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Greek Acoustics

The ancient Greeks knew a thing or two about, well, about a lot of things.

For example, they built outdoor amphitheaters with amazing acoustics.

One theater in particular, built in the 4th century B.C. in Epidaurus, is especially impressive. Sit in the very back row, hundreds of feet from the stage, and you can hear musicians play, and actors speak with amazing clarity. For years scientists have struggled to figure out how, exactly, the Greeks pulled this off.

Until now. Enter Georgia Tech acoustics expert Nico Declercq, who published a paper purporting to solve the mystery of the theater's acoustics. Declercq initially thought that the pristine sound quality was due to how sound waves climbed the slope of the theater's 55 rows of limestone seats. However, numerical models and experiments with ultrasonic waves revealed that the theater's acoustical magic lies in the seats themselves.

The limestone acts as an acoustical trap, removing low frequency sounds, like wind and crowd noise, and amplifying higher frequency sounds, such as music and actors' voices. Although the material also mutes low frequency sounds coming from the stage, the brain is able to fill in missing tones, a phenomenon called virtual pitch.

Evidently, even the ancient Greeks who built the theater had a hard time figuring out what made the acoustics so good. Numerous attempts to match the sound quality of the Epidaurus theater all failed, in part because different materials were used for seating. The secret of the theater's superior sound was so mysterious, in fact, that it took centuries to come to light.

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