One topic that comes up quite often on Audio Branding is audio technology, and how far it’s come over just the last few years. Whether it’s choosing the right sound equipment, deciding if you should record with noise cancellation turned on (and just for the record, you shouldn’t), or taking advantage of advanced recording options like 3-D audio and Dolby Atmos, there’s a lot to consider when it comes to sound. But you might be surprised to learn that the science of sound optimization is a lot older than surround sound, or stereo recordings, or even audio recordings at all.

Sound has been a part of our lives for as long as we’ve been around, and it turns out that we’ve been finding ways to boost sound quality and reshape the acoustic landscape around us for just as long. From ancient Roman amplifiers to prehistoric boulder harmonies, our ancestors explored the possibilities of sound in ways that scientists today are still trying to understand.

Creating just the right sound experience can be a big enough challenge for modern-day concerts and movie theaters. How do you do it when you don’t have any microphones or speakers? This was the problem faced by Greek and Roman architects, and the science of archaeoacoustics, of how sound was shaped and used in ancient times, hasn’t entirely unraveled their solution. According to the ancient Roman architect Vitruvius, they used “acoustic jars,” or “echea” in Greek, small brass cups built into the walls between each of the seats. He didn’t invent them, though, so we aren’t sure who originally came up with the idea. These echea were believed to resonate and amplify spoken voices, boosting their sound for each listener like a set of personal speakers. They were arranged according to precise mathematical rules that differed depending on the theater’s dimensions.

Did they really work? They must have worked well enough, since they were popular not only during antiquity but also in medieval times, with over a hundred cathedrals in France alone putting them to use. But research continues on just how they worked as well as they did. Some studies suggest that they didn’t actually amplify sound, but instead absorbed some of the surrounding frequencies to muffle the background noise: the world’s first noise-cancellation technology, more than two thousand years before headphones. But a 2011 presentation at the Acoustics of Ancient Theatres conference suggested that maybe their resonance effect did amplify sound. The verdict’s still out.

If you’d like to hear an echea’s resonance for yourself, here’s a clip of a sound sculpture by Michele Spranghero that puts one to haunting use:

https://www.youtube.com/watch?v=vb57mGHy4OE

Rome wasn’t the only ancient civilization to take advantage of sonic resonance. More than a thousand years earlier, and several thousand miles away, lies the Peruvian archaeological site of Chavín de Huántar, once the capital city of the Chavin civilization. Its temples, plazas, and surviving buildings have been studied for many decades, and lately that research has helped uncover the role that sound and harmonic frequencies played in its religious ceremonies.

One artifact that’s been consistently found there is the pututu, a wind instrument that’s also known as a conch trumpet since it’s made from the shell of a conch. This may be a little surprising since the ocean’s well over a hundred miles away, but there might be a surprising reason why so many ancient conch trumpets have been recovered from the Chavin temples.

A research team from the Acoustical Society of America, accompanied by Stanford researcher Dr. Chris Chafe, investigated the acoustical properties of their chambers and discovered that they’re designed to resonate with the pututu’s distinctively warbling frequencies, not only amplifying them but pulling two or more pututu players into a musical harmony that’s felt as much as it’s heard. This effect can be experienced elsewhere – it comes from the rhythmic “beats” that emerge from its natural interference patterns – but it’s stronger inside the buildings. Some researchers have suggested this resonant harmony was a key part of the city’s religious ceremonies and that the temple’s soundscape was intended to create a profound experience for the musicians and their audience.

If you’re curious about what a pututu sounds like, here’s a short clip:

https://www.youtube.com/watch?v=J5PkUXBo4NI

There are plenty of soundscapes and resonant frequencies all around us, of course, and one of our earliest encounters with them might have been as simple as tripping over a rock. They’re called ringing rocks, or singing stones or sonorous rocks, and their discovery by prehistoric tribes all over the world led to one of the first musical instruments ever made, the rock gong or stone chimes.

Ringing rocks are volcanic rocks, such as dolerite or basalt, and even though they aren’t made of metal and they aren’t hollow, they ring like bells when they’re struck. Groups of singing stones can be found throughout the world, from Ringing Rock Park in Pennsylvania and the Bell Rock Range of Australia to sonorous stone fields in Africa and Europe, and the science behind their sound isn’t as simple as you might think. According to a 1965 study by geologist Richard Faas, the rocks actually create a series of inaudibly low, or infrasonic, audio frequencies, but those overlapping frequencies constructively interfere with each other to create sounds that our ears can detect.

But where do those low frequencies come from in the first place? Science is still working on that mystery, and some theories suggest it has to do with the rock’s structural tension, making it a kind of stone guitar string that vibrates with a hard tap. And if that isn’t mysterious enough, the Singing Stones of Brittany clearly didn’t come from the place they’re found today, but no one knows when or how they arrived. Did ancient people recognize their acoustic properties and relocate them as oversized musical instruments? Or were the stones, as legend has it, left there by the Devil?

Check out this clip of a visitor at Ringing Rocks Park in Pennsylvania using six singing stones, each with its own distinctive note, to play a familiar melody:

https://www.youtube.com/watch?v=LKtkbH6ANyk

Sound has connected us to each other and the world around us since the dawn of time, and we’ve been discovering new ways to harness its power for just as long. As we move into the future, learning those lessons could help us reshape the way we experience it in the years to come.

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