Vitruvius described Helmholtz resonant modes, not mere amplification

Evidence

Note that Vitruvius does not say the sound will be louder. He emphasizes clarity, and the presence of a note “in unison with itself,” correctly describing a form of resonant enhancement. Could resonators placed at various locations within the audience, far from the source of the sound, enhance the sound? It seems certain that Vitruvius was talking about the Helmholtz modes for each of his bronze vessels. While other resonances can exist in semiclosed vessels, normally the Helmholtz mode is most noticeable. — Eric J. Heller, Why You Hear What You Hear- An…, 1254

Categorization

• XREF: Connects to the chapter’s central Helmholtz resonator concept and its applied history in Greek and Roman theater acoustics.
• CANDY: Nice trivia: the ancient Greek theater sound-enhancement scheme was about clarity and resonant unison, not volume.