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Fig. 7. Amplifiers and conductors of sound.
Architectural acoustics. Section IV of the first Book of the Phonurgia nova also illustrates typologies and modalities of constructing buildings together with architectural acoustics, and the descrip- tion of particularly interesting places, according to Kircher, from the point of view of their acoustic potentialities. Some of these places still exist today, and they have been famous since antiquity. In these cases, Kircher tried to comprehend the recondite modality of the production of particular sonorous effects or to explain their inner architecture. However, there are a few places he describes in detail which are actually pure Kircher inven- tions, intended to give entertainment, delight and provoke the curiosity of the contemporary wealthy nobility.
Heidelberg’s echo. In Section IV of the first Book of the Phonurgia nova, Kircher described the interior structure of the Palace of the Powerful Elector of Heidelberg that he personally visited. Inside the palace, there was a particular room characterized by an extraordinary echo. Within the circumference CGEF (Fig. 9), words spoken in a soft voice at C could be perceived by another person at positions C, G, or F. The same phenome- non is present within the cupola of the Basilica of St. Peter in Rome (the whis- pering gallery). This room in the palace of Heidelberg possessed a remarkable capacity to amplify sounds, due especial- ly to its circular shape and the vaulted ceiling, which contributed to a surprising acoustic effect. However, Kircher
Fig. 9. Heidelberg’s echo.
Fig. 8. Experiments with echoes.
Kircher’s Phonurgia nova 13