are normally used in archaeoacoustics (which have six to eight channels, or it would be better to say that they have three or four stereo tracks).


 Fig. 1 - The eight-track digital interface (MOTU 896mk3 fw 800 digital interface) that was used to connect the various microphones to the computer


The test used microphones for the air diffusion of sound (Sennheiser),underwater microphones (Hydrophones) and ultrasound microphones connected to a detector (Pettersson D 1000X) that directly transforms ultrasounds into audible sounds as well as two sensors (Demiurg sensors) with different sensitivity to electromagnetic waves.

Up to this stage only one spectrum analyzer had been used (model Spectran NF -3010 of the German factory Aaronia AG) to signal any nearby radio sources potentially disturbing recordings.  For a greater reliability of results if there are any magnetic fields nearby, now these can be recorded simultaneously with sound vibrations.

The graph on the computer will immediately report any radio waves in the surrounding areas that may interfere with the microphones.


 Fig. 2 - The image shows on the computer screen the six tracks (three-track stereo) obtained with the digital recorder. The two graphs in the middle, which were obtained from electromagnetic sensors with different sensitivity, point out some of the noises picked up by one of the sensors, while the other tracks show the recorded sounds from the microphones (these monitoring operations were carried out in the laboratory in Zagreb)


The equipment was also tested in the areas of Piljenice, Sisačko-Moslavačka (Croatia), located about 100 kilometers from Zagreb, in order to derive the basic guidelines for archaeoacoustics . This area is totally surrounded by the Croatian plain and it is completely free from anomalous electromagnetic phenomena, thus it was used to create a baseline in absence of acoustic or electromagnetic anomalies.


 Fig. 3 – A small lake in the Pilijenice area was used for baseline calculations in water with Aquarian Hydrophones (photographs by I.Tomek)



 Fig. 4 – Some images taken during the standard-checking recordings. Close to the digital recorder it is possible to see the Pettersson D 1000X detector



 Fig. 5 – The new sensors with different sensitivity (300Ω) built in the Demiurg laboratories  (Zagreb) which transform electromagnetic impulses from the environment, into electrical impulses used by the digital recorder



Once the basic standard of archaeoacoustics has been determined it is possible to check whether in a particular archaeological site there is any acoustic or electromagnetic phenomenon, either induced or natural, that will certainly affect the psyche of a person staying in that area. It is now equally possible to immediately identify a spurious phenomenon resulting from current human activity in the area, which could affect the recordings made in a specific archaeological site.

For this purpose as well as to have a comparison, recordings were also collected from an industrial environment of Zagreb where there are very high-levels of electromagnetic pollution.

Microphones were also subject to numerous tests in the Zagreb laboratory to investigate their sensitivity to electromagnetic phenomena by means of a radio waves generator, which provided further evidence of the very low sensitivity to radio waves of the shielded cables and of all the equipment used for the tests. The latter finally put the word “end” to all criticism raised some time ago over the inaccuracy of the method. Indeed the results strongly confirm all the data previously published by the research group.

The newly-devised procedure will be used in all future archaeoacoustic missions by SBRG and it constitutes a repeatable standard of reference for anyone doing research within the field of archaeoacoustics.

Paolo Debertolis – September 30, 2013




  Base line equipment for archaeoacoustics


2 PC computers and one mac pro

MOTU 896mk3 digital interface fw 800

ProTools 9.0.6 editing software

BatSound 4.0 audio analyzing software

Audacity audio editing software

Praat phonetics analyze software


2 Sennheiser mkh 3020 condenser microphones (10-70.000Hz)

2 Aquarian N2a hydrophones (10-100.000Hz)

4 Electromagnetic ”Demiurg” (300Ω) sensors

1 Tascam (Teac group) DR-6806-track digital portable recorderat 192 kHz sampling rate, 24-bit

1 Pettersson D1000x ultrasound detector

2 Genelec active studio speakers


Audio and electromagnetic recording range 10Hz-96kHz. With Pettersson device 500Hz-305kHz audio recording range

Simultaneous recording analyze 8-tracks of 192kHz audio.


Feed 1: microphone

Feed 2: hydrophone

Feed 3: electromagnetic sensor 1

Feed 4: electromagnetic sensor 2

Feed 5: Pettersson frequency division algorithm

Feed 6: Pettersson heterodyne algorithm

Feed 7: electromagnetic sensor 3

Feed 8: electromagnetic sensor 4




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