关键词： 古希腊,歌剧院No need to shout 何须狂呼！ Mar 29th 2007 From The Economist print edition Why the acoustics of ancient Greek theatres are so good
为什么古希腊歌剧院的音响效果如此之好 “SO BY the arrangement of theatres in accordance with the science of harmony, the ancients increased the power of the voice.” That is how Marcus Vitruvius Pollio, a Roman architect, described the design of Greek theatres. He thought the important factor was the theatre's slope, designed to “trace the voice as it rose”.
That is not a bad guess; but it is wrong, according to Nico Declercq of the Georgia Institute of Technology, in Atlanta, and Cindy Dekeyser of its European campus in Metz, France. These two researchers recently applied modern acoustic theory to explain why actors who perform in the Hellenistic theatre of Epidaurus sound almost as loud to audience members in the theatre's outer seats as they do to those in the front row.
As well as the slope, the researchers considered the seats themselves. These are stone benches arranged in rows, which give the semicircular bowl-shape of the theatre a corrugated surface. In a paper about to be published in the Journal of the Acoustical Society of America, Dr Declercq and Ms Dekeyser calculate how each frequency of sound behaves as it diffracts off the rows of seats.
Epidaurus's perfect acoustics are indeed the result of what its audience sits on. Theatre-goers receive sound from the front, reflected off the theatre's foreground, as well as from behind them, backscattered by the seats. The seat rows only backscatter frequencies above a certain threshold, though, so they act, in effect, as a sound filter. Conveniently, Epidaurus's threshold is about 500 hertz. That is the usual upper limit of the noise of wind rustling through bushes and of the murmurs of an audience, which might have drowned the actors out.
Dr Declercq points out that it does not matter that the theatre design also removed fundamental tones of the human voice because the brain reconstructs these from the available high frequencies. Millions of people experience this daily without noticing it when they listen to somebody else's voice through the telephone.
Dr Declercq has previously demonstrated why a handclap in front of the stairs of the great pyramid of Chichen Itza, in Mexico, has an echo that sounds like the chirp of a beautiful bird called a quetzal. His is indeed a tough job, but somebody's got to do it.