Ancient Acoustic Architecture

Byzantine church acoustics: "look at the walls and realize that they were looking at things acoustically. It wasn’t just about the architecture. They had these big jugs that were put up there to sip certain frequencies out of the air ... They built diffusion, a way to break up the sound waves by putting striations in the walls. They were actively trying to tune the space.”

Go have a read. I'd never heard of those chambers being used in a church before. I knew amphitheaters had resonators, though.