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We continue our researches into Archaeoacoustics at the Hypogeum of Cividale of Friuli


TAG: archaeo-acoustics, archaeoacoustics, hypogeum, Cividale, resonance, ultrasound, SBRG, SB Research Group, Paolo Debertolis

On the night of February 26th 2013, the SBRG researchers returned again to the hypogeum of Cividale of Friuli to delve into the phenomena of archaeoacoustics present in this ancient structure.

This time we took into consideration the upper chamber of the hypogeum which is very small allowing at most of three people inside.



Fig. 1 - The upper chamber of the Hypogeum of Cividale is located just below and to the left of the entrance


In this case we used our professional equipment as used before, that is becoming the new standard protocol of SBRG. This consists of a digital Tascam DR-680 recorder and Sennheiser MKH 3020 microphones, equipped with shielded cables Mogami Gold Edition XLR and gold-plated connectors. In addition, we also used a tone generator to verify the possible existence of a resonance frequency and if present, what the tuning frequency of the room was.



Fig. 2 – The researchers examined the resonance frequency of the belowground room by the electronic tone generator


The sound file present below is an example of using the electronic tone generator to search the "knot" of the underground room. Or rather, where there is greater sound response in relation to the point of emission of sound. In it the microphones are stationary and the emitter is moving. If you have high fidelity stereo headphones you can hear perfectly the sound change when we get close to the node. The tone emitted is already tuned to the resonance frequency of the underground chamber (here).


Fig. 3 – To obtain the best resonance response, we must put on a very specific knot that is determined by a clear niche carved in the conglomerate and that in these photos is illuminated by the hand flashlight

By analyzing the sound, it was found that this room has a resonance frequency of around 95Hz. This is the same frequency range (95-120Hz) also found in some Neolithic temples of the South of England and Ireland from the studies of Robert Jahn of Princeton University in the 90s.

These frequencies correspond to the pitch of a low male voice singing or praying. The human voice cannot maintain a fixed tone, but revolves around the basic tone that sets the officiant in prayer and that must be close to the resonance frequency of the system. The female voice set to the higher harmonic does not seem to trigger this phenomenon.

To simulate the way of praying, Buddhist mantras were used which maintained a fixed tone of prayer. These tests were carried out with three voices, two male and one female.


Fig. 4 - To simulate the way of praying, Buddhist mantras were used to maintain a fixed tone of prayer


Below is one of the recordings in compressed mp3 format. The resonance effect can be felt from the second n.38, ie when the voices are heated (here). The original recordings have many more nuances in the audio collection recorded by uncompressed format with 192KHz sampling rate.

You can perceive the triggers of the resonance phenomenon only when the voices arrive at the precise frequency of resonance, hearing a vibration that has nothing to do with the voice. The female voice as you can hear, does not trigger anything. It is recommended to use a high-fidelity headset only with a large component of bass to listen this sound file.


Fig. 5 - The microphones were placed at a distance in order to better capture the effect of resonance without distortion


Further tests of the acoustic capabilities of this ancient underground structure will be made in the coming weeks.

Paolo Debertolis - March 3, 2013


Translated by Nina Earl


A sincere thank you from the SBRG research group to the owners of Cividale del Friuli hypogeum for their helpfulness and kindness in yielding even at night their ancient monument for our experiments. Heartfelt thanks also to Mr. Federico, who patiently gave us the keys of the hypogeum to our researches at all hours of the day.



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