From today's Washington Post:
Seating in Ancient Greek Theater Found to Help the Acoustics
The Greek theater of Epidaurus has long been considered a marvel of acoustics. Over the years, people have come up with a number of explanations as to why those who sit in the back of the semicircular theater, built in the 4th century B.C., can hear performers on the stage with such clarity.
One theory was that it had to do with the wind patterns in the area, but modern actors performing on windless days sounded just as clear.
Researchers at the Georgia Institute of Technology this month showed that the secret is in . . . the seats. Nico Declercq and Cindy Dekeyser found that the seating, which is carved from limestone, creates an acoustic filter that screens out low frequency crowd noises and reflects higher frequency sounds from the stage.
In a paper in the April issue of the Journal of the Acoustical Society of America, the researchers said that while the filtering also suppressed part of the range of frequencies of the human voice, "the human nerve system and brain are able to reconstruct this fundamental tone by means of the available high frequency information."
