The Mystery Of The Greek Amphitheater Solved

For centuries acousticians have argued over the secret to the excellent acoustics at the amphitheater of Epidaurus in Greece.

Crowds of up to 14,000 people have been able to hear the actors and musicians perform in the theater completely un-amplified, even in the back row, but yet science has been able to say exactly why that was possible.

The amphitheater, which dates back to the 4th century BC, is a masterpiece of architecture by Polykleitos the Younger, but its acoustics have never been duplicated (even by Polykleitos) regardless of the increasing sophistication of measurement equipment at the disposal of the modern acoustician.

Researchers at the University of Georgia have finally unlocked the secret though - it's all in the seats!

In findings presented in an issue of The Journal of The Acoustics Society of America, the scientists involved in the research found that the limestone used in the seats provide filtering and absorption, thereby decreasing crowd noise and low frequencies that might interfere with the performance. All the frequencies below 500Hz are attenuated.

That's not all. It seems that the slope of the seats reflect the high-frequencies back towards the audience, making it easier for them to distinguish the sounds of the performers.

Then there's the fact that corrugations of the seats act as bass traps, which then lead to the listener filling in the frequencies psycho-acoustically, just like what happens when listening to an MP3.

So lets see - absorption, bass traps, reflection angles - sounds like modern recording studio building techniques to me. It just goes to show that no matter how things evolve, they still manage to stay the same.

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