Featured Research

from universities, journals, and other organizations

Ancient Greek Amphitheater: Why You Can Hear From Back Row

Date:
April 6, 2007
Source:
Georgia Institute of Technology
Summary:
The theater at Epidaurus has been known for centuries as an acoustic marvel that allowed spectators to hear in the back row. Georgia Tech researchers have discovered that Epidaurus' limestone seats created a sophisticated acoustic filter that carried instruments and voices all the way to the back row.

The Theater at Epidaurus on the Peloponnese in Greece.
Credit: Image courtesy of Georgia Institute of Technology

As the ancient Greeks were placing the last few stones on the magnificent theater at Epidaurus in the fourth century B.C., they couldn’t have known that they had unwittingly created a sophisticated acoustic filter. But when audiences in the back row were able to hear music and voices with amazing clarity (well before any theater had the luxury of a sound system), the Greeks must have known that they had done something very right because they made many attempts to duplicate Epidaurus’ design, but never with the same success.

Researchers at the Georgia Institute of Technology have pinpointed the elusive factor that makes the ancient amphitheater an acoustic marvel. It’s not the slope, or the wind — it’s the seats. The rows of limestone seats at Epidaurus form an efficient acoustics filter that hushes low-frequency background noises like the murmur of a crowd and reflects the high-frequency noises of the performers on stage off the seats and back toward the seated audience member, carrying an actor’s voice all the way to the back rows of the theater.

The research, done by acoustician and ultrasonics expert Nico Declercq, an assistant professor in the Woodruff School of Mechanical Engineering at Georgia Tech and Georgia Tech Lorraine in France, and Cindy Dekeyser, an engineer who is fascinated by the history of ancient Greece, appears in the April issue of the Journal of the Acoustics Society of America.

While many experts speculated on the possible causes for Epidaurus’ acoustics, few guessed that the seats themselves were the secret of its acoustics success. There were theories that the site’s wind — which blows primarily from the stage to the audience — was the cause, while others credited masks that may have acted as primitive loudspeakers or the rhythm of Greek speech. Other more technical theories took into account the slope of the seat rows.

When Declercq set out to solve the acoustic mystery, he too had the wrong idea about how Epidaurus carries performance sounds so well. He suspected that the corrugated, or ridged, material of the theater’s limestone structure was acting as a filter for sound waves at certain frequencies, but he didn’t anticipate how well it was controlling background noise.

“When I first tackled this problem, I thought that the effect of the splendid acoustics was due to surface waves climbing the theater with almost no damping,” Declercq said. “While the voices of the performers were being carried, I didn’t anticipate that the low frequencies of speech were also filtered out to some extent.”

But as Declercq’s team experimented with ultrasonic waves and numerical simulations of the theater’s acoustics, they discovered that frequencies up to500 Hz were held back while frequencies above500 Hz were allowed to ring out. The corrugated surface of the seats was creating an effect similar to the ridged acoustics padding on walls or insulation in a parking garage.

So, how did the audience hear the lower frequencies of an actor’s voice if they were being suppressed with other background low frequencies? There’s a simple answer, said Declercq. The human brain is capable of reconstructing the missing frequencies through a phenomenon called virtual pitch. Virtual pitch helps us appreciate the incomplete sound coming from small loudspeakers (in a laptop or a telephone), even though the low (bass) frequencies aren’t generated by a small speaker.

The Greeks’ misunderstanding about the role the limestone seats played in Epidaurus’ acoustics likely kept them from being able to duplicate the effect. Later theaters included different bench and seat materials, including wood, which may have played a large role in the gradual abandonment of Epidaurus’ design over the years by the Greeks and Romans, Declercq said.


Story Source:

The above story is based on materials provided by Georgia Institute of Technology. Note: Materials may be edited for content and length.


Cite This Page:

Georgia Institute of Technology. "Ancient Greek Amphitheater: Why You Can Hear From Back Row." ScienceDaily. ScienceDaily, 6 April 2007. <www.sciencedaily.com/releases/2007/04/070404162237.htm>.
Georgia Institute of Technology. (2007, April 6). Ancient Greek Amphitheater: Why You Can Hear From Back Row. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2007/04/070404162237.htm
Georgia Institute of Technology. "Ancient Greek Amphitheater: Why You Can Hear From Back Row." ScienceDaily. www.sciencedaily.com/releases/2007/04/070404162237.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com
U.K. To Allow Driverless Cars On Public Roads

U.K. To Allow Driverless Cars On Public Roads

Newsy (July 30, 2014) Driverless cars could soon become a staple on U.K. city streets, as they're set to be introduced to a few cities in 2015. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



    Save/Print:
    Share:

    Free Subscriptions


    Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

    Get Social & Mobile


    Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

    Have Feedback?


    Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
    Mobile: iPhone Android Web
    Follow: Facebook Twitter Google+
    Subscribe: RSS Feeds Email Newsletters
    Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins