Decoding the mysterious knocking sounds in Finnish caves.

The Pirunkirkko Cave in Finland , which means "Church of the Devil" in English, is located in the Koli National Park and is famous for its sounds resembling intermittent knocking.

Decoding the mysterious knocking sounds in Finnish caves.

The sound resembles knocking coming from the Pirunkirkko cave. Video : University of Helsinki.

A research team from the University of Eastern Finland has discovered the cause of the strange noises in the Pirunkirkko cave, Mail reported on November 27. According to researchers Riitta Rainio and Elina Hytonen-Ng, it is due to a special resonance.

Pirunkirkko is a 34-meter-long, Z-shaped cave. Legend says it was a meeting place for sages to communicate with the spirit world. In new research, scientists are exploring whether the cave's acoustic characteristics could help explain the legend associated with it. Analysis of the cave reveals a characteristic resonance phenomenon that both amplifies and prolongs sounds at specific frequencies.

The research team suggests that this phenomenon is caused by standing waves between the smooth, parallel walls of the cave. This creates an acoustic sound at the cave's natural frequency of 231 Hz, audible for a second after sounds such as clapping, drumming, or pounding.

The research team also interviewed and recorded a modern-day shaman who used the cave for rituals. They discovered that the sounds he produced were amplified by the cave at its natural frequency.

Although quite common in buildings, resonance is relatively rare in natural environments, mainly due to the lack of parallel solid surfaces. For this reason, the research team suggests that the resonant sounds in the cave may have made visitors feel as if spirits were present.

An Khang (According to Mail )

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