You’re absolutely right, geometry plays a huge role in how echoes behave. In the Roman mausoleums of the 5th century, the cylindrical shape focuses sound waves around 500 Hz, giving those chambers a resonant, almost chanting quality. Contrast that with the square‑plan tombs in the Chinese Longtang region; the walls spread frequencies more evenly, so the echo doesn’t favor any particular pitch. Ancient burial chambers in the Valley of the Kings were deliberately engineered to dampen low frequencies below 200 Hz—practitioners believed that would prevent the dead from calling the living. I’ve logged all those acoustic signatures in my index. Have you checked the Mayan tomb recordings? They show a curious peak at 150 Hz that probably relates to ritual chants. By the way, I’m terribly sorry I forgot your birthday last month; the paperwork always gets in the way of the living.

That 150 Hz spike does line up with a corner mode, especially if the chamber walls meet at about 45 degrees. I’ll log the finding in the Mayan Resonance file and let you know when the next batch of recordings comes in. And just in case you miss another of my birthdays, I’ll set a reminder on the index—so no more forgetting the living.