Located in Finland’s Koli National Park is a famous 34-meter long cave known as Pirunkirkko or the Devil’s Church Cave. In local folklore, this cave was believed to be a place where wise men of the area would gather to make contact with the spirit world. Even today, it is visited by practitioners of shamanism who hold percussive sessions inside the cave.

A new study by researchers Riitta Rainio from the University of Helsinki and Elina Hytönen-Ng from the University of Eastern Finland sought to investigate the acoustics of the Devil’s Church Cave and understand if its acoustic properties could explain the beliefs associated with it and why it was chosen as a place for sound-related activities and rituals.

Through their research, the scientists discovered that the Devil’s Church Cave exhibits a distinct resonance phenomenon that amplifies and extends sound at a specific frequency. This acoustic effect likely had a significant influence on the cave’s associated beliefs and experiences.

Historical records revealed that several renowned healers and wise men operated in the Koli area. The most famous was a man known as Kinolainen, sometimes called Tossavainen, who used the Devil’s Church Cave for magical rituals.

According to folklore, Kinolainen would bring patients to the “church” to speak with the Devil about the causes and cures of their ailments. These healing rituals often included loud shouting, stomping, banging, and pounding – activities that produce sharp acoustic impulses.

Hytönen-Ng also interviewed a modern shamanism practitioner who uses the cave for rituals. He described feeling a special energy in the cave that creates a strong connection to the surrounding nature and his own roots. During percussive sessions in the back of the cave, he claims to have experienced “opening new horizons.”

Acoustic measurements in the smooth-walled rear passageway revealed a strong resonance phenomenon caused by a standing wave between the parallel, even surfaces.

This generates a tone at the cave’s natural frequency of 231 Hz that remains audible for about a second after sharp impulses. Vocalizing tones near 231 Hz inside the cave causes amplification and extension by the resonance. Recordings of the shaman vocalizing repeatedly at 231 Hz were then amplified by the cave to its natural pitch.

Resonance is common indoors but rare in natural environments lacking smooth, solid, parallel surfaces.

The sound sample shows the phenomenon of resonance in the Pirunkirkko (“Devil’s Church”) cave in Koli, Finland. When clapping, the resonant tone of the cave fills in the gaps between the clapping, creating the illusion of a timbre that wavers in space.

The researchers believe the Devil’s Church Cave’s distinctive resonance would have been an exceptional acoustic phenomenon for locals centuries ago. Similar resonances have been measured in paleolithic caves featuring rock art.

The scientists suggest a persistent, resonance-amplified tone was likely audible during rituals. Its subtle, unconscious effect may have significantly shaped the cave’s associated beliefs and experiences.

Where an acoustic researcher hears resonance, past people may have sensed a spirit’s presence, and a shaman a special energy – each through their own lens.


University of Eastern Finland | Rainio, Riitta & Elina Hytönen-Ng 2023. Ringing Tone and Drumming Sages in the Crevice Cave of Pirunkirkko, Koli, Finland. Open Archaeology 2023 (9): 20220328 doi.org/10.1515/opar-2022-0328

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