Hörrohre in einem Gebäude (Abhöranlagen)

The image shows monumental, trumpet-like funnels embedded within the masonry of a palace to capture and transmit sound. One tube terminates in a 'speaking head' statue in a private room, while a massive vertical funnel hangs over a public gallery to overhear conversations from the groups of figures below. Letters throughout the diagram serve as a key for explaining the physics of sound reflection and propagation.

Athanasius Kircher, a Jesuit polymath, viewed acoustics as a branch of 'natural magic'—the use of hidden physical laws to produce seemingly miraculous effects. These designs represent the early modern obsession with surveillance and the 'theatre of the world,' where technology could be used to reveal secrets through the manipulation of the senses.