Geschlossenes Sprachrohr (Kommunikationsrohr)

The image shows a large, arched architectural space where two figures explore the properties of sound through hidden channels in the walls. On the right, a man speaks into an opening in the masonry marked with the letter 'C', while his companion stands at the opposite end at point 'A' to receive the transmitted voice. This technical illustration demonstrates the early modern concept of the 'speaking tube' used for secret communication in large buildings.

Athanasius Kircher used such illustrations to demonstrate 'natural magic,' showing how scientific principles could achieve effects that appeared miraculous to the uninitiated. His study of acoustics, or 'Phonurgia,' was part of a broader project to understand the hidden harmonies and invisible forces that connect the physical and spiritual worlds.